Dimmer Switch + Motor

Burchtree

Burchtree

KnifeMaker & Moderator
Moderator
Joined
Mar 15, 2002
Messages
5,368
This is probably an extremely dumb question, but what would happen if you spliced in a dimmer switch to the power cord of a buffer, or grinder motor?

Obviously, I'm not an electronic whiz, but I was just wondering.
 
It might work for a short while, Mike, but the amps of the motor would probably fry that wimpy dimmer switch in no time.
 
All the dimmer does is decrease the voltage to the motor. I'm not talking about a speed controller, but a dimmer. Your motor needs a certain wattage to run. Wattage is figured as:
Volts X Amps = Watts

A drop in the voltage will cause an increased demand for amperage to run the motor.

the formula for that is:
Decreased volatage + increased amperage =SMOKE
 
There are also simple, cheap speed controls for AC Motors, ala router speed controls.

However, larger AC motors are generally capacitor types. These won't work with simple speed controllers.

How do I know? I went back and forth with a motor controller company. That's the distilled version.

Steve
 
You can install a potentiometer on a fractional horsepower(1/10 to 1/3 aprox.) motor, and it will work. But like the others have said, you will ruin a bigger motor in short order.

Nice try ;), but knifemakers have tried all these things in the past.

The only way to get variable speed is bite the bullet and get a complete AC VFD, or a DC VS setup. :eek: :D
 
Burchtree,

You can get a 2hp DC treadmill motor for about $20-$40

http://www.surpluscenter.com/sort.asp?UID=2003092411231191&catname=electric&keyword=MBDD

I'm using the second one on this page:

http://www.sciplus.com/category.cfm?subsection=18&category=174

Then watch ebay for a controller.

I bought a new circuit board and made one for about $150, but you can find 'em cheaper on ebay.

In any case I know of 2 professional smiths using open treadmill motors full time. Mine has been in use for 7 months.

Steve
 
Michael, about the dimmer and grinder motor, forget it.

If you like I can help you look for a good DC motor drive on Ebay or if you prefer the more expensive route I can help you look for a VF drive on Ebay for an AC motor.

Regardless, be sure to shop for a reversable drive.

Although I think I would prefer AC all the way, my DC motors have not let me down at all and drives for them (controllers) are available at the right price if you know what you are looking at.

RL
 
Michael, you can take Steve's and Roger's word as gospel. These two guys helped me get my Sciplus motor running. Steve helped me make sure I found an appropriate controller, Roger fixed it for me when the one I bought was fried! :o These two guys are super, thanks gents.

Speaking of this very thing, my disk grinder is nearly done. All I have to do is try to find some sheet aluminum today to build a housing for the motor (I'm not willing to let this open motor run in my nasty grinder environment!).

It sure has been fun playing with it as I've been building it. :D :D

Last night (I must have really needed something to do besides work) I made a little angle that'll allow me to set the table at 30 deg (the table is 120 deg to the face of the disk). Yes, that is pushing it just a bit... :rolleyes:

Dave
 
Looking for some hardware for my machine I found these guys, R J Leahy , who are super to deal with. Just thought I'd share this since it can be hard to find someone willing to do such small orders (mine was under $5 and they were cheerful and wrote many emails to get what I wanted.).
 
Looks like you are about to join the ...I LOVE MY DISC GRINDER group.

I use all my grinders but day in and day out, I use the disc grinders more than the belts!
 
I'm with you Peter, on the disc-grinder thingy. I like to hog off stuff on my disc grinder first before I go to the belts. In my feeble mind it makes for less time and less cost, ie belt costs.
 
I don't do much hogging on my disk grinder. It's just too much fun to slap on a 36-grit and melt some metal. :D
 
Peter I've been meaning to ask - what grit paper is most recommended?
Click to expand...

It's no different than your belt sanders Dave. It depends on what you are doing. I have to admidt that I have more than one disc grinder. I have a fast heavy one to hog steel (a job I hate on a belt grinder) I have a slow heavy one for more finished work I have a light slow one for even more refined work, I have one that has a velcro pad so I can use the velcro backed discs and I am working on one with a magnetic cover.

I use 36 to 80 to hog and go up from there. I also use elmers spray adhesive to make my own PSA sheets from some discs that were not intended for PSA work. Home depot sells very heavy, cloth backed grinder discs that are intended to be used on grinders that have the hole through the disc pad. They last forever and I attach them with the elmers.

I could make OSHA break out in hives with some of the stuff I glue on them but it works.

Good luck and have fun!
 
Thanks Peter! John Andrews gave me a pile of heavy duty (and I mean really heavy duty) discs like you mention. Don't know that I'll be doing any hogging on this machine - it just doesn't feel that strong regardless the 2 hp rating - but I bet I will be able to cut some steel with those babies.

I guess it's not too hard to change paper on these things. That always seems daunting to me. Course I've never done it. I'll look for the Elmer's, all I've seen is 3M and that stuff is virtually permanent.

Dave
 
Funny the disk grinder thing came up.

I just setup a second DC treadmill motor for my disk. (I now have 2 disks running.)

Cool thing about DC controllers - you only need one!

Then as many motors as you'd like.



Dave, You wouldn't believe how gooked up my DC motor was last time I blew it out with the compressor. I mean full of wood and steel grit! (I have a chicken that lays eggs on the grinder table - different story. Let's just summarize that the dust covers on the motor are gone.) Something about a $40 motor, you just don't take care of 'em.

Steve
 
Originally posted by itrade

Cool thing about DC controllers - you only need one!

Then as many motors as you'd like......Steve
Click to expand...


Steve, how are you hooking multiple motors to one control, without having them all start at the same time? :eek: :confused:
 
Mike, I would guess Steve is connecting the DC drive to each motor as he needs to use it.

Steve, I haven't blown my grinder motor out yet. I'll bet its full of everything also. It hasn't thrown sparks yet though. I have two of the tread mill wonder motors. One is a double shaft variable speed-reversable buffer and the other runs my Coote. So far so good. I also use a DC drive to run my edge grinder. I put an enlosed DC motor on it.

Dave, thanks for the adda-boy. I was very happy to be able to repair it for you, especially now that you'll need it to grind that Collab. knife :cool: :cool:.

RL
 
Yeah Roger that's what I'm thinking - I'm going to get the flats and the tang on the collaboration knife really flat... :D

But I'm just way too cheap to let my $40 motor get gunked up! Steve you crack me up.

I got most of the sheet metal done last night.

Edited to add PS: You'd laugh your asses off if you saw my lichen-encrusted bending brake!!! :D

Dave
 
You must log in or register to reply here.
Back
Top