Anybody knowledgeable about OLD AC motors?

[gadget73]

Changing speed with the controller has a curve, but I'm not sure what it is. Off-zero rpm torque is pretty good with that type motor though so I doubt you'll have a lot of trouble with it.

If you need significantly lower speed but with good torque you want a mechanical reducer of some sort. Pullies, gears, whatever. That will multiply torque at the same ratio it divides RPM at. Larger lathes have whats called a back gear for high power / low speed work. Mine will run down to something like 50 rpm at the spindle and the motor runs at 1750 rpm. Its slow but it will happily rip the arm right out of your body if you get wound up in that thing and that flat leather drive belt is not going to slip before it happens.

 

[ghazzer]

I cleaned the commutator. I lightly chucked the shaft in the drill press and put the other end in the bearing in the short end of the housing....



...in an attempt to avoid any wobbling. It was very stable, so I am also pleased with the new DP.



I limited the abrasion by re-using an old strip of emery cloth and ran the DP at its slowest speed. This seems to have worked very well as its appearance didn't change much, but the slight ridge that I felt with my fingernail is no longer obvious.



Now I need to clean up my workbench, again.

 

[gadget73]

Cool. I did similar with a starter earlier in the week. Don't need a lot of sanding, just enough to break the glaze and smooth out the ridges a bit will do it. Just flush off the comm bars afterward. CRC Lectra-Motive cleaner does perfect for that.

 

[ghazzer]

I was waiting for a warm day to clean out the housing with CRC's Lectra Clean. Today was 54°, but I forgot and washed the car instead. May get another chance this week.

 

[ghazzer]

It has been a good week. Maybe I can close out the year on a win streak.

I washed out the housing with Lectra Clean and it seems to have cleaned out all of the obvious carbon dust. It really stunk up the back yard so I'm glad I didn't do it in the workshop. I used a hair dryer to blow it out and evaporate as much as I could. It was still pungent so I left it in the garage overnight.

The 4mmX4mm brushes from China may not be here until late January so I decided to start working with the 6mmX6mm ones. Put a sheet of emery paper on a board and clamped a small piece of cherry with a 90° angle to that. Then I did my best to rub the carbon brush in the corner that formed and alternate until it got down to ~0.150"X0.150". Either my technique is poor or the carbon piece doesn't wear evenly, but I worked it slowly, made a lot of corrections, and eventually got something that is functional. It slides evenly in the housing, and is not loose.

Received some 5/32" O.D. compression springs from an on-line order and they are small enough. Used a fine emery board to file one end of the brush down just enough for the spring to fit on it snugly. Now I can push the spring/brush into the housing and slide it back out. This is tedious work.

One more brush to modify and then I can bed them to the commutator and start putting it back together.

 

[ghazzer]

Here is what I have done recently:

Replaced "vintage" wiring
Added toggle switches for ON/OFF & FWD/REV
Carbon dust cleaned out with Lectra Clean.
Commutator cleaned
Re-sized carbon brushes

What I did yesterday:

Shaft cleaned & lubed
Rotor re-inserted
Housing closed & secured
Brushes replaced.
Oil Pads re-installed
Checked wiring connections
Fingers crossed
Power applied

Motor Runs

No Smoke
No vibrations

Not as quiet as I'd like, but this part is mostly done.

 

[ghazzer]

Wouldn't you just know it?

Two days after getting this buttoned up and checked out I got one of those small tan envelopes from China with no Chinese symbols at all. I guess that everyone in their 'post office' can read English.

It was the 4X4X18mm brushes that I thought wouldn't arrive until the thaw. All the effort to resize the 6X6X20mm brushes was not wasted: Now I have a neat pile of carbon dust for a dry, conductive lubricant.

I probably need to start another thread and see if someone has any knowledge about how to open up the head stock on this lathe.

Maybe when it gets warmer . . . .

 

[ghazzer]

Just in case it helps someone else, here is an approximate drawing of where the brushes sit in the housing.

 

[BillWojo]

Steve, I would check on the watch makers forum for some info. Personalty, I would oil it well numerous times and run it at a slow speed to start off with. I think the only adjustment I would make is to get some of the axial (end play) out of the spindle. You have dial indicators, set it for between 0.0005 and 0.001 of an inch. If the oil starts to run through clear, your good. Just keep an eye out for bearing temperatures.
I ran a lot of plain bearing headstock lathes when I was coming up in the trade. Most had the old brass and glass drip oilers. I just set the drip rate and would check bearing temps from time to time. Most were trouble free.

BillWojo

 

[ghazzer]

Thanks Bill! I want to ring out the head stock before I start using the lathe. The pulley block seems 'frozen' to the spindle and I cannot get it free.

There is a place inside the spindle where there used to be a pin or key that would engage the slot in the collets. This would keep them from turning and making it MUCH easier to tighten & loosen them from the drawbar. I can just barely see where the pin was, but have no idea if it can be replaced.

 

[ghazzer]

I am satisfied with the motor and have started another thread to see if anyone can help with the headstock.

Thanks - - -

 

[BillWojo]

Steve, your best bet is to look at a watch makers forum. Also join both Practical Machinist and the Home Shop Machinist forum. Practical Machinist is geared more to professional machinist but there are some smart folks over there.

BillWojo

 

[ghazzer]

Nearly 3 (THREE) months later: I chased my tail with the head stock and finally gave up on trying to research and replace the pin that holds the collet in place.

Today it took me three tries to do a decent job of "welding" the urethane tubing into a loop for a drive belt. I was fortunate that I remembered that the urethane tubing had to be threaded thru the pulley before melting the ends together with a piece of tin over a candle.

With the drive in place I applied oil to the motor and lathe bearings and "fired that mutha up". It appeared to be running fine, forward and reverse, but still sounded a little "gravely" as reported in my previous post. But that didn't last. I heard the pitch of the motor down shift just a bit. Turned it off and sniffed, but it didn't smell burnt. Turned it back on and it didn't budge, until I gave it a little nudge, and it was lumbering.

I removed the belt and turned it back on. it was running slower and I could see white arcs of sparking through the inspection holes and I shut it down.

Now I will have to pull the bell off the motor and see if I can figure out what went wrong.

I may have to swap in the sewing machine motor and use the speed controller. The K&D motor is spec'ed at 3,500 rpm and the sewing machine motor is spec'ed at 6,000rpm.