Another dumb question......Is the diameter of a pulley measured by the overall outside diameter or the smaller inside diameter where the bottom of the belt rides?
PULLEY MEASUREMENT
Dec 11, 2005
3 Replies
Not dumb at all, unfortunately the answer is neither the bottom of the groove nor the OD. The pitch diameter, which is what you need to know if you're calculating ratios, should be close to where the cords (which are molded into the belt at its neutral axis) lie in a v-belt properly fitted to the pulley. If the pulley can be used with more than one belt section, both A and B, for example, it will have a different PD for each.
Ned Simmons
Outside.
Technically, it's the "pitch diameter" but everyone just measures the OD. You can easily see this at the hardware store, measure a 2-3-4" step pulley and you'll see the OD of the small end is 2", big end 4" ..
GWE
Just a side comment... The bottom of the vee is meaningless... If the belt were to "bottom out," it would slip.
Jerry
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