FFE 350 (forkless front-end, Yamaha RZ 350 powered) experimental sport bike
Motorcycle and text by Julian Farnam
The year after I graduated from college I moved to San Francisco and started a
new job at Team Machina, a start-up product development agency. I still missed
my days of working on motorcycles at GKDI and thus began designing
motorcycles again. The following descriptions and photos are of that first bike.
Freshly painted for the Los Angeles International Motorcycle Show
In the first year of development I still had several connections at YMUS (Yamaha
Motor Co, USA). Mark Porter in their testing department had taken interest in the
bike and had brought John Gale into one of the early meetings. John expressed
great interest in the project and pledged support from YMUS.
By this time, a rough frame had been built. The rear suspension had been
design and attached, as well as the beginning of the front suspension was
The notion of a single-sided swingarm front suspension wasn’t new to them as
the GTS 1000 was currently on the market. However, there were two new areas
of interest that I wished to explore. I wanted to achieve the same stopping
power as modern sport bikes with dual front disks, and new ways of connecting
the frontend to the handle bar.
After looking at several multi-disc brake arrangements used on aircraft, I came
up with the idea of two twin rotors sandwiched into a single caliper on one side of
the wheel. To do this, both discs would need to fully float and there would be a
third floating brake pad (double sided) integrated into the caliper between the
During those first years, Road Racing W orld ran an article about the bike even
though it wasn’t finished. A few weeks after the article was published I received
a call from Robert Bakker (brother of well known motorcycle builder Nico
Bakker). He was curious about my project, but even more so, he wanted to talk
about Nico’s work. He made one comment about Nico’s race bikes having vague
feedback in the steering linkage (Nico’s FFE bikes use a scissor linkage to
connect to the bars). This got my mind turning again.
Over the next few weeks I sketched many linkage designs and finally came up
with a beautiful system. Redundant link rods working in a double parallelogram
with the suspension. To make this work, everything needed to be equal
length… swingarm, upper arm, and both link rods. The links would be routed
from the upright member to a bell-crank under the fuel tank and then back up to
the handle bars. The individual rods would be put in tension pulling against each
other and placing the upper arm in compression. The net result was the ability to
adjust out all free play in the system. This worked exactly as expected and
results in flawless steering feedback.
Early 2-D CAD layout. Notice the steering axis is shown through the front wheel. A second line
represents the pivot points of the swingarm, upper arm, and linkage, thus forming a double
Getting back to the brakes, a PM caliper was modified and custom spacers
added to support the center pad. The twin rotors ride on a single carrier and
freely float side to side. Again, this worked exactly as expected with negligible
brake drag and excellent stopping power. Some future experimentation is still
need with caliper piston ratios to gain better feed back at the lever.
Front suspension. Note twin-disc brakes and redundant steering linkage.
In those early days with YMUS, Ed Burke also became involved with the project.
Several design renderings were made to show Ed what the bike might look like
Early concept drawings. Several drawings show a push-pull handle bar
arrangement which was never developed.
The frame is often mistaken as being from the stock RZ350. There are two large
gussets that support the swingarm. Both were grafted out of the original RZ
frame, otherwise the new frame is in fact completely designed and built from
scratch. Each side is a continues piece of tubing that wraps up over the top of
the engine and reconnect back at the bottom.
The only major chassis component taken from an existing motorcycle is the rear
swingarm which was off an FZR400RR. The front swingarm was designed to
resemble the FZR swingarm in terms of manufacturing methods and finish. It
consists of three individual sand castings that are welded together with aluminum
plate between each segment. A356 was chosen for the casting alloy as it has
very similar heat treating properties to 6061 which was used for the sheet
segments. The castings are hollow and feature internal ribbing and internal
bearing bosses that pass through. I spent over a month building the match boards
(patterns) and core boxes to create the sand castings. The castings were
provided as cast, then welded together and returned to the foundry for final heat
treating. As a test to the rigidity of the final assembly, no noticeable warping was
detected after heat treating.
Front swingarm. Note multiple castings with sheet segments between. Two round holes can be
seen in the side. The larger hole is access to an internal boss, while the other is a small opening
(pass-through) for the core-print.
Because the front swingarm is a very unique design and also the single load
bearing support for the front of the bike, it was an area of structural concern. In
school we had learned to test for stress and strain using strain gages and a test
meter Being a poor single person putting every dime I earned into materials for
the project, I didn’t have the extra money to invest in such equipment. And at the
time, FEA CAD programs were ridiculously expensive so only one alternative
remained. The swingarm would be tested the old fashioned way. Make it, then
I had gone through two foundries and the first had many problems with the
castings. I took one set of castings that were so badly flawed they would
otherwise never be used. The segments were welded together as a complete
swingarm for testing. Next, a simple holding fixture was created and a stub that
simulated the front ball joint was machined and attached to the swingarm. The
fixture and swingarm assembly was mounted onto a hydraulic press and loaded
to the point of failure. Along the way the pressure was built up and backed off
little by little. I wanted to see where plastic deformation would occur and then
finally catastrophic failure.
I figured in the gross weight of vehicle and rider with 100% weight transfer to the
front wheel, then multiplied by a safety factor of 10 to get my goal number. This
was the minimum I’d be testing for. The press was fitted with a pressure gage
and by calculating against the diameter of the ram it was very straight forward to
know the forces used to deflect the swingarm. Despite the poor quality of the
test part, the outcome was a very high number and I was satisfied my good
swingarms (several extras were built for spares) would be safe to use on my
Because I wanted the front to feel like a conventional forked bike, I designed the
suspension geometry to result in an axle rate that would be the same as with a
conventionally sprung fork. At the time, kinematics software was hard to come
by. However, someone in my office pointed out that Excel (the spread sheet
program) could handle trig equations. So there was the basis for a suspension
analysis program. I spent the next two months working on Excel stringing
equations together till I had the perfect solution. I had created a spreadsheet that
would analyze and plot a graph of the geometric progression of my swingar m
and linkage. I could change the length of any portion of the assembly as well as
mounting points and input any spring rate. The resulting graph represented the
actual spring rate through the suspension travel as it would be at the axle. From
here it was a bit of trial and error till I understood the impact of subtle geometry
changes and before long I had my geometry dialed in.
Along the way of designing the suspension linkage came some interesting
observations. In order to test my spread sheet, I reverse engineered numerous
modern sport bikes. I tested various models from different eras, and of different
sizes and weights. Two trends became noticed that are never mentioned in any
magazine articles. First, I noticed the relationship between vehicle weight and
(axle) spring rate and how rider weight plays a decreasing effect as the GVW
weight gets larger. I could have foreseen this, but is was nice to measure this
first hand off of several bikes. Next was a trend I hadn’t expected. Motorcycles
manufactured over a 10 year period had a migration in the slope characteristics
of the rising rate curves. Again, this was measured and observed over many
different motorcycle models and brands spanning about a 10 year period.
As the rolling chassis came together I made plans to do non-powered testing.
With a few friends along to act as traffic control, I made several runs down the
1.25 mile Del Valle grade outside Livermore. All worked perfect. No wobbles or
anything odd. The brakes didn’t bind, and worked flawlessly at the bottom of the
Bike in race trim. Testing session at Sear’s Point Raceway.
Next the engine, body work, electrical system, cooling system and other small
details were finalized. Then it was off to Sear’s Point Raceway for real testing. I
held a current roadracing license and entered the bike in a class that was on the
slow side so I wouldn’t be in the way of bigger and faster machines. On the track
the bike was awesome to ride.
I gradually worked my way up to race speed that first day at Sear’s Point. The
bike would eventually be ridden on two other tracks and by two other riders. Tom
Dorsey rode the bike in a practice session at Button Willow Raceway and lapped
the track at times that would have put him on the podium in the 450 SuperBike
class. John Joss would also ride the bike at Button Willow for a follow up article
for Road Racing World. Everyone had great things to say about the bike.
Track testing at Thunderhill Raceway.
At race speed it had a very nice balance between being stable and easy to
control, yet would lean and turn quickly without anything odd happening. The
only noticeable difference from a conventional bike is that with hard application of
the brakes there was no front-end dive. The front would settle due to weight
transfer, but not do the radical nose dive associated with a forked bike. The
brakes could be applied mid-corner while leaned over and the bike would slow,
but not upset the direction or lean angle. It was very predictable.
There were two notable areas for improvement. First, as mentioned earlier, there
is need to adjust the piston ratio of the front master brake cylinder as the front
brakes tended to be a bit grabby and very easy to apply too much pressure. A
master cylinder with a larger piston will easily solve this and give better feedback
at the lever. Second, because I tended to error cautiously with the design of all
components on the front of the bike, there is a great amount of un-sprung mass
in the front. This tends to make the ride a bit harsh in the bumpy sections of the
track. Everywhere else though, the ride is very nice. Fast, stable, and v ery
Cosmos image - FEA analysis of front wheel “spider showing side loading stress.
Since those first test sessions the bike has had a lighting system added, the
frame has been “blue tagged” and it is now street legal. I am re-engineering the
wheels and several of the front suspension components to reduce un-sprung
mass. Finally, several changes to the body work are planned. Then, hopefully, it
will be ridden and enjoyed as much as possible.
FFE 350 prototype and AK-1 pre-production prototype.