Originally Posted by DCBIKEFOROSAZE
Greetings to all:
I am interested in buying, building or modify a bike for my 2 1/2 year old son who has spinal muscular atrophy. At this point I just want something he can sit on with some upper body support (chair type) and for him to pedal with very low resistance.
Longer term I want sensors in the pedals to detect level of effort and relay the detected effort to a small motor to assist with propulsion....
The Bionx electric assist operates exactly this way
, activated by pedaling exertion (by measuring chain tension): http://www.bionx.ca/en/main/default/1.shtml
Note that it has a 20" wheel as an option.
The Bionx normally has a 20-mph top speed; for such a young child you might contact Bionx and explain the situation and there may be a way to program in a lower speed-limit to the assist (-I know that the 20-mph upper
limit is programmed in, and can be bypassed with a special code).
The bike is another whole problem, not a lot of bikes around for children that young that use a 20" rear wheel. There's also an 18" wheel option, but I know even fewer bikes that use it.
Greenspeed isn't cheap, but has done some custom child's trikes in the past: http://www.greenspeed.com.au/
Alternately, you could look into obtaining a KMX trike and modifying it for the rider's smaller size (shorter pedal boom and seat): http://www.kmxkarts.co.uk/index.html
The KMX already comes with a 20" rear wheel. (NOTE--there are no US dealers for the KMX trikes, so you'd have to order from UK/Europe to get them)
This page shows some kid-sized recumbents, some of which are trikes. Many are homebuilts, but some are commercially-made examples you might be able to track down and use.