The Rude and Crude Old School Springer Build
I still think that our original CBH Springer is about one of the finest designs on the market today but even though it is simple to build we still get requests for a design that is even less complex and less expensive to fabricate.
In response to this demand we’ve prepared this modern revision of a true Old School Springer very similar to those we used to build in the sixties. The fancier CBH Springer we published in 2005 was actually just a refinement of this old original design.
We call this one the ‘Rude and Crude Old School Springer’ because that’s exactly what it is; pretty rude and pretty crude but it rides and handles very well and you don’t need to do any fancy machine work or have any special tools. All of the components are readily available, nothing is custom made, and it is a relatively economical fork system to build if you want an affordable Springer on your bike.
Springers have been used on bikes for decades, in fact the first were introduced way back in the 1800’s on bicycles and Harley was an early adopter for their motorcycle applications but they didn’t become the ‘cool’ thing to do on chopped bikes until custom builders exceeded the limits for ‘modern’ hydraulic forks in the early sixties.
Once you start to rake the neck angle on a bike and then combine it with extended forks the effectiveness of the so-called modern hydraulic forks soon start to fail and fail very fast. It didn’t take to long for bike builders to realize that running hydraulic forks on any bike having a rake angle of more than 35 degrees was asking for trouble so the fall-back at first was just some ‘solid’ legs with no suspension system at all except for the springy bend in the legs themselves. These long raked ‘solid’ forks behaved almost exactly like a set of non-performing hydraulic forks only better. The drawback was that over time they began to take a ‘set’ and looked like they’d been run through a ring roller. To counteract this tendency we started to add a girder truss to the backside of these ‘rigid’ legs and it worked up to a point where you still had a little ‘springiness’ but beyond this point you simply ended up with a very rigid, non-yielding set of forks with no suspension component at all since they didn’t flex even a few fractions of an inch.
(For those of you who still remember the old rigid forks you might be interested to know that Freddie Hernandez still builds them but he builds them a lot better than they used to be so give him a call if you want something unique).
The solution for raked bikes ended up being a resurrection of the old original Springer except with massively extended legs. This concept worked and it worked no matter how long the forks were and believe me back in those days we were building some incredibly extended forks for bikes with outlandish amounts of rake. The old Springer suspension kept working no matter how far we pushed the design envelope. Even today on a radical bike the old extended Springer design concept will provide a good suspension solution to a tricky design problem. An excellent example of this old technology that has been optimized can be seen in the work of Springer builder extraordinaire, Sugar Bear (Al Myers), seen below.
This old snapshot from his web site shows one of his famous 60-inch over Springers, which believe it or not weren’t all that uncommon back in the early days of the craft.
There are several other noted Springer builders out there today. Mondo at Denver’s Choppers comes to mind as well as Jeri Exner, Big Al Wilkerson and one of the pioneers of the craft, Freddie Hernandez, but this article isn’t about where to buy a good set of forks but how to build them.
About all you need to build these forks are a hacksaw or reciprocal saw, belt sander, small drill press, mini-grinder and access to a welder. Depending on which rocker system you decide to use you might also have to buy a tap to thread the rockers. Of course more tools are great if you have them but for a guy just starting out these forks require a minimum of gear. For a complete rundown on tools and some substitutions or workarounds see the Girder building article as it goes into considerable depth on the subject.
I get a little bent when I hear about people postponing a project because they don’t have a complete computerized machine shop at their disposal since if we all waited for that day to arrive nothing would ever get done. I figure that if guys like Burt Munro can build a record setting bike with nothing but hand tools and a power drill then it seems to me like anybody with the desire can accomplish amazing feats of engineering and fabrication.
Materials and Costs
To build these forks you need relatively few raw materials and in fact most people who have been building their own frames probably have a lot of the appropriate stock already at hand in their scrap pile. You can very easily do some creative scrounging at local fabrication shops and come up with the steel needed for the project just by digging through the box of ‘drops’ most fab shops have in the corner of the shop. If push comes to shove you can buy on-line through suppliers such as ‘Online Metals’ which I’ve had excellent results with. In fact I now use this resource as my main steel supply outlet as they usually beat the prices and delivery times from my local sources.
As of 6-14-08 the costs for all of the steel and tubing for this particular design ordered on-line, which is premium prices, is $146.93, which includes shipping. Local sourcing and scrounging can bring this down significantly. Unfortunately Springers compared to other types of forks are somewhat material intensive so it is pretty hard to save a bunch of money on the raw materials. The raw stock doesn’t have to be ordered all at one time so the cost can be spread out as you’re working on specific parts of the design and if you’re willing to do some scrounging you can save some very big bucks. I built my first Springer entirely from scrap and swap meet parts for fewer than thirty bucks but then again that was almost forty years ago so you have to factor inflation into the picture.
My goal for this project was to keep the finished product ready to install at under three hundred and fifty dollars minus powder coating.
The pre-made materials and parts such as the springs, retainers, bushings and spring rods can be purchased from a wide variety of sources. I prefer to do business with only a few companies for these parts, the first being ‘Bitter End Old School Choppers’ and the second being ‘45 Restoration Company’. I don’t get any kickbacks in case you’re wondering. Both outfits offer below average prices and far above average services and I’ve tried doing business with a lot of suppliers. Both of these shops stand out against the rest and they stand behind what they sell which is very unusual today.
On average, including shipping, the cost for all the springs, rods, retainers, nuts, sleeves and other small parts ran $157.85 (chromed) so you can see we’re already up to $334.78 paying full retail and buying everything on-line. To me this is expensive but compared to $800 for a cheap imported piece of junk it looks pretty good. Compared to a top flight American made Springer at $2500 it looks really good indeed.
Projects like this one aren’t always about saving money but more about gaining the pride and satisfaction of doing something yourself that makes your bike unique and a truly personal creation.
I’m kind of a fanatic about material prep and the older I get the more obsessed I become.
The first thing I normally do when receiving an order of stock is to clean it with lacquer thinner. On tubing I also swab out the interior bores, as they are usually full of filth.
The snapshot above is the crap that came out of a relatively clean section of DOM tubing.
Once the tubing is clean I’ll check it for straightness. You’d be surprised to find how many times you receive tubing that has a slight bow to it. If you end up with some distorted sections you really can’t use it for Springer legs. If you’re lucky and have some nice straight stock then you need to examine every square inch of the exterior surfaces and look for any significant gouges, nicks, dents, cracks or other imperfections.
Unfortunately steel products are treated like crap at most distribution yards so it’s rare that you receive some good virgin material. I have to admit that I’ve been getting some good stuff from the online sources. In some cases far better that what I can purchase locally but it does cost more.
On flat stock I try to remove as much mill scale as possible before I do any pattern layout. At least I give it a quick sanding and knock off any sharp edges where the material has been cut to order. Whatever you do don’t try to use hot-rolled material for anything as it takes far to long to get down through the mill scale to find a good surface and even then it’s probably going to be marginal. It’s tempting to buy it as it’s a lot cheaper but I don’t think worth it in the long run. Every now and then however you have to use it to get the sizes you might require so if that happens be prepared for a lot of prep work.
From my standpoint I look at a typical Springer as being made up from four basic elements. There are the legs or fork tubes, both the front and the rear. Then there is what I call the structural elements, which are the bridges, perches and trees (yokes). Then there are the suspension elements, which are the springs, rods, rod bushing, spring seats and associated fasteners. Finally there are the rockers themselves and their associated hardware and fasteners. I give the rockers a separate class of their own and treat them as distinct elements because there are several different rocker variations that can be used with any suspension system.
I typically design a Springer from the bottom up. I start with a rocker design and then work upward through the other various elements. During fabrication I use the same procedure, which is opposite to what many builders do. There is nothing special about my personal method. It is just how I was taught to do things so you can work from the top down if that better suits your particular fabrication habits.
Almost the worse thing you can do to a chopped bike is to install an ‘off-the-shelf’ Springer as in almost 90% of the cases the pre-made item will not suit the design characteristics of your particular bike. Springers are a little peculiar and what works with one bike geometry won’t work with another. Of course the factory spent years designing their own forks and rockers and they work wonderfully for the bikes they were designed for. Bolting a stock fork to a little custom made Bobber with a 32 degree neck as opposed to the stock 28 and 30 will result in entirely different handling characteristics unless the rockers are modified to suit the new bikes geometry. This is just a fact of life and it’s the reason that custom fork builders are still in business today. Canned solutions for chopper forks just don’t work very well since each bike is unique. Unfortunately most people don’t know what’s good and what’s bad so they settle for what the mass-producers give them and assume that’s how it’s supposed to be even if it’s a really horrible ride.
That’s not going to happen to you because you’re going to build your own Springer and it’s going to be designed for your particular bike.
We’re going to start at the bottom and get this thing built for as little money as we can without sacrificing safety or quality.
Rocker to Leg Attachment
In my forty years of building Choppers I have probably seen just about every conceivable method used to mount the rockers to the legs on Springers and no matter how bad the lash-up was I have never seen a failure at the rocker connections themselves and I have seen some pretty poor examples. I’ve seen bikes where the rockers were connected to the legs with just regular old hardware store bolts run through bare holes with separation provided by brass washers and some of these forks had seen hundreds of thousands of miles of use and still worked. I wouldn’t recommend this method but I just wanted to point out that almost anything can and does work. Some methods are just better and safer.
The weak point of Springers is not the rocker connection but the tube legs themselves and especially the junction point where the rear legs enter the lower fork tree.
I have seen hundreds of Springers with bent and broken rear legs but in almost all cases the front (sprung) legs were not nearly as badly damaged which goes to show where the stress points actually are on a set of Springer forks. The rear legs are the weak link in the system.
There are at least six basic rocker to leg mounting designs available to the builder and within these six basic arrangements there are several variations with respect to the arrangement of the various parts.
Everybody claims that their own unique arrangement is the best but in reality all of these designs and their variations perform satisfactorily so it’s up to you the prospective builder to select a system best suited to your particular applications.
Note that in the pseudo-sectional drawings to follow that we have not shown shim washers, which are typically used to adjust the clearances and compression for the bushings and thrust washers.
The first method involves rockers that have a ‘trunnion’ that houses the pivot bushing and this is the method seen on the old original Harley rockers and many modern forks as well. This method greatly simplifies building the fork legs but makes the fabrication of the rockers much more complicated. Figure 3 illustrates a stock connection configuration.
The big advantage these types of rocker have over flat-plate types is that they provide much more bearing surface so the bushings will last much longer before needing replacement. In fact some old springers still in use today are still using their original bushings from the forties so the theory has been proven in reality.
The second method is a modern rendition of the old stock arrangement except a shoulder bolt replaces the stock ‘stud’. In almost all respects this design as seen in Figure 4 is a good substitution for the factory connection.
The third method involves the use of what we call ‘flat’ rockers. In other words rockers that are fabricated from flat steel stock with no integral trunnions for the bushings and this is the style most often seen on old Springers from the sixties and seventies and the basic construction is shown in Figure 5.
The fourth method also involves ‘flat’ rockers but adds a trunnion or boss to the ends of the Springer tube legs instead of a flat tab to house the bushings as shown in Figure 6. This is a nice way to finish off the ends of the tube legs but since the sleeves protrude a little into the space between the legs it does reduce the space available for the wheel so it’s typically only seen on wider Springers.
Figure 7 illustrates another popular alternative on this theme but in this case the shoulder bolt actually threads into the rocker so the bolt and rocker both rotate within the bushings inside of the sleeve welded to the tube leg.
Figure 8 depicts a method popular in the sixties and still used today by many builders. The sleeve bolt is usually custom-made but they were available from Paughco at one time and perhaps still are. This is the same arrangement you’ll most often find on the forks that Sugar Bear builds. It’s very clean and the relatively flat fastener heads leave plenty of clearance for disc brakes on a wider hub than you can usually run with other connection methods.
As already mentioned there are numerous variations on each of the basic schemes just outlined. I don’t think any particular arrangement is better than another. They all work just fine so pick one that’s easy for you to build and go with it.
There are several methods we haven’t illustrated since their construction is obvious, like the method used by Redneck Engineering for instance.
If you’ve already considered building a Springer I assume that you’ve also already purchased plans from Crime Scene Choppers, BCC Orlando, and the several others out there selling Springer plans. I also figure that you’ve probably downloaded our free Springer plans as well. You can see the wide variation in design used by the different suppliers just by an examination of the various plans. If you visit various Chopper web sites you’ll see even more variations in rocker/leg connection designs. The possible combinations are perhaps endless as every builder tries to improve on the work of others in an attempt to perfect the ultimate configuration. This is somewhat ironic considering that the old original design has been in reliable and economically practical service for over 50 years with few problems beyond owner neglect.
The reason I’ve gone into so much detail about this particular aspect of Springer design is because there are so many variations. It’s looks complicated, and to a point it is as there are certain engineering and fabrications constraints that apply to any single arrangement.
Before you start your project I want you to go out and look at bikes at shows that have Springer’s installed. Take a critical look at the rocker connections you see. Try to reverse engineer them in your own mind. You can look at my drawings all day long and they won’t make nearly as much sense as seeing the real thing up close and personal. In my opinion this single aspect of Springer design is the most critical but more often than not it the last thing people normally consider when they first begin to approach a new project.
Figure 9 shows a very old Springer, most likely built between 1966 and 1969, that uses flat rockers and flat rocker mounting tabs on the ends of the legs. There are no trunnions at all. According to the various Internet discussion board Springer ‘experts’ this particular arrangement can’t possibly ‘work’ to begin with but I know the history of these forks and can say with certainty that they have just a little under 150,000 miles on them without any rebuilding of any kind and are still very tight even though the bronze thrust washers are worn almost paper thin.
You have to excuse the axle ‘bolt’ as we didn’t have an axle that would fit when we took this picture but you get the idea of what I’m trying to convey.
This is a very good example of flat rockers mounted to flat tabs on the tube legs and we’ll ‘dissect’ these rockers later on in the article, as they are a classic example of why ‘modern experts’ on Chopper fabrication can’t be taken to seriously. There is a bushing in there but you can’t see it once the parts are bolted up.
Figure 10 shows a mockup using a stock H-D Springer rocker ‘stud’ which is shown in the exploded sectional drawing labeled figure 3.
Basically this stud has a short shaft on one end with an unthreaded portion that is very near 5/16 of an inch in length and then a threaded section about one half inches long. The stud mounts to the 5/16” thick pivot tab, shown here as a piece of 5/16 x 1.5” steel strap stock, by just being inserted into a 1/2” diameter hole in the pivot tab at the end of the fork leg. A nut and lock washer secures the stud in place. The rocker trunnion slides down over the bushing and is secured in place by the large diameter hex head bolt and lock washer.
This system is relatively primitive but it’s cheap and easy to duplicate and it does work very well as history can testify. If you decide to go with this route you can also use stock H-D rockers from the old flathead Big-Twin bikes.
This will save you a huge amount of fabrication time but will also cost you about $165 for the studs, bushings and rockers.
There is however a way to replicate the easy fabrication method adopted by the factory and save about a hundred dollars at the same time and this is to substitute readily available shoulder bolts for the fancy machined studs and special rockers.
There are two ways of doing this and we’ll show both methods. Keep in mind that what follows is just a mockup so don’t pay any attention to the size of the particular fasteners. We’ll get into specifics later. For now this is just meant to illustrate the general methods that can be used.
Figure 11 shows one method utilizing a standard shoulder bolt. The threaded portion of the shank is placed through an unthread hole in the pivot plate that welds into the tube end. The bolt is pulled up tight with a jam nut and topped off with a cap nut for the sake of appearance. The bushing and rocker ride on the shaft of this bolt. This method is almost identical in every respect to a stock factory arrangement but far cheaper and easier to implement.
The downside to this method is that any shear stresses are placed on the bolt at a point of its smallest diameter. This is also a problem with the factory installation although I have never heard of a stud ever being sheared off.
Another method simply reverses the shoulder bolt but more than doubles its load carrying capacity as seen in figure 12.
In this particular snapshot that is a smaller shoulder bolt than shown above but I was too lazy to drill the hole in the pivot plate out to the larger size. The concept still applies but I do not recommend that you use smaller bolts.
As you can see what we’ve done is to bore a hole in the pivot plate, the tab that’s welded into the bottom of the tube legs, that’s the same diameter as the shoulder bolt. By doing so the shear stress is now applied to the bolt at its largest diameter. This makes for an incredibly strong connection with respect to bending loads as well as shear loads. This method is about three times stronger than either the method shown in Figure 11 or the stock factory setup.
The bushings we’re using in these mockups are just very cheap plain bronze material but for the real thing you need to use at a minimum SAE 841 bronze (oilite) bushings which are not only much better at resisting impact loads but also much more precise in dimensional characteristics (plus or minus 0.005”).
The rocker bushing and rocker are then slipped over the exposed portion of the shoulder bolt shaft and secured with either a jam nut and cap nut, or a lock washer and cap nut. We’ll get onto detailed descriptions of specific fastening methods later on.
This is the method we’ll be using for this specific project to mount the rockers to the fork tubes since it’s probably the easiest and cheapest for the home-based builder to fabricate and implement. It’s not the ultimate setup but it works very well, is easy to maintain, cheap and easy to implement and very strong. It’s also a very flexible method and allows room for improvements and refinements over time if you decide to build rockers having trunnions some day. It’s very easy to simply change out the bolts for another size so you’re never locked into a specific design element as you are with some other connection methods.
Once you decide on how you want to secure the rockers to the tube leg tabs it time to decide on what the rockers look like and how they relate to the forks and the wheel axle from a geometric standpoint.
Even a quick look around the Internet and a trip through a couple of bike shows will reveal the wide variety of shapes and sizes seen in custom Springer rockers. They range from mild to wild and even super-wild. Unfortunately about 90% of the designs you’ll see were developed purely for looks and have nothing to do with improving the handling characteristics of the forks. In fact some designs, even those that appear to be conservative or traditional, actually hurt the steering and suspension geometry. Equally surprising is that some designs that appear to be ultra radical in appearance were actually designed specifically to improve handling. For this reason one can’t go by looks alone.
Figure 14 is my so-called ‘standard’ rocker shown in the ‘loaded’ condition, which means supporting the weight of the bike plus the rider. Note that the axle is about 1” higher than the rear leg pivot point.
This is a somewhat ‘extended’ rocker design but it’s not radical. By pushing the axle 1.375” further forward than a stock rocker it permits the use of a wider hub in a narrow set of fork tubes and reduces trail to 2.625-inches on a bike with a 40-degree neck.
Figure 15 is another design I use quite often. It is virtually identical to the standard pattern with the exception of the axle location. Note how much higher the axle axis is located relative to the rear pivot point. It is also 1-inch further forward reducing trail even more.
In general the higher the axle axis is relative to the rear leg rocker pivot point the less tendency for the front wheel to flop. It’s a combination of geometry and weight distribution that reduces flop but the biggest factor is weight; that is, the more weight you have below the axle axis the less likely the wheel is to suddenly flop. By placing the ends of the fork tubes, the rockers and the associated hardware below the axle line you’ve lowered the center of gravity of the wheel assembly relative to the rotation axis. This is one of the primary reasons why bikes having scimitar type rockers behave so well despite their radical appearance; they just have a lot of weight below the axle axis. Of course the same anti-flop elements can be accomplished by just running a lightweight wheel and tire to begin with in the first place and then you don’t need to worry about anything else but for some reason in this day and age simple stuff like this seems to get lost somewhere.
Figure 16 represents a stylized sketch of what we used to call ‘Scimitar’ rockers that were popularized in the early sixties and still built today by Sugar Bear and a few others.
If you take the time to look at Springer geometry over a wide range of neck rakes you’ll soon find that there is a mathematical relationship between the values for trail and the location of the axle axis relative to the rear leg rocker pivot point. If you make a plot you’ll end up with something very similar to that shown above.
If the curve is drawn accurately it closely resembles a segment of what’s called a Fibonacci spiral but this gives you some idea of how and why such rockers were developed. In practice their effectiveness really doesn’t come into play until you start building long forks for bikes with fairly deep neck rakes. Figuring all this stuff out will keep you busy for a couple of decades so good luck if this is the direction you want to follow.
Most custom builders have developed a comprehensive number of patterns over the years that suit a wide variety of fork geometries and bike configurations. We’ve included three different patterns with the plans that work well on our particular fork designs and with most choppers having necks raked from 35 to 42 degrees. There is always room for improvement and experimentation so don’t be afraid to try out several different configurations for your particular project. If you accept the factory stuff you’re only cheating yourself.
On this build-up we’re going to make two different sets of rockers. One set will be very simple and another set will be a little fancier and take longer to make.
For the simple set all we need is some 1/2” thick steel strap 1.5-inches wide and about 14-inches long. We cut this in half and have two straight segments (the cutting pattern is at the end of this article). The overall dimensions are shown below.
We’re going to be using 5/8” shoulder bolts with 3/4" bushings so we bore two 3/4” diameter holes in each rocker for the pivot pins. Since this is a narrow Springer it’s likely that you’ll be using a small spool hub wheel or one of the mini-brake hubs and both normally use 5/8” axles so bore the axle holes with a 21/32nd drill bit. At this point, if you want, you can hold off drilling for the axle until you finally get the wheel and axle you actually want to use.
Figure 17 shows the various parts in the progress of being shaped and sanded down prior to being finished. They don’t look to pretty now but we’ll dress them up a little as we go along.
Even thought these rockers are about as simple as one can build they work just as well as some fancy curvy design but they do need more clearance with the tube leg termination caps than a ‘sculpted’ or ‘radiused’ type of rocker. You may have to grind a deep scallop on the upper inside edge to provide clearance for the tube leg as the rocker moves through its complete cycle.
Once the rockers are finished I’ll usually cut the pivot point tabs that weld up into the tubing of the front and rear legs. I normally make these from 3/8” by 2” cold-rolled strap but all I had in the shop was some hot-rolled. Please don’t try to use this stuff, as it just takes to long to get a good finish on it.
I do the rough cutting with a saber saw or a reciprocal saw as can be seen in the piece to the left in figure 18 and then dress down the sharp corners with a belt sander to the rough shape as seen on the tab to the right in the snapshot.
I do the final shaping and polishing later on at the same time as I’m fitting the tabs into the tube legs. I use the same tabs for all projects, Girders, Leafers and Springers and have a different pattern for various tubing sizes. The patterns are included in the drawings and at the end of this article.
It’s not shown but once I have the tabs roughed out I usually drill a ¼-inch pilot hole at the pivot point location.
Whenever you’re working on parts that have ‘mates’ so to speak it pays to sometimes drill extra ‘indexing’ holes and stack the rough-cut parts so that you can grind, shape and dress all of the separate pieces against a ‘master’ that you’re satisfied with. The index holes can be plugged and welded closed if necessary later on in the fabrication process.
Figure 19 shows a set of pivot tabs being shaped.
The piece on the top is my ‘master’ and the piece on the bottom is in the process of being shaped on the belt sander. The goal is to eventually end up with both pieces being virtually identical in all respects.
Figure 20 shows the backside of the same pieces where we’re getting close to matching the profile after some sanding.
The big disadvantage we home based builders usually have is not having any fancy machine tools so each and every part we cut is actually a one-off. We spend a lot of time trying to make all of the parts identical and we do this with blood, sweat and tears. It takes a lot of time and a lot of labor.
Fortunately we don’t pay ourselves so we can afford to take the time to make things right even though it may be a lengthy process. At one time garage-based building got a bad name because people weren’t taking the time to do things right and just slapped things together as fast as possible. Thankfully those trends are gone and most home-built choppers today are just as good, if not a lot better, than anything being made by the manufacturers.
Always remember that you only get back what you’re willing to put in and you can’t go wrong.
After the tabs are roughed out I’ll cut the notches in the tube legs. I normally keep a small supply of tubing on hand precut in 2-inch increments for the more common Springer lengths. I always use DOM tubing on Springer legs. ERW is perfectly fine for Girders and Leafers but Springer legs take a lot more abuse plus we often have to add threaded slugs or pivot bungs inside the tubes so we need a nice accurate inside dimension that DOM provides.
I still cut all of the notches with a hand held mini grinder using an abrasive disc. I’d probably still do it this way even if I had a milling machine since it just takes a few minutes to do all four legs.
I normally skip the first step shown below but to do this properly you really should start the notches by drilling a 3/8” diameter hole (to match the tab material thickness) completely through the tubes exactly on center as shown in Figure 21.
You can see my layout marks in felt marker pen.
The finished product should look like figure 22.
Cut the notches with the grinder. You can clamp on a section of angle or channel to serve as a straight edge if you need to. The cuts should be clean and straight and slightly less in width than needed for the 3/8” tabs.
Figure 23 shows the initial cuts. Note that the notch is smaller in width than what’s required. To do the final dressing I use a large piece of 3/8” strap material and the grinder to slowly and carefully widen the notch until the strap will just barely slip into place. Using this rather large piece of steel makes it much easier to see if the notch is trying to veer off center when you sight down the tube from the end to end.
Once you have a nice tight fit you can square up the ends of the notch where the drilled hole was by just using some hand files. We’ll add the bevels for welding later on as we’re doing the final fitting on the pivot point tabs.
Once the slots are cut nice and straight we can go back and do the final rough work on the pivot point tabs. Figure 25 shows how much we’ve cut down the pivot point tabs since we initially roughed them out earlier. At each step we’re getting closer to the final product but it takes time when you’re doing this with relatively primitive tools.
Everything is an iterative process where you work on the various bits and pieces a little at a time until all the parts are nearly ready for the final assembly. Many pieces won’t actually reach their final stage of shaping until after everything is assembled.
I kind of break the work of making these small parts into several stages. The first is what I call ‘hacking’ for lack of a better description. That’s the stage where you take the chop saw, reciprocal saw, saber saw, mini-grinder or whatever and slice away cutting off as much stock as possible to get somewhat close to your pattern outline. The next stage is what I call ‘rough’ shaping where I’ll use a grinder and belt sander to knock down the sharp edges and corners working the piece down even closer to the pattern outline. This is the stage where any contours are developed and you’ve got a crude outline of the part. The next stage is what I call ‘dressing’ and this is where you use the belt sander to bring the part down to almost touching your pattern outline maybe being just a 32nd of an inch shy of being perfect. I do 95% of all my layout, fixturing and trial fitting while the parts are in the ‘rough’ stage saving the dressing until I’m almost ready to start tacking things together. The last stage usually involves fine sanding and/or polishing where the parts are brought to their final state of completion prior to painting or plating.
Almost all of the parts shown above are in the early ‘rough’ shaping phase so the contours haven’t been fully developed yet.
Getting back to the pivot point tabs there are several ways to finish the raw ends of the leg tubing where it meets the flat plate stock. Many builders like to use tubing caps and these do work well. Usually they are welded on before you cut the notches. Other folks just weld in a small segment of 3/16-inch plate set at a 45-degree angle that is cheap and fast but doesn’t look to great. I was taught to use what we call ‘bullets’ to finish the ends.
A bullet is just a wedge shaped piece of tubing that gives the tube end a nice tapered transition down into a piece of flat stock. Depending on what angle you cut the bullet it can be long or short and that’s up to you. The welds around the bullet are purely cosmetic so don’t be afraid to grind them down into a nice transition.
I personally like long bullets which create the look of a very long taper but to use these effectively you have to have very deep legs on the tabs you’re welding into the tube legs and this takes a lot of time to do.
This gives you an idea of what a long bullet might look like on a typical tube leg. Notice how deep you’d have to make the plate so that it had at least 2-inches of good structural weld before the bullet starts. On a custom bike it might be worth the work.
When I first started working in a chopper shop cutting bullets was all that I did all day long. I think I was making $1.25 and hour and my boss sold the pieces for a dollar each and he was selling hundreds a week to shops all around the country. I got to where I could cut and dress about 20 an hour so he was doing pretty good on these little beauties.
I still like bullets but to be effective from a time standpoint they can only be about 1.5 inches long. I think regular tube caps look like some kind of crap that a manufacturer would use.
You can also create what I call a ‘coved’ tube end that wraps around the rocker but it’s even more work so I’ll leave that one for a later day, maybe a discussion board item.
Remember that no matter what type of tube-end termination you use it is vitally important that you leave enough clearance between the lower portion of the cap or bullet and the upper inner edge of the rocker so that rocker can cycle through a full range of travel without hitting your tube cap. This seems like a logical matter but you’d be surprised how many people don’t think about the rocker movement when they’re capping the tube ends.
Here’s a rocker mounted in a mockup. Imagine that it swivels around the axis point in a up and down direction and you’ll soon notice that in the arc of travel it gets very close to the full diameter of the tube leg that occurs just above the cap. This is why you need plenty of clearance between the end of the termination cap and the uppermost edge of the rocker bearing washer or bushing or even the rocker itself, especially if you’re using ‘flat’ style rockers. This will come back to bite you if not accounted for which is why I’ve tried to restate the situation and make it as clear as possible. Don’t be afraid to make your tabs a little on the long side. In fact they actually look better if there’s about a half inch of clear space between the rocker and the termination of the leg cap. The leg in this picture is very tight and I should have scraped it but it works but just barely.
Tab Welding Fixture
With the pivot point tabs being close to finished it’s time to give them a trial fit in the tube legs. I’d actually hold off welding them until later in the progress of the project but since this segment of the work is related I’m showing it here somewhat out of sequence.
I was taught that you never build a jig for anything where a simple fixture would do just as well so for welding tabs into tubes I was shown this simple method I still use today.
This utilizes the materials themselves to become almost self-aligning so it’s really hard to make a mistake.
Basically this consist of using two sections of 1”x1/2” steel channel which is available at most hardware stores or builders outlets. You drill holes near the ends of the channel that match your pivot pin size. Needless to say the holes have to be exactly on the centerline of the channel. A piece of dowel is run through the upper channel, through the pivot tab and into the hole on the lower channel. A level on the upper channel insures that the tube leg and the tab are aligned in both directions and perfectly plumb and square.
The snapshot below shows the set up in a little more detail. You can add precision washers top and bottom to center the tab with the tubing in the transverse direction but I’ve found that if the notches were cut accurately this isn’t really necessary.
With minor modifications this fixture and be made to handle multiple connections if you’re doing a lot of similar items but for the home builder doing each leg one at a time is good enough.
Pre-tacking the tabs in place using this fixture makes it a lot easier to get everything aligned down the road when we’re ready to do the final welding on the entire fork assembly. If these tabs are tacked plumb and square with the tube legs then everything else can be based on the relationship of these parts. Ironically they are the smallest but most important parts of the entire fork assembly. If these tabs are crooked or skewed or cockeyed in the least bit you’re up shit creek so take the time to do it right.
I make both the rear and front legs at the same time and do all of the final welding for the tabs and tube caps or bullets at a single sitting. Just make sure to leave the tube legs longer than you anticipate using on the final set of forks.
The Spring Pedestal, sometimes called the Fork Bridge, and also the Cross Bar, is that relatively short structure that connects the two front legs together at the top where the lower springs and spring rods mount to the legs. This should not be confused with the Spring Perch which will be described elsewhere.
This is one area of the forks where you can really let your imagination run wild, as there are literally hundreds of ways to design this particular piece. What we’re using is the simplest method since this is supposed to be a low-buck straightforward project.
To begin with we need a section of 1”x1” cold-rolled steel bar stock about 8” long. To make the spring pads we need a short 6” long section of 3/8”x3” cold-rolled steel strap. (Actually 5/16” material works just as well and in many ways looks better).
We make the spring pads by simply drilling two circles out of the 3/8” material using a 2-1/4” hole saw as seen below.
This will give us two nice pads having an outside diameter of almost exactly 2-1/8 inches since you have to subtract the wall thickness of the hole saw and this is exactly what we want to match our springs. Verify the diameter of the springs you will be using and make adjustments as required.
Using a 1” hole saw we make a cut at each end of the cross bar using our 6.5” center-to-center dimension shown on the plans between the front fork legs. This creates the pockets where the tube legs will eventually be welded. Add a ‘fat’ sixteenth to this length for welding shrinkage.
We then drill two 1/4" pilot holes for the spring rods at 3” on center as can be seen above.
The two short sections of tubing are there just to illustrate how the cross bar fits between the front fork legs and are not part of the final assembly.
When we’re finished we’ll weld the round spring pads to the spring pedestal and once it’s welded between the tube legs we’ll have an assembly that looks like Figure 35 below.
Remember that the short sections of tube are just representational and not part of the assembly itself.
Another method I use for heavier bikes is to substitute a section of 1x2 rectangular tubing for the 1x1 solid bar stock as seen below.
This creates a very strong and clean arrangement but it does take longer to fabricate since you have to weld solid plugs below the spring pads that are drilled and taper reamed to match the spring rod ends.
Once I have the pedestal roughed out I typically enlarge the ¼-inch pilot holes to 3/8-inch diameter and then using a taper reamer the holes are slowly and carefully enlarged to match the final dimensions of the spring rod tapers. For the rods we purchased the taper is ¼-inch per foot and the small end diameter is .4375 and the large diameter is .5-inches.
You can do this with a hand held reamer but it will take almost forever so invest in a good drill driven reamer or take the parts to a local machinist. The fit should be as close to perfect as possible as it’s the taper on the rods that prevent the springs from simply pushing the rods through the pedestal.
In my opinion this is one of the best design characteristic Harley came up with for the old original Springer but some modern builders prefer to just use regular straight rod with threaded ends that screw into taped holes in the cross bar.
You can see the slight taper on the ends of these stock H-D spring rods and we’ve tapered the bores through the spring pedestal to match. The nuts that come with these rods are special heat-treated material so always buy a complete set and not just the rods alone.
It is somewhat of a pain to use these original H-D designed tapered spring rods but it’s worth the trouble as you’ll never have a problem with the rods pulling threads which is a relatively common problem on the cheaper method used by many builders. Once you do one set and get used to using the reamer it goes faster but the first project can be touchy since you have to be so careful not the ream out the pockets to much. The goal is that when viewed from the bottom with the rod in place, at least one thread is still up inside the pocket or right at the edge of the hole. This indicates that the taper is nearly perfect and should last for a couple of lifetimes. The nuts should be torqued to 20 ft. lbs. (14 ft. lbs. if loc-tite is used.
Figure 38 shows the spring pedestal after we’ve welded the spring pads in place and are in the process of fine-tuning the tapers for the rods. The blue tape reminds me which hole still needs some work.
Figure 39 is just another shot with the main springs set in place. You can buy all of these parts already chrome plated but this is a ‘budget’ project that will be painted or powder coated so we opted for a Parkerized finish.
What isn’t shown here, since I don’t have any yet, is the aluminum or bronze stepped washers that serve to keep the springs centered on the pads and act as bearing plates to prevent wear on the springs and the steel pads.
As you can see we’re working from the bottom to the top and so far we haven’t really needed any special tools beyond the taper reamer and we’re still a ways away from having to build an assembly and welding jig.
From my standpoint, coming from how I started with choppers, the whole thing about these bikes is that they were originally intended to represent their owner which in the old days was the also the builder. It didn’t make much difference if you were a good builder or a bad builder. The whole deal was just about building your own stuff no matter how it looked or what other people thought about it. Even today I can’t understand why anybody who wants to own a real chopper would even consider letting anybody else build their parts but this attitude comes from my upbringing so I can’t help it. I realize that in today’s society a bike doesn’t have the same importance as it once did and that not everybody has the time or the resources to do everything themselves so it pays to take advantage of the other people out there who can help with a project. Farm out the stuff you can’t do at home but to be honest I don’t think there is anything involved with building a good set of Springer forks that almost anybody can’t do in their own garage with a few simple tools. If it’s your bike do you want somebody else’s forks on it?
Fork Trees and Spring Perch
These are usually the parts that most people say they can’t possibly build at home since they don’t have any fancy machine tools. I say that these are actually the easiest parts to build at home.
You start out with a slab of 3/4” thick steel and then make it do your bidding with whatever tools you have at hand. I have known people to cut the trees with nothing more than a hacksaw and at least one guy who carved them out using a hand held mini-grinder so anything is possible. If you have access to a reciprocal saw you’re in like Flint as this tool will make short work of cutting this material. Rent one if you have to.
The secret to cutting thick stock is to make short and fast passes whittling away the excess material in small straight cuts working down towards the outline of your pattern one little section at a time. You can make 5 or 6 small cuts in thick material about twice as fast as trying to make one or two big cuts. If your using a reciprocal saw you also need a blade with an aggressive tooth count. The mistake most people make is to buy a blade designed to cut sheet metal with a tooth count in the range of 12 to 14 when what you really need for thick stuff is a tooth count more like 8 or 10 and 8 is preferred for sure.
Don’t try to follow any contours in the pattern as attempting to ‘bend’ the path of the blade will only slow down the cut or break the blade. Make a series of short cuts that ‘approximate’ the curve you’re trying to follow. You do the ‘blending with a grinder or belt sander later on.
Stick the material in a vice or clamp it to your bench top and start whacking at it. You’ll be amazed at how fast it goes. The whole secret is in the blade selection and you absolutely need to have a relatively course (and short) blade.
Believe me when I say that cutting this thick material is easy and fast if you have the right blade and I would not hesitate even for a moment cutting stock as thick as 1.5 inches using this method. It’s far superior to using a cutting torch and vastly less expensive than having parts farmed out to be plasma cut or cut on a water-jet machine.
The Rude and Crude Old School trees are about as simple as you can get. In the old days we just used to square off the ends and cut the stock with a hack saw. Basically you start out with some 3/4” thick by 2” cold-rolled strap and cut it into two short 8.5-inch sections.
There is zero offset in these trees so all of the holes are in the same line. Nothing gets as simple as this and these are exactly the same type of trees the factory first built back in the twenties and thirties for their own Springers.
Figure 42 shows the trees in two different stages. The lower tree, which is at the top of the picture, has just been roughed out with the reciprocal saw and we’ve drilled the pilot holes for the penetrations. The upper tree, which is in the bottom of the picture, is in the process of being shaped to the final contour with the ends being radiused and we’ve bored the holes for the tube legs and stem with a hole saw.
Many people think that trees with zero offset are somehow inferior to so-called ‘modern’ trees than can sometimes have offsets in the area of 2.5-inches but this is just an old wives tale and in almost all cases the less offset one has to have in a set of forks the better the bike will handle especially if it has a steeply raked neck.
After we got these trees to the rough shaping stage it just looked to me as if this whole deal was just way to simple and perhaps kind of boring for most of the readers so I decided to make another set of trees that are far more complicated to fabricate. There is nothing wrong with what we started out with. These are great trees and I plan to use them on a little Bobber but to mix things up we decided to show how to use our narrow Springer trees instead as it involves a lot more work. All of the following procedures are identical it’s just that we’re using a slightly more complex set of trees on the project. You can build your forks using either design and the only difference will be in the offset. Even the spring perch is identical for either set of trees.
As you can see from the pattern these trees are going to be more challenging to work on but actually not any harder to make even though it will take more time.
Here are our two narrow CBH trees, in figure 44, after only a few minutes of taking the rough blanks down to size with a multitude of small short cuts. If you’re really good and really patient you can keep making small nibbles with the saw and get these blanks almost to perfection using just the saw. I personally don’t have any patience so I’ll do the rough shaping on the belt sander and with a grinder.
Generally I try to drill at least the pilot holes for all the bores in trees while they are still in the ‘square’ before I cut the shapes out but these were so simple I just went ahead and chopped them out.
Drilling this material isn’t hard it’s just a little slow and you do need nice sharp bits to get clean bores. For the larger holes I still use hole saws. Be sure to use a good quality lubricant whether you’re using bits or hole saws. I prefer the wax sticks for lube and regular old spray-can WD-40 as a coolant.
Remember that the bore in the upper tree for the stem nut is 1.25-inches and the hole in the lower tree for the steering stem is 1-inch. Try to hold off drilling that bottom hole until you actually have your stem so you can get an accurate measurement.
On this Springer the legs are 1.25” tubing so the tube bores are cut with a 1.25” hole saw so the holes will be very tight. To get a little clearance use some emery cloth wrapped around a dowel rod but don’t go overboard. (The leg hole size in the upper will depend on how you decide to attach the tree to the legs).
In figure 44 the tree in the foreground is in the process of being final shaped to match our cardboard pattern. Note that the sides are already becoming very smooth. The tree in the background is being rough shaped and so far only the corners have been knocked down and we’re working on blending the right hand radius and working down the right hand side of the flat area between the rounded ears. When they are finished they will look almost as good as any fancy machined set of trees and cost about $10 each for the material.
Upper Tree Configuration
There are two basic ways of building the upper (top) tree. One involves the use of so-called ‘blind-bores’ or ‘counter-bores’ and the other is a simple ‘full through’ bore for the tube legs.
A blind-bore simply involves counter-boring the tree to accept the tube legs and this counter-bore only goes about 1/2-inch deep. This is the method we show on the fancy version of the standard CBH Springer trees. It involves machine work that the average garage-based builder isn’t likely to have access to. There is a work-around called the ‘shade tree’ counter bore. This is pretty crude but it works every time so don’t laugh at it until you’ve tried it.
You bore the tube leg holes in the top tree all the way through with a 1.25” hole saw and then you cut two plugs with a 1.375” hole saw out of 1/4 or 3/8-inch material so that the plugs are just a wee bit shy of being 1.25-inches in diameter.
You weld these plugs into the holes in the top tree, flush with the upper-most surface as seen in the mock-up shown in figure 48.
You end up with a nice recess in the top tree that’s exactly like a fancy machined counter-bore as seen in this mock-up snapshot of the underside in figure 49.
Make sure you have a really deep welding bevel on both the tree bores and the plugs as the top surface and the crown of the weld bead will be sanded off smooth during finishing. You do not do any welding on the inside bore, as it needs to have a clean and sharp recess.
After welding and final grinding and sanding to get a perfectly smooth and seamless surface on the tree you can drill the boltholes in the plugs to the final dimensions for your cap screws.
The full-bore method involves drilling the top tree tube hole to match the outside diameter of a lug welded into the leg tubing. In most cases the lug is 1-inch in diameter. The tree itself is secured to the tube leg with large washer and a bolt into this threaded lug. There are advantages to this method as the tree is not ‘locked’ to any particular steering neck dimension and can ‘float’ by up to three eighths of an inch pretty easily just by using some stainless steel shim washers under the bolt head or around the lug. This is the method I suggest for the first time project since it provides some flexibility during fabrication and at least a little adjustability afterwards. In many cases the 1-inch lug will need a short section on the bottom turned down in a lath to match the inside diameter of your leg tubing.
Figure 50 illustrates a mock up showing how this method works in practice. The top tree is bored to match the diameter of the lug and when installed rests on the shoulder created by the diameter of the main leg tubing shown here by the short section of 1.25” tube on the bottom. The tree is secured with either a bolt or a nut. Off course you would use a nice chrome or stainless washer instead of the zinc one shown here.
Figure 51 shows a mockup up using a threaded insert inside a hollow lug (plug welded in practice).
Figure 52 shows an alternate method where a shoulder bolt is welded inside a hollow lug, which in turn is welded inside the tubing leg.
Using some imagination you can usually come up with a simple method suited to your particular project that doesn’t involve any machine work.
Lower Tree Installation
One of most important and perhaps the most critical aspect of building a Springer is knowing where to weld the lower tree to the tube legs. On most plans, including mine, this ‘magic’ dimension is usually shown as ‘to be verified by the builder’. The reason for this is that there is no way of me knowing what the dimensions are of your particular steering neck assembly. There are ‘standards’ for this measurement but unfortunately almost nobody including the factory actually adheres to these standards.
In a perfect world where everybody plays by the rules the length of a ‘standard’ big twin steering neck is 5.625-inches. On each end of the neck are pressed in place bearing cups, usually called neck cups. These cups once installed are supposed to add another .75-inches at each end of the neck for a total finished length of 7.125-inches.
The bearing cones when installed will stand proud of this dimension by another sixteenth of an inch on each end and we have to add in the dust shields which adds another sixteenth so we end up with 7.3125-inches. On top of this we have to add in the bearing adjuster nut that is usually .3125-inches to the shoulder for a total of 7.625 inches needed between the upper surface of the lower tree and the lower surface of the upper tree at an absolute minimum.
You can see the bearing adjuster nut in figure 48. Note that it has a shoulder on the upper surface and this shoulder rides inside the 1.25-inch bore we put in the upper tree. If the trees are properly spaced the upper will not actually bear down on this nut but will be about one sixteenth to three thirty-seconds of an inch clear of touching the index surface below the shoulder protrusion. If the tree actually bears down on the nut it will potentially loosen and tighten every time the forks are turned.
Most custom builders set this inside height between trees at 7.75-inches but many aftermarket manufacturers set this measurement at 8-inches. You can use either measurement but the point I’m trying to make here is that you really need to know what this dimension is on your particular build especially if you’re using some weird aftermarket custom wiz-bang steering neck that a lot of people are selling since they look ‘cool’. Eight inches clear is usually the ‘safe’ bet if you have to build without being able to actually measure the neck on a particular bike. Minor adjustments can be made with shim washers if necessary.
You can see the shoulder of the adjuster nut inside the upper tree bore in figure 49 and the shoulder on the stem cap nut lying on its side.
The Spring Perch is the next major item to be cut. For this set of forks the perch is made from a section of 5/8” by 6” hot-rolled steel because we couldn’t find a suitable piece of cold-rolled as big as we needed on short notice. We transfer the cutting outline using a paper pattern taken from the plans and using the reciprocal saw we cut the perch out just like we did with the trees.
After the part is cut I use a small 3” belt sander to begin cleaning up the edges. A 50 grit belt works wonders and you can quickly bring the piece down to the pattern lines. The perch, shown with the spring pedestal, is in the process of being shaped in the snapshot below.
At this juncture we need to decide on what type of spring rod bushing we’re going to use in the spring perch. I prefer the stock units since they have a built-in spring seat which saves a lot of work but some builders prefer to use regular old bronze bushing, either flanged or plain sleeves.
The reason bushing are needed in the first place is because the spring rods, when the rockers are actuated, move up and down a few inches so we need some way to guide and gently restrain them to a limited amount of lateral movement without creating a situation where they get bound up.
The spring rods don’t gyrate but instead move slightly back and forth at the juncture of the spring perch so the ideal bushing would be shaped like an oval but nobody makes anything like this, including the factory, but they came up with a really neat solution which is a bushing that sits in an semicircular seat so it can pivot slightly.
This snapshot shows a very good modern rendition of the bushing socket cut into a custom spring perch with a ball-end milling bit. This of course is the perfect way to do it but most of us don’t have access to this type of machine tooling.
A lot of builders over the years had noticed however that the old stock rod bushing will still slightly rock back and forth if it’s just placed inside a 1.25” diameter hole in the perch since the only thing restraining it is the spring and as the spring follows the path of the rod so does the bushing as it pivots back and forth on its flange. This is the route we’ll be taking on this particular fork and a method we’ve used for decades. It does work and it works very well and it saves a lot of time and in fact it’s far superior to the shortcut of using regular old bronze bushings as many commercial builders do. Perhaps they don’t realize that this shortcut actually causes the rods to bend in the middle or maybe they just don’t care.
Here are the stock rod bushings set into a 1.25-inch diameter hole in the perch. Note the integral spring retainer on the stock items. If you use the standard bronze bushing shown in the bottom of the picture you will need to make a pair of retainers.
With the perch finished and the bushing installed it’s time to do the trial fit of the springs, rods and forward leg spring pedestal.
Now the fun begins as in order to install the upper springs we’ve got to fully compress the lowers and it’s here that you really gain some appreciation into exactly how stiff those lowers really are.
I just happen to have a C-clamp large enough for this operation but you can buy or build a simple spring compressor made from two short sections of 3/4” bar stock with 5/8” all-thread rods and nuts. If you buy a 12-inch clamp from one of the import houses I can almost guarantee that it’ll eventually break. There is huge amount of pent up force in these springs as they are being compressed. Even my good American made clamp bends a little bit when I really crank in the last few turns on the handle. It takes a ton of pressure to bend 1-inch steel so you can kind of appreciate what you’re dealing with here.
This is not a casual operation as the force generated by those springs is considerable and if something slips there will be hell to pay so never stand downstream of the springs while doing this and if you have any doubts at all about your clamps don’t attempt this to begin with until you have some kind of apparatus that you have confidence in. People have actually been killed by a mishap when doing what looks like a simple procedure so this isn’t something to do after having a few beers some evening.
You can usually push the upper springs down by hand just enough to get the retainers installed. Sometimes it’s great to have an extra pair of hands for this operation so it might by a good day to have a friend come by.
Figure 57 shows our spring perch with the springs installed on the spring pedestal and it looks as it should with no tendency for the springs to bind or the rods bending.
Once you get the perch finished you’ve finished the last of the fabrication of all of the cut parts and we’re ready to address the overall configuration of the forks but before we can start welding things together we need to get some accurate dimensions for the legs.
There has been so much misinformation posted on the Internet about tube lengths that I’m having a hard time trying to figure out where to start so that people can have a uniform basis for measuring fork length. You can visit a dozen or so web sites and each one will have their own method of figuring out tube length. Some sites even have fancy interactive calculators and a variety of pundits trying to explain how to measure for the forks for your particular build. Ninety percent of the time all of the so-called experts and high-tech computer programs are wrong and if you believe their pitch you’re forks will usually be to short. This is one of the reasons why forks are the most popular items being resold on auction sites and at swap meets. Almost everybody who orders forks based upon ‘published’ dimensions and computer programs ends up with a set that is too short for their specific bike. In one case out of a thousand somebody might actually get a set that are to long but this is extremely rare.
One of the problems is that most, if not all, of the pundits providing recommendations about forks have never actually built any to begin with but they have some catalogs and tables that they can consult for making selections.
I have to admit that the problem can’t be stacked entirely on the pundits and the published tables on the Internet as bike owners have a certain share of the responsibility in providing fork suppliers with good accurate dimensions and measurements.
Some people imagine that you can order forks for a hypothetical frame just by quoting the up and out stretch and the neck rake along with the wheel diameter by using a set of mathematical calculations or as mentioned before, some tables from a catalog. I guarantee you that this doesn’t work.
The old original de-facto standard for fork length is based upon the classic UL Springer which measures 19.5-inches from the top of the bottom tree (bottom of the lower bearing cup) to the center of the rear leg rocker pivot point. These old forks had zero offset and we’ll see a little later that is an important factor.
As time progressed the FXWG fork became the standard and is still used today by almost all builders when calculating extension. This particular fork was introduced in accompaniment to a new factory frame that was about 2-inches taller at the neck than earlier models to house the upcoming ‘new’ motor.
According to the factory this fork measures 31.75-inches from the underside of the upper tree to the center of the axle hole but we have to remember that it also incorporates a 2.25-inch offset in the trees and this is important with respect to measuring real fork length.
For example lets suppose we wanted to replace our stock FXWG with a new reproduction Springer. We can translate hydraulic fork measurements back to Springer forks measurements by just subtracting 8-inchs from the hydraulic dimensions since Springers are measured to the bottom cup and hydraulics are measured to the top cup. For this example it works out that we’d need a Springer that was 4.25” over stock (19.5”) or in other words a 23.75” leg length.
If this is all that we did we’d end up with a reproduction Springer that was actually to long because the originals have zero offset in the trees. The difference comes to almost 1.875-inches on a bike with a 40-degree rake. What we really need is a Springer with a 21.875” leg length or a Springer with a 2.25” offset in the trees and the 23.75” legs.
I know a guy who bought a very expensive Santee softail frame that was supposed to be 4 up and 2 out with a 40-degree neck. He ordered a very expensive custom made chrome plated Springer from a noted maker and when he finally received both the frame and the Springer the forks were almost 4-inches to long. The reason was simple. The frame neck angle was actually closer to 38.5 degrees and the up stretch closer to 3-inches and the out stretch was about 1.5-inches.
The only way to get good accurate dimensions and angles is to do a full scale mockup or better yet mockup the actual frame and use some closet rods and wooded trees to simulate the characteristics of the forks you plan on buying. Even then however you have to be careful to double-check everything.
Figure 58 illustrates a fairly typical chopper with a Springer Front-end. These particular forks have a one-inch offset in the trees, which is pretty common on modern custom forks. The frame is sitting level with 4.5-inches of ground clearance shown as ‘FH’ (frame height) in the diagram. The front wheel/tire has a radius of 13.5-inches. The neck height shown as ‘NH’ in the drawings is 32-inches measured to the lower most edge of the lower bearing cup. The rake angle, ‘RA’ is 40-degrees and the neck length, ‘NL’ is 8-inches. This configuration uses a Springer that has a rear leg length of 27.75-inches measured from the center of the rear rocker pivot hole to the top surface of the lower tree.
Figure 59 is the same bike but we’ve raised the front portion of the bottom rails to 5.5” ground clearance by pivoting the frame assembly around the rear axle axis by two degrees, which changed the neck height to 33.75-inches. This configuration uses a leg length of 31.25-inches, almost 3.5-inches longer than if the lower rails sit level. This doesn’t seem to make much sense since we only raised the front of the frame by an inch so why do we need legs that are 3.5-inches longer?
Remember that the neck rake is relative to a line perpendicular to the ground so when we rotated the frame by 2-degrees to add a little ground clearance up front we changed the effective neck rake to 42-degrees. Two degrees is a lot of additional rake and that’s why the forks need to be so much longer.
The point of this long section is to illustrate why a real mockup is necessary to get a prefect fork fit on any particular chopper. You don’t actually need the trees or the forks or even the wheels to do a good mockup but you do need a frame and you have to get accurate measurements of the wheels and tires you propose to use. You don’t even need an angle finder to determine the neck rake because your mockup will automatically take rake into consideration.
The reason this section of the article is so far into the build-up is because you actually don’t need to do any accurate dimensioning on the legs until you’ve already made about 95% of all the parts you need for the forks. It’s only when you have to finally determine the length of the leg tubes that you need access to the frame. In addition many home based builders do Springer forks as a side-line out of their garages and build on speculation leaving the tube lengths long until they find a potential customer at a show or a swap meet or via the Internet.
To do a good mockup start with your bare frame and sit it on blocks at the exact ride height you intend for the bike to have in it’s loaded condition. If you have the wheels and tires this is great because you will be guaranteed that the frame height will be exact. If you don’t have the wheels and tires then go a friends house, a shop or a store and get a good measurement on a set that match what you want to use. All you need is the distance from the ground to the centerline of the axle hole.
Keep in mind that it’s a good idea to have the forward portion of the frame lower rails slightly higher than in the rear. I personally try to place the front height, about where the down tubes begin their upward curve, about 1 to 1.5-inches higher. After the bike is finished and fully loaded and the springs take a set over time this will usually drop by at least half an inch.
The easiest, cheapest and fastest way to do a good mockup is to cut out wood templates of your proposed Springer parts. These can be really blocky and crude looking as long as the relevant centerlines for all of the holes are accurately located.
When you’re working with a bare frame you probably won’t have the bearing cups installed yet so just cut some 3/4” thick spacers to simulate the cups.
I did these using hole saws but they can be cut square; it really doesn’t make any difference in the accuracy of the project. In practice you just run a 1” bolt up inside the neck. You can adjust the spacing to suit your actual finished neck by adding some washers as shims.
Cut some pieces from 3/4” plywood or solid stock to roughly serve as the trees. Make sure that the borehole for the stem in relation to the centerline of the rear leg is accurate with respect to the offset for your finished trees.
Here’s another shot of our mockup trees installed with our wooden bearing cup spacers. You can add 1-inch washers between the trees to shim the space to exactly match your actual dimension if needed.
Cut some ‘legs’ from 1x2 stock with a pivot hole in the bottom. You can cut these to almost any length so long as you’re sure they are longer than your finished forks.
You can get as fancy as you want with the mockup and even make some wooden rockers but usually you can get a pretty good eyeball idea of what’s needed to be done with the real steel without going overboard.
For this particular setup I spent about twelve dollars in wood and about thirty minutes in time cutting everything out and bolting it to the frame. It does look crude and primitive but believe me when I say that it’s about 1000% more accurate than anything you can do with a CAD program or some online computer program and I actually use CAD drawings every day of the week. They are not intended to be a substitute for a mockup. With this setup I can move the frame around in the horizontal by adding or subtracting spacers to look at various wheel/tire combinations and even see the results of using some dropped rockers or other ideas. It’s far faster than trying to draw the various scenarios; if it ‘works’ with the wood it’ll certainly work when we do it all in steel.
I personally don’t know of any fabricator who actually uses the data derived from computer generated drawings to do their layout work so think about this for a moment. Even if you do a fancy drawing the shop owner is going to do a mockup anyway so why shouldn’t you. There is a time on every project when you have to stop dreaming and thinking and planning and actually start to do something out in the garage otherwise you’ll never have anything to show for your ideas.
Here’s a shot where we’ve made the transition from wood to steel. It’s our first mockup using the actual components of the final Springer.
Notice in this shot that we’re still using the wooden bearing cup simulation spacers since we don’t want to install the real cups at this stage of the frame fabrication.
It’s hard to see in this snapshot but we’re not using any expensive sleeve collars to hold the tube in place but instead just using cheap hose clamps that work very well for doing the initial setup. The bolt sleeve on the clamps serves as a good stop.
The overall length of the tubes in steel in comparison to our wood mockup was almost perfect and the relationship of the tube pivot point and the wheel axle is with a sixteenth of being spot on the money for the ride height we’re looking for.
You can tell from the dirt and primer residue that this is a trial fit. This is the type of work that the TV programs don’t like to show as it means somebody has to do something beyond just bolting on some part to make a bike.
These same mockup techniques can be adapted for any fork system whether it’s a Girder, Spirdur, Leafer or Springer or even some type of hydraulic front-end. Just make sure you’ve accurately accounted for the offset in your trees.
Keep in mind that on a Springer or a Leafer you can have considerable flexibility as to final ride height by making rockers with more or less curvature which changes the location of the axle hole in relation to the rear pivot point. For this reason I often make the legs almost 2-inches longer than the mockup says is necessary, especially on a bike with a lot of rake. This provides a little wiggle room if the owner decides to switch to 19” rims someday or switches springs to a shorter version than the 8-inchers I prefer to use.
Lower Tree Attachment
Once we have determined the length of the rear legs from the rocker pivot hole to the upper surface of the lower tree we can get that tree tacked into place.
At this point you need to decide if it’s worth the trouble to actually build a welding jig for the forks. If you’re planning on building several sets it will probably be a good idea but for one or two sets you really don’t need anything fancy. I actually don’t use a jig as such but a series of fixtures instead as Springer forks are in many ways kind of self-aligning if you watch out for any racking or twisting in the legs.
My main setup is simply a pair of runners I clamp the rear legs into. Those shown are made for sections of 1 by 1 square tubing with some 1 by 1/2-inch channels on top. This gets the legs up and off of the welding table so I can fit the lower tree and the spring perch.
Notice I’ve run a rod through the pivot points on the legs to keep the legs parallel with the bore-holes in the lower tree. The upper tree temporarily holds the upper portion of the tubes. Using a level and machinist square you simply verify that each tree and the temporary axle rod are square to the legs and level in the transverse direction. It’s hard to see in this snapshot put I also have a long rod made from 1-inch DOM with a section of 1.25-inch material that I run down through the steering neck holes. I then run a piece of 3/4-inch drill rod down inside this tube and verify that the bore is exactly on center relative to the ends of the legs at the pivot holes. This entire operation is far simpler than it sounds and if you’ve drilled all of your holes accurately the forks will be very nearly perfectly aligned without any tweaking at all.
Take one last check with the square and level to insure that the lower tree is plumb and square and tack it in place to each one of the rear legs. Then repeat for squaring and tacking the spring perch and that’s the end of the hard work.
Front Legs and Spring Pedestal
Building the front legs is very simple since we use the tacked together trees and rear legs as a holding fixture.
After the rear leg assembly is tacked up we reinstall the springs in the perch and to the pedestal for the front legs. Run some rods through the pivot points and install the actual rockers. Hold everything properly spaced by using shim washers and shaft collars. Use a protractor or angle finder to set your rockers at the desired angle for the ‘no-load’ condition of the forks with the lower springs fully extended. Then slip the upper ends of your front legs into their notches in the spring pedestal. Note that I just use a small bungee to apply tension so the legs don’t drop out of their sockets. Mark the legs where you want to
Clamp everything together. Verify that the front legs are parallel with the rear legs, that the rockers are at the proper angle and that the spring pedestal is at exact right angles to both the front and rear legs and then tack the tubes to the pedestal. It’s hard to see in this picture but I have a piece of 1x1/2 running transversely under the front legs that automatically insures that they are level and square with the c-channel.
I can assure you that it feels pretty good to have built something like this especially considering the cost and the time it has taken.
Here’s a shot taken from the other side showing one of the alternate trunnion style rockers in place. Note that at this stage with final connection for the upper tree has not been made and we won’t do this last step until the bikes frame is finished and the bearings and cups are installed.
From the start to stage this work has taken about 38 man-hours spread out over the course of three weekends. About 95% of that time was involved with cutting and shaping the various parts. The final setup, tacking and assembly only took about two hours.
Top Tree Attachment
The top tree is secured to the tube legs with bolts that threads into a taped lug welded inside the upper portion of the tubing with plug welds. The bolts can be almost anything you want. The ones in figure 48 are 1/2-18 tube plug bolts from a stock wide glide but you can use cap screws, button head machine bolts or virtually anything that looks good. Keep in mind however that if you’re using the ‘through bore’ method of drilling the trees you’ll need washers at least 1.5-inches in diameter under the bolt heads.
If you don’t have access to a lath you’ll need to pay somebody to machine the lugs but they shouldn’t cost very much.
This is usually the very last thing I do on a set of forks as holding off until the end generally allows me to make a few minor adjustments.
We’ve already mentioned the sources for pre-manufactured items like springs and rods and bushings and retainers which brings me to my major complaint about building a Springer and that is that you have to buy a certain amount of stuff up-front before you can even get off of square one so that you have products to verify the dimensions with.
You really can’t start a Springer project unless you at least have the springs you intend to use as they form a critical part of the overall design. You need to know the actual diameter and length of these springs in order to make design decisions.
Unfortunately there are at less four or five basic spring sets being sold by a variety of vendors and none of them are identical. I got so frustrated a long time ago that I just made the arbitrary decision to only use stock WL/UL spring sets which I still do but that shouldn’t be taken as some kind of endorsement. You need to use what you personally prefer and modify the plans, any plans, according to the items you have in hand.
I think that in the worse case scenario this means having springs that are 2” shorter and .5” less in diameter than what I specify on the drawings so keep this mind as we go forward on this project. The spring length to some extent will determine where the spring perch is welded to the legs.
Always measure each and every manufactured part you buy. Never take anything for granted. Just because you ordered 8-inch springs or 12-inch spring rods doesn’t necessarily mean that the specified dimension is accurate. In fact it seldom is. In reality 12-inch rods from various makers can vary by as much as half an inch. Always use the actual field measured dimensions taken from your parts in all aspects of the fabrication and don’t just blindly follow a set of plans or go by catalog measurements.
I’ve said it before and I’ll say it again. If you are not a professional welder then simply tack your components into place as best that you can and take the forks and the jig to a welding shop you trust to do the final welding.
The welds on a Springer are minimal compared to a Girder so I’d be surprised if you had to pay anybody more than a hundred bucks to do a first class professional job on your forks and even if you spend more it will be money well spent in the long run.
Pay special attention to the welds where the lower tree attaches to the rear fork tubes and use minimal heat and minimal penetration at this juncture. In fact this connection only really needs to be welded on the upper side of the tree and not on the bottom. For several years now I’ve been contemplating brazing this connection or using a Nickel solder, as this is where Springers fail on a routine basis. Many people think that putting a solid lug in the legs at this spot is a cure-all but even Springers with solid steel rod legs fail at this point so it’s not a matter of materials or sizes but just a bad element in the design of Springers in general since this is the one spot where 90% of all stresses are concentrated. Tapered legs solve the problem so you can see why the factory came up with what they did. It’s a perfectly logical solution but impractical for most custom builders to apply unless they want to build custom tapered legs. It can be done for sure but it takes a lot of time.
Likewise use minimal heat and penetration where the spring perch welds onto the rear legs. This connection does require welding on both sides of the attachment but go easy.
A very small 1/8-inch bead (or less) in both places is more than enough. If you get heavy handed you’ll just be creating hard-spots in the tube runs which won’t last very long when the forks are in use. In both cases the key word is ‘cool’. Small, very short welds, spaced far apart in time to minimize heat buildup in the tubing is the way to go for these connections. If you perform a conventional tube-connection type weld like you’d use on a frame tube junction the forks will always have a weak point which is the ‘hard-spot’ created in the HAZ by the weld itself.
When welding the pivot tabs into the tube legs use large and deep bevels as all of the bead crown will eventually get sanded and polished down flush with the tubing so you need deep penetration at this area.
In general the welds points on a typical Springer actually don’t have much stress placed directly on the bead itself so you can go very light in most of these connections with far less penetration than you’d use in a conventional juncture with the exception of the pivot tabs as just mentioned.
About 75% of all the Springer failures I’ve seen occurred at weld points so this has to be saying something about what we’re doing wrong by approaching these structures as typical fabrication elements. Most makers have kind of ignored the ‘message’ the forks are sending to us and just doubled up in tubing wall thickness as a ‘solution’ or gone to solid steel rod legs and even heavier welding. Failures are still occurring in bikes that are abused so again heavier materials and bigger welds are not a solution. It should be noted however that general failures in Springers are actually pretty rare on bikes that are driven and used normally even over decades of time so when something gets bent or broken it is usually the result of misuse, hitting a really deep pothole, doing wheelies or improper brake installations.
Now that all the major work is out of the way we can look at some refinements, alternates and details that we’ve been holding back on.
One thing is building a set of nice fancy rockers with trunnions, sometimes called bushing sleeves or bosses, as shown on our old original Springer plans. For some reason many people feel these are far to complex for the average garage builder to fabricate but after getting this far in the project I doubt you’ll ever think anything is impossible again.
To build these easily it’s best to start out with some 3/8” cold-rolled flat bar and hack out the profile you decide to use with the reciprocal saw as we’ve done for other parts and smooth the edges with the belt sander so you have two blanks to work with.
Drill some ¼-inch pilot holes at the pivot and axle shaft points being sure to stack the plates and drill through both halves in a single pass to insure that the hole locations are identical.
Next cut the holes for the bushing trunnions or sleeves with a 1” hole saw at the rear and front pivot pin locations.
For most of my rockers I use 1” by .125” wall DOM tubing for the sleeves that allows the use of bushings with a 3/4-inch O.D. and a 5/8-inch I.D. for the shoulder bolts. If you think a little thicker wall might be needed for a heavy bike use 1.125-inch by .188” wall tube and up the hole saw size to a 1.125-inch unit.
The length of the tube sleeves can be almost any dimension you desire but I’ve found that .875-inch to 1.125-inch works out the best. In this case we cut the tubing to a 1-inch length.
Figure 73 illustrates the direction we’re going with this assembly. We’ve cut the rockers and the sleeves and now we’re going to weld those short sections of tubing inside the rocker plates to form some bushing trunnions.
At this point you can decide to weld the sleeves with the full protrusion extending to only one side of the plate so that the back-side is flat or center the tube sleeve so that an equal amount protrudes from each side. Alternatively you can offset the sleeve so that on one side of the plate you have an eighth inch protrusion and on the other a half-inch protrusion which is what I elected to do for this project.
By offsetting the sleeves you can custom tailor the inside width between the rockers to suit a specific hub or axle configuration so keep this in mind.
If the sleeves are offset or flush on one side remember that you’ll be creating a ‘left’ and a ‘right’ side rocker. If the sleeves are equal on each side of the rocker plate either rocker can be used on either side of the bike and this can be an important design consideration if you’re think about doing some production work down the road.
Figure 74 shows two of these alternatives. The rocker in the top of the photo has the sleeve centered in the plate so there is a protrusion on each side and the rocker in the bottom has the sleeve flush on one side with all of the protrusion extending to the opposite side of the plate.
Regardless of which direction you decide to go you can make a small fixture to hold the parts for welding.
This is a quick and dirty little fixture using some scrap as spacers between the plates. You can’t see them but there are short slugs of ¾-inch rod inside the sleeves to hold them in alignment as well. This fixture is just used for tacking the parts together. If you want to do the complete welding at one pass you need a fixture that provides more room to work.
After I get the parts tacked on one side I remove the fixture and run some bolts through the sleeves when the two rockers are sit side to side and do the final welding. The two sections of tubing are used as spacers to give me room to weld in the tight spots.
When everything is finished you end up with some very nice trunnion rockers that are every bit as good as the factory originals and they are custom tailored to your specific dimensions.
I prefer to use flanged bushing on each side of the tube sleeves as shown installed here but you can use straight sleeves and oilite thrust washers as shown in the bottom right of the picture if desired.
Rockers with sleeves pick up a lot of strength from the ‘beam’ effect of the sleeves themselves so you can get pretty fancy in their fabrication compared to regular old flat plates.
Figure 78 shows a set of sleeved rockers that somebody made and posted on the Internet that have been skeletonized. To bad they didn’t do better work on the forks themselves and the fasteners used on the rockers as the rockers are just great as a stand-alone item.
This snapshot shows a pretty typical example of a great idea but poor execution and how a production company handles the end termination of tube legs, which is almost to horrible to imagine on a custom bike. I think you can take some of this as inspiration and some of it as something not to do on your project.
Shoulder Bolt Considerations
We’ve already briefly touched on the various types of rocker connections but I’ve been asked on many occasions to go into more detail about how to properly fit these assemblies.
Shoulder bolts have certain specific design factors that often go unnoticed by those who haven’t had a chance to work with them. First of all they actually have two shoulders that serve as bearing points. One shoulder is that surface where the bolt head joins the smooth shaft. The second shoulder is that surface where the shaft meets the threaded shank.
The nominal ‘length’ of the bolt is the length of the smooth shaft. The thickness of the head and the dimension of the threaded shank are not counted. Smaller shoulder bolts usually come in 1/8- inch increments. Bolts 1-inch and over in length come in only 1/4-inch increments so keep this in mind when designing your rockers and leg end fittings.
There are two schools of though about rocker mechanics in general. One group holds that it’s better for the bushings to be a tight press fit into the rockers so that the entire assembly rotates around the bolt shaft. The other group holds that its better if the bushing fits tightly on the bolt shaft and the rocker then rotates around the bushing. Both concepts work equally so it really doesn’t make much difference. What you never want however is for the shoulder bolt itself to rotate in its socket. The bolt should always remain stationary and rigid. I usually try to build rockers where the bushings are a tight fit in the rockers only because it’s usually the easiest method to accomplish.
The objective of the rocker connection is to create two ‘walls’ or ‘surfaces’ of hard unmoving steel at each end of the shoulder bolt. On one end this is accomplished by the pivot point tube leg tab itself. One the other end this is accomplished with a steel washer and nut on the threaded shank. This concept is best seen in figure 79 below.
The rocker is not shown here for clarity but it would be surrounding the bushing if it were installed. Note that the bushing and its bronze thrust washer are ‘captured’ between these two surfaces of steel but are free to rotate around the smooth shaft of the bolt only because the distance or length of the bolt shaft is fixed and is slightly greater by a few thousandths of an inch than the length of the bushing.
What is often puzzling to people is how to control the almost microscopic clearance needed between the bushing length and the bolt shaft length and this is where the power of shoulder bolts really comes into play.
The secret is the use of precision shoulder bolt shim washers. There are two types. One is used to make a bolt longer and the other is used to effectively make a bolt shorter. Both types are shown in figure 80. Lengthening shims are used on the threaded portion of the bolt and shortening shims are used on the smooth portion of the shaft next to the head of the bolt.
If you were careful during fabrication you probably won’t need to use any of these shims but it pays to know that they exist since apparently many people aren’t aware of them as most tech articles seem to omit the fine points for some reason.
These shim washers come in a huge range of sizes and thickness and used in various combinations you can adjust the dimensional length of a bolt up or down as fine as .001-inch increments.
I think that in most cases the only time you’ll really need to have some of these on hand is if you’ve made your rockers to wide or to narrow or you’re trying to salvage some old worn down flange bushings or thrust washers.
If this becomes the case keep in mind that all bushing need at least some load on them or the rockers will have far too much play. Ideally if the bushings are properly loaded the rocker should have a tendency to very slowly drop from a horizontal to vertical position if left unrestrained. If it just ‘falls’ down fast it means the connection is way to loose. If the rocker stays in one position or drops in a series of stops and starts it means the connection is a tad to tight or the bores are out of alignment.
If this all seems to be to complicated you can do what used to be done in the old days and that’s not to use flange bushing anywhere but sleeve bushing with oilite thrust washers instead. To adjust clearances with this system you just use conventional shim washers on the outside surfaces of the thrust washers. This is quick and cheap and especially easy to maintain over time.
Spring Rod Modifications
I found that on this particular project that the so-called 12-inch spring rods we ordered were actually about 11.5-inches long and as a result with the long springs I prefer to use I got what I call ‘puckering’ in the upper rebound springs so I’m going to get some new rods. At the same time I’ve decided to add some inner helper springs both top and bottom so we need some different spring retainers to handle this change. These are minor changes but they are part of the fine-tuning that may have to be done as you fully develop your particular set of forks.
Spring Fine Points
Fine-tuning a Springer may take some time and it can’t be done to perfection until the bike has some road-time on it so the first pass at construction actually only sets a point where further work needs to be done. In fact some of these small points start to show up during the initial construction but you have to be paying attention to the details.
For instance I noticed that as we went through several trial fittings of the springs that each time we installed them and then demounted them their length got shorter and shorter as we were taking the ‘set’ out of the temper of the coils. This is pretty routine and I expected about an eighth of an inch but on these particular springs we got more like three eights of an inch before they finally ‘settled in’. This tells me that they are what I call ‘soft’ springs and I expect them to settle even more over time as the bike is ridden so I need to take this into account. Sometimes you’ll get what I call ‘hard’ springs and after a few trial compressions they actually grow in length by as much as a quarter to three-eighths of an inch.
These minor dimensional variations need to be accounted for when you’re locating the spring perch and the clearance to the spring pedestal on the front legs.
It’s also important to make sure that the springs you get are in fact identical in height to begin with and that the ends have been ground square to the body. Most springs are very nearly perfect in this respect but every now and then you’ll get a pair made from different runs or from a less than perfect manufacturer and they might be a little cockeyed so square them up and match the length to the shortest of the two with your belt sander. These small touches will have a significant effect on the spring performance once installed.
If one spring is even slightly longer than its mate the longer unit will actually be doing most of the work in the normal course of riding where the movement is very slight and over time this can become a problem.
If you look closely at the snapshot of figure 81 which is an old sixties Springer you can see that the perch on the left side in the picture has actually started to bend slightly upwards after decades of riding with one spring longer than its partner since that side of the pair was carrying most of the load most of the time.
Modern Springers are a lot tougher than these old timers but this is a good example of how much you can potentially loose in spring performance if you’re not running a matched pair. Even a quarter inch difference can change the rate from 150 pounds to around a 120 pounds so it’s like walking around all day with one leg shorter than the other.
Keep in mind that the spring really should be installed with identical rotation. That is all of the springs need to be seated with the cut ends oriented as close to the same position relative to the plates as possible.
Figure 84 illustrates what I’m trying to describe. I’ve put some soapstone on the cut ends on these springs so it’s easier to see. When you’re installing the springs place each one so that these ends are oriented in pretty near the same position on each perch pad. It’s a small thing and probably doesn’t make much difference but I’ve found that every little bit helps.
Spring Rates and Spring Ratios
As we’ve mentioned elsewhere there are several sources for springs and several sizes from each supplier. Nobody that I am aware of will actually publish their spring rates so unless you buy from one of the racing spring makers you’re kind of gambling on what you’ll get. In general most of the springs that I’ve actually measured the rate on have fallen between 100 and 175 pounds per inch (in the compression springs). If you have some barbell weights around the house you can measure your own pretty easily. Just keep piling on weight until the spring compresses one-inch and there you have the rate.
On the springs we used for this article the lower compression springs had a rate of 150 pounds each and the uppers were 50 pounds each for a ratio of 3 to 1.
I can’t really say whether of not that’s typical or average since I generally don’t care much for the exact spring rates but rather am concerned with the ride characteristics. In general a bike that has a ratio where the lowers are heavy and the uppers are light, a ratio of something like 4 to 1 (160#compression and 40# rebound) will have a very hard, almost jolting ride even on smooth pavement and you will experience what is called ‘pogo-sticking’ where the forks actually bounce back up in oscillation after hitting a bump. If the opposite situation occurs and the rebound springs are stiffened up to much the bike will be jittery with a lot of hopping and bouncing.
Usually the lowers are just about right at around 150 pounds each and you can do a lot of tuning just by changing the uppers, which is great since the springs cost less. In effect the upper rebound springs are just shock absorbers and their function is to prevent or at least dampen the ‘bouncy’ behavior of normal compression springs
You don’t necessarily have to buy different springs to fine tune a ride as simple spacers under the spring seats or longer rods will change the preload very easily and it doesn’t take much to make some pretty drastic changes. Changes of as little as an eighth of an inch either plus or minus changes the rates significantly.
If you have to go with the dreaded internal ‘helper’ springs inside the lowers I don’t think you’re building a Chopper but something more like a ‘Lead Sled’ and I can’t give you one bit of advice about something like that. Helpers inside the upper springs however can prove beneficial if you’re experiencing pogo-sticking.
Buying or building a Springer is just the first step in a long process of getting it fine-tuned to your particular bike if you want to optimize it’s performance. It’s very much worth the effort compared to the handling you get from a hydraulic setup as once you get everything dialed-in just right you’ll really appreciate what a good front-end can be like.
Leg Tubing Selection
On the plans we have included tables of suggested minimum tubing specifications for various extensions over stock leg lengths. These are included here with a new table based upon using 1.25-inch materials for the rear legs, which many people have requested.
Table SP1.1 Rear Leg Tubing Specifications for 1.125” Tubing
Table SP2.1 Rear Leg Tubing Specifications for 1.25” Tubing
Table SP3.1 Front Leg Tubing Specifications for 1.00” Tubing
I personally violate these tables almost constantly but I have the advantage of actually seeing the bike that I’m build stuff for so I know how much it weighs and I have a fairly good idea of how it’s going to be treated and this is important design information.
On the other hand you have to constantly remember that a well built Springer will have a useful lifespan of several decades and over time it may be mounted on dozens of different bikes and you will have no control over what kinds of use those forks will see or how heavy the cycles might be. This is why most production forks are built with such huge safety factors and weigh so much.
The loads placed on forks isn’t proportional to the bikes weight but more like an exponential factor so the difference between a 400 pound Chopper and a 600 pound sled with respect to the stresses placed on the forks isn’t 30% but more like 90% with respect to the loads the forks will actually be seeing. This doesn’t even begin to consider the ‘abuse’ factor with guys doing wheelies and hitting curbs at bars so if anything these tables are to be considered bare minimum standards to be used as a starting point before anything is factored in. If you’re building forks with more than 12-inches of extension you need to do your own engineering as there is almost nothing in the empirical data for choppers with tubes exceeding that magic 12-inch number, at least nothing that anybody will admit to or stand behind as being a certainty.
If you’ve set yourself up to build some Springer forks it’s about a four-hour operation (eight at the most) from start to finish to have a set welded up and ready to go out the door in the ‘raw’ state. Unfortunately this is only the beginning to having a set ready to bolt to a bike and it’s the finishing that’s a killer from a time standpoint.
To a huge extent it’s the ‘finishing’ part of the work that you pay for when you’re buying a set of forks from a custom maker as this is incredibly tedious and detailed handwork that has to be paid for somehow as somebody has to do the work. I actually think that a good set of forks requires almost double the amount of handwork that we’d be putting into an entire custom bike frame.
It doesn’t make much difference whether the forks are to be painted, powder coated or chromed the amount of work is the same only the procedures are different.
Over the course of this article we’ve shown many shortcuts and workarounds that a person can take but even though there are simple methods for doing certain tasks it doesn’t means that you give up on accuracy or quality.
For example we’ve shown a quick method to build a fixture for welding the pivot tabs into the tube legs. It does work really well and it looks simple but what we can’t show is how long it takes to get the tabs properly shimmed and positioned so that they are absolutely in alignment with the legs and perfectly parallel with the companion tab in the other leg. On a typical job it may take thirty minutes, or even more, to perfectly shim and align each tab before they are tacked into place. You have to work accurately no matter how you do the work.
The objective is for you as the builder to come up with new and even better shortcuts than those I was taught and to share those ideas with other prospective builders so we can make fabrication easier and more accurate at the same time.
Back in the sixties and early seventies home-built Springer forks were pretty common but as more and more people got into the ‘manufacturing’ business fewer folks had a reason to build their own stuff and as a result a lot of knowledge was simply lost over time. We’re trying to resurrect that knowledge base at the Handbook.
Today there are at least twelve manufacturers making Springers and a handful of custom makers. The custom stuff is first rate for sure but the manufactured forks can range from fairly good to god-awful. I’ve had more than a few of the $800 Springers in the garage and to be honest I wouldn’t mount these things on a minibike. I have yet to see one where the pivot tabs were actually aligned from one side to another and in some cases the legs themselves were out by an eighth of an inch in comparison to the matting side. I won’t even begin to talk about weld quality. They do look good with glitzy chrome but for the most part these are junk components and the chrome by the way starts to peel away almost as soon as you bolt this crap to your bike.
I hope the readers don’t go this route and support the importation of cheap crap. You can build a very nice Springer yourself in your own garage or you can buy a quality product from some of guys we’ve mentioned in this article. As long as people are willing to buy shit somebody is going to be willing to package it and it becomes a vicious circle.
In a similar vein with respect to quality people forget that machine tools weren’t invented during the industrial revolution in order to make better products but to make products that were as good as hand-made but produced much faster. For a long time these machines and their operators weren’t up to the task so mass-produced products were actually looked down on. As time progressed the tools got better and their operators got way better. Today a skilled operator with the right machines can produce incredibly accurate and beautiful products but they do come at a price a lot of us can’t afford. Those of us in this situation have to fall back on hand-made parts but we don’t have to sacrifice quality if we’re willing to spend the time on the parts we create. There is no reason in the world why a hand made Springer can’t be a thing of beauty and perfection if the builder is willing to put the time into it.
There is a point however that you have to consider and that is whether or not you really want to make a part that looks ‘machine made’ to begin with. I personally like to see at least a little ‘handwork’ on chopper parts. That’s what gives the component some character as opposed to something cut on a CNC milling machine.
Here’s a shot of our Springer almost finished. We’re still waiting on a stem and the stainless acorn nuts but it looks pretty good especially considering how much it cost.
If you can’t spend the time to build a set of forks yourself you can check out the products from the folks in the links that follow. Mark Foran at Tixe USA builds some incredible forks at a very reasonable price and Big Daddy Al Wilkerson at Bitter End Old School Choppers actually still builds real Old-School Springers just like they used to be back in the day.
Both outfits will treat you right, as they are real chopper builders and not showroom operations trying to sell forks.
Links To Some of the Best Springer Resources
Chopper Builders Handbook
45 Restoration Company
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