Belt Skip?

Our team wants to use a belt to run an elevator (two belts actually) using 12T HTD to 36T, this is to link it to a jackshaft connected to chain, I’ve read a lot about teams having issues with belt skip on arms and such, but when do we need to worry about belt skip?

The main thing you will be fighting is belt wrap. In this case the 36T is likely fine but the 12t does not have many teeth engaged. This is fine for high speed low load applications but low speed high load will suffer.

As loads increase the higher likelihood the 12t/belt will skip. Belt tension is key, but at a certain point you can only tighten so much.

You can combat this with larger pulleys or swapping to something with more positive engagement, such as #25 chain.

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As stated in the post above teeth in mesh is critical. I used to work at a timing belt and pulley manufacturer and the baseline guidance we gave our customers is that you must have at least 6 teeth fully in mesh around the smaller pulley as well as adequate belt tension in order to avoid skipping teeth and in the long term shearing the teeth off the belt. So for a 12 tooth pulley you need 180 degrees of wrap in order to achieve this. Switching to larger pulleys, adding a back-bending tensioner to increase wrap, or switching to chain are all good solutions.

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