# Need help to find the shaft RPM

• Automotive
Hi guy here's an example in the picture for my project.
i need to find the shaft rpm to find what size pulley D will be.
Pulley B attached with a belt that come from a motor.
17.5 hp
3400 rpm
3 inch pulley
if im right and pulley b is 8.4 inch
rpm 1214
torque 76 ft/lbs i think

the shaft pulley is 5/8

thanks

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berkeman
Mentor
Hi guy here's an example in the picture for my project.
i need to find the shaft rpm to find what size pulley D will be.
Pulley B attached with a belt that come from a motor.
17.5 hp
3400 rpm
3 inch pulley
if im right and pulley b is 8.4 inch
rpm 1214
torque 76 ft/lbs i think

the shaft pulley is 5/8

thanks
Is this question for schoolwork?

Is this question for schoolwork?
no for myself why?

berkeman
Mentor
no for myself why?
Because the drawing looks like it came from a textbook problem, and we handle schoolwork questions differently from project questions here at the PF.

Did you do that drawing yourself? It's pretty impressive. What drawing CAD package did you use? Is this for your snowblower project?

Because the drawing looks like it came from a textbook problem, and we handle schoolwork questions differently from project questions here at the PF.

Did you do that drawing yourself? It's pretty impressive. What drawing CAD package did you use? Is this for your snowblower project?
thats a picture from the internet as an example of the samething im doing

CWatters
Homework Helper
Gold Member
Consider these four variables...

Motor rpm
Motor pulley diameter
Pulley B diameter
Pulley B rpm (=shaft rpm).

To work out any one of these you need to know the other three.

Start by writing an equation that relates these four variables an rearrange to give you one for the pulley B rpm.

berkeman
Consider these four variables...

Motor rpm
Motor pulley diameter
Pulley B diameter
Pulley B rpm (=shaft rpm).

To work out any one of these you need to know the other three.

Start by writing an equation that relates these four variables an rearrange to give you one for the pulley B rpm.
ok so the rpm for the pulley B will be the same for the saft if i understand

CWatters
CWatters