Steering

[BPACH]

Many moons ago I built a few zombie bikes, then life got in the way. I am now retired and have time again and want to start another project. I found a couple Rebike semi recumbent bikes that I would like to join together to make a 4 wheeled tandem bike. Hooking them together wont be a problem, but I am wondering how to do the steering. I am sure trying to get proper geometry will be tough. As they are now, the steering wants to flop to the side at low speed. I am wondering if I used the plans for the TriCruiser I could make it work.
I am open to any suggestions.

 

[Radical Brad]

The most difficult part is going to be frame twist.
On uneven ground, one wheel will be up, putting heavy strain on the frame.
How about ditching the tiny front wheels for another single 26 and going to a trike?

Brad

 

[BPACH]

That may be the best idea.

 

[Popshot]

Generally 3 wheels will work better than 4 for the reason brad has stated but the problem then becomes that you have a central steering wheel but each rider is offset to the steering. Not an insurmountable problem but not an easy one either. You also have the problem that with only 1 rider the weight is unevenly distributed to one side of the triangle meaning turning to the empty side can lead to it falling over. This effect will be exacerbated by the relatively high seating position keeping the weight distribution high. It gets worse though because that seating position is also as far to the side as possible in a trike or quad configuration. Ideally you want to be seated inside the paired wheels not above them. I'd not want to be seated in that position in either a trike or quad configuration. Better to start with a blank piece of steel than adapt this IMO.

 

[BPACH]

Generally 3 wheels will work better than 4 for the reason brad has stated but the problem then becomes that you have a central steering wheel but each rider is offset to the steering. Not an insurmountable problem but not an easy one either. You also have the problem that with only 1 rider the weight is unevenly distributed to one side of the triangle meaning turning to the empty side can lead to it falling over. This effect will be exacerbated by the relatively high seating position keeping the weight distribution high. It gets worse though because that seating position is also as far to the side as possible in a trike or quad configuration. Ideally you want to be seated inside the paired wheels not above them. I'd not want to be seated in that position in either a trike or quad configuration. Better to start with a blank piece of steel than adapt this IMO.

Thank you for those comments. They were things I never considered. I agree with you though, I think I would be better off using them for parts and building something else.