Reversing a HF Grinder (3 wire AC motor)

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srcarr52

We can't stop here, this is bat country.
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What the knock off manufacturer should have done (4 wires from the motor)!

Most people will tell you that you can't reverse a 3 wire AC motor but you can by switching the capacitor lead from the starting windings to the primary windings. But this will run the motor with less power then normal but it will still run and not over heat. I know because I ran my NT grinder like this for an entire 44" full comp rocked chain and it kept working but I was disappointed with it's power so I decided to open the motor and uncouple the common from the primary and the starting windings.

First thing get the front cover off and the rotor armature out of the motor. You'll have to remove the fan cover and the fan to pull the whole armature out of the motor case. Once you get all the wires loose you'll notice that the common (red) is connected to the primary (thick wire) and the starting (thin wire) windings.

IMG_1017.jpg


I had to cut both wires to untangle them after the little silver thingy which I'm assuming is some heat based overload resistor or something of the sort. Whatever it is, you'll have to solder it back in.

IMG_1018.jpg


All soldered up. Now the wiring is:
Primary + = Black
Primary - = Red
Staring + = White
Starting - = Blue

IMG_1019.jpg


Here it is all shrink wrapped and zip tied into place.

IMG_1020.jpg


Next is to get all the wires through the wire loom. It can be done!

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Sorry this picture has been posted before but after adding the 4th wire you can do the standard reversing wiring, it goes something like this using a standard DPDT (Dual pole, dual terminal) switch.

reverse.jpg


Here is the switch I used. Nice n' little.

IMG_1023.jpg


All the wiring fits under the stock cover.

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Outside shot of the reversing switch.

IMG_1026.jpg
 
Did anyone notice the rapidly disappearing margarita in the background? I should probably pay better attention to the background of my pictures but I have so many things torn apart on the bench now waiting for parts to be put back together I'm running out of boxes to put stuff in.
 
We USED to be able to edit the title of our post. We'd click "go advanced" after clicking the "edit" tab. That allowed you to change the title, go to the smilies list, and other things. "Go advanced" doesn't work anymore however............at least not for me...
 
Nice work, Shaun.

Heimanm started explaining to me how to do this to mine.......I heard, first you have to blah flop boop blah blah a huh
 
Nice work, Shaun.

Heimanm started explaining to me how to do this to mine.......I heard, first you have to blah flop boop blah blah a huh

I can bring up the bits to do it at the GTG. It only takes 1/2 hour if I have a bench and an electrical outlet for my soldering station.
 
I can bring up the bits to do it at the GTG. It only takes 1/2 hour if I have a bench and an electrical outlet for my soldering station.

So the question becomes is the power equal forward and back ward on the NT grinder now? People aslo talk about a grinder being symetrical... if the NT model isn't... can you mod it to make it symetrical??? IF so you need to complete this post on how to mod a cheap grinder to make it better...
 
So the question becomes is the power equal forward and back ward on the NT grinder now? People aslo talk about a grinder being symetrical... if the NT model isn't... can you mod it to make it symetrical??? IF so you need to complete this post on how to mod a cheap grinder to make it better...

They are not precise. To bad the search function blows. There is a very good thread on modifying the northern tool and Carlton grinders.
 
They are not precise. To bad the search function blows. There is a very good thread on modifying the northern tool and Carlton grinders.

Haven't you figured out how to use google to search a site yet? Site:arboristsite.com NT grinder

Nathan, yes it's full power both directions, no they are no symmetrical you have to know how to fudge it to get the same length/angle on both sides but it can be done pretty easy.
 
Haven't you figured out how to use google to search a site yet? Site:arboristsite.com NT grinder

Nathan, yes it's full power both directions, no they are no symmetrical you have to know how to fudge it to get the same length/angle on both sides but it can be done pretty easy.

Ya I'm just lazy. Besides if I complain, someone usually digs it up for me. :cheers:
 
As far as I remember the DPDT switch simply reverses the starter circuit so the motor starts backwards.
Also remember that on some cheaper grinders they'll back the nut off the shaft so you'll have to use Loctite or similar. Had it happen on an el cheapo Chino Plastico...
 
I wired my 511A to run both ways 3yrs ago. Works perfect. I've never had an issue with bolt coming loose but I make sure I get it fairly snug before I turn it on. The drill idea is pretty cool. I wish I'd thought of that instead of re-wiring mine. Oh well.....
 
I wired my 511A to run both ways 3yrs ago. Works perfect. I've never had an issue with bolt coming loose but I make sure I get it fairly snug before I turn it on. The drill idea is pretty cool. I wish I'd thought of that instead of re-wiring mine. Oh well.....

Where you at in Kansas? Parsons? I'm in Salina. Sorry to get off topic.

je
 

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