Internal Suspension Girder Forks - Page 2
Before we go much further
the reader needs to understand a few things about the ISG system and also the
clones of the design. First of all John Harman didn’t really invent the
internal suspension girder as there were already several very old ‘Sprung
leg’ type designs you can find by doing some simple patent searches.
Most people actually credit
H-D with the ‘Internal Suspension Fork’ System patented in 1907 as being the
first successful commercial rendition of the concept but J.W. Gates was building
a much-improved version back in 1905. Unfortunately he did not receive a patent
The design that most closely resembles the Harman however is that fork system used on the 1912 Thor racing cycle as shown below. I've talked about these forks and the Thor bikes in other parts of the site. I'm very surprised more builders haven't tried to bring a modern version of these forks back into production.
This is a pretty poor picture but it was the best I could find. It's kind of hard to see but this fork system utilizes an internal spring rod with clevis and an internal spring in the rear legs just like a Harman. The lower end caps are castings which is why they look somewhat bulky and they are canted the same 160-degrees front the leg tubes as a Harman.
In many respects this
system and the one invented by Gates are 'improvements' over the Harman
because they incorporate both rebound and compression springs, basically
acting like shock absorbers. Thor and other makers used this design up until 1919 when
conventional Springers finally became popular.
Much to his credit however Harman most
certainly invented the besting looking implementation
of the system with his rendition of the ISG.
A lot of people don’t realize that Harman’s forks were actually an evolution of a design he used to build in the sixties that were just conventional Girders. Later he dropped the traditional Girder spring and started to experiment with’ Leaf Springs’ but still kept the girder links. Harman was building these forks while he was still in High School in 65 and his shop teacher did the welding work. The three snapshots below, taken from one of the discussion boards, illustrates a set of these very early forks.
These Harman 'leafer' forks are pretty rare. Bill Holland thinks that only two or three set were ever made but I think there were more. One of the guys at Jockey Journal had two sets, There is a guy in Germany with two or three sets and I sold two sets when I moved out to Texas. Back in my 'Biker Hippie' days, between 1967 and 69 when I lived in Big Sur, I remember seeing a lot of bikes with these 'leafer-girders' so they weren't as uncommon as some say they are. Of course they're rare today because not to many were well cared for.
I've seen some discussion board threads where people have stated that John had the small leaf springs custom made but I have it on good authority that he just bought farm implement seat springs (for Internationals) at Sacramento Spring Company and then shortened them.
By the way these were the first forks John ever built for a H-D bike so they were considered experimental. According to the chatter at JJ the snapshot below shows the first Big Twin Harman bike with the same style of forks mounted. Apparently this frame and fork set has been up for sale several times with no takers because everybody thought it was just another modified Harman and therefore worthless. Nobody realized that the frame was one of his first Big Twin chop jobs.. I understand it was bought and then shipped back to Bill Holland for safe keeping.
You can clearly see the distinctive profile style of the Classic Harman forks in this photo. It became his trademark but some in the know say that all he did was copy a style of girder already popular in Sweden that used what we call 'six-bend' bars and simply built them integrally into the fork tube legs to get this 'look'.
I really don't care how he did it because it just 'works' and that's all that is important. To my eye these are the most beautiful forks ever built.
John did however have
competition for that ‘style’. Most notably was American Chopper Enterprises
who made the ‘torsion’ bar forks shown in the old magazine shot below.
In many ways this was a pretty slick fork design. It utilizes small torsion bars as seen in the photo below. You can just barely see them running between the ends of the Girder links. The spring rods run all the way down through the rear legs to the rocker and terminates in a clevis on the rocker like Harman's.
Both Harman and
were also often customized and modified by Bob Dorn who also sold his own variations
of the ISG during the early seventies.
Dorn was a very talented Designer/Builder in his own right but you don't
hear a lot about him. The picture below illustrates the lower end of his
fork design. Note that he utilized a single rocker with a large clevis at
the main pivot point and also used torsion bar suspension. He built several
different variations of his version of the 'Spirder' over the years.
Dorn was a very talented Designer/Builder in his own right but you don't hear a lot about him. The picture below illustrates the lower end of his fork design. Note that he utilized a single rocker with a large clevis at the main pivot point and also used torsion bar suspension. He built several different variations of his version of the 'Spirder' over the years.
These are just a few of
the outfits that built forks similar to John's but I also personally know of
one builder in Vegas who built custom ‘clones’ of the Harman forks in the
mid seventies and in most cases you cannot tell these apart from the originals
unless you’re an expert. He also built conventional Girders with the same type
of integral handlebars and several ‘show’ Spirder/Girders that didn’t have
any suspension system at all. In other words they were ‘rigid’ forks but
they looked identical to the Harman’s.
Friends have told me that they also knew several California shops who were
duplicating the Harman forks in the early seventies and into the eighties.
Friends have told me that they also knew several California shops who were duplicating the Harman forks in the early seventies and into the eighties.
There were, and still are,
a lot of Harman copies out there. Most have been built in shops back in the old
days but you’ll run across some from modern day independent garage builders,
especially from guys in Europe. I
don’t think I’d be buying any from ebay or at swap meets unless you know how
to accurately identify a ‘real’ Harman.
Best thing to do is take some good photographs and send them to Bill Holland
before you open your wallet.
Best thing to do is take some good photographs and send them to Bill Holland before you open your wallet.
The Harman forks, at least
the oldest originals had a lot of problems. I suppose the worst was rocker
failure, which we mentioned earlier. We used to do a lot of repair work on bikes
that came in from California and broke down in the desert mostly around Baker or
Barstow. The Harman forks almost always had bent, twisted or cracked rockers.
The stress point seemed to be the main pivot bolt hole. Bill and John modified the rocker design in the mid seventies and this
solved some of the problems.
The forks were generally well made, actually far above industry standards of
quality at the time, but didn't seem to hold up to well to the
heavy weight and constant shaking and vibration of Big Twin bikes. Cracks in the
HAZ along the welds were a fairly common occurrence but I've never seen a weld
The forks were generally well made, actually far above industry standards of quality at the time, but didn't seem to hold up to well to the heavy weight and constant shaking and vibration of Big Twin bikes. Cracks in the HAZ along the welds were a fairly common occurrence but I've never seen a weld failure.
One of the problems was probably because the forks were originally designed for light bikes and made from 1"x.058" wall chromoly tubing with no stress relieving of any kind. Back in the day few people knew about the problems associated with high tensile steels in road bikes. Today we know there are much better lightweight alloys than chromo. For forks even DOM mild steel would have been a better material to have used for the Harley bikes. Later forks were fabricated from 1"x.063" wall tubes and these are significantly stiffer.
In general the Harmon forks, at least the early ones, did not have a very good reputation among serious bikers who did more that just bar-hoping. They did look good on show bikes and the magazines always wanted to feature bikes with Harman forks on the covers but this didn't do anything for sales or for Johns reputation. I've heard that he and Harry Holland (Bills brother) only built 20 sets of forks to the original specifications before ceasing production. I don't personally believe that number but it's been published several places and so far nobody has corrected it. Somewhere around 1974 it seems that John formed a new business. Harry Holland went on to other things and his brother Bill Holland became Johns partner. He and Bill came out with a new design for the rockers and spent some money advertising that the forks had been 'improved' and were being 'reintroduced' under the 'Grand Prix Racing' label.
Bill Holland is currently building his own 'improved' version of the forks under the trade name of 'Executive Choppers' out of Roseville California. The new forks are made from larger 1.125" tubing and are fully adjustable for neck lengths and different trail settings. I've seen the forks in person and they are of outstanding quality. Unfortunately like a lot of custom chopper related businesses there are ups and downs. As of this writing (May 5, 2014) the executive chopper site is no longer working and the application for the Harman & Holland trademark has been abandoned. I'm sure this is just a temporary situation.
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