Another thing to consider is what happens when you turn the front wheel on a typical bike, to make your turn. the front end of the bike actually drops slightly due the angle of the headset. If you have fixed rear axles that will cause the load to shift from the rear axle to the front axle of a tandem setup as you turn.
If you are set on having tandem rear axles...think of how to self steer one or install one axle with a caster like attachment for each wheel. Also consider some sort of suspension for at least one rear axle. Otherwise you might build a bike that only works for straight line or very slight turns on hard surfaces.
How many drive wheels will you use? Each wheel added to the rear setup means less of the load on a single driver, and less traction.
Not saying it can't or shoujldn't be done, but you will need to do some development of your ideas to get it to function well. Maybe we are being too technical and it will work just fine....you won't know until you build and pedal it.
If you are set on having tandem rear axles...think of how to self steer one or install one axle with a caster like attachment for each wheel. Also consider some sort of suspension for at least one rear axle. Otherwise you might build a bike that only works for straight line or very slight turns on hard surfaces.
How many drive wheels will you use? Each wheel added to the rear setup means less of the load on a single driver, and less traction.
Not saying it can't or shoujldn't be done, but you will need to do some development of your ideas to get it to function well. Maybe we are being too technical and it will work just fine....you won't know until you build and pedal it.