Mark V shaft turns by hand but cleaned motor won't run

robfish · Post by **robfish** » Tue Jul 10, 2012 12:06 am

I have a Mark V that I bought new in the late 70's. I believe is a 500 series. The serial number is 75617, and it has the original 1-1/8 hp GE electric motor.

I recently moved it to a detached garage and have used it a handful of times in daylight where the only thing running was the Shopsmith. Last night, I had two 100 watt light bulbs turned on while I worked. The light bulbs dimmed every time I turned on the the electric motor. When the electric motor came up to speed, the lights brightened again and everything worked well.

The garage is on a dedicated circuit and I'm guessing there is about 60 to 65 feet or wire between the 15 amp circuit breaker and electrical outlet in the garage.

Last night I turned the Shopsmith on and off four or five times while doing some routing. The last time I flipped the switch on, the Shopsmith groaned but the electric motor did not run. I turned the electric motor off before the circuit blew. I could turn the shaft easily by hand and all the output shafts rotated. I then tried turning the shaft by hand as I started the motor. Lights dimmed, but the motor didn't run.

I put the Shopsmith in horizontal mode, installed the disk sander, and drove the sander by hand as I turned on the electric motor. Lights dimmed, motor didn't run.

After reading a bunch of info in these forums, I removed the electric motor, blew it out, and tried running it on my work bench. If I spun the shaft by hand, it rotated freely for a pretty long period of time. When I gave the electric motor power, the motor groaned but the shaft did not turn.

I pulled the back cover off the electric motor, cleaned out a bunch of sawdust that was still in there, and then spent a fair amount of time making sure everything was as clean as possible. I'd read about the centrifugal switch and tried to figure out how it worked. The first couple of times I pulled the round disk towards the back of the electric motor, while the disk was easy to pull back, the switch stayed in place for a brief period of time before snapping forward. I blew out the area around the switch and used a cloth to polish all the parts of the shaft that I could reach. After doing that, the switch snapped back into place as soon as I released it.

Before putting the electric motor back together I made sure the disk was snapped towards the shaft end of the electric motor, assuming that is the "at rest" position.

When I applied power to the electric motor, nothing had changed - the motor groaned but the shaft did not turn. With power off, the shaft rotates freely.

I'm hoping someone can give me some suggestions about what might be causing the problem. If it might be the capacitor, do I just wander over to Grainger and pick up a 110v 60h unit rated at 161-1933 MFD? (that's the info that is printed on the old capacitor).

Thanks in advance for any suggestions!

paulmcohen · Post by **paulmcohen** » Tue Jul 10, 2012 4:03 am

robfish wrote:
I'm hoping someone can give me some suggestions about what might be causing the problem. If it might be the capacitor, do I just wander over to Grainger and pick up a 110v 60h unit rated at 161-1933 MFD? (that's the info that is printed on the old capacitor).

Thanks in advance for any suggestions!

I don't know what is going on but it is odd the bulbs would dim unless they are connected to the same circuit at the Shopsmith. A Shopsmith 1 1/8 HP motor draws every bit of 15 amps when it first powers up (assume the speed is set to slow), possibily more if set to higher speeds. I would also check that you actually have 110/120 volts at the outlet, the long run may be causing excess voltage drop.

robfish · Post by **robfish** » Tue Jul 10, 2012 7:24 am

paulmcohen wrote:I don't know what is going on but it is odd the bulbs would dim unless they are connected to the same circuit at the Shopsmith. A Shopsmith 1 1/8 HP motor dra.

Thanks for the quick reply. The entire garage is on one dedicated circuit breaker, with all the lights and outlets sharing that one breaker. So yes, the lights and the Shopsmith were on the same circuit when the problem occurred.

When I disassembled the headstock and electric motor, I was in the basement, trying the electric motor on one of the basement's 15 amp circuits. I used an outlet that is about 12' from the service box and I made sure the Shopsmith's motor was the only active device on the circuit.

My multitester has a 50 ACV setting, a 250 ACV setting, and a 500 ACV setting. With the 250 ACV setting, the needle shows just a hair under 125 volts on both the garage and basement circuits. I'm thinking, though, that I should also be measuring amps. The nice folks at Amazon should be delivering an ammeter today.

While I had my multitester out, I removed the capacitor from the electric motor. With the ohm meter set to "X1K" resistance, touching the multitester leads to the capacitor's terminals initially showed no reading. After shorting the two capacitor leads with a screwdriver, the needle jumps about halfway down the scale towards the 0 setting and then, over a period of about 3 seconds, slowly moves back to its resting point on the "infinity" side of the scale. When I retest, the needle won't move unless I first short out the capacitor's terminals.

My expertise is in hydraulics (I teach a one-day "Basic Hydraulics" boot camp), but from what I've read on the Internet, it sounds like the capacitor is good. Grainger has one on sale for $6.00 so I think I'll install a new capacitor before trying out that new ammeter.

If anyone has suggestions for anything else I might check, I'd appreciate hearing them.

Thanks!

pennview · Post by **pennview** » Tue Jul 10, 2012 8:00 am

You haven't confirmed that the speed dial is set to slow. If you were routing and left the dial set on high speed, the motor will draw more amps than when set to low speed when you start it. This could cause the circuit breaker to pop.

If it is on high speed, attach the sanding disk to the spindle and rotate it while you slowly turn the speed dial to slow. Then remove the disk and see if it runs. Mine is on a 20 amp circuit, so I don't have that problem.

robfish · Post by **robfish** » Tue Jul 10, 2012 8:20 am

Before I could remove the electric motor from the head stock enclosure, I removed the drive belt. The drive pulleys are still on the electric motor shaft, but the shaft is not driving anything.

dusty · Post by **dusty** » Tue Jul 10, 2012 8:29 am

robfish wrote:Before I could remove the electric motor from the head stock enclosure, I removed the drive belt. The drive pulleys are still on the electric motor shaft, but the shaft is not driving anything.

I don't think that ammeter is going to help you correct this problem. Amperage is not what you need to know right now. If you have confirmed that you had 120vac to the motor, you now need the ohmmeter function of your multimeter.

Now that the motor is out on the bench, does it run. If not, what does it do when you apply power.

I hope that it just hums (if it does not run). If it hums, don't let it do that for very long. It should start running immediately. Allowing the motor to draw current when it is not running will result in heat and then smoke and then a new motor.

I guess I'll just wait for the progress report.

Hope it runs.

JPG · Post by **JPG** » Tue Jul 10, 2012 9:21 am

Your description of the multimeter(1kohms) and the capacitor sounds 'normal'.

You describe the start switch as a 'round disc'. That would be the start switch 'actuator'. It causes electrical contacts to 'make'.

Your attention need be directed to the actual switch.

The switch is a simple Single Pole Single Throw that you need to ascertain if it is 'making' in the 'at rest' position of the disc. Usually the actuator(disc) is spring loaded to the rest position, and a centrifugal rotating weight mechanism forces the actuator to 'open' the contacts.

One side of the switch will be connected to one of the capacitor terminals. The other side of the switch will be connected to motor winding wire(s).

Check the operation of the switch by connecting the multitester(ohms) across the switch while moving the actuator.

Finally a 15A circuit with > 50 ft of run of #14 wire will surely be stingy delivering start up current. As already mentioned, starting with it set to a fast speed creates a larger inertial load for the motor during startup.

Think of a bucket being filled by a small diameter pipe and that bucket suspended on a movable arm that is held in position by a spring. The small pipe will limit the flow rate of the fluid, and the position of the bucket on the pole corresponds to the motor speed setting.

rwilabee · Post by **rwilabee** » Tue Jul 10, 2012 10:33 am

I wonder if the starting capacitor has gone bad.

Rich

beeg · Post by **beeg** » Tue Jul 10, 2012 11:06 am

rwilabee wrote:I wonder if the starting capacitor has gone bad.

Rich

VERY Doubtful.

robfish · Post by **robfish** » Tue Jul 10, 2012 11:20 am

JPG40504 wrote:Check the operation of the switch by connecting the multitester(ohms) across the switch while moving the actuator.

Item 1 in the attached photo is the red wire that goes to the capacitor.

Item 2 points to the switch terminal for the blue wire that goes to the electric motor's windings.

When I first tested for continuity across the switch (from the red wire's terminal to the blue wire's terminal), nothing happened.

Item 3 points to what I believe is the switch actuator. When I touched the switch actuator, I got continuity across the switch... until I rotated the electric motor shaft by hand. As I rotated the electric motor shaft by hand I found two or three places in the rotation where I would momentarily get continuity as the shaft turned, but there was no continuity for the vast majority of the rotation.

If I pull the actuator towards the back of the electric motor, I can get continuity across the switch.

If I push the actuator towards the electric motor's shaft end, continuity comes and goes as I'm moving the actuator, but I when the actuator reaches the end of its travel I cannot get continuity.

Item 4 is the right leg of a "Y" shaped yoke.

Item 5 is a rubber boot that covers the area where the two legs of the "Y" meet.

If I press on just about any part of the "yoke" or on the rubber boot, I get continuity across the switch. The continuity gets broken as soon as I start to turn the electric motor's shaft.

Item 6 is one of two bolts that appear to hold the entire switch assembly in place.

While moving the actuator towards the electric motor's shaft, I discovered more sawdust. I blew out the area with compressed air as I moved the actuator in and out. It didn't have any affect on the switch's continuity, but as you can see at item 7, the back end of the bearing attracted a fair amount of sawdust.

In addition to suggestions on how to get the electric motor running, I'd also appreciate suggestions on what lubricant I should use on the bearing after I get all the sawdust cleaned away.

JPG40504 wrote: Finally a 15A circuit with > 50 ft of run of #14 wire will surely be stingy delivering start up current.

Yeah... at my old place I installed a 20 amp breaker and used #12 wire to power the Shopsmith from an outlet about 15' from the electrical box. I didn't even think about the availability of current in the new location until the lights dimmed the other night.