Slowing a motor

[dighsx]

I'm not sure if this is the right place for this post but here it is. I have a buffer motor that spins at 3450 RPM I'd like to do one of two things. Either drop the RMP in half or make it variable speed. I'm attaching two pictures; one of the motor specs and one of what I believe is the starting capacitor. Also a word of warning I understand basic electronic and have put together some kits but I'm no wiz. This isn't as simple as just changing that capacitor is it?

Thanks

[Al_The_Man]

A single phase split-phase motor, which this is, is not practical to control the speed.
Any method is not going to be really cheap, unless you source off of eBay etc.
One way is to change the motor to 3ph, and use a VFD (variable frequency drive) with single phase in, but most have a minimum in of 240vac so you would also have to provide a 240 1ph plug-in.
Al.

[sdantonio]

If you slow the motor down won't you also slow down the air flow through the motor and possibly run into problems with it burning out prematurely?

Steven

[Al_The_Man]

True, If using any motor at high torque - low speed it pays to put an external cooling fan on the end bell, unless its a TENV style.
Al.

[svenakela]

Just as a note, there are plenty of frequency converters for 1 phase control. But it is as the boys says, if you lower the RPM the heat will increase.

If I where you, I would go for a lower RPM motor and a freq. converter instead. Usually the motors can take about 100% increase in speed through a converter. About 100-120 Hz is what a standard engine can take.

[Al_The_Man]

The trouble with single phase motors using converters you cannot go very low in RPM and they tend to drop out of run when loaded at lower rpm, also they must be Capacitor-start capacitor-run style.
This tends to make the 3ph alternative attractive, with the modern flux vector drives, they can simulate DC motors, right down to zero rpm.
Al.

[dighsx]

Sounds like I might be cooked. This might sound stupid but what if I just put a 3 inch pulley with belt to a free spinning shaft with a 6 inch pulley on it. That would cut it down too right? Just kinda gear it down with pulleys? Doing it this way I could have both 3400rpm and 1700rpm. Is my logic correct?

[Al_The_Man]

Not stupid at all, its done all the time.
Al.

[dighsx]

Wow maybe there's hope for me yet. Hey thanks all you guys for the advice and input.

[svenakela]

Check out all "budget" milling machines and drills, they all have a kind of gearbox with belts. Put another wheel on and get a third gear too.