Oops...

I know it's been a bit of a while but somebody pressed my 'get a life' button again and I've changed jobs (while still teaching as well) and a home (re)construction project has been filling what is euphemistically termed spare time. Never mind, I'm back now and I suppose I had better get on with some non-paying real work.

One of the requirements for RGB racers is a working reverse system, something that the majority of bikes (and all bikes if you don't class a Honda Goldwing as a motorcycle) don't seem to have fitted. If you've gone for a longitudinal installation of your engine then it's relatively easy to have an extra gearbox between output cog and differential. Unfortunately, I seem to have plumped for a mid-engine layout which makes for a much simpler differential layout (using chain and sprockets just like the donor bike) but does hamper the ability to go backwards under the influence of the engine. A lot of racers use a second starter motor acting on the drive chain but these seem to have a relatively large failure rate (and failure when tested is an automatic disqualification) not to mention issues with how the torque is delivered. The fact that I'm a mechanical engineer rather than an electron herder seems to be pushing me down a purely mechanical option.

So knocking out a quick specification for a black box, I get the following list of desirable features:

1. Lightweight and compact
   
2. User switchable between forward and reverse
3. Minimal transmission losses in forward mode

And that's about it... I'm still at the brain storming stage but I can envisage a system that is basically the reverse gear and top gear from an old gearbox. With one of these you have direct drive from input to output in forward mode and a small geartrain in reverse.