Can you add a rheostat to a buffer?

Shaun @ Tru6 · 12-13-2016, 04:23 PM

I have a bench top buffer that spins at 3600 RPM. I want to slow it way down to 500 to 2500 depending on what I'm doing. Can you wire one in that will slow the motor speed? Will it hurt the motor in any way?

Developed a new polishing technique that requires many different speeds.

stomachmonkey · 12-13-2016, 04:53 PM

Variac.

$50-60 on Amazon.

Or get a router table speed controller. HF has them for like $20.

Just plug it in and go.

Charles Freeborn · Charles Freeborn's Garage

Depends on type of motor. If universal (with brushes), like a router or drill, yes. Induction, no. You can speed control an induction motor only if it's engineered to be variable speed.
What You Must Know About Motors - Popular Woodworking Magazine

rusnak · 12-13-2016, 05:02 PM

Like this? It might limit your top end speed, but if you need more speed maybe you can wire in a bypass.

dad911 · 12-13-2016, 05:06 PM

I believe that will reduce power considerably.

Can you use a smaller diameter wheel? That will reduce the surface speed at the edge of the wheel.

The 'porsche' mod would be a 3 phase motor with a VFD.

M.D. Holloway · 12-13-2016, 05:14 PM

swap out the gears...

Shaun @ Tru6 · 05:32 PM

Quote:

Originally Posted by stomachmonkey

Variac.

$50-60 on Amazon.

Or get a router table speed controller. HF has them for like $20.

Just plug it in and go.

Thank you! Here's the spec plate (looks like 3450 RPM), which one do I need to get? It's a 1/2 hp motor.

https://www.amazon.com/s/ref=nb_sb_noss_2?url=search-alias%3Daps&field-keywords=Variac

Shaun @ Tru6 · 12-13-2016, 05:31 PM

Quote:

Originally Posted by dad911

I believe that will reduce power considerably.

Can you use a smaller diameter wheel? That will reduce the surface speed at the edge of the wheel.

The 'porsche' mod would be a 3 phase motor with a VFD.

The wheel size I use is important so I have to stay with that. What do you think of the Variac that Scott posted?

dad911 · 12-13-2016, 05:43 PM

No experience with Variac, sorry.

id911T · 12-13-2016, 06:19 PM

Looks like an induction motor. The 3450rpm gives it away. You will need a single phase VFD to vary the speed. If the motor wasn't designed for a VFD, you will be limited on how much you can reduce the speed though.

stomachmonkey · 12-13-2016, 06:51 PM

It is a single phase motor.

Marked on the tag.

You are not going to slow that down easily or cheaply.

You'd be better off and probably save money by swapping for a 3 phase.

Charles Freeborn · Charles Freeborn's Garage

Or swap it out for a 1725rpm motor. To run a 3 phase you have to have 3 phase power to your shop.
My buffer is belt drive so I can change speeds with different pulleys.

A variac will not work on yours.

M.D. Holloway · 12-13-2016, 07:52 PM

Used variacs in the lab all the time for stir bars and plates, hot plates, round bottom flask heaters. Used to hook them up to motors but all were 1725 if I recall.

Shaun @ Tru6 · 12-14-2016, 02:30 AM

Quote:

Originally Posted by id911T

Looks like an induction motor. The 3450rpm gives it away. You will need a single phase VFD to vary the speed. If the motor wasn't designed for a VFD, you will be limited on how much you can reduce the speed though.

Quote:

Originally Posted by stomachmonkey

It is a single phase motor.

Marked on the tag.

You are not going to slow that down easily or cheaply.

You'd be better off and probably save money by swapping for a 3 phase.

Quote:

Originally Posted by Charles Freeborn

Or swap it out for a 1725rpm motor. To run a 3 phase you have to have 3 phase power to your shop.
My buffer is belt drive so I can change speeds with different pulleys.

A variac will not work on yours.

OK, thank you. I have 3 phase for the Cerakote oven but sounds like it's more trouble than it worth now.

1990C4S · 12-14-2016, 04:08 AM

Automationdirect has a lot of cheap VFD drives.

Their selection chart is here: https://cdn.automationdirect.com/static/specs/driveselection.pdf

javadog · 12-14-2016, 04:42 AM

Buy a used drill press that has belts you can reconfigure to change the speeds and use that as a buffer motor.

JR

Charles Freeborn · Charles Freeborn's Garage

Guitar makers ( like me) use lower speed buffers with large diameter wheels (12" on mine). Grizzly tools has a good selection.

Shaun @ Tru6 · 12-14-2016, 10:40 AM

For the short term I modified my new technique to use the high RPM.

Just did a test of a quarter window vertical, polished and then anodized.

Pretty close to chrome so I'm happy overall, but would like the safety of the lower RPM.

Shaun @ Tru6 · 12-14-2016, 10:41 AM

Quote:

Originally Posted by Charles Freeborn

Guitar makers ( like me) use lower speed buffers with large diameter wheels (12" on mine). Grizzly tools has a good selection.

I am limited to the size of the buffing wheels I use. A 12" one would be ideal but they are not available.

stomachmonkey · 12-14-2016, 10:46 AM

Quote:

Originally Posted by Shaun @ Tru6

Pretty close to chrome so I'm happy overall, but would like the safety of the lower RPM.

I seem to recall you may have a handful of spare parts lying around.

Dig out some shafts and gears and build a transmission for it.

Use it in your marketing, "Polishing done by our one of a kind 915 Shinomatic"