Sears tractor keeps destroying pulleys

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DerbyDad03 wrote:

________________
So he did. And it is. I misread. Actually, there is a star at both ends of the mandrel shaft...a beefy one for the blade, another smaller for the pulley.
Just going by memory - I'm not going to go drop my deck to look :) - there are two pulleys on the left...one for idler, another for the blade drive belt.
On my deck there is also a large washer *under* both the left and right blade pulleys. It's location there is kinda counter-intuitive as usually washers go between the nut and whatever is being held on but the reason for it being under the pulley is to elevate the pulley so it's hub is completely on the shaft's "star". (IIRC correctly, the washer also creates sort of a broader base for the pulley to resist wobble.) If the washer is missing (or on top) the pulley's hub only partially engages the drive on the shaft. Which means it would strip more easily.
--

dadiOH
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Normally, they use shear pins or keys on shafts that are gear/chain/direct drive, so if you have an abrupt stoppage, you don't damage the engine or transmission or gears. With belt driven components, they tend to rely on belt slip for protection.
My Cub Cadet, for example, has a shear pin on the driveshaft between the engine and the (hydraulic) transmission.
In contrast, the Cadet's attached equipment (mower deck, snow blower etc) are belt driven, and have (at least) two slip points: the first one being one or more belts (there are two belts between the PTO pulley and side blades). The second being the PTO engagement clutch.
They don't necessarily slip much - if I run the blower into a snowbank that's too much for the 12HP engine, the engine _will_ stall. However, it takes several revolutions with loud squealing from the belts. At least it's not instantaneously - which could do damage.
Cadets are built _tough_. This thing is from the early 70's, and I use it almost like a bush hog at times. It had the bearing on the main cutter blade wear out, the two idler pulleys that feed the mower deck have destroyed their bearings twice each, and I've had to replace the main mower belt several times (this belt is rather fussy. Standard V belts aren't deep enough, and I screwed up once and got too big a pulley which caused the belt to rub). The mower deck has had to be unbent once. Aside from that...
On the Cadet, the side blades (it has three) are run by a long belt (never replaced that I know of) from the center pulley, and tensioned with a idler pulley on a spring.
In the OP's case, I'd:
1) Make sure that the deck isn't bent/distorted especially on the side of the blade that destroys its spindles. It could be getting restricted at the blade tip and very subject to jamming, or perhaps the spindle mount is bent out of plane with the others.
2) See if he can slacken the belt a bit.
3) If it has a slippable engagement clutch, see about backing it off slightly. Only slightly, otherwise he'll burn it out. You only want it to slip on a stall.
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
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On Fri, 30 Nov 2007 18:55:05 -0000, snipped-for-privacy@nortelnetworks.com (Chris Lewis) wrote:

(multi-posted)
Agree about the belt. Over tightened belts will cause faster wear on bearings, bushings, etc. I've seen this happen on alternators and older car generators.
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John wrote:

Can't say for sure but it sorta sounds like there is vertical wobble at the star (shouldn't be). One thing sure, hitting a stick should *NOT* cause what is happening...I regularly hit oak roots and fallen branches - branches up to 2" in diameter - with no damage other than dulling the blade which is always dull anyway. I don't mow, I thresh :)
I've never even had debris stop the mower unless it is physically big enough and oriented so it gets kicked up and wedged in the blade housing. In that case, the blade drive belt slips. And smokes if I don't shut it off. You sure your belt isn't too tight and that you are using the correct length (BTW, belts are a lot cheaper at auto stores). No wobble in the pulleys? All the bearings good?
--

dadiOH
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wrote:

Is this a spline shaft?

Steel is not just steel. Properly heat treating the correct type of steel makes a huge difference in the longevity of a splined connection.
Are your replacement parts aftermarket parts? Did Sears change their supplier of parts? Can you swap left from right to troubleshoot this possibility.
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On Fri, 30 Nov 2007 15:20:29 -0500, snipped-for-privacy@mucks.net wrote:

Isn't a pulley pressed onto these spline (star) shafts?
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I don't know how these pulleys are attached. It sounds like either a sliding spline connection or a press fit spline like you say? Either way the metallurgy involved may be the problem.
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On Fri, 30 Nov 2007 16:36:16 -0500, snipped-for-privacy@mucks.net wrote:

Failure at the shaft/pressed pulley...SWAG.
Before replacing several and waiting to solve the problem - I would spot weld the first failure (if, applicable).
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So you are saying that this assembly is swaged together as one piece at the factory?
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On Fri, 30 Nov 2007 18:06:38 -0500, snipped-for-privacy@mucks.net wrote:

No, my simple wild ass guess :)
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John wrote:

Yeah. You bought a Crapsman.
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id be sure your pinching the pully good when tightening the bolt, if pully isnt getting pinched it will wear out inside.. maybe locktight it and tourqe it.. then recheck after you mow each time to see if its loosening. i had a pully on a deck kept comming loose,forget now what tractor, i got a grade 8 bolt,red locktighted it and socked it down tighter than it should be..fixed it. lucas
http://www.minibite.com/america/malone.htm
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