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JustinLiang 12-05-2013 04:34 PM

Oversized Pulley Bore Hole
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What would happen if the bore hole of a pulley in a conveyor was significantly larger than the shaft like in the figure below:

I would imagine if the RPM was high, the whole system would shake violently. However, what if the RPM was around 30 RPM. Would the conveyor still function properly? At such low speeds I feel like it would still work, however, I have never seen something like this in the industrial world which is why I am curious.

Walker 12-05-2013 04:50 PM

If it is an idler it will flop around until self destruction. If it is a driver then the shaft spin and wear itself a groove through the side.

cutter 12-05-2013 04:55 PM

Justin, please read our FAQ. We do not post embedded images for reasons explained there.

milomilo 12-05-2013 05:20 PM

What are the dimensions of the shaft and the bore?

JustinLiang 12-05-2013 06:13 PM


Originally Posted by milomilo (Post 576711)
What are the dimensions of the shaft and the bore?

The shaft diameter is approximately 1 inch and the bore is approximately 2 inches.

Ricker 12-05-2013 08:25 PM

I made a tension pulley for one once similar to the drawing.
I used 1" pipe ang 1/2" round bar stock. Ran for a couple years
in a factory setting not sure if its still there or not. FYI the conveyor
wasn't in constant motion and thr "pulley was at about 40-60 rpm.


camdigger 12-05-2013 08:28 PM

At low speeds, the behaviour may just be to roll on the shaft IF the tension is just right.

Even so, with such large clearance, the behaviour of the pulley wheel will be unpredictable. Hopping, flopping side to side, etc may happen depending on the dynamic load fluctuations.

Better to just put in a 1x2 bushing imho....

kbs2244 12-06-2013 02:28 PM

If both shafts are rigidly mounted, and you have good traction on the mateing surface, what you have is a gear reduction.
This was a somewhat common way for the old slow water wheels to speed up the shafts in the mill.
They would have gear teeth on the inside of the outside rim that would mesh with a gear on a shaft going through the mill wall.
20 to 1 ratios were common (20 foot wheel and 1 foot shaft gear)
This was an alternative to having the wheel axel come trough the wall and doing the speed up inside.

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