looking for pulley/RPM formulation
looking for pulley/RPM formulation
(OP)
I plan on build a 4' x 6' fur/hide tumbler for breaking leather and am wanting a rough idea of the final RPM of my tumbler. I plan on using a 2hp elctric motor with a speed of 1800 rpm. The plans I have call for a 3 inch pulley on the motor going to a 8 inch pulley on a 16 inch mandrel with a 3 inch pulley on the other end (of the mandrel or "jackshaft"). Running from the 3" pulley I will have a 173" v-belt (A) going around a 4' (yes 4 foot) wooden pulley on the end of the 6 foot diameter drum. I am wanting between 16 and 18 RPM for my final drive. How can I calculate this before I build it for a rough idea?
Thank you,
Jim
Thank you,
Jim





RE: looking for pulley/RPM formulation
1800rpm * (3/8) * (3/48) = 50.6 rpm
Ted
RE: looking for pulley/RPM formulation
rather than the pulley size?
RE: looking for pulley/RPM formulation
The 3" pulley on the motor drives the 8" pulley on the jackshaft. 3" pulley on the jackshaft output drives the 48" wheel on the drum. The pulley on the motor turns at the motor speed regardless of the motor shaft size. Unless the motor is a synchronous motor, the motor shaft speed is probably 1750 rpm and not 1800 rpm.
Ted
RE: looking for pulley/RPM formulation
Jim
RE: looking for pulley/RPM formulation
The basic principle is the linear speed of the belt is approx the same at each pulley -> rpm1*D1 = rpm2*D2. rpm2=rpm1*D1/D2.
Start with input speed. Then for each belt, multiply by ratio of drivinG pulley diameter to driveN pulley diameter.
Two belts. One has driving pulley 3 and driven pulley 8. The other has driving pulley 3 and driven pulley 48.
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RE: looking for pulley/RPM formulation
Jim
RE: looking for pulley/RPM formulation
One change would be change the 8" to 18".
Then 1800 * (3/18) * (3/48) = 18.75rpm.
Or to 20", then 1800 * (3/20) * (3/48) = 16.88
Ted
RE: looking for pulley/RPM formulation
Thank you!
The 20" pulley is going to be the tough part. My jackshaft would have to be raised by just over 10" in order for a 20" pulley to spin on the shaft. By keeping the 3" pulley on the motor and using a 2" on the opposite end of the jackshaft, what would I be looking at as far as the larger pulley?
RE: looking for pulley/RPM formulation
One way or another you are looking for a 100 to 1 change is speed. 1800rpm input/18rpm output = 100
Ted
RE: looking for pulley/RPM formulation
Add one like the one you have with a 3" and 8" pulley would give you an ouput speed of 18.1rpm
If you add one with a 3" and 7" pulley you would get an output speed of 15.8rpm.
Ted
RE: looking for pulley/RPM formulation