Pulley Load Question

[CGF]

Morning all,

Please could you offer your thoughts on the below?

We use a motor driven sash & counter weight system and i would like to clarify what the best option would be.

Please see attached diagram. We have a motor consisting of 1 x motor driven pulley with 2 x freewheeling pullies in a triangle formation as seen in attached diagram. The design is currently configured in the set up 1 orientation with the driven pulley at the top of the triangle. We have experienced a few little problems and we believe that the weight of the sash & counterweight as caused the top pulley to lean over slightly and come out of alingment with the two support free wheeling pullies.

If we mounted the pulley arrangement as per set up 2, with the driven pulley at the bottom of the triangle, would the 2 x free wheeling pulleys (now at the top) take some of the load away from the driven pulley? Would this be the preferred arrangement?

Many thanks,

CGF

 

[Mongrel]

A different perspective - perhaps you could look at extending the motor shaft, or bolting an extension onto the pulley, and using a bearing there to help carry the extra weight?
Another thought - if the weight is enough to tilt the motor (and presumably mounting frame) - I wonder how the motor bearings are holding up?

 

[dvd]

Tension is maximum at the drive pulley, so your idler/bend/deflection pulleys won't take away any of the load. Why are there so many pulleys? It is possible to run off of a drive pulley and counterweight only.

 

[Compositepro]

There is no significant difference between the two arrangements. Also, in this case, the belt tension will be essentially constant unless the acceleration is high.