Motor question

Hello Mike,

It is an interesting motor!

It is and open frame motor with an internal fan for cooling. This might be bad news since the air will have grinding grit that will get sucked into the motor. It is not my first choice for an "ideal" motor....but it has a very nice price tag for the 2hp performance....at $80, it is hard to pass up even if it only lasts a short time.

It is rated for 3210rpm @130V.....so if you use a standard DC controller (180V output).....you'll have the potential to run the motor up to about 4400 RPM @180V. With that in mind, I would connect it to the grinder with a 1:1 ratio on the drive pulleys....then set the max speed pot on the controller to about 80%. This will cap the motor speed around 3500rpm wide open which will be a great speed for hogging. From there you can just turn the knob to slow it down for more delicate jobs.

I have had good luck with surplus center in the past and would not hesitate to do business with them again.

I think this particular motor has some great potential for the KMG....but the dust/grit needs to be keep out somehow.

If it was me....I'd probably try it out anyway. ....that's because I'm hard-headed and don't like people telling me that I can't do something...(hee hee).

Good luck with it...and have fun.

Sincerely,
Rob


back to edit spelling and grammer
 
I don't like the looks of those holes, Mike. Maybe I'm wrong, and you could wrap a filter around it, but personally I wouldn't want anything but a TEFC (totally enclosed fan cooled) motor around a grinder.

You should probably listen to Rob. He knows these things better than me, in all honesty.
 
I shoulda said this when I posted the link. Having been around a dirty, gritty knife shop most of my life, I'd be hard pressed to used an open motor. It needs air to cool it and no matter what you do, except maybe a high dollar filter system, it will suck in grit and dust. Most of that grit and dust has a chance of igniting.
Bottom line is that it's your call, though.
I've also dealt with SurplusCenter with no problems.
 
After reading the replys, I am thinking of trying maybe to make a half round cover from sheet aluminum, or a piece of furnace duct with at least 3 inches clearance around the motor and cut furnace filters to go over both ends of the cover. Having found out on the above posts that the motor has a fan, it should get enough air to cool it through this type filter and the furnace filter should stop a good deal of the dust, (comments welcome) (Thanks Fitzo for the idea) Thanks Rob for the speed info and also rlinger for going the extra mile to help a total stranger, also to Kit and everyone helping me get the right stuff, you'al have already saved me a bunch of coins (I have just spent more money on a single tool than I ever did in my life and I am saving money;)) Really, I apreciate it fellows. You'all have a good Thanksgiving, Mike
 
Mike,

I told you if you mention open motors you'll get it ;) ;)

There are 2 camps on this:

Camp #1 - the conservative, big$$ group, that likes everything just so. They like totally enclosed stuff - for good reasons.

Camp #2 - The 'but I've been using an open frame motor for years without trouble' group.

I'm in camp 2, but have only been using it for 10 months. Heck the dust covers came off after the chicken episode, and I only blow it out once a month, just to see all the crap fly out (metal dust, wood dust, antler dust, dried egg yoke dust).

I have a $40 open 2hp motor with an external, plastic fan. Yeah it might break an a few years, but ....

Really I wouldn't worry about an enclosure. After you sell a dozen knives, if you still want to you can get a proper enclosed motor.

Steve

OK Camp #1 give it to me! I can take it. I want to hear about an open motor that did fail and how long it took.
 
I lost a shopvac to metal dust some years ago. Their motors are open to the top, and I had this one too close to the grinders I guess. Started it one day, and got a fireworks demonstration, with smoke. Metal grinding dust does no good for an open motor.

I now keep a cloth over the top of the shopvac when it's not in use. :eek: :D
 
Try a pantyhose over the motor,it may work.somtime trying to save a little bit of money ends up costing you more money and head ach in the long run;)
 
Originally posted by Nathan House
Try a pantyhose over the motor,it may work.somtime trying to save a little bit of money ends up costing you more money and head ach in the long run;)
Click to expand...
That is what Dan Gray does after he is done wearing them.:eek: :eek: :p :D
HEHEHE!!! He is on the road and will not see this till Monday.:D :D :D
 
Rob, he will not be using a 220 V. input motor drive so the output will be limited to ~120 V. max. If you recommend a higher RPM he'll have to step it up with a pulley and that makes me wonder about torque on the very lower RPM range.

His other immediate motor choice is a 4800 RPM 1HP (~11 amp.).

What think ?

RL
 
Roger,

On my KMG I'm using a 120vdc/4800 rpm motor too.

However, my controller only does 90vdc. Actually with pulleys in a 1 to 1 everything is fine. Runs as fast as I want! It comes out to about 3600 RPMs at 90 VDC.

Steve
 
Great Steve. That is ALSO the kind of thing Mike needs to know. I can give him 100 V. out. I think I may have mentioned 120 V. above. One hundred is probably as high as I'll cal. it for him.

RL
 
Roger,

The grinder speed is very subjective to personal preference. When using coarse grit belts...say 36,50,60, I like to fun the drive shaft as fast as 3500-4000 rpm. But I only run the grinder this fast with these belts. Most everything else is down slower 3000rpm and less. When I use the hoggers...I really don't care much about control, I just want to take some meterial off. Running a 36 grit slow at 3000rpm is terribly inefficient ...and brutal to the belt.

I wouldn't worry much about torque loss at lower speeds. Lower speeds imply delicate work with more precision rather than power...and torque issues really never come up.

If you are setting the motor/drive up, I would configure everything to produce at least 3000rpm on the drive shaft. My personal preference is for about 3500 on the high end.

Thats just my thoughts,

Sinceely,
Rob
 
Rob, then I've been running my 60 grit belts too slow. Thanks, on my next grind I'll speed the course belts up. I thought they were wearing faster than they should.

RL
 
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