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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16 years ago
Sears tractor keeps destroying pulleys
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16 years ago
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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16 years ago
So you are saying that this assembly is swaged together as one piece at the factory?
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16 years ago
No, my simple wild ass guess :)
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16 years ago
The end of the mandrel is shaped rather like an asterisk. It's maybe
3/4 - 1" in diameter and the blade has a matching hole that fits over it. Belt turns pully, pully turns mandrel, mandrel (star) turns blades.Nope. It isn't weak.
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16 years ago
Yeah. You bought a Crapsman.
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16 years ago
loose object it gets
gets wedged and stops
Then, no matter how tight the belt, the belt would slip. Not believable.
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16 years ago
Are there shear pins somewhere on the drivelines to the blades? If there are, I would be that the left one isn't a shear pin but rather an ordinary bolt or the shaft is frozen in place perhaps through corrosion.
The machine is meant for cutting grass....not punishment.
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16 years ago
re: mandrel is shaped rather like an asterisk...the blade has a matching hole
But the OP said the *pully* mates with the star shapped shaft, not the blade.
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16 years ago
________________
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.
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16 years ago
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
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16 years ago
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.