upon contemplation of a cog
11-17-04, 08:06 AM
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upon contemplation of a cog
Why do chainrings have more pointed teeth while most cogs have teeth that are flat at the top?
The only exception I've seen are track cog teeth which are more pointed like chainring teeth.
tim
The only exception I've seen are track cog teeth which are more pointed like chainring teeth.
tim
11-17-04, 08:18 AM
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It's to aid shifting so the chain doesn't get caught up on the points as it moves from one sprocket to the next. On a double or tripple chainring it is less of a problem because of the larger diameter. On a fixed srocket the chain does not move sideways.
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11-17-04, 08:18 AM
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On a shimano cassette, at least, (a) not all the teeth on each cog are the same shape and (b) the teeth on neighboring cogs are "offset" from each other. Sheldon Brown has a good article on the various things done to make cassettes shift better.
I am pretty sure that the flat-top teeth are needed for these shifting improvements, but that pointed teeth have less frictional energy loss, because the chain rollers slide off of them in a smoother manner. So track cogs can be pointed, cause it's singlespeed.
I am pretty sure that the flat-top teeth are needed for these shifting improvements, but that pointed teeth have less frictional energy loss, because the chain rollers slide off of them in a smoother manner. So track cogs can be pointed, cause it's singlespeed.
11-17-04, 08:31 AM
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Originally Posted by TimArchy
Why do chainrings have more pointed teeth while most cogs have teeth that are flat at the top?
The only exception I've seen are track cog teeth which are more pointed like chainring teeth.
tim
The only exception I've seen are track cog teeth which are more pointed like chainring teeth.
tim
11-17-04, 07:12 PM
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wonderful responses all. especially the one offered up by sydney. now I'll have to find another part to contemplate. I'm think about dwelling on the stem for a while.
tim
tim
11-17-04, 08:21 PM
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How about cup and cone bearings? I've taken them apart plenty of times, but still find them mysterious, maybe because you can't actually "see" them working...
