Hi Folks, I'm planning to build a recumbent three wheel pedal cycle. It will be a tadpole (two wheels at the front and one at the back).
Now because one usually rides these things feet first :) and drives rear wheels, one usually needs about 5 m of chain with dragging it over jockey wheels and through plastic tubes.
As my feet are near the front wheels, I want to drive those.
Because steering and driving (especially two) wheels, at the same time is constructionally difficult and beyond me in any efficient way, I intend to steer the sole rear wheel and drive only one of the front wheels.
I realise this single wheel drive may tend to affect my steering, but at 60, and unfit, I doubt my maximum 1/4 horsepower will be a problem to correct, especially as the same brain will be causing the power application and the correction :) I will power the left wheel so that it may help to compensate for any camber in the cycle paths.
Now to the rear wheel steer. I've read in the archives of this group that rear steer is considered "unstable". I would suggest that it is very "sensitive". There is an old Canadian rear steer trike that has a sensitivity adjustment. Sensitive for speed, but harsh for slow speed manoevring.
Anyhoo, I will be using 20" BMX wheels for robustness, seeing how they stand up to the punishment that kids deal out to them. I'm wondering about the castor setting for this rear steering wheel. Originally I thought that having zero here would avoid power or braking effects on the steering. But then I wonder if there is no "centering" tendency, the steering might be a bit skittish. There are two angles involved in this adjustment. The angle of the turning axis to the vertical, and the angle that the wheel axle is ahead of this axis of steering rotation. I wonder what effects these have on steering function in this set up.
The other query would be the front two parallel wheels. Should they be set exactly parallel? Or perhaps a little toe in or out, or does this depend on the tyres chosen? (Like a car)
Brakes on the front wheels only will be self compensating by cable to cantilevers on the "forks" applying blocks to the rims.