mark VII speeds up on its own above 1800 rpm

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lahola1
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Location: Sedona,AZ

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

Post by lahola1 »

thanks for clarification.
i put my original belt back on,(od approx 30.25" w .530" thick.300").
tach now says 870rpm @700 setting; 2730rpm@2400 setting. belt ia approx 1/8" from top od of idler sheave is fully open; spring compressed max AND motor belt is slightly rubbing on frame for the worm gear that moves headstock back and forth. Sooo, I can only move the fan sheave closer to the motor.
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 »

by the way; back to the original reason for this thread, I put in 'the fix' similar to yours, JPG ( drilled speed shaft and tapped for an 8-32 screw, made some washers and tightened speed control down. now the speed control works good.
thanks for your insight and engineering.
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
Gold Member
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 »

i meant to say that the motor sheave is fully open and the spring is fully compressed.
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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Location: Lexington, Ky (WILDCAT territory)

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

Post by JPG »

Relocating the fan sheave closer to the motor will shift the speeds downward.

I feel it is 'risky' to not have hard control of the fan sheave/motor clearance. Risky in that it is subject to moving due to vibration.

IIWY, I would reposition the fan sheave 1/16" from the motor.

I believe that will also move the belt away from the headstock positioning parts.

Do realize with out an 'original' belt, the speed range will be 'different'.

The dial markings are an estimate at best.
╔═══╗
╟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
Gold Member
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 »

i moved the fan sheave closer to the motor (i guestimate it to be .090-.100" from motor cover.
tach now say 838rpm @ 700 setting; motor belt is now slightly away from worm gear frame and spring is not quite fully compressed on the moving motor sheave.
it's noisier now. i think the fan sheave is rubbing on the tin cover over the motor. i'll have to see if i can lock that down somehow.
btw, JPG, i think i read somewhere that you purchased an OEM motor belt.
did you install it? did you get rpm readings closer? what are the dimensions of the OEM belt?
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
User avatar
JPG
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Joined: Wed Dec 10, 2008 7:42 pm
Location: Lexington, Ky (WILDCAT territory)

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

Post by JPG »

I have not yet installed the oem belt.

I do not have much faith re measuring belt lengths - however the M VII belt (507490) is 3.5" longer than a Mark V belt (504193).

Since 26.5 is the 'nominal' agreed upon length of a Mark V belt, 30" seems to be what a Mark VII needs.

IIRC, I added the idler pulley stuff to effectively make the 30.5" belt act like a slightly shorter belt(also due to narrowness of belt).
╔═══╗
╟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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