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round one , square one
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Discussion Starter · #1 ·
Doing some routing maintenance and found that both the hydraulic pump belts had decided to flip themselves. I'm reading a variety of reasons that this could of happened, IE..too loose/tight/ pulley pitted/worn, bad cord, belt wrong size....................
Has anyone had this happen to them and care to share the why's and remedies??

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U1000Ag
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Pump pulley in good condition ? Reason I ask is that mine had a huge chunk missing - conceivably something like that could upset the belt dynamics - other than that, no idea..
 

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U1450L DOKA
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Just a guess - since they both flipped, and the pump has a double pulley on it, I wonder if the pump is out of alignment, relative to the crank pulleys.
A side load, with one side of the pump pulleys
‘Pushing’ on the side of the belts might induce them to ride up and roll over. Worn or loose belts would probably make that more likely.
I’d put a straight edge on the face of the pump pulley and eyeball it against the crank pulley grooves, to see if you can verify if they are parallel.
 

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85' U1300L Holset Turbo VA A/C, 66' Propane 404.1 rock mog, 1975 416 Doka, G500, Volvo C303
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I’m going with out of alignment. You can use a cheap bullet laser or similar to check alignment.
 

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1988 U1300L RW1 Working gears Dual Tanks AC Rigged for Camping Plus: 91 F250 HD 4x4
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Doing some routing maintenance and found that both the hydraulic pump belts had decided to flip themselves. I'm reading a variety of reasons that this could of happened, IE..too loose/tight/ pulley pitted/worn, bad cord, belt wrong size....................
Has anyone had this happen to them and care to share the why's and remedies??
First question: is the hydraulic pump putting out proper/ usable flow?

Second question: Did the answer to above change at any time during your possession of the truck?

Third question: Do you see any whip/ wobble or erratic behavior of the belts while operating, even at idle/ no hydraulic load?

Fourth question: Have you examined the profile of the side of the belts that are currently facing into the pulley grooves?

Reason for questions: Double sided vee belts are made, for serpentine applications, although I have not been able to find any that are segmented on one or both sides.

For example: Gates Double-Sided V-Belts for Sale | VBeltSupply.com

Final thought: If it ain't broke, don't fix it.

Lee
 

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round one , square one
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Discussion Starter · #6 ·
Thanks All (knock on wood)
Seems it was out of alignment...I was able to put a straightedge on the balancer and measure to the H. pulley...40mm to one side 44 to the other... With the wife's help I snugged up the hydraulic mount(was a few threads short of Gutentight ..I will keep an eye on it for now but when I flipped the v-belts the first time they flopped over in seconds, this time around they did not go anywhere!
Does anyone know the exact belt length for ordering new... Belt on there now is 13 x 950, I manual says 13 x 975, another 12.5 x 925 ?? OM366??
 

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1250v
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We have this happen on our crushers and screener regularly. It's normally as the belts are getting worn, and what causes it is something gets into the pulley. In our case it's almost always a rock that gets someplace it isn't supposed to. Sometimes it will throw a belt off the pulley or into one of the other belts and make a huge mess. Other times we will end up with 4 or 5 out of 8 flipped on one end. They normally run many more hours like that, but once most of them have flipped it's time for a new set. In our experience once they flip they will not stay the right way no matter how perfect everything is in the pulleys or alignment.

This does seem more common on worn pulleys than new, we change the drive pulleys every other set of belts, on the crushers it's cheap insurance, the pulley cost $400 and the belts $2000.

Ben

In the case if the unimog, if the pulley looks good, I would put 2 new belts on it, and I expect it will go for years with no issue.

Another option that reduces this a great deal is to get a double banded belt. 2 vbelts with an outer band holding them together. It's normally the same part number as the single belt with a /2 after it.
 

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In looking at my spares, purchased from Scott (I believe),
I have a 13 X 950 labeled for the Hydraulic Pump.
OM366A.



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