QD Belt Temps Field Testing

[mountainhorse]

From the Gates Carbon manual regarding idlers. (Pg. 99)

Ideal is on the inside of the belt (toothed side) but if minimum idler diameters are taken into account, they can be used effectively as proven in the C3 Ski Doo drives last season.

12. Use of Idlers
Use of idlers should be restricted to those cases in which they are functionally
necessary. Idlers are often used as a means of applying tension
when the center distance is not adjustable.
Idlers should be located on the slack side span of the belt drive. General
size recommendations are listed for inside grooved, inside flat, and backside
idlers. In some cases, such as high capacity drives utilizing large
sprockets, idlers as large as the smallest loaded sprocket in the system
may be more appropriate.

Idler Size Recommendations
Outside or backside idlers should be flat and uncrowned; flanges may or
may not be necessary. Drives with flat inside idlers should be tested, as
noise and belt wear may occur.
Idler arc of contact should be held to a minimum. All idlers should be rigidly
mounted in place to minimize movement or deflection during drive startup
and operation.

 

[mountainhorse]

If the Tension Ratio should be 8:1 - 10:1 generally for a power transmission drive according to the EPI sheet... which I've used in the past on belt drive design for boat drives...

Figure about 100 ft lbs of torqe max at sea level for stock sled (1200 inch lbs).. Pitch radius of the upper is 1.515 approx (22 tooth x 11mm pitch converted to inches)... about 792 lbs of driving force tension on the tight side of the belt.

The range of 10:1 to 8:1 would be 79.2 to 99 lbs of preload tension on the loose side for proper tension.... with 90 lbs of preload if you take the middle of that scale.

Another important point that the Gates manual points out that the correct tension (preload) on a belt is different for one that is broken in and a used belt... how can you adjust to have that proper tension when the belts loosen up from the teeth wearing/bedding-in ????

Are the belts made to be too tight when new....placing a lot of load on the bearings and shafts??? Or, are they too loose when bedded-in and prone to ratcheting??

With a fixed center design... one scenario has to be true... Given the break-in schedule and recommend light-load use during the break-in period, I would think the first of these two scenarios.




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[mickyd32]

Wow. First off thanks for all the technical data that I just don't have the time to research myself. I'm very interested to see how this thread plays out.


I can very quickly test the exhaust temperature theories regarding heat displacement to the drive system

Here's what I've envisioned for a test

Sleds will be my 13 155 with SLP exhaust for testing the ceramic coated system
Buddies stock 13 155 to test stock can heat
Ill also have my dads 12 there with an MBRP can that we will be able to quickly swap to the stock sled for a test of an aftermarket can

Now what I'm not yet sure is best locations for collecting my temps,
Any idreas on this? I could use the same locations in AK'S original test data. Or I could modify. Thoughts?

 

[geo]

Great info. Love reading engineers perfect world scenarios but Murphy`s Law says even a perect set-up will fail for someone. Then you have to think like a farmer and look to simpler things.
There doesn`t seem to be an epidemic of belt failures to me. That could be a selfish point of view (`cause I`m still good) but there seemed to be a few with multiple failures (something different there). IMO they are the ones that need new sprockets or something.
The odd single failure may be as simple as a bad belt (or just riding it like you stole it from min. one). My belt was not cut or molded square. I have a high spot (wear mark on the side for about an inch) with a corresponding high spot, 180 degrees away, on the other side. Those wear marks tell me that the little wobble on the slack side I see on the stand is from the belt not sprockets. My belt will walk from side to side (about a 1/16") at slow rotations on the stand. It also shows quite a bit of scrub-wear on the teeth.
But it still lives. Close to 850 miles now.

I find the picture of the belt above, with 150 miles, very interesting. How can the break-in "wax" as it was described to us, still be there. My belt continued to throw that stuff around for 150 miles or more. When it was finally done and staying clean I felt it was broken in. But for another 150 miles or so I noticed the tension (cold) loosening up.
I took my time warming it up, cooled it when I stopped and payed attention to throttle on landings for probably over 300 miles cause it didn't "feel" right yet. Since that point in time (when the track rolled easy on the stand and the sled coasted easy on a trail) I have just rode it with the handful of snow habit when stopped.

Did it take 300 miles plus to break-in my belt? Is that because it was not built right from day one? Are ther more like mine out there?
I sure would like to see my belt look like the one in the pic after 150 miles.

I hear Poo has be putting on new belts for some. Unusual for them lol. Maybe they know something maybe they are just being nice.

 

[AK IQ Pilot]

Ak IQ Pilot....


What numbers are you using in your calculations for proper tension values?

How are you accurately measuring deflection?
1/64 of an inch or a couple of lbs here or there makes a big difference.



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No offense at all MH I really appreciate the in depth feedback.

I didn't actually measure the drive belt tension on any sled. I was just going by experience. I have owned and operated a 5 second Blown Alcohol dragster for 20 years. I have used Gates GT belts, both 8 and 14mm, for the same length of time. I think it's safe to say I know how tight a synchronous belt should be. That being said I didn't measure the belt tension with any type of tool. I pushed the coast side of the belt in and out and I twisted the belt slightly several times and to me the the belt deflection (tension) seems just about perfect.

Obviously this drive system and a BAD are two completely different animals. It just feels to me like there is no need for an idler.

So what do you make of the heat issue and the potential for heat to be a contributing factor in the belt failures? It seems like these belts are being exposed to lots of heat on and around the top sprocket.

We will continue to evaluate the issue and communicate our findings.

 

[mickyd32]

I will be doing my testing hopefully Saturday afternoon. It's the first chance I will have to ride

 

[mountainhorse]

AK IQ...

Your comment on roots blower belts had looking a bit.. and found this interesting info on 11mm pitch belts

WOW... 800 hp just to drive the blower on a Top fuel car!

From here CLICK

NHRA supercharger drives are notoriously hard for belts to survive on. The application is extremely demanding, and requires a unique belt to perform as needed. The two top classes that use superchargers are Top Fuel and Funny Car. In a typical 1000 foot race, a Top Fuel car will have elapsed times in the 3.8 to 3.9 second range.


HP requirements to drive the supercharger are typically quoted in the 800 HP to 1000 HP range. This is with the driving crankshaft being around 8000 - 9000 RPM.

If it was just a question of handling 800 to 1000 HP, the drive (while large), wouldn't be that difficult to design to work properly. However, the system has a lot of unique load situations that really stress the belt. The torque fluctuations from the engine resemble barely controlled explosions. The speeds are high. The heavy loads make it likely that shafts will flex and belts will track to the outside flange edge. During tire spin conditions, drivers have to "pedal" the car. This is a method of getting off and back on the throttle very rapidly in an attempt to get the tires hooked up and stop the tire spin. When this happens, the driving RPM drops nearly instantly from 8000+ RPM to a couple of thousand RPM. The inertia of the supercharger takes over at that point and it tries to become the driving shaft. This creates havoc in the belt, as the tight and slack side spans in the system are reversed, creating high shock and compressive loads in the tensile cord. Add in the virtually instantaneous load application when the cars leave the starting line, and you have a very difficult, very damaging application.

An 11mm pitch Poly Chain GT belt was specifically designed for this application. The 11mm pitch gives more speed ratio flexibility than the previous 14mm pitch belts, and 11mm belts have more strength and ratchet resistance than 8mm pitch belts. A specially designed tensile cord is also used to handle the loading situations described above.

 

[mountainhorse]

Heat thing... belts and sprockets not meshing properly or the belts not having proper tension and trying to "climb" the pulley.... Draggging brakes.... pulley run-out... out of spec/tolerance parts???

The exhaust radiated heat concept...not so much for me as that is one of the constants in design on the sleds and most people are not having problems. But hey.. if one sled is running "fat" and making huge heat...Hmmm?

 

[mickyd32]

Heat thing... belts and sprockets not meshing properly or the belts not having proper tension and trying to "climb" the pulley.... Draggging brakes.... pulley run-out... out of spec/tolerance parts???

The exhaust radiated heat concept...not so much for me as that is one of the constants in design on the sleds and most people are not having problems. But hey.. if one sled is running "fat" and making huge heat...Hmmm?

I agree with you MH, but its one aspect that I actually have the means of testing, and thus can actually make a contribution to this thread with

 

[geo]

So has anyone confirmed if high temps cause the plastic-rubber compound to degrade?

185F, is that the point of possible delamb or a change in compound stability?
Is heat even an issue for these belts (before we get into building heat shields and stuff lol)?

I may have found my heat source yesterday (nothing to do with the exhaust). I'll post what I found with my sled in the jackshaft bearing thread.

 

[LoudHandle]

Upper bearing?

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]

Perhaps if cooling fins were bolted to the top sprocket, to help shed the heat, belt temps could be signficantly reduced. Something like the old Roman Chariot spokes that ripped up your competitor's wheels, except with a cap plate on it to make it a little more user friendly, and then an OSHA approved cover to keep your scarf from getting caught.

 

[mountainhorse]

I keep getting back to the huge majority of people that are not having problems with their 2013 Pro RMK's... Stock, Mod and Turbo.

NOT to say that there are many that are having problems... Because there ARE many that are having seriously frustrating problems.

To me... seems like a production, QC and mfg-tolerances issue with those having problems.

Driveshaft needs to be a more solid unit.

Sprockets and shaft need to be checked for minimal run-out by the factory before shipping.. or by the supplier as a matched unit.

Brake dragging needs to be ELIMINATED by the factory on these sleds.

Belts need to be the best quality available... and be less expensive for consumers to buy... $190 is pretty steep for this part... VERY steep in fact.

Those that are having problems.. and there are many of them... but NOT the majority, IMO, have something "out of whack" on their sleds.

In a ideal world, I'd like to see a better, more accurately built/durable driveshaft.
Higher quality bearings, Machined (not cast) sprockets, a tensioner to permit adjustment for optimal tension and variation in production throughout the wear-life of the belt.. ie... too tight when new..or too loose when broken-in... on some sleds.

I still believe that urethane top sprockets would be a great idea and make the system more resistant to shock loads and minor misalignment issues which even a perfect sled can experience in use, under heavy load.

I know some of the engineers at Roseau... and I KNOW their dedication to making a great product... but in this day and age... the "bean counters" often rule the decisions and don't allow the engineers and production to be all they can be.


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[mountainhorse]

geo:
185F, is that the point of possible delamb or a change in compound stability?

One way to find out... PLEASE... someone take a ruined belt...put it in boiling water, at less than 7500 feet (198 degrees F), and see if there is any major softening of the belt.. test with your fingers or a fork!... Do a before and after test at room temp and boiling water.




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[winter brew]

Just my thoughts....
Is the C-C changing under load? With that lower shaft insert having only 1/2"-ish of penetration into aluminum, I don't see that as a very "stable" foundation for the lower pulley...even going through the bearing, the whole side of the bulkhead could flex just slightly...you can push it in and out with your hand with the shaft out . Doesn't seem like it would take much movement in this stackup of what appear to be "under designed" parts (based on the failures of the shaft) to allow that belt to have excessive slack under the right conditions.....that's why I mentioned a tensioner. It might be properly tensioned at rest, but does that change at any point during operation? I have installed a few different belts now, and all went on with a different amount of tension and all went on by hand with no tools. None of those have failed...knock on wood.

 

[mickyd32]

Just my thoughts....
Is the C-C changing under load? With that lower shaft insert having only 1/2"-ish of penetration into aluminum, I don't see that as a very "stable" foundation for the lower pulley...even going through the bearing, the whole side of the bulkhead could flex just slightly...you can push it in and out with your hand with the shaft out . Doesn't seem like it would take much movement in this stackup of what appear to be "under designed" parts (based on the failures of the shaft) to allow that belt to have excessive slack under the right conditions.....that's why I mentioned a tensioner. It might be properly tensioned at rest, but does that change at any point during operation? I have installed a few different belts now, and all went on with a different amount of tension and all went on by hand with no tools. None of those have failed...knock on wood.

Just looking for some clarification here Winter. When you say by hand, I'm assuming you mean with the alignment tools and not just sliding on unassisted?

When mine failed at 700 miles I took it to the dealer to be replaced. I assisted their best tech (they were flooded with other work and didn't have the time to even work on mine but did me a favour since they like me), just so I could see how the process was supposed to go.

At that point, the dealer had only swapped out one QD belt, this was on a unit where the shaft had failed in under 10 miles. As we changed the belt, the tech and I exchanged all sorts of conversation regarding the pros. We were stuck on the belts for a while, after some fighting with mine as it was very snug, the tech says "well this is weird, I never had to use the tools last time to do this, I was able to do it by hand"

Out come the tools off the shelf and within 5 the sled is back together. Seeing this first hand I know there are variances, and apparently fairly large ones somewhere.

This brings me back to my question. Completely unassisted or with the tools? And what is going to be better for longevity?

 

[winter brew]

Unassisted except for my home-grown zip tie method to hold the belt in the approximate shape....then slide the upper pulley on....not loose, but not tight, able to do it with my wimpy hands, no bullets.

 

[mickyd32]

Unassisted except for my home-grown zip tie method to hold the belt in the approximate shape....then slide the upper pulley on....not loose, but not tight, able to do it with my wimpy hands, no bullets.

Ah ok. We were using 2 sets of hands to do it and it was just too crowded and awkward. This makes sense

 

[mountainhorse]

I've had three that I could slip on by hand... 2 that required the "bullets"

So there IS some variance or tollerance stacking IMO.

For $45... the Aluminum "bullet" tools from Happy-Face products are a must have to keep on your sled. In the field.. you dont want to be futzing around with the gymnastics to get the belt on. Their design is better, cheaper and lighter than the SPX/Polaris tools.... and much easier to order.


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[winter brew]

So many threads, but I'll ask it here.....has there been any belt failures when using the old steel driveshaft or one of the Fastrax hex steel shafts?