[ST] Re: Al v. steel sprocket

["B Parker" <bparker15@xxxxxxx>]

<The stress is so low that steel is not needed.  If you are worried, S.S.
has a gray hard anodizing that lengthens the sprocket [life].  The stress
is *roughly* 1/3 that of the front sprocket because there are so many
teeth engaged.  The alloys S.S. uses is a little stronger than mild steel,
even.>

the wear may be divided over more teeth on the rear [19/43, etc], but the
point load on a chain drive is similar to the point load of a bolt. on a
bolt, fully torqued, typically the first three threads take the majority
of the load. on a sprocket, because of the same minimal stretch effect,
the first few engaged teeth take most of the load.

the actual force on the tooth is the same tension at driving and driven
ends, but the driven end has better 'leverage' [imagine you had to make
the torque by hand, pulling the chain against the two sprockets - it would
be 43/19 easier to twist the rear]. so the rear lasts longer, and aluminum
is adequate.

next thing you know i'm gonna be dragging physics books off the shelf.
somebody stop me...

bp


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