Wire Bike Update:

Hi all -

I’m the guy that has been giving Ecosystems a little engineering help lately and figured it was time to give a quick update on the status of the wirebike:

We pushed the MIT bike for as much as it could give us — and we did get a modified version of it working for one rider. I made a little digital movie of it that’ll I’ll put online soon…. It had some serious problems however. The max desired speed for the wirebike 10km/hr and with the MIT bike in the easiest gear, a 1 rot/sec gave a speed close to 30km/hr. This had a few ramifications — the amount of force on the pedals needed to start the bike from a dead stop going up a 1% grade was enough to torque the bike frame out of alignment causing the chain to fall off soon afterwards. Now, when the chain comes off there is no way to brake — a real problem at 30+ km/hr. (the brake pads are located on the large wheel rim — not the drivewheels themselves.) Also: because of the necessary force on the pedals — installing "teeth" on the wheel rim was the only way to keep the chain from slipping. The teeth we made turned out to be screws with the tops of them sanded down to look like the traditional teeth on a bike gear. They worked adequately — but again, there were a lot of alignment problems which were aggravated by the fact that the mount for the bearings was on a type of a swivel system that would shift the angle of the gears when a force was applied to it (self aligning).

We dismounted the large newly "toothed" rim and the tweaked drive gears - directly connecting the crank gear to the front wheel gear. With this system, (along with some hacked cardboard and string to keep the chain on the gear and some other slight modifications) we got a slow, reliable (although brakeless!) vehicle with a top speed of about 5 km/hr. Unfortunately, the wheels that came with the bike really were not desired to survive in Nepal. They were already starting to fall apart and it took two seconds of the bike loaded with two passengers before the entire thing crashed to the ground.

I’m now thinking it is time to start fresh. I’ve been digging around for info on Sturmey Archer bike hubs (some of which have cable operated drum brakes installed). I would love to find a hub that works like a socket wrench, ie: its free wheeling direction that can easily be reversed.