Tandem bike conversion to 1-seat tri-mode Recumbent

[bluesrocks]

I am creative inventive type. I have arthritis throughout my body but mostly effects my back. So a recumbent ride would help out greatly. I want to build an all wheel tilting recumbent trike, but I don't have the workshop laboratory to be able to accomplish it yet, so I am simplifying the project to converting a tandem bike into a city commuter (power assist) long-wheelbase recumbent bike.

This way, if I design it right, I may have 2 or possibly even 3 different seat to pedal orientations. This would provide a maximum ergonomic comfort, max performance for various modes of travel,, i.e. road, off-road, uphill=hard vr downgrade=easy, tight stop-&-go traffic vr open cruising. Three modes would be standard upright, crank forward and fully recumbent. With power assist, the extra power train friction is negligible.

Recumbents are notorious for bad uphill performance, but outstanding downhill. So I might preserve the rear seat position (not sure yet, this is mostly good for uphill and some offroad) by inserting a rearward seat post adjustment. But Im thinking of mostly just using the front two postiions, the crank-forward and full recumbent modes.

Question
Has anyone else done this?? I'd love to see similar projects.



Inspiration
Pain. Two kinds actually. First is my arthritic back pain that also gets to my legs/knees. The better your seating options, the more comfortable and easier on the body by emphasizing different muscle sets for each mode. The second sort of pain, comes from the knowledge of learning about safety problems with low to the ground recumbent trikes. A friend's brother in law was killed here in America riding a low rider recumbent. He was not seen, and that was his last mistake. So I am determined to build a safer and more flexible bent.

Here's a photochops (simple paint program) of the basic concept.

Let me know what you think.

 

[MikeFairbanks]

I've thought the same thing (but not so much detail).

I also thought of getting a tandem, putting a dummy in the front and somehow control the steering from the back. Put a hub motor on it and freak people out.

I also thought of getting a pedicab with a motor and a dummy on the seat and doing the same thing.

In all seriousness: Good luck. I hope it's successful. I wish I had advice but I don't. Other guys will chime in with good words, however (because they actually know what they are talking about).

 

[John in CR]

I'd forget the complication of the extra set of cranks up high in favor of a set or two of pegs or other leg rests. You could always add it later if you deem necessary, but in a fixed position you could take it to a whole new level of aerodynamics and comfort for distance cruising letting the electric motor handle the cruising load. Then fresh legs would be ready to help in the torque department where they excel, eg starts, up hills, into a big headwind, or simply extra speed or acceleration.

Last year I picked up an old Italian tandem to do something very similar to your plan, but when my friend found out how I planned to hack up what he considered a classic, he insisted that I sell it to him.

 

[dogman dan]

Yeah, chop up some Schwinn, not a nice vintage frame. Leave original pedals in place, then make footrests you actually use. Unless light pedaling helps your arthritis.

My back issues are different, crushed disks. But they led me to want to ride full suspension bikes. No FS longtails, so I built my own.

Also, look seriously into just welding two frames into a long bike. Use the same methods I used for my longtail. A square taper crank fits perfectly into the rear dropouts of another frame. So it becomes easy to connect two frames.

A 20" bmx bike in the rear would get you a nice low seat.

 

[bluesrocks]

Here's an updated design. I like the idea of two pedal positions. The top one for smooth airflow road cruising, the bottom for stop and go, high traffic, tricky and uphill conditions. Ergonomic bonus, easier to ride longer using two pedal positions. Notice I shortened the wheelbase for improved steering responsiveness and shorter turning radius.

 

[bluesrocks]

Here's the latest mock up,,, I like this one the best so far. I prefer more of a medium wheelbase for control and turning radius, but the medium long wheel base is next best thing. Front=3" from smaller tire, 1" from recumbent position improvement = 4" front. Rear=1 inch closer to frame, plus 4-5 inches less frame=5-6" rear for a total of about 9" reduced wheelbase! I do not know what the wheel base is for that tandem, wish I knew. I'm hoping to be able to turn around in a wide single lane,,, but even if it's close, that would be much better than needing most of two lanes like with a tandem to do a U turn.

Main design requirements:
-more than one pedaling position for max performance up hills and ergonomic and aerodynamic benefit
-higher seating position than typical tadpole trike, sit near automobile seat height.
-recumbent position for max comfort and better performance
-build for 50% or less of the cost of retail version

Having two pedaling positions seems like such a good idea for something like a daily commuter or general and mostly road bike.

peace!

 

[bluesrocks]

Here's a mockup of my present bike. I might do this as its much cheaper than buying a tandem to modify, and better turning radius and easier to store.