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mark VII speeds up on its own above 1800 rpm

#236582 by lahola1 » Mon Jul 17, 2017 11:05 pm

hi all
i'm a new member from sedona,az and 1st time shopsmith owner.

i bought a mark VII last winter ( not working; motor would only buzz, not hum)and have been reading the mark VII repair threads with great interest. with the help from these threads and comments from jpg, robinson and others i was able to get it running (bad start relay).
it runs quite well although noisier than i thought it would be (i've never been close to a shopsmith before).
but when i turn the speed up to approx 1800 rpm it tends to keep going up; sometimes to 3600,sometimes all the way up. the detent pins and springs appear to be functioning properly.
i've moved the fan sheave to 3 different positions but the speed moved the same or worse. i don't remember seeing a thrust spacer between the fan sheave and the motor (i didn't see one on JPG's teardown and rebuild thread.
how do you align the motor belt without one; what are it's dim's?
are there any other known causes for this speedup (my motor belt's width is .504". i have ordered new belts for it).

lastly, thanks for all the great posts. they have been MOST helpful.

---

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

#236583 by JPG » Mon Jul 17, 2017 11:48 pm

Sorry I did not show the spacer in the reassembly thread.

Here is a pix of it in the disassembly thread.
mark VII fan sheave spacer.jpg
mark VII fan sheave spacer.jpg (396.05 KiB) Viewed 4977 times


IIRC it was embeded into the sheave.

I do not recall it's dimension but I believe it was 3/16 to 1/4". I think it is the same as current MV spacer.

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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'/ 10E(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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Re: mark VII speeds up on its own above 1800 rpm

#236586 by JPG » Tue Jul 18, 2017 12:10 am

It is 'hidden' behind the retaining ring 'fix'.

IIRC it bears against the inner race of the bearing.(substantially into the end cap).
m vii motor spacer fix.jpg
m vii motor spacer fix.jpg (342.02 KiB) Viewed 4972 times


This places the fan sheave VERY close to the motor end cap.


As for the speed increasing, I feel the mark VII is prone to doing that if the detents are worn or the knob is sloppy on the shaft(the knob tilts away from the detent gizmos). Also the spring tension in the gizmos is likely weaker that original. The fix likely involves all that. I acquired a better knob. I damaged the initial knob by assembling it incorrectly(too tight and it caused the detents to become 'grooved'). Also the original knob was very sloppy on the shaft.

I have discovered that wear can make the Mark VII less than desirable and have substituted several less worn parts for those original parts that are worn.

Wish I had a magic bullet for this!

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╔═══╗
╟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'/ 10E(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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Re: mark VII speeds up on its own above 1800 rpm

#236589 by lahola1 » Tue Jul 18, 2017 1:34 am

thanks for the reply.
i will investigate my thrust spacer area more when i get my new belts.
when i 1st installed the fan sheave i had it in far enough that it would rub on the tin shield on the motor (a.o. smith btw).
luckily i have good plastic cam and gear rack.
i tried to upload pics. i don't think it worked

---

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

#236591 by JPG » Tue Jul 18, 2017 7:51 am

lahola1 wrote:thanks for the reply.
i will investigate my thrust spacer area more when i get my new belts.
when i 1st installed the fan sheave i had it in far enough that it would rub on the tin shield on the motor (a.o. smith btw).
luckily i have good plastic cam and gear rack.
i tried to upload pics. i don't think it worked


You likely need 'the fix' as well.

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╔═══╗
╟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'/ 10E(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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Re: mark VII speeds up on its own above 1800 rpm

#236600 by lahola1 » Tue Jul 18, 2017 3:45 pm

i don't know a whole bunch about belts and pulleys and less about expanding and contracting sheaves but i know belts and pulleys should be in alignment.
if the motor and idler sheaves expand and contract in opposite directions wouldn't that put them out of alignment all the time except the initial setup position.
if that's true by design wouldn't it be best to be in alignment at the highest speed and most out of align at the slowest speed?
or am i missing something in the design?
as i said i'm new to shopsmiths.

---

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

#236603 by jsburger » Tue Jul 18, 2017 5:33 pm

lahola1 wrote:i don't know a whole bunch about belts and pulleys and less about expanding and contracting sheaves but i know belts and pulleys should be in alignment.
if the motor and idler sheaves expand and contract in opposite directions wouldn't that put them out of alignment all the time except the initial setup position.
if that's true by design wouldn't it be best to be in alignment at the highest speed and most out of align at the slowest speed?
or am i missing something in the design?
as i said i'm new to shopsmiths.


The expansion and contraction does not in any way change alignment. What it does do is effectively make one pulley larger in diameter and the other one smaller in diameter. The alignment remains the same. As one gets larger the other one gets smaller thus changing the diameters in opposite directions. The effect is a change in the rotational speed (RPM) of the quill spindle. The ratio of the diameters of the two pulleys determines the RPM.

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John & Mary Burger
Eagle's Lair Woodshop
Hooper, UT

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

#236604 by lahola1 » Tue Jul 18, 2017 6:15 pm

yes, your right now that i think about it more.
thanks for straightening my thinking out before i get too far onto left field.

---

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

#236606 by JPG » Tue Jul 18, 2017 7:05 pm

At slow, the floating sheave(on the motor shaft) is positioned open placing the belt deep within the pulley resulting in the belt 'center' being away from the motor/quill shaft end of the headstock.

At that setting the control sheave is positioned closed placing the belt center again(still) away from the quill end of the headstock.

As the control sheave is opened(changing speed towards fast) the belt moves towards the quill end of the headstock.

The floating sheave will react by closing causing the belt there to also move towards the quill end of the headstock.

Thus the belt is always in alignment with both pulleys.

The slope of the interior sides of the pulley sheaves is the same on both pulleys.

The position of the motor pulley fixed sheave is essentially the same as the position of the idler pulley movable control sheave when the speed is set to fast.

The position of the motor pulley movable floating sheave is essentially the same as the position of the idler pulley fixed sheave when the speed is set to slow.

A lot to digest, but that is the way it is. ;)

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╔═══╗
╟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'/ 10E(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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Re: mark VII speeds up on its own above 1800 rpm

#236610 by lahola1 » Tue Jul 18, 2017 7:58 pm

yes, i see that now.
somehow i knew that my thinking was wrong; i knew a flawed design would not last since the '50's but my thought pattern couldn't get past the 2 opposite movable sheaves not equaling an offset belt.
thanks for clearification.

---

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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