mark VII speeds up on its own above 1800 rpm

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jerryricht
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Re: mark VII speeds up on its own above 1800 rpm

Post by jerryricht »

I am a new member, and arguably the owner of the best model of ShopSmith .. a free one!

My Mk VII is also humming instead of running, and I am currently in the process of replacing the bearings, replacing all of the leads because of severely cracked insulation, and replacing the external start switch. (A.O. Smith with external start switch)

First, a BIG THANKS to Everett Davis for the restored MK VII Manual! I confess I know nothing about Mk VII's and would be at a total loss without it.

Anyway, having just disassembled my motor I noticed an obvious difference from the picture that was provided.

There is no way the C Clip retainer ring should be external to the motor housing!

The front bearing has C clip retainer rings on both sides of the bearing. There is also one ring retainer on the internal side of the back bearing.

There is no way the motor shaft could migrate forward to the extent that it has in this picture without BOTH of those other retainer rings missing.

I would guess someone replaced the bearings and forgot to put the retainer rings on BEFORE they pressed the bearings. Its almost impossible to put them on after the bearings are installed.

So you will probably need to pull and replace both bearings (less than 10.00 a pair)and remember to put the retainer rings on before you press the bearing on.

Of course I could be totally wrong... as I said I know nothing compared to you guys.
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JPG
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Re: mark VII speeds up on its own above 1800 rpm

Post by JPG »

The most likely cause of humming instead of running is the power switch. It controls the polarity of the start circuit.

The start relay is not likely a contributor to the problem(albeit possible).

I would suggest by passing the power switch by directly connecting the motor leads. If you need details post that.

If you are referring to my placing a retaining ring 'external' to the motor housing, realize that was merely to space the fan sheave spacer to eliminate the result of the spacer digging in to the fan sheave. If not ignore this, but please explain where that comment came from. I am not familiar with the A O Smith version motor.

Please explain 'this picture'. If the one I posted a while back - see previous paragraph.
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╟JPG ╢
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Goldie(Bought New SN 377425)/4" jointer/6" beltsander/12" planer/stripsander/bandsaw/powerstation /Scroll saw/Jig saw /Craftsman 10" ras/Craftsman 6" thicknessplaner/ Dayton10"tablesaw(restoredfromneighborstrashpile)/ Mark VII restoration in 'progress'/ 10
E[/size](SN E3779) restoration in progress, a 510 on the back burner and a growing pile of items to be eventually returned to useful life. - aka Red Grange
jerryricht
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Re: mark VII speeds up on its own above 1800 rpm

Post by jerryricht »

Thanks JPG

Yes I was referring to the retaining ring in the picture. Thanks for the explanation I did not understand that. It certainly beats replacing the sheave.

Thanks for the advice on the switch. Continuity checked out, although I understand that does not mean there is not a problem. Good idea, I will bypass the switch when I test the motor after get it back together.

I assumed it's the motor, or start relay , because it will run if manually spun although it did start easier in reverse than forward.

Switch or not, the cracked and missing insulation on the lead wires was shocking. Pun intended:)
New leads were going to have to be soldered on to the windings so the motor was disassembled to do this. Thus new bearings while at it.

I opened the start relay and found significant corrosion so I ordered a SUPCO universal relay for about 13.00 to replace.

Like anything that's over 5o years old (including me) you usually find more problem the more you look. Or, if it's not broke ...it's fixing to break..
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JPG
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Re: mark VII speeds up on its own above 1800 rpm

Post by JPG »

jerryricht wrote:Thanks JPG

Yes I was referring to the retaining ring in the picture. Thanks for the explanation I did not understand that. It certainly beats replacing the sheave.

Thanks for the advice on the switch. Continuity checked out, although I understand that does not mean there is not a problem. Good idea, I will bypass the switch when I test the motor after get it back together.

I assumed it's the motor, or start relay , because it will run if manually spun although it did start easier in reverse than forward.

Switch or not, the cracked and missing insulation on the lead wires was shocking. Pun intended:)
New leads were going to have to be soldered on to the windings so the motor was disassembled to do this. Thus new bearings while at it.

I opened the start relay and found significant corrosion so I ordered a SUPCO universal relay for about 13.00 to replace.

Like anything that's over 5o years old (including me) you usually find more problem the more you look. Or, if it's not broke ...it's fixing to break..
Do NOT throw the 'corroded relay' in the trash - you might need it later(when 'universal SUPCO' proves to not be a solution.
╔═══╗
╟JPG ╢
╚═══╝

Goldie(Bought New SN 377425)/4" jointer/6" beltsander/12" planer/stripsander/bandsaw/powerstation /Scroll saw/Jig saw /Craftsman 10" ras/Craftsman 6" thicknessplaner/ Dayton10"tablesaw(restoredfromneighborstrashpile)/ Mark VII restoration in 'progress'/ 10
E[/size](SN E3779) restoration in progress, a 510 on the back burner and a growing pile of items to be eventually returned to useful life. - aka Red Grange
lahola1
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Re: mark VII speeds up on its own above 1800 rpm

Post by lahola1 »

I finally took my fan sheave offto look for a spacer on the motor shaft (ao smith).
I have no snap ring; I have no spacer. I see in the parts manual there is a different p/n for ao smith and ge motors.
so I set my space between fan sheave hub and motor cover to approx, .170". hope that's close enough.
I finally got my new idler shaft bearings and belts. I put in the same motor belt a JPG.
runs good but tach says 1030 rpm when set at 700; 6000 rpm @4500.
motor belt is up to approx .150" of the od of the idler sheaves.
I'll do more investigating tomorrow.
SS Mark VII(sn 405025), SSband saw, SS 4" jointer, SS Mark V 1980,
Smithy SuperShop 720, Craftsman RAS, Ridgid TS2412 Table Saw,
Delta 12" planer
lahola1
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Re: mark VII speeds up on its own above 1800 rpm

Post by lahola1 »

btw JPG, do you think that the supco relay may not work for long? are there parts to rebuild the original one? mine was somewhat fried.
SS Mark VII(sn 405025), SSband saw, SS 4" jointer, SS Mark V 1980,
Smithy SuperShop 720, Craftsman RAS, Ridgid TS2412 Table Saw,
Delta 12" planer
lahola1
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Posts: 90
Joined: Sun Jul 09, 2017 11:43 pm
Location: Sedona,AZ

Re: mark VII speeds up on its own above 1800 rpm

Post by lahola1 »

jerryricht :
my motor problem WAS the start relay.
mine would buzz, not hum.
mine motor would not start if i spun the motor by hand.
hope this helps.
SS Mark VII(sn 405025), SSband saw, SS 4" jointer, SS Mark V 1980,
Smithy SuperShop 720, Craftsman RAS, Ridgid TS2412 Table Saw,
Delta 12" planer
jerryricht
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Posts: 9
Joined: Sun Jul 16, 2017 1:03 pm

Re: mark VII speeds up on its own above 1800 rpm

Post by jerryricht »

Thanks lahola and jpg.
BTW, I measured my spacer at .89 inches slightly more than 7/8th.

JPGs comment made me curious, the contacts in the SUPCO are not nearly as robust. So yes I will keep the old relay
However it does have a auto disconnect and auto reset to protect those old start windings. We will see how long it lasts. It may be worth replaceing occasionally than sourcing and buying another motor.
lahola1
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Location: Sedona,AZ

Re: mark VII speeds up on its own above 1800 rpm

Post by lahola1 »

jerryricht:
so your saying with your spacer, your fan sheave hub is a full 7/8" away from the motor cover?
SS Mark VII(sn 405025), SSband saw, SS 4" jointer, SS Mark V 1980,
Smithy SuperShop 720, Craftsman RAS, Ridgid TS2412 Table Saw,
Delta 12" planer
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JPG
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Joined: Wed Dec 10, 2008 7:42 pm
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Re: mark VII speeds up on its own above 1800 rpm

Post by JPG »

lahola1 wrote:jerryricht:
so your saying with your spacer, your fan sheave hub is a full 7/8" away from the motor cover?
IIRC, the spacer butts up against the inner race of the bearing(mostly inside the outer surface of the motor housing). The fan sheave to motor housing is very small(< 1/8"). I assume the difference in spacer is because of different positioning of the bearing.
╔═══╗
╟JPG ╢
╚═══╝

Goldie(Bought New SN 377425)/4" jointer/6" beltsander/12" planer/stripsander/bandsaw/powerstation /Scroll saw/Jig saw /Craftsman 10" ras/Craftsman 6" thicknessplaner/ Dayton10"tablesaw(restoredfromneighborstrashpile)/ Mark VII restoration in 'progress'/ 10
E[/size](SN E3779) restoration in progress, a 510 on the back burner and a growing pile of items to be eventually returned to useful life. - aka Red Grange
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