sequence of event before my belt blew

[akrevrider]

Fabricating a QD belt heat shield?

That is exactly what I found too. Under normal mountain riding the rotor has no affect on belt and pulley temp. Top of belt will continue to increase in temp after the sled stops.

A heat shield is in the works and will be installed before my next ride. I will continue to measure belt temp and post my results.

Can you please post up a pic of the heat shield & the specs/dimensions of the metal that you fab it out of? Thank you.

 

[AK IQ Pilot]

Can you please post up a pic of the heat shield & the specs/dimensions of the metal that you fab it out of? Thank you.

Be glad to. I don't get back to my sled until Friday but I plan to have something installed soon after.

I'm looking at pictures of the belt, drive and brake now trying to come up with a solid design.

Probably going to be very simple.

 

[Ephratafarmer]

I have already put a heat shield between the exhaust and the Q belt, of both my sleds. I just used plastic like from the snow flap, and covered it with heat shield reflect tape. So far working fine, I'll get some temp readings during next ride or two. Tied it in place with strap ties, so far so good. I also heard that Fire & Ice was making a carbon fiber one.

 

[akrevrider]

I have already put a heat shield between the exhaust and the Q belt, of both my sleds. I just used plastic like from the snow flap, and covered it with heat shield reflect tape. So far working fine, I'll get some temp readings during next ride or two. Tied it in place with strap ties, so far so good. I also heard that Fire & Ice was making a carbon fiber one.

Excellent idea! pics please..

 

[LoudHandle]

Anybody checked their upper bearing? They may have installed a cheaper one on the production sleds than the demos, or maybe when you are loading it heavily the jack is flexing and misaligning the races generating the heat from the shaft out, as seems to be the indication from AK IQ Pilot's heat study?

May need a quality bearing, a stiffer jack shaft, or add an outboard bearing?

 

[whoisthatguy]

The most obvious top gear heat generator is the friction of the cogs sliding into the gear teeth, on the back side of the top gear. The same friction should be generated on the bottom gear, from the cog sliding out of the bottom gear teeth. But since the bottom gear is larger, it has more volume to store the heat and more surface area to shed the heat.

The second most obvious heat generator, comes from first assuming the cogs heat up from this sliding friction. Where those hot cogs go immediately after they heat up, decides what is going to happen to that heat. On the bottom gear, the hot cogs immediately become airborne so the air can absorb some of that heat. Then the hot cogs come into contact with the top gear to apply the remainder of the bottom gear generated heat to the top gear. But on the top gear, the cogs that became heated from sliding into the top gear, are immediately in contact with the top gear teeth and push that extra heat immediately into the top gear.

So there are three or four reasons why the top gear is a lot hotter than the bottom gear.

 

[geo]

WITG; I think your wrong on your heat transfer theory. But the bottom pulley will shed heat better (I mean "duh" it's got holes lol).

I've checked mine many times (to say the least). At least once a ride since new. Never have I found the belt warmer than the pulleys. So, your theory is actually IMO exactly backwards. I think if anything (but the belt is not a good conductor of heat anyway, you know that) the belt cools the pulleys lol.
What have you found when checking yours?

IMO, the majority of heat generated at the top pulley is from side load on that bearing. The rest is from loose parts flexing around.

 

[whoisthatguy]

WITG; I think your wrong on your heat transfer theory. But the bottom pulley will shed heat better (I mean "duh" it's got holes lol).

I've checked mine many times (to say the least). At least once a ride since new. Never have I found the belt warmer than the pulleys. So, your theory is actually IMO exactly backwards. I think if anything (but the belt is not a good conductor of heat anyway, you know that) the belt cools the pulleys lol.
What have you found when checking yours?

IMO, the majority of heat generated at the top pulley is from side load on that bearing. The rest is from loose parts flexing around.

Then using your theory, the top gear bearing would then be even hotter than the top gear. Since the top bearing is sealed, the plastic that contains the grease, should be close to melting.

The belt does not have to be a good conductor of heat. The heat could transfer into the cogs with friction and then transfer right back out with contact to the top gear. The belt is not in the heat transfer loop. Eh?

 

[LoudHandle]

Then using your theory, the top gear bearing would then be even hotter than the top gear. Since the top bearing is sealed, the plastic that contains the grease, should be close to melting.
………………………..

If you have read AK IQ Rider's post as far as what readings he has taken on the QD, you would know that the bulk of the heat in the upper sprocket is concentrated in the hub and diminishes in intensity as it radiates outward towards the teeth. Which led myself and others to question the bearing, there is also a pretty compelling YouTube video with no upper bearing left in someones QD. A good 1/4" of slop is the result, hence my comment about inferior or inadequate upper bearing quality or Jackshaft flex inducing the heat load.

 

[whoisthatguy]

A chaincase upper bearing would constantly be sprayed with cool oil, even though it is a sealed bearing.

 

[geo]

The belt is not in the heat transfer loop. The belt is not in the heat transfer loop.

I'm going to chant that to my primary and secondary during todays ride.

 

[m8matt]

I blew another belt this weekend...only took 50 miles. Anyway the next day we brought a heat gun. It was reading 156f on the top pulley. That doesn't strike me as belt damaging heat. I caught the belt after a days ride in deep deep pow over the hood. Working the sled hard all day. Came back to the trailer and inspected it. Found one cog came off and the three behind started to shear of as well. It almost seem like the material the cog portion is made of is to brittle . Does that make sense? That tells me that maybe a new belt should be in the works that can handle the load better and our problems will be solved. High hopes I think. At this rate I'm gonna spend $1400 in belts this year! hahaha

 

[AK IQ Pilot]

I blew another belt this weekend...only took 50 miles. Anyway the next day we brought a heat gun. It was reading 136f on the top pulley. That doesn't strike me as belt damaging heat. I caught the belt after a days ride in deep deep pow over the hood. Working the sled hard all day. Came back to the trailer and inspected it. Found one cog came off and the three behind started to shear of as well. It almost seem like the material the cog portion is made of is to brittle . Does that make sense? That tells me that maybe a new belt should be in the works that can handle the load better and our problems will be solved. High hopes I think. At this rate I'm gonna spend $1400 in belts this year! hahaha

On the bold, It seems this way to me as well. Kind of like the outer circumference of the belt is very stiff and the teeth are soft and not adequately bonded to the belt in the manufacturing process.


When you checked upper pulley temp at only 135f had you been working the sled really hard in the deep snow. That is not very hot compared to what i have seen.

 

[m8matt]

When I checked it was after a few little draws through the trees and ripping through meadows. I wanted to check it as if I was just boondocking around. Not one long pull after another. That wouldn't give me an accurate reading as I usually take little breaks between long climbs. I'm almost convinced this problem can be fixed with a quality belt.

Sorry one more thing. The top pulley was 156f. Not 136. Still not to bad I thk.

 

[m8matt]

I just heard from my dealer today and my belt was covered under warranty. No issue. He even gave me a new belt at no cost until he found out if it was covered or not. I officially have faith in Polaris! They just kept me as a every two year new sled customer.