1140 rpm Gorton 9j downfeed motor running at 120 rpm?

katou · Oct 27, 2014

I am the proud owner of a 9J. I'm trying to get the downfeed working. The downfeed motor appears to be running at about 120 RPM.

I have disassembled it, and tried it on power with no load attached. Still the same problem.

It also doesn't want to start rotating. I have to give it a little spin with a screwdriver, and then it starts rolling. If I try and spin it the other direction on start-up it will also run in the opposite direction.

I'm really hoping that it's not pooches. This motor is integrated into the drivetrain of the downfeed. It would be very hard to replace.

I don't think pictures will help much, but I'm attaching a picture or two just in case.

Edit: I've been searching the archives, and the recommendation seems to be to check the voltage, and the resistance of the motor terminals. I will check this tomorrow, but I'm a bit skeptical because the same VFD runs the other motors on the mill, and none of them show the same strange behaviour.

Thanks for any ideas,

Katou

katou · Oct 28, 2014

I disassembled the gear train and detached it. The motor is not attached to anything at all, the shaft turns freely by hand. Judging from the wire terminations, the wiring was original.

I will verify the exact voltage later on today.

It's a headscratcher alright.

Katou

SteveBausch · Oct 28, 2014

Sounds like a classic case of single-phasing of a three phase motor.

katou · Oct 28, 2014

Testing voltage now:

At main panel on machine:
L1:L2 - 460 v
L1:L3 - 400v
L2:L3 - 370v

So far, so good. Machine is 440v, supplied by VFD and transformer. Readings taken while main motor (but no others) running.

Downfeed motor panel - here's where it gets weird.
L1:L2 - DMM reads infinite?
L1:L3 - 420v
L2:L3 - 450v

I will also check the terminal side of the downfeed box.
T1:T2 - DMM reads infinite again
T1:T3 - 550v
T2:T3 - 450v.

I sure hope this makes sense to you people, because I've got nothing. How does the voltage INCREASE over the supply? WTF?

Katou

Ps, I may not know the electrics, but I can clean parts just fine. These parts are now free of that hardened grease. Aaahh! That's better.

katou · Oct 29, 2014

Ok, so I'm checking to see if any of the phases are shorted to the others?

I guess I'll also check if it's shorted to ground, or the machine casting itself.

Is that right?

BTW, can I wash the stator down with Varsol (Stoddards, white spirits, solvent etc)? It's pretty greasy/messy.

I'm starting to feel a little optimistic I might get this working soon!

Katou

4GSR · Oct 29, 2014

Fire up the spindle motor and then start the feed motor and see if it runs smoother. Your spindle motor being larger will act like a alternator and should help the operation of the feed motor.

Gorton dis-continued making the feed unit available on later 9J mills. Never knew why, the service manual has that section marked out saying "obsolete". This could be the reason.

katou · Oct 29, 2014

I have determined that there is a short between two phases, somewhere between the main breaker box on the mill, and the downfeed motor.

This means that the short is either:

A) in one of the wires leading from the Cutler-Hammer starter box to the downfeed box

B) inside the starter box wiring

I was afraid of this result because electrical troubleshooting is not my strength, and I know nothing about starting circuits.

If anyone can refer me to general information on these sorts of things, or tell me what I'm looking at, I would be grateful.

The box is a Cutler Hammer 9736H25C

Katou

katou · Oct 31, 2014

Problem solved, found another one...

The problem with the short between two phases was caused by a new addition to the box. A previous owner added a line feeding a transformer in the sump. I can't figure out what it was for, but removing it fixed the short.

The new, bigger problem is that the removed line was connected to the circuit that runs the spindle motor.

I've had a problem with the spindle motor since I got it. The motor is a two speed. The low speed runs fine, but when I try the high speed, the main power kicks out.

I think this must have been caused by the new circuit to the little transformer I removed.

There are 5 wires running to the spindle switch. Now, everything looks good, except for one loose wire running to the spindle speed switch. I feel like if I could just figure out where this one wire goes, it would all set. The wire in question is the white wire at the top.

Help?

Katou

katou · Nov 1, 2014

I did a bit of research on 3 phase switches, and it appears that 5 wires is standard.

2 wires could go to a contactor to activate main power to low speed windings.

Same for high speed windings.

And the extra wire would be for.... a stop? I'm not sure how that would work.

Anyway, I guess I'm going to have to open up the switch and do some more testing, find out which wire does what.

Any ideas from people who have wired a 3 phase switch?

Katou

4GSR · Nov 2, 2014

Katou,

Our 1938 model 9J mill had that exact same CH contactor arrangement. I got tired of trying to trouble shoot and figure out why this would not work or that would not work. I segregated the wires for the high speed side of the motor and capped/taped off the ones to the low speed side. Next I removed the entire control box from the mill and chunk it into the scrap bin.

In it's place, I mounted a little bit newer AB forward-reverse size 0 contactor in it's place. I had to run a separate 120v single phase line to the box to operate the contactor. Used the same push button control up on the head to start-stop the spindle motor. Instead of having two speeds, now only one speed with forward and reverse. The two speed motor we had on the mill was 220V 3-phase. And we had 3-phase at that shop back then!

Ken

katou · Nov 2, 2014

Thanks Ken, I traced the dark green from the start into the starter and it goes to the overload switch. I wish I knew what that means!

I did a quick search for a new starter as you did, and I couldn't find one that would have two contactors to run both speeds. I just want to find one to get a rough idea of price. Can anyone point me to an appropriate unit?

Katou

4GSR · Nov 3, 2014

katou said:
I did a quick search for a new starter as you did, and I couldn't find one that would have two contactors to run both speeds. I just want to find one to get a rough idea of price. Can anyone point me to an appropriate unit?

Katou

Last time I priced one, they started at $2K for new one!

But with the older Gorton (Master brand) motor that you have that has six leads. You can use standard starters, but you must electrically interlock them from each other, so they don't both accidentally turn on at the same time.

this is where my expertise ends...

Maybe, another more knowledgeable expert can chime in and explain how to wire up a two speed starter.

IMHO, at this point, I would run that motor on a VFD. Be a lot cheaper in the long run....

4GSR · Nov 3, 2014

Bill,

You actually can change speeds on the fly on the Gorton mill. You could start the motor in low speed, then push the "high" button and go to the higher motor speed without pushing the "stop" button first. And likewise, start in high and go to low speed.
The only situation I recall where I could not start in high was when we had the one mill running off the big Avey drill press, before the days of having 3-phase power. You had to start the DP motor first, then start the mill motor in low speed first, then go to high.

Ken

katou · Nov 3, 2014

I have done a bunch of thinking. I am fairly certain that the white wire needs to be hooked to L3 in the starter box.

This should put everything to rights. I will try it out tomorrow, and report back. If it is wired as I suspect, this will solve all the problems and get it back running in its original state.

Wish me luck.

Katou

Search

Largest Manufacturing Technology Community on the Web

Search

1140 rpm Gorton 9j downfeed motor running at 120 rpm?

katou

Aluminum

Attachments

katou

Aluminum

SteveBausch

Stainless

katou

Aluminum

Attachments

katou

Aluminum

4GSR

Diamond

katou

Aluminum

Attachments

katou

Aluminum

katou

Aluminum

4GSR

Diamond

katou

Aluminum

4GSR

Diamond

4GSR

Diamond

katou

Aluminum

Similar threads