Very Senior Member
Join Date: Aug 2001
Location: Central Pa
Bikes: 2000 Bianchi San Remo and a mint 1984 Trek 720
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Do you know what a ratchet is? If you have used a socket wrench set, the handle that the sockets attach to is a ratchet. If you take a ratchet wrench and turn it one way it will turn the nut, but if you turn it the other way it will slip and make a clicking sound. This way you can put the ratchet wrench on the nut and just move he handle back and forth. The nut will turn when going one way but the wrench will ‘slip’ when going the other way.
A ratchet is a mechanical setup that enables something to be turned one way but to ‘slip’ when turned the other way. Inside your bike's rear wheal is a ratchet mechanism that allows you to pedal one direction and coast (or slip in the other direction)
A ratchet is made up of a series of little ramps around a wheel. Going one direction the ramps rise gradually up and then abruptly drop straight down. Leaning against the wheel is a pawl held by a spring. Think of a pawl as an arm shaped like a 7. The top left edge of the 7 is riding over the ramps on the wheel. When the wheel is turned in one direction the 7 hits against the steep side of each ramp and this engages it so that it is forced to move with the wheel. Rotate the wheel the other way and the 7 rides up the gradual rise of the ramp and then drops of the edge, then rides up the next gradual rise. This slipping over the ramps and dropping off is what causes the clicking.
It's easy to understand if you see a picture of a ratchet. Hope this helps.
It's better to cycle through life than to drive by it.