Pulleys/RPM/SFPM

[LIVVI]

Hello

I am interested in using G5549 Bench Mandrels - 5/8", Ball Bearing. And, the G2533 Motor 1 HP Single-Phase 3450 RPM TEFC 110V/220V. Or, the G2532 Motor 1 HP Single-Phase 1725 RPM TEFC 110V/220V. Grizzly hardware. I have not decided if torque or speed is the way to go.

However, I don't know what size pulleys should be attached to the motor, in order to maintain RPM at the mandrel or in the reverse. Other than size, what difference is there between 2, 4, 5" double V pulleys. Guessing the purpose is to change speed between motor and mandrel. You really can't change RPM just by changing the size of pulley can you?

SFPM changes with diameter in relation to a set RPM, but how would SFPM play into turning two different sized diameters?(pulleys)

Don't see how SFPM would have anything to do with pulley stacks.

I feel like an idiot here, 'cause I'm sure this would've been something covered in a high school education not learned

Thank You for any assistance.

[baz]

Originally Posted by LIVVI

Hello

I am interested in using G5549 Bench Mandrels - 5/8", Ball Bearing. And, the G2533 Motor 1 HP Single-Phase 3450 RPM TEFC 110V/220V. Or, the G2532 Motor 1 HP Single-Phase 1725 RPM TEFC 110V/220V. Grizzly hardware. I have not decided if torque or speed is the way to go.

However, I don't know what size pulleys should be attached to the motor, in order to maintain RPM at the mandrel or in the reverse. Other than size, what difference is there between 2, 4, 5" double V pulleys. Guessing the purpose is to change speed between motor and mandrel. You really can't change RPM just by changing the size of pulley can you?

SFPM changes with diameter in relation to a set RPM, but how would SFPM play into turning two different sized diameters?(pulleys)

Don't see how SFPM would have anything to do with pulley stacks.

I feel like an idiot here, 'cause I'm sure this would've been something covered in a high school education not learned

Thank You for any assistance.

ok, yes pulley size has a great deal to play here
heres a quick example ,
motor with 1750 rpm with 2 inch puley and mandrel with 2 inch pulley
in this scenario the wheel on the mandrel will be 1750 rpm

same 1750 with 2 inch pulley but 1 inch on mandrel
in this scenario the wheel on mandrel will be 3500 rpm

same size pulleys =same rpm
smaller on motor and bigger on mandrel end =slower rpm on mandrel
bigger on motor and smaller on mandrel end = faster rpm on mandrel

here a link you can use to find exact ratio and also to find the size of belt you need
http://www.csgnetwork.com/pulleybeltcalc.html

[mpierich]

Originally Posted by LIVVI

Hello

I am interested in using G5549 Bench Mandrels - 5/8", Ball Bearing. And, the G2533 Motor 1 HP Single-Phase 3450 RPM TEFC 110V/220V. Or, the G2532 Motor 1 HP Single-Phase 1725 RPM TEFC 110V/220V. Grizzly hardware. I have not decided if torque or speed is the way to go.

However, I don't know what size pulleys should be attached to the motor, in order to maintain RPM at the mandrel or in the reverse. Other than size, what difference is there between 2, 4, 5" double V pulleys. Guessing the purpose is to change speed between motor and mandrel. You really can't change RPM just by changing the size of pulley can you?

SFPM changes with diameter in relation to a set RPM, but how would SFPM play into turning two different sized diameters?(pulleys)

Don't see how SFPM would have anything to do with pulley stacks.

I feel like an idiot here, 'cause I'm sure this would've been something covered in a high school education not learned

Thank You for any assistance.

The size of the pulleys _does_ change the rpm. A 4" pulley on the motor going to a 2" pulley on the tool will give the tool double the rpm's of the motor. The converse is also true. It's a direct ratio.

Think of it this way...say the 4" motor pulley moves one rev, which say moves the belt 6" (or whatever the circumference is) along its path. It also moves 6" at the 2" tool pulley, but since the 2" pulley is only half as big, it has to move more than one rev...two revs to be exact, since it is half as big as the 4".

Hope that wasn't too involved. In short, if you want the same revs, use the same size pulley at both ends.

[LIVVI]

Originally Posted by baz

ok, yes pulley size has a great deal to play here
heres a quick example ,
motor with 1750 rpm with 2 inch puley and mandrel with 2 inch pulley
in this scenario the wheel on the mandrel will be 1750 rpm

same 1750 with 2 inch pulley but 1 inch on mandrel
in this scenario the wheel on mandrel will be 3500 rpm

same size pulleys =same rpm
smaller on motor and bigger on mandrel end =slower rpm on mandrel
bigger on motor and smaller on mandrel end = faster rpm on mandrel

here a link you can use to find exact ratio and also to find the size of belt you need
http://www.csgnetwork.com/pulleybeltcalc.html

Thank you baz. I understand it now. That link is a good tool to have.

[LIVVI]

Originally Posted by mpierich

The size of the pulleys _does_ change the rpm. A 4" pulley on the motor going to a 2" pulley on the tool will give the tool double the rpm's of the motor. The converse is also true. It's a direct ratio.

Think of it this way...say the 4" motor pulley moves one rev, which say moves the belt 6" (or whatever the circumference is) along its path. It also moves 6" at the 2" tool pulley, but since the 2" pulley is only half as big, it has to move more than one rev...two revs to be exact, since it is half as big as the 4".

Hope that wasn't too involved. In short, if you want the same revs, use the same size pulley at both ends.

Thank you mpierich, a fine re-enforcement of what baz revealed. I now understand, for myself this is going to be a more flexible, and less expensive route to buffing.