Thread: How do you slow down an electric motor?

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here is mine i try to get a shot at the rpm of the motor looks like 3000 rpm

Thanks guys for all the suggestions and info. Not sure which direction I am going to go, but you all have given some good sources to start checking. I do have one of those handheld tachometers that you hold up against a spinning shaft and will check it when I get to the shop today.

Pat, mine looks VERY much like the one you pictured, in fact I think they are the same. 3000 rpms seems about right. Here are a couple of pictures of mine. I have the top portion of my belt assembly removed as I am replacing the bearings.......it was wandering and it looks like the bearings being worn might be the culprit.

Don

Man that band saw would come in handy. It was a pain cutting the spacers for my alternator bracket with a hack saw!

Steve, that horizontal bandsaw in the one picture has been a lifesaver. We've worked that thing hard for about 4 or 5 years and it has improved the quality and ease of our work so much. It flips up to become a vertical bandsaw too, but it was always marginal at that aspect.........runs too fast and blade too wide. So I have been looking for a used metal cutting vertical one for a while. Finally found the grey one in the other picture, bought it from the same older guy who was closing up shop. We've only begun to use it, but love it already. The speed is super slow and it cuts curves like one should.

Tools really do make the job so much easier. What I would give for one of those waterjet babys like you see on American Chopper !

Don

yep it the same one and it is 3000 on rpm .it will burn wood if you try to sand it them two screws at the top tune in the belt to track see my belt is not very wide they will move when the belt starts to wear in and start to track dif .i know 2 guy s that have the same sander s and you have to play with it some .here a tip leave the side tin cover off till you get the belt to track a fresh belt will cut thru it if track is off. i can tell you i have had the belt sander for some time about 5 years it runs fine .but it a china motor and if you try to slow it down i would bet you will burn it up .just get use to the speed thats where it needs to be .i run 40 grit on the belt .you have to watch it when the belt is fresh. i have had it take 1/8 plate steel eat it and spit it back at me .do not sand any thing that can get thru the air gap from the table and belt

I agree Pat, these things are wicked. I put a hand held tach on it tonight and the tach goes to 3500 and it passed it up by 500 rpms, so I guess it runs at 4000! I did play with the belt adjustment trying to get it to track straight, but the problem is, when you first start the motor the belt goes to the left, then as the motor speeds up it goes to the right. I watched it spin, and the bottom drum tracks straight, but the top one wobbles a little. I pulled the bearings out and they seem to have some slop, so I am going to hit the bearing house and replace them.

If that doesn't do it, I am going to have the top drum trued up on a lathe, but I can't see how a steel drum would have gotten deformed. We've pretty much decided to concentrate on getting the belt portion working and forget the disc part. We already have one 12 inch disc sander that runs at a sane speed, so we will continue to use that one.

Don

Originally Posted by Itoldyouso

I agree Pat, these things are wicked. I put a hand held tach on it tonight and the tach goes to 3500 and it passed it up by 500 rpms, so I guess it runs at 4000! I did play with the belt adjustment trying to get it to track straight, but the problem is, when you first start the motor the belt goes to the left, then as the motor speeds up it goes to the right. I watched it spin, and the bottom drum tracks straight, but the top one wobbles a little. I pulled the bearings out and they seem to have some slop, so I am going to hit the bearing house and replace them.

If that doesn't do it, I am going to have the top drum trued up on a lathe, but I can't see how a steel drum would have gotten deformed. We've pretty much decided to concentrate on getting the belt portion working and forget the disc part. We already have one 12 inch disc sander that runs at a sane speed, so we will continue to use that one.

Don

the track is very touchy look at the side there a flat plate .the guy i know added another spring plate to it he did seam to think that help. some belts just do not track as well as other sanding belts. that is why mine is so thin .the best thing is to do is just bump the start button and see wich way she going and move the thum wheel the other way. them two up top just a very very small bit till you can hold the button on and have it track good .on the top drum you do not want to turn it flat. it should have some crown to it it will hold track .you cut that out it will be very hard to keep true or put some more crown in

you may want to play with the flat plate the belt backer so it not holding up the belt .we all pick up are belt sanders at the same time. the other two guys did not work as good as mine .my budy was not happy .but i played with it a bit the othe two guys pick up a wear backer made from teflon from grizzy tool i think

That was one thing we thought of, it seems too tight against the belt. BTW Pat, what HP are these things?

Don

if i go to the shop today i get that for you

Thanks.

Don

here is what is on the motor tag.. belt speed 5000 sf.p.m
motor r.p.m 3000
1 hp motor.
cycles 60/65
voltage 110/220
use only wheel suiltable for 3600 rpmwe know thats right

Dan mentioned last night that he sort of noticed a nick in the sanding disc before he started using it, so maybe that was why it fractured. He didn't think anything of it at the time, but in hind sight it may be been the problem.

Thanks for that info Pat. Now I kind of have an idea of what I'm dealing with.

Don

Don,
You can buy one of these for $300....
http://grizzly.com/products/Combinat...-Series/G1014Z
Mine is about 12 years old, has been through about a half dozen belts, and is doing fine.

Yeah, I would have been better off, I paid $ 250 for the one I bought because I was in a tool buying mood. We have some Grizzly tools, like our metal brake, and their stuff is nice.

I may give this one to someone I really don't like very much. Reminds me of a 12 gauge shotgun that I sawed off short one time years ago. . Made a pistol grip on it ,barrel was like 12 inches long, kept it next to the bed for protection. One day a buddy talked me into shooting it so we went to a dump and made a target out of a 55 gallon drum. When I fired it the d*** thing blew right out of my hands and the hammer acted like a can opener, slicing my hand between the thumb and finger. Didn't even hit the barrel! Went home with a rag wrapped around my bleeding hand.

I never fired that gun again and said that if someone broke in I would hand them the gun and tell them to shoot me.......they would be hurt more than I would. That gun now resides in some long forgotten river, in a million pieces. This sander reminds me of that gun.

Don