Instead of Repairs, Can Mark V Run Lowest Speed Only?

[ALarryAaron]

I apologize in advance for this long post. There are several related issues/questions involved.
My 2 big questions are:

1. "How can I figure out what exactly caused my machine to trip the breakers so I can assemble and use the machine?"

2. “Can my 39-year old Shopsmith Mark V be forced/rigged to run ONLY in its slowest speed?"

I ask that because I’ve had some damage to my machine (See below for details on those.)

If this amounts to hundreds of dollars in parts (I’ll be contacting Shopsmith to get a quote on parts cost and delivery time), I may not want to get it fixed, especially if I can operate it satisfactorily without changing speeds.
What I need to know from you folks is:

1. Is it possible for my Shopsmith Mark V to be forced to run in its slowest speed only and not change speeds? (After I reassemble the motor, I wonder if I can leave off the V belt that drives the sheaves to shift which changes the speed output.)

Since I run my machine on the slowest speed 95% of the time, it may not hurt me much. I primarily use the disc sander, drill press/horiz bore, lathe and band saw attachment.

2. Is there any mechanical or safety reason why I shouldn’t allow my machine to operate ONLY at its lowest speed?
================================================

Here’s what has happened to my machine:
Problem #1.
The circuit breaker was tripping instantaneously when hitting the Shopsmith’s “On” button and when set at its slowest operating speed.
A. I got the same result plugged into another circuit.
B. No other high-amp machines in my shop plugged into those same 2 circuits tripped the breakers, so I knew the problem was not the house wiring but rather the Shopsmith.
C. I tested the Shopsmith’s power cord using a volt-ohm meter up through and including the switch, but didn’t find a continuity problem there.
D. I disassembled the headstock from the mounting tubes, shimmied the v-belt belt off the sheaves, and hauled the motor into a local electrical motor repair shop.
E. Motor repair shop found nothing wrong with it: the capacitor, windings, switch, wiring, everything as AOK.[/list]

I need to figure out what caused the breakers to trip so I can get my machine up and operating again. I can use all the help you can muster to get up and operating.

Problem #2.
When I removed the motor from the headstock, I found an O-shaped clip broken-off and laying in the bottom of the headstock’s pan. I can’t figure out where this part came from. [This is the same ring addressed in my most recent post. I’ll assume that the ring was left inside the case by a prior owner and so, I’ll move on assuming that the broken ring was not the cause of my circuit breaker tripping and I’ll move on.]

Problem #3.
After detaching the motor, I tried to turn the speed dial to move the sheaves for oiling. It did not move easily, so I added a bit of pressure. That snapped the Speed Control Bracket casting (part #89) in 2 places—on the top and bottom extensions which have holes in each to hold the Rollpin (part #88) and Quadrant Assembly (part #87) with the Worm Control Shaft (part #87). I’ll likely have to replace this unit at some exorbitant Shopsmith price.[I am posting a photo of the broken Speed Control Bracket casting.]

I’m considering operating my machine in single speed only based on the viability and safety in doing so based on what I hear from you folks in this forum.

Problem #4.
Examining the other engine shafts and sheaves, it appears that the neck of the Motor Shaft’s Floating Sheave (part # 117) has some fractures and missing fragments around its circumference and will likely need to be replaced. [I am posting 2 photos of this part.] I will likely have to replace that sheave. {That’s even more More Shopsmith parts to buy. :O)

Please chime in with tips and advice.

Thanks,

A. Larry Aaron
Jacksonville, FL

[DLB]

There are circuit breakers with other features than overcurrent protection, e.g. GFCI for a ground fault. But unless you say otherwise I assume overcurrent protection only, and that the SS is the only thing drawing current through that breaker. Instantaneous tripping of the circuit breaker probably means a short circuit, either a current path from hot to neutral or from hot to ground (a ground fault). Look at the wiring, especially between the switch and motor, and make sure it is routed carefully and away from moving parts that could have damaged the insulation. On many headstocks both hot and neutral are switched, you'd see both black and white wires (two of each) going to the switch.

One possible cause of a short circuit is that someone has removed the wires from the switch and put them back incorrectly. A pic of the back of your switch showing the wiring would help.

If that does not help I would remove the wire connections to the motor, unplug the unit, turn the switch on, and measure resistance between all of the pairs of the three conductors on the power cord. All should measure high with the motor disconnected.

The headstock can be modified to run at only one speed and it is not detrimental. However, when I did this the floating sheave on the motor shaft was working correctly. Yours is not, which introduces some complexity because that also normally tensions the belt. Let me think about this one...

The part failures you currently have seem unusual/extreme to me. The speed control is relatively high failure but usually those holes wear or the legs bend. The cardinal rule for SS is never adjust the speed control unless the system is turning, and especially do not adjust it to a slower speed.

- David

[lahola1]

from your post I would assume the repair shop plugged your motor into 120volts and it ran fine.
from the look of your broken sheave and speed control I am guessing that your are not starting at slow speed but actually starting at full speed, causing the circuit to trip. slow speed requires the floating sheave to be fully open; spring fully compressed. I don't think your getting that with your broken, possibly siezed sheave. my guess is that if you replace the broken parts and lube it up well (floating sheave should compress fairly easy with hand pressure) it should work as designed with full speed control.

[rpd]

I apologize in advance for this long post. There are several related issues/questions involved.
My 2 big questions are:

1. "How can I figure out what exactly caused my machine to trip the breakers so I can assemble and use the machine?"

2. “Can my 39-year old Shopsmith Mark V be forced/rigged to run ONLY in its slowest speed?"

I ask that because I’ve had some damage to my machine (See below for details on those.)

If this amounts to hundreds of dollars in parts (I’ll be contacting Shopsmith to get a quote on parts cost and delivery time), I may not want to get it fixed, especially if I can operate it satisfactorily without changing speeds.
What I need to know from you folks is:

1. Is it possible for my Shopsmith Mark V to be forced to run in its slowest speed only and not change speeds? (After I reassemble the motor, I wonder if I can leave off the V belt that drives the sheaves to shift which changes the speed output.)

Since I run my machine on the slowest speed 95% of the time, it may not hurt me much. I primarily use the disc sander, drill press/horiz bore, lathe and band saw attachment.

2. Is there any mechanical or safety reason why I shouldn’t allow my machine to operate ONLY at its lowest speed?
================================================

Here’s what has happened to my machine:
Problem #1.
The circuit breaker was tripping instantaneously when hitting the Shopsmith’s “On” button and when set at its slowest operating speed.
A. I got the same result plugged into another circuit.
B. No other high-amp machines in my shop plugged into those same 2 circuits tripped the breakers, so I knew the problem was not the house wiring but rather the Shopsmith.
C. I tested the Shopsmith’s power cord using a volt-ohm meter up through and including the switch, but didn’t find a continuity problem there.
D. I disassembled the headstock from the mounting tubes, shimmied the v-belt belt off the sheaves, and hauled the motor into a local electrical motor repair shop.
E. Motor repair shop found nothing wrong with it: the capacitor, windings, switch, wiring, everything as AOK.[/list]

I need to figure out what caused the breakers to trip so I can get my machine up and operating again. I can use all the help you can muster to get up and operating.

Problem #2.
When I removed the motor from the headstock, I found an O-shaped clip broken-off and laying in the bottom of the headstock’s pan. I can’t figure out where this part came from. [This is the same ring addressed in my most recent post. I’ll assume that the ring was left inside the case by a prior owner and so, I’ll move on assuming that the broken ring was not the cause of my circuit breaker tripping and I’ll move on.]

Problem #3.
After detaching the motor, I tried to turn the speed dial to move the sheaves for oiling. It did not move easily, so I added a bit of pressure. That snapped the Speed Control Bracket casting (part #89) in 2 places—on the top and bottom extensions which have holes in each to hold the Rollpin (part #88) and Quadrant Assembly (part #87) with the Worm Control Shaft (part #87). I’ll likely have to replace this unit at some exorbitant Shopsmith price.[I am posting a photo of the broken Speed Control Bracket casting.]

I’m considering operating my machine in single speed only based on the viability and safety in doing so based on what I hear from you folks in this forum.

Problem #4.
Examining the other engine shafts and sheaves, it appears that the neck of the Motor Shaft’s Floating Sheave (part # 117) has some fractures and missing fragments around its circumference and will likely need to be replaced. [I am posting 2 photos of this part.] I will likely have to replace that sheave. {That’s even more More Shopsmith parts to buy. :O)

Please chime in with tips and advice.

Thanks,

A. Larry Aaron
Jacksonville, FL

Problem #1 - Check the width of the drive belt (V-belt) If it has worn to less than 1/2" it can drop down too far in the sheaves and jam, which will stall them motor and cause the breaker to trip. Since the motor checks out okay, that is the most likely cause.

Problem #2 - I think you are correct, and the control sheave looks in good shape, so it was likely replaced by the previous owner.

Problem #3 - All the crud in the quadrant teeth probably didn't help. The picture of the quadrant doesn't show the condition of the teeth, if they are okay it can be reused, however it is likely they are damaged and the worm gear is likely bent also.

So worst case scenario you are looking at $140 plus shipping
Shopsmith Shopping Cart
Item Description Amount
504208 Floating Sheave 34.96
521682 Drive Belt 19.99
504198 Speed Control Assm 84.99
Subtotal 139.94

To jury rig it for single speed you would need a belt, plus two pulleys, and plus messing around to get it to work properly, and get reduced functionality and a reduced resale value.
The price for those parts doesn't look that exorbitant, to get it working properly again, I suspect it would cost you a significant portion of that to bodge it.

[ALarryAaron]

David and lahola, thanks for your replies.

I'll get into that switch but nobody has tapered with it, taken it apart, switched wires. It's the same as it was when I bought it. I'm the only owner and the unit is almost 40 years old. Never took anything apart until this incident popped up.

So I am confident that the problem was generated by the Shopsmith. I have no other problems with any other machines running on those circuits and that includes a 15 amp table saw. I don't think the house wiring or breakers are the cause. No GFCIs on any of the breakers although there are some on duplex outlets in wet applications like the kitchen, bathroom and outdoors.

I've run continuity tests on all wires from the plug back thru the switch and there is no short but I'll take another gander at it.

I think replacing the damaged motor sheave would be a good step but I'll need to make sure that there's no electrical problem causing the breaker to trip.

Yes, I know about always having the machine running when changing speeds. However Jacob Anderson's videos say repeatedly that once the drive belt is disengaged from the motor, you can rotate the speed dial to shift the sheaves. Is that not correct?

The motor repair guy hooked it up to a 120 volt circuit and it runs perfectly.

I rarely change speeds on the unit and run it 99% of the time on low. I always start at the low speed.

Is it possible that if the motor sheave failed and caused the spring to decompress (forcing the sheaves to close therefore starting automatically at high speed), could that trip a breaker due to the start-up amps needed at a high speed?

Not sure if you can tell from photos, but when I opened the case, I found the motor sheaves as shown---sheaves are together and spring is not compressed.

Tx for the dialogue fellas. I'll keep watching and will report any other discoveries oveer the next several days.

[JPG]

A possible scenario: Speed control broken/stuck with idler pulley wide open. Floating sheave(motor pulley) fully closed. That describes 'fast' speed. Plug motor in and turn on the switch. Motor attempts to start, but the belt gets caught in the vanes of the idler pulley. Motor stalls and the breaker trips. Makes sense if the motor shop says motor ok.

So I think thee should get a new floating sheave and speed control part(s). i.e. replace the broken stuff.

I would not attempt the slow only project(too many squirrels).

I hope you learned the lesson(if it don't move like it should, do NOT force it).

[lahola1]

you should be able to test your motor easy enough. take the broken sheave half off the motor shaft; put the motor back in the headstock temporarily; connect the motor wires to the switch and now, without the belt on try and start it. if it starts, there is no problem with the SS wiring; if it trips the breaker, you have some wiring problem along with the broken parts.

[ALarryAaron]

I am greatly encouraged by all comments, so will order broken parts.

Will also attempt motor test as suggested, but JPG's explanation of sheave/belt orientation seems to make most sense to me as to what is tripping the breaker.

I will chime in with my repair results.

You folks have been most helpful. Thanks a lot.

[DLB]

I was (overly?) focused on the word "instantaneous" in my earlier response. By design, circuit breakers are slow devices. In my experience when something is preventing a SS motor from turning I can always turn the machine off before the CB will trip and do it for me. The greater the overload the faster the trip, but I'm thinking at least a couple of seconds in this case. I associate 'instantaneous' with an electrical short circuit. As lahola1 said, you can easily test the motor in your machine without the motor belt to confirm everything is well.

Yes, I know about always having the machine running when changing speeds. However Jacob Anderson's videos say repeatedly that once the drive belt is disengaged from the motor, you can rotate the speed dial to shift the sheaves. Is that not correct?

That's correct as long as the drive belt does not get pinched between the sheaves on the 'idler' shaft. The resistance you felt could have come from elsewhere.

- David

[ALarryAaron]

Latest on Sheave replacement and circuit brkr tripping repair.

My repair parts are in plus I ER disassembled the spring-loaded parts from the end of the motor shafts sheave.

The neck of the sheave had sheared off of the sheave and had slipped to the extreme end of that shaft and had likely jammed the whole mechanism, thus causing an immediate short circuit.

I'm not much of a mechanic-- more of a woodworker, so I have some mechanic's question to you mechanical gurus.

1. The diameter of the hole in the neck of sheave is IDENTICAL to the motor's shaft, not even a 1/64th to spare. It comes in at exactly 5/8" diam.

1A. So am I supposed to add penetrating oil lubricant to the hole and shaft and tap it on w rubber mallet?

1B. Or should I use emory cloth on the shaft removing 1/128" or so?

1C. Other tips?

I do know that the sheave neck's key slot needs to align w key mounted in shaft.

2. When done with that task, I'll be swapping out the speed changing mechanism that broke, but that looks like a simple operation other than:

2A. How to zero-up the speed dial with the worm gear?
2B. Should sheaves be in expanded or closed positions on the shaft when zeroing up to slow speed?
2C. I know motor is to always be started up in slo-mo, so how do I attain that w sheave positioning on both shafts plus V-belt install?

Tx in advance for the addtl help.