Pulley Diameters, and torque?

8ntsane

8ntsane

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Hi Guys

I have a question regarding the pulley diameters, and torque.
A friend is re powering his lathe, and we got on the topic of pulley diameters. To keep things simple, lets just say the motor pulley was 7 inch dia, and the spindle pulley was 7 inch, so its 1 to 1 drive ratio.

Does it affect the torque if say the pulleys are reduced to say 5 inch, and 5 inch? Sill keepin the 1 to 1 drive ratio, would this in fact effect torque in any way? In my own mind, I think it would not. So correct me if Im off base in my thoughts please.

I am aware that the diameter of the pulleys do make a differance on abitity for the belt to hang on to it. The larger dia, will put more belt wrapped around the pulley, and a small dia will have less, but at this point , thats not what is in question. That would be another topic all together.

OK gear heads, straighten me out on this one!
 
Right, power transfer will be the same. There will be a very slight loss due to the decreased radius that the belt runs around the smaller pulley, but for most purposes it's negligible.

At some point though, as you mentioned, there is a limit to the power transmission ability. But, as you said, that's another, deeper subject. 1000 hp thru a single A section belt? Not going to happen regardless of pulley size. (practically)
 
Repower?
A great opportunity for 3 phase/VFD or the adapted treadmill motor. Increases the versatility of pulley drive equipment.
 
+1 on the treadmill motor. Or even better a power wheelchair motor too. Then you can run as fast or as slow as you would like and still have full torque available. Steppers and treadmill motors have an upper limit for speed that drops a lot of torque, but that would be well into the milling speed range so really doesnt apply here either. Treadmill and chair motors are generaly thrown away, so the cost is negligable, all you have to do is mount and wire it and your off to the races. Definately worth a look, esp if your going 1:1 Ratio on driven/driving pulleys.
Bob
 
Thanks for the replys so far guys.
Though it seems every where I check, the motor is what is producing the torque, and being 1 to 1 ratio, it should have no torque loss from a change to a smaller dia pulley. It was just somthing that had come up while chatting.

I was just wondering what others had thought on the topic. If anyone else has thoughts on this, your wellcome to comment.

Burnrider, and Bob
The motor has allready been chosen.
3hp 3 phase vector drive, on VFD
 
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