Hello,
I thought I'd post my progress on RailGun, my 500cc SC-G (sidecar) challenger.
I had no intention of building this bike, but I kept having so many ideas I just had to make it happen. I wanted to make this bike as low and as thin as possible keeping the frontal area to a minimum, and also to keep it as light as possible.
The key design aspects -
* Using the Kawasaki EX-500 engine (again), it's an over-square, DOHC 4-valve with a 6 speed gearbox. It produces decent power and great reliability. There are more powerful 500cc engine options, namely going 2-stroke (eg. RG500), or de-stroking a modern 600cc, but to keep things economical, I decided to see how far I could push the EX500.
* Design a novel low and rigid front end. I looked at a number of options but ended up designing a front end that was going to keep the frontal area to a minimum, but also provided excellent rigidity. It's basically built from hydraulic tubes, off the shelf shocks/springs, and CNC-milled triple tree clamps.
* Central chain drive. Most motorcycles have a chain running from the engine to the rear wheel directly, but this is very inconvenient for the riders legs/feet since they have to be "outside" of the chain putting them out in the air stream. With this design ,the chain runs right down the center of the bike allowing my legs and feet to be completely tucked in.
* Aluminum construction. While steel construction was possible, I felt I could build it in aluminum to save a lot of weight. Weight is not the biggest factor to high speed, but rolling resistance is not trivial and in fact can be significant on salty surfaces. Also, Bonneville is basically just a long drag race, so getting up to terminal velocity before/at the speed trap is critical. Some will know that welding aluminum generally adds "weakness" since it de-tempers the aluminum, so the solution is to over-engineer the frame, and every joint with extra gussets.
* Fuel Injection. There never was a fuel injected EX500, and there are few aftermarket options, so I thought I could build a system myself. With greater flow capability and much better fuel atomization and timing, I feel a 15% gain in power is possible. This system is driven from a $15 Arduino microprocessor and so far I have the bike running fairly well.
* Fiberglass body construction. Having a decent experience with fiberglass building my first bike, I'll be going down this road again, but not for a few more months.
I have plenty of construction pictures, but here is where it started, with a wooden prototype to determine all the key dimension points
Cheers, Mike
