Prototype adjustable cranks on eBay

Hey -

What do you make of these crank arms? Are they splined or something? I like the adjustment mechanism, and I’ve never seen one like it.

lol these cranks are really wierd … they do have a pretty good adjustment idea, but the cranks are specially made for workout bikes and they go all diff directions there is another thread about this


Somebody had better buy these and put them on a unicycle (how I know not…)

PowerCranks are a very strange product. I tried them on a stationary bike at the Seattle Bike Expo a few years ago. It was as if I didn’t know how to pedal at all. I could not keep the cranks even remotely 180 degrees from each other. I quickly turned the stationary bike into an almost kangaroo bike. If anyone gets a chance to try them on a stationary bike take the opportunity. They are that strange.

The product descriptions and video clips on the PowerCranks site will explain the concept behind the cranks. The cranks are on one-way bushings that apply force on the bottom bracket spindle only in the forwards direction. They will not turn the bottom bracket spindle when you pedal backwards. There is nothing mechanical forcing the cranks to stay 180 degrees from each other. The cranks are free to spin independently of each other.

The bearings that you see on the spindle end of the cranks in the eBay pictures are the one-way bushings. The eBay cranks seem to be missing the part that actually fits on the bottom bracket spindle. That adapter would be either fit a square taper or one of the road bike spline designs (like the Shimano design). Without the other parts the cranks in the auction would just be a paper weight. It’s not even clear if he has one left crank and one right crank. They could be both right side or left side cranks.

I wonder if a square taper could be fixed aside the round holes. Anyway, it was an interesting item because of the adjustability.

They could still be an interesting buy for a unicyclist if the price doesn’t go up. You could buy them just for the one-way bushings (bearings) and use the bearings to make a custom coaster unicycle. A coaster unicycle is a unicycle that you can pedal forwards but not backwards. I don’t know how much the one-way bearings are worth by themselves, but probably more than the current bid plus S&H.