Pulley sizes with fixed belt length

[Tull]

I've searched for help with this, but I'm not sure of the terms, I'm finding the wrong things, or I'm just plain dense! I can find many sites where I can calculate belt lengths for pulleys and wheel sizes and all sorts, but the approach the problem from a different direction to that which I need.

I have a motor which has a fixed speed, two pulley wheels of fixed size and location, and one belt between the pulleys of a fixed length.

What I need to do is adjust the size of the pulleys to change the final drive speed. The actual speed is immaterial.

I can obviously measure the size of the current pulleys, but what I need to know is: if I increase the size of the motor pulley, how do I calculate the size of the final pulley for use with the same belt?

Many thanks.

 

[mmm4444bot]

I have a motor which has a fixed speed, two pulley wheels of fixed size and location, and one belt between the pulleys of a fixed length.

What I need to do is adjust the size of the pulleys to change the final drive speed. The actual speed is immaterial.

I must be misinterpreting that statement. If the speed doesn't matter, why not leave the system as is?

Also, you seem to have said that the motor's drive speed if fixed, yet you want to change it?

Two pulleys attached by a belt comprises a system involving things like rpms, linear velocity, angular velocities, and the radius of each wheel. Generally, if we know most of these, we can determine the rest.

Can you provide a specific example, to help me better understand what you're trying to accomplish? :cool:

 

[tkhunny]

Hey, I have an old Drill Press with just such a 5-Speed pulley system and a single speed motor. There is only one belt.