Sixties Era - Raised Transmission Frames

Back in the late forties and into the early, and even mid-sixties, there was a chopper frame modification that came to be called the 'Raised Transmission' style.

Historically speaking there are actually two different 'versions' of the 'raised transmission. The original version came about when flat-trackers and hill-climbers were needing to get more clearance between the ground and the primary case. They did this by simply 'raising' the transmission within the frame. The amount of raise depended upon the application and ranged from .5 to as much a 1.315-inches. Kits were sold by aftermarket suppliers than included spacers, sectioned oil tanks, and new mounting studs. This was a pretty simple modification, especially on the older bikes having tin primaries but is a little more complicated on electric start bikes using cast aluminum parts.

On high powered modified bikes raising the transmission also resulted in significantly improved chain alignment and went a long way towards eliminating 'pulled' tranny case studs. Most 'performance' oriented riders routinely raised the tranny so it was a very common modification that the average rider could perform at home.

The second version of the 'raised transmission' is the one I want to write about in this article and it came into being somewhere between 1959 and 1963, first being seen on Southern California 'chopped' bikes. In fact the methods used to modify a stock frame for this particular application of the 'raised tranny' is one of the many reasons that the word 'Chopper' started to be used.

I know that I'll get some static about that statement but it's the truth. I was there. I saw it happen. The average guy on the street thinks, based upon the horrible propaganda of the so-called 'Chopper' magazines, that the word 'Chopper' came to be used because guys were cutting the 'necks' of their bikes to increase the rake. That is indeed part of it all but long long before anybody chopped up a neck casting they were 'chopping' on the ass-end of their bikes.

The term' raised transmission' is actually somewhat of a misnomer for the early sixties era SoCal bikes in that the tranny was never really 'raised' inside the frame rails as one might expect from seeing this terminology. What happens instead is that the entire upper rear section of the frame (wishbones) is bent 'upwards' by about 1.5-inches and often stretched towards the rear by about another 1.5-inches. As a result the transmission mounting studs on a modified stock frame end up being 'short' so you need to insert some 'spacers.

A lot of people are probably asking themselves why this was done in the first place? The answer is simple. It was done for 'looks'. Of course you'll hear some folks talking about how this modification improved the 'angles' of the drive chain and other 'technical' stuff but the truth of the matter is that it was a purely 'cosmetic' modification. There is some benefit to using the raised tranny concept from a mechanical standpoint but in this application it was of little significance.

Back in late fifties and early sixties nobody in their right mind wanted to ride around on a bike that had any 'upstretch' in the forward frame tubes. That modification, which eventually became popular in the early seventies (upstretch), was considered not only stupid looking but it created a pretty poor handling bike. That's still my personal opinion today. Raising the steering head is still about the worse thing you can do to a frame but we all do it nowadays, again just another modification that's done entirely for 'looks'.

The 'look' everybody was after, both then and now, was that classic 'wedge' created by the bikes backbone and wishbones being in 'alignment', a straight shot from steering head to axle plates. More than anything else a person can do to a bike this simple alignment of frame members truly defines the 'Chopper Look' as opposed to a bike having the appearance of a 'Stocker' or a 'Bobber'.

The photo below, from the Chris Kallas Mc-Art site shows a typical chopper having a 'raised tranny'. You can easily see the 'straight line' from the neck to axle plate and how low the bike sits in the rear where the lower rails sweep up to the axle plates. This is the 'look' that Southern California Choppers were adopting in the early sixties, especially in a region of Los Angeles people called the 'South Bay'.

 

 

This particular bike however was built in the early seventies by Dick Allen but it's still a good example of the overall concept in practice. The bike has that nice 'wedge' but no up-stretch in the down-tubes which creates all that 'open space' above the motor that a lot of 'modern' builders like the OCC crowd seem to love so much. Of course it should go without saying that all of these 'Choppers' needed to have 'raked' necks and long forks.

Another side benefit to running this second version of the  'raised transmission' for us Chopper folks was that the whole bike sat about 1.5-inches lower in the rear.

Keep in mind that the reason for doing this 'raised tranny' thing to begin with was because people were working with stock Harley frames. Nobody had yet started to build Chopper frames from scratch which largely eliminated the need for this particular modification.

From my experience in the 'business' or the 'industry' or the 'craft', however how you want to define it, the first of what I would call 'production' Chopper frames were built by Dick Allen. I know that I'll get challenged on this as there were dozens of other fabricators doing the same thing around the same time period but in 71 or 72 Allen was definitely ahead of his competitors with respect to doing 'good' custom frames and I'm pretty sure he had a 'production' frame on the market in 73. I saw some of his frame drawings in 69 so he was already thinking his way 'forward' even way back then.

The frame on the bike pictured above is credited with being one of Dick's early 'Blueprint' frames just for the readers information.

There is some controversy about this family of frames from his shop. Some people say the 'blueprint' name came about because the first frame was to be painted 'blue'. Others say that it was because he actually had 'blueprints' made of his drafted drawings for what he wanted to build. I prefer the later story because I saw prints of his frame drawings. In fact I met with Dick in late 68 or early 1969 to show him the 'prints' for my frame design and he showed me 'prints' of his frame design. We had a very long and drawn out discussion about Chopper frames and he actually 'marked-up' my drawings with what he thought were good changes. I disagreed with some of his ideas and that's the last time I saw Dick Allen. He had a lot of patience but not a lot of patience with people who disagreed with him.

Our disagreement wasn't about the basic design of frames but more about how they were to be made. Dick saw the future and realized that in order to make a product for the 'masses' it had to be capable of being produced in volume for a reasonable expenditure of funds so it had to be simple, the bends easily repeatable, use the minimum amount of raw materials and be a lot 'lighter' than a stock frame.

He was talking about using thin wall chromoly and 'gusseted' mount plates, almost like a person would build a 'drag frame'. It was a major departure from the techniques used in the construction of the old Harley frames. He was 'way-out-there' with respect to frame construction back in those days. All of his ideas with respect to 'mass-marketing' have proven to be correct with the exception of 'weight and materials'. It took a long time for the custom frames makers back in the day to realize that Choppers actually benefited from having a somewhat 'heavy frame' but that a story for another time.

Dick was way ahead of his time and always thinking outside of the box most of the time about 'new stuff' but he was also a creature of habit and fell back into his 'comfort zone' when he was working on things that to him were 'routine' or 'typical'. There is no doubt in my mind that he was a creative genius but he was also the type of person who adhered to the old adage of 'If it's not broke don't fix it' and he had mentally locked into the 'idea' of the 'raised transmission' for his future frames.

 

The crude illustration above shows how a 'raised-transmission' frame was made from a stock Harley rigid. The image on the right is a stock frame while the image on the left shows a typical 'raised-transmission' modification to the stocker. Basically what you did to begin with was cut the lower rails right at the juncture where the rear lower rail was coming out of the 'upbend' towards the axle plates. Next you heated the wishbones where they intersected the frame backbone and then you had a big fat guy sit on the frame and 'squish' it down until the wishbones were aligned with the angle of the stock backbone. What you end up with is that 'classic' wedge shape we talked about earlier. For the technically oriented folks the change in angle was 5-degrees 45-minutes. Some builders went a little under this and some builders went a little over so you can say that the change ranged from 5 to 6-degrees from stock. The exact accuracy was largely dependent on the weight of your particular shops 'fat guy'.

If you look again at the sketch on the left you'll notice a 'missing' segment of tubing where the lower rail sweeps up to the axle plate. During the wishbone  'bending' process it just so happens that this space can be filled perfectly, without any misalignment, by slugging in a short (2.375") section of tubing.

If you look yet again at the sketch on the left you can see where I left in the old original vertical centerline to the rear axle shown dashed and the old original ground line, also dashed. You can see that the 'rotation' of the upper wishbones lengthens the wheel base by 1.25-inches over stock. At first glance this fact doesn't sound to important but for the students and historians of Chopper frame evolution it's a critical factor and explains why almost all later frame manufactures incorporated 'rear stretch' into their frames. This rear stretch was just a 'hold-over' from the old days and really isn't needed in a 'new' frame built from scratch but old traditions die hard and a lot of the so-called 'modern' frame builders didn't understand the overall geometry of the old modified stock frames that had been 'chopped'.

A lot of my friends have bought up these old chopper frames from the sixties and in almost all cases the necks have been 'raked' but most people are completely unaware that the rear portion of the frames were so heavily reworked since the modifications, if done well, are virtually invisible.

Keep in mind while you're reading this article that the height of the stock steering neck has not been changed in the least bit and this aspect of the overall frame geometry is what separates 'old' choppers from 'new' choppers with respect to frame configurations.

If you look again at the sketch on the left side of the image you'll be able to perceive that the rear tranny mounting posts are now about 1-inch lower than they used to be relative to the rear axle location. If you tried to install a tranny in the stock location on this frame you'd have a terrible alignment problem with final drive chain chewing away your primary. The solution was to add 'spacers' at the rear mount posts. The result was having a 'raised transmission' but done for reason others than what were originally intended back in the old days.

 

If you look closely at this old frame you'll notice some 'brass colored' spacers added between the tranny mount posts on the frame and the transmission plate.

The snapshot shown above is one of Allen's early frames and they eliminated the spacers on the later versions as shown below.

 

 

You have to look closely but you can see than the rear tranny mount posts have been increased in height significantly and if you've got really good eyes you can also see that the motor mounts aren't parallel with the lower frame rails as they are on a stock frame.

Allen was the first to build a production chopper frame and he did have some great design concepts but he made the mistake of trying to build a lightweight frame and it came back to bite him. Even some of his friends have said that riding on these chromo frames was like riding on a big rubber band or wet spaghetti.

For those folks who want to know about how to do the 'rasied' tranny trick in any type or vintage of frame they can dig up a copy of Keith Ball's old publication called 'Tech Tips and Tricks, Volume 4'. Keith had a series of these booklets published under the old 'Easyriders magazine' banner. The article on raised transmissions is excellent, one of best I have ever read and it is a neat trick that's still applicable today for high performance choppers even though it has become one of many 'lost arts' of bike building.

 

 

Anyway this short little article is intended to fill in some the 'blanks' in both Chopper History and the evolution of Chopper Frame design. Allen was headed in the right direction and if he had lived longer there is no doubt in my mind that he would not have dominated the industry.  It's unfortunate however that so many of the early 'mass-production' frame makers like Daytec, Kraft-Tech and Santee actually had no real chopper frame building experience. That's why we ended up with such horrible monstrosities hitting the market in the mid seventies and continuing even today. Some of these outfits had no idea about the dimensional requirements for bikes and made frames that are literally 'oversized' by a wide margin. Some of these frames look like they're about 1.5 times larger than a stock frame and weigh a ton to say the least.

There are literally hundreds, if not thousands, of ideas and concepts developed back in the dark ages of Chopper building that are being completely ignored by today's builders. The reason that these 'Dark Arts' are being overlooked are many. Some folks simply just don't have a clue about Chopper History, especially at the technical level.  Some people don't think that this 'old' stuff is applicable in today's environment. Some folks just think that they already know 'everything' there is to know. Some folks just like to go with the flow and be 'popular' using the latest bolt-on Do-Dads and Shiny stuff from the 'name' vendors. Some folks like to be told what to do by the 'experts' at some discussion board. Some folks just don't like to wrench or build anything much anymore and need to buy what they ride.

All I can say is that if you don't understand the 'Chopper History' then you really need to get educated and get your hands dirty. Armed with good information the average guy on the street can build a really incredible bike that far outstrips anything that they could buy 'ready-made'.

 

 

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