Pulley speeds

[gt14rider 864]

Good morning, bought a bandsaw at a flea market . Need to reduce speed, so it will cut metal,  I was thinking of running a jack shaft.  Need to figure out what pulleys to run. Is there a formula to figure out the speed of the pulley combinations

I need to be around 100/120 rpm at the bandsaw,  one problem is i can only run a 4 3/4" pulley at the bandsaw shaft,  5" would be real close to hitting. Motor turns 1725 rpm  Any thoughts?                            Thanks 

 

Edited April 28 by gt14rider

[gwest_ca-(File Mod) 11,266]

Motor rpm x drive pulley diameter divided by the diameter of the driven pulley = rpm of the driven pulley.

[Ed Kennell 40,607]

https://www.ebay.com/itm/356443921022?_skw=110v+electric+motor&itmmeta=01JSYM21Z7H1CX2E6MA33K85HM&hash=item52fdb69a7e:g:4qQAAOSw88xgEczl&itmprp=enc%3AAQAKAAAA8FkggFvd1GGDu0w3yXCmi1fepdUCdOCT7Q7l2OSrvZxOE53jT8V9DWTlZar%2BpX4XnOHTI7p1h39kD28uTUwuwL0nBDsE%2F31QoFac%2B%2FPP0KqOZIg1ikuk4NUTTkVfU92u7iy%2FOppAwO6I%2FXLSGbVmvVgccJlgiGGjtuwaErSzdfKxdkV2QKvGcrm0URfs%2Bo4RH9wxqEp78%2F6MCfT%2FmYuYP9G3o1Du1J2ARl%2BN%2FGZLlsYhntdCvO1lWXV45P1DbsQzcs5VWYGXsws0yLprTwftm8%2Fhxoe1zm%2FXM%2BZOjVOMTGhnw3aKGaIZnBN51y%2FMyr7DYQ%3D%3D|tkp%3ABk9SR_afiNTPZQ

[ri702bill 9,022]

The bandsaw most likely has an induction motor on it. If by chance it has a brush motor, you may want to consider a ii0 Volt Motor Speed Controler. Super easy to use - plug the Controller into the outlet, plug the saw into it - done. We use one on an old router to lower the speed for certain materials. The reduced speed still gives decent torque. It will NOT work on induction motors.

[wallfish 17,549]

I'm with Ed, maybe slow the motor speed with a speed controller.

[Ed Kennell 40,607]

It's best to be able to set the blade linear speed to match the material and blade tooth specs.

     Wood, lead, copper, brass, iron, steel,and sst can all be cut but require the correct blade and  speed.

[gt14rider 864]

Thank you all,  I like the speed controller, but have a question about the motors horse power rating. I read the saw should have 1/3 hp. How do you figure  out what motor will fit my needs.               

 Electrical is a learning experience for me. 

                                                     Thanks 

[lynnmor 7,589]

2 hours ago, gt14rider said:

Thank you all,  I like the speed controller, but have a question about the motors horse power rating. I read the saw should have 1/3 hp. How do you figure  out what motor will fit my needs.               

 Electrical is a learning experience for me. 

                                                     Thanks 

1/3 HP is about 240 watts.

[gt14rider 864]

Thanks for the info,  still can't wrap my head it.  This is the motor ed sent me the info on. Will it run the saw?    110v.  15w  ac. ?     Lynnmor said you need 240 Watts to make  1/3 hp ???

[Ed Kennell 40,607]

11 minutes ago, gt14rider said:

Will it run the saw?

Not if the saw needs 1/3 HP.    I did not size the motor, just wanted to show  variable rpm motors are available.   A jack shaft with several different diameter pulleys drill press style may also be a good option.

 

[lynnmor 7,589]

For reference this motor is 1/3 HP and draws 690 watts.  There are other motors similar to Ed's link that are more powerful but much higher cost.  Like Ed says, you may not need the entire 1/3 HP, the current draw will be in relation to the load.

[wallfish 17,549]

The motors in that link have a gear reduction built in. That adds to the output torque vs using just a straight shaft motor without one.

 

[gt14rider 864]

Thank you all,   I did like the gear reduction motor, but  I think I'll stick with pulleys and jack shaft. Used the formula Gwest posted and I figured out what pulleys to use, now just need some bearings and 5/8 shaft and have an old 1/3 hp motor have to dust it off it's been sitting for a while. I'll post some pic when I do.