driveshaft runout?

Melfjord · Feb 17, 2013

So I guess I got one of the sleds that eats belt's. My second belt after 460 miles. Both of them lost 1/3 of the teeth. So I tried to measure the runout of the driveshaft, and got 0.007 (0.2mm). Anyone know spec for the driveshaft?

This was measured ontop of the teeth on the bottom sprocket without the drivebelt on.

I've noticed that the belt is alot looser after a couples miles compared to a new installed belt. So i guess the runout is one of the reason's why my belts is failing.

winter brew · Feb 17, 2013

I would be curious to know how much the shaft is deflecting under a load....both shafts. A high speed camera on a track dyno would be about the only way to see this.
In other words, is your .007 turning into something much bigger under a load?
It will be interesting to see what Polaris does for a fix next year.

geo · Feb 18, 2013

If you think about it a shaft stub end untrue would look like a wobble on the edge of the lower pulley and should be visible on the trackstand (.003" at the shaft carried across the radius length would be fairly obvious).

Measuring .007" at the top of the teeth would be hard to do accurately IMO but quite possible with a casting.

A better way (cause your trying to prove a tight spot or loose spot) would be to measure belt deflection. If you index the lower pulley and rotate it 90 then again and again til you do a full rotation you should be able to find a position of the lower pulley that points to a spot in the rotation that is consistantly tight or loose every time the pulley passes that index point.
If you have a tight spot that doesn't correspond to the pulley rotation after rotation you may have a tight spot on the belt (that's what I found with my belt). But I know from mine, that will wear in.

Brew pointed out high heat in turbos and belt failures there. Have you ever checked the temp of your top pulley when you stop?

Melfjord · Feb 18, 2013

I've checked the top pully once after a hard pull in the deep snow, and it was to hot to touch. I guess the belt strech if the driveshaft got runout. And that makes the belt to climb the top sprocket.. if i got it right. I realy dont think the heat from the exhaust will kill the belt since cmx and c3 got belt uprades that doesnt fail. The fact that there is sleds out there that still runs on their first belt, gives me a feeling that the driveshaft is the problem. Ofc added snow on bottom and heat from exhaust does not make it easier for the belt.

I taped the bottom sprocket when i measured it so the pin didnt fall into the "grooves". so i could turn the driveshaft with a wrench.

byeatts · Feb 18, 2013

winter brew said:
I would be curious to know how much the shaft is deflecting under a load....both shafts. A high speed camera on a track dyno would be about the only way to see this.
In other words, is your .007 turning into something much bigger under a load?
It will be interesting to see what Polaris does for a fix next year.

Yes that deflection is likely growing under load. I would be looking for a steel shaft and call it it done,,, The clamp will be worked looser and looser as time goes by until failure.

mountainhorse · Aug 30, 2014

TTT...

This seems to be a 2013 issue more than the newer models... but still... check it out on your machine for a good season of use.

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driveshaft runout?

Melfjord

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winter brew

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geo

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Melfjord

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byeatts

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mountainhorse

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