Double Ratchet experimental design

Wed, 1 Jun 2011

Ratchets are interesting mechanisms I'm sure you'll agree, I like the way the back and forth movement of a handle is converted into rotary motion. The problem is, though, that the drive wheel only turns as the handle goes one way. When it returns to the start the drive shafts sits there – stationary.

Would it be possible to make the drive shaft turn on both the forward and return stroke of the handle? Here's my first attempt to see if it is possible. 

Two ratchet gears, both fixed on to one shaft. Two separate ratchets, each ratchet has a sprung pawl inside it which engages with the gear teeth in one direction only. As one ratchet moves forward, the other returns to its start position. By moving them back and forth like this the drive shaft should move almost continually. At the moment the two ratchets housings are unconnected. To complete the mechanism I need to connect them so that as one moves forward, the other moves back.

Here are three possible ways I could link the ratchets together

Rack: A small gear on the top of the housing connecting the two ratchets with a rack gear. As the left hand ratchet moves down the gear turns anti-clockwise driving the other ratchet upwards.

Link: The two ratchets are joined together by a bar that pivots on the top of the box.

Belt: A belt loop running between the two ends of the centre box connects the two ratchets.

Time to crack out the sketch book and the double espresso.