broken drive shaft

[Bocephus]

The belt drive is also wider than the chain , so when the belt is going threw its twisting motions (floating from side to side) it is also probably creating more load on the shafts , wanting to bend them . These belt pulleys do not have a grip on the shafts , a single bolt is used .

lets say something like this is "possible". dont you think when polaris was testing these sleds they would have had issues?

or did polaris cut the "testing" phase out of their production to save costs too lol....we need some smiles in this awful post!

 

[apex jeff]

Concerning belt tension (or lack of tension) and it's effect on the driveshaft....I would think the highest load placed on the shaft from the belt would be the added/changing tension under a high load, not from the initial tensioning of the belt....the side of the belt that is pulling will increase in tension while the other side will decrease tension or even go slack....with or without a tensioner...apply the brakes and the opposite side of the belt goes tight/slack, but this is no different than when using a chain. Chains see the the same thing and are MUCH more prone to breaking if they are too tight or too loose....rarely a problem when properly tensioned.

Yes the load forces to the belt, should be as you describe. But the initial tensioning of the belt is too tight causing extreme leveraging on the axle stub even at rest. The belt is so tight that even with sheared teeth the belt still moves the sled, as posted else where. The steel drive axle or a reinforced aluminum drive axle will stop the shaft issue,only to transfer the overtightened belt pressure to the bearings and the belt itself. I would like to see track dyno results, belt drive vs. chain drive. I have a feeling the excessive belt tension load forces,would cut horsepower just from rolling resistance on the upper and lower bearings. I wonder what the belt manufacturer specifies for tension?

 

[apex jeff]

lets say something like this is "possible". dont you think when polaris was testing these sleds they would have had issues?

or did polaris cut the "testing" phase out of their production to save costs too lol....we need some smiles in this awful post!

It sounds like Polaris may not have tested the problem drive axle? I don't remember them mentioning the light weight drive axle early on, only showing the belt drive. Many on here have stated the prototypes and demos used the '12 style steel shaft? Anyone have inside knowledge? Were the lightweight shafts subject to any real world testing,or were they merely torsionally engineer tested before install on production units??

 

[Bocephus]

It sounds like Polaris may not have tested the problem drive axle? I don't remember them mentioning the light weight drive axle early on, only showing the belt drive. Many on here have stated the prototypes and demos used the '12 style steel shaft? Anyone have inside knowledge? Were the lightweight shafts subject to any real world testing,or were they merely torsionally engineer tested before install on production units??

IF THAT IS THE CASE.....then my theory of engineers still holds true. at work we call them dreemgineers. they dream it, we build it, it doesnt work.

 

[LoudHandle]

Yes the load forces to the belt, should be as you describe. But the initial tensioning of the belt is too tight causing extreme leveraging on the axle stub even at rest. The belt is so tight that even with sheared teeth the belt still moves the sled, as posted else where. The steel drive axle or a reinforced aluminum drive axle will stop the shaft issue,only to transfer the overtightened belt pressure to the bearings and the belt itself. I would like to see track dyno results, belt drive vs. chain drive. I have a feeling the excessive belt tension load forces,would cut horsepower just from rolling resistance on the upper and lower bearings. I wonder what the belt manufacturer specifies for tension?

Actually Polaris undertensioned it if you crunch the numbers. I ran the numbers about the time the demo sleds were running the circuit. If you run it any looser, the centrifical tensioning takes place and it's forces are greater than if properly tensioned. If you want to learn more Google the Gates Carbon tech manual.

 

[apex jeff]

LoudHandle, could you direct me to the actual Polaris info? My google search only led me to bicycle belt drives?

Thanks

Jeff

 

[apex jeff]

Maybe this is how Polaris should have done the belt drive?


http://www.crazymtn.com/sifiso/pages/cmxds.html

 

[whoisthatguy]

IF THAT IS THE CASE.....then my theory of engineers still holds true. at work we call them dreemgineers. they dream it, we build it, it doesnt work.

It is pretty obvious to an engineer, that Polaris has no real engineers on staff. Engineers do not specify bonding agent to hold together a critical joint through which the entire power of the engine is transferred, when that bonding agent creeps 30% prior to failure, when that bonding agent is likely heated up from the belt drive, when that bonding agent is at least 1300% overstressed, and the assembly resembles a fence post cap shoved onto a hollow aluminum bed post. Blunders like that only come out of the Bosses office, because nobody dared to overrule him and nobody is being fired.

 

[jsandgren10]

It is pretty obvious to an engineer, that Polaris has no real engineers on staff. Engineers do not specify bonding agent to hold together a critical joint through which the entire power of the engine is transferred, when that bonding agent creeps 30% prior to failure, when that bonding agent is likely heated up from the belt drive, when that bonding agent is at least 1300% overstressed, and the assembly resembles a fence post cap shoved onto a hollow aluminum bed post. Blunders like that only come out of the Bosses office, because nobody dared to overrule him and nobody is being fired.

Why would you claim it is 1300% overstressed? Do you have actual numbers on the stress on that driveshaft or just a guess? Do you know what the Shear strength is on the Lords?

 

[Bocephus]

the only lords ill be putting on my cat is a little traveler of lord calvert in the chest pocket of my bibs

 

[mountainhorse]

It is pretty obvious to an engineer, that Polaris has no real engineers on staff. Engineers do not specify bonding agent to hold together a critical joint through which the entire power of the engine is transferred, when that bonding agent creeps 30% prior to failure, when that bonding agent is likely heated up from the belt drive, when that bonding agent is at least 1300% overstressed, and the assembly resembles a fence post cap shoved onto a hollow aluminum bed post. Blunders like that only come out of the Bosses office, because nobody dared to overrule him and nobody is being fired.

I wasn't going to chime in... rarely do for this kind of thing...
But you are SO off-base on this one it is not even worth the breath do defend the counter.

 

[mountainhorse]

Back to the discussion.

Looking carefully at this stub/cap... the adhesive channel around the hex of the cap does not have any residue of the adhesive in it. It simply did not bond to the steel of the cap.

Compared to this one where the entire channel is still filled with adhesive and what looks like flecs of aluminum.

Things that Make you go HMMMM?

.

 

[mountainhorse]

Things like this are what leads me to believe that there is a problem with the vendor to Polaris that is supplying these driveshafts

And

Not the driveshafts themselves.

There are some guys on Turbo sleds with 3" tracks that have ZERO problems... and some that didn't make it off the trailer.

I GUARANTEE that Polaris is taking this seriously, and like any other publicly traded company in our economy, has certain protocols to manage the issues.



.

 

[Hawkster]

Nice catch on the shafts MH , Two different subjects right there .

 

[Going West]

Things like this are what leads me to believe that there is a problem with the vendor to Polaris that is supplying these driveshafts

And

Not the driveshafts themselves.

There are some guys on Turbo sleds with 3" tracks that have ZERO problems... and some that didn't make it off the trailer.

I GUARANTEE that Polaris is taking this seriously, and like any other publicly traded company in our economy, has certain protocols to manage the issues.



.

Just got off the phone with my dealer. He said he just had a long talk with his dealer rep and from what he tells me there was a screw up with the company that was contracted to build the shafts. Basically the end piece was supposed to be much longer then it was. At some point this mistake was corrected but they were not notified of the issue and there is no way to track which shafts are good and which are not.

Claims that Polaris tested a batch of shafts from inventory and found about a 20% failure rate.

Sounds like its going to have to be a total mass recall.

How much of this is true I dont know, just what is was told.

 

[VOHK]

Drive Shaft Reinforcement

I contacted Kelsie several weeks ago regarding the driveshaft failues which we had been experiencing during early season testing of some engine packages we were working together on for our turbo applications. During the conversations that ensued, we agreed a common sense preventative measure should be immediately developed and made available to alleviate the mayhem caused by such failures. There is more than one way to achieve such a repair, however Kelsie’s part offers a non-invasive solution, and thus far we have not experienced a single failure with said part employed. Common sense and good judgement applied, it seems at the very least, cheap insurance…

 

[whoisthatguy]

Why would you claim it is 1300% overstressed? Do you have actual numbers on the stress on that driveshaft or just a guess? Do you know what the Shear strength is on the Lords?

Go back a day or two and the actual numbers are given on one of the driveshaft threads. Lords 406 failure shear strength is 1980 psi at 180 degrees F. Making allowances for full stress reversals every revolution and the normal factors of safety, and the allowable working stress came to about 80 psi in shear. Unfortunately, the 2500 psi tension failure strength was accompanied with 30% elongation. Which means that one possible failure condition is that the steel fence post cap can pull out of the aluminum, causing stress concentrations in the aluminum at the corners, before the Lords 406 actually fails completely. It looks like the glue is normally slipping about .035 inches under normal belt tension loads from engine torque alone. Which is a lot. Throw in an "at rest belt tension" and you can add it to those numbers. It would seem that the glue slips, then the cap gets pushed back in, then slips again, then gets pushed back in again, etc. , until the glue just decides that it has had enough of this BS and the bond fails completely on either the aluminum or the steel surface. It looks like bond failure on the aluminum surface.

 

[whoisthatguy]

Just got off the phone with my dealer. He said he just had a long talk with his dealer rep and from what he tells me there was a screw up with the company that was contracted to build the shafts. Basically the end piece was supposed to be much longer then it was. At some point this mistake was corrected but they were not notified of the issue and there is no way to track which shafts are good and which are not.

Claims that Polaris tested a batch of shafts from inventory and found about a 20% failure rate.

Sounds like its going to have to be a total mass recall.

How much of this is true I dont know, just what is was told.

Are we going to be made privy to the informaton as to exactly WHEN they tested those driveshafts from inventory? Before or after the sleds were shipped? The proof will be in the pudding. Are they going to wait for the driveshafts to fail, let owners bring in their issued driveshaft before it breaks or are they going to replace all of them on their dime? I cannot imagine that Polaris would take a chance on replacing the replacements. My guess is that they go to the Assault driveshafts and kiss this problem goodbye.

 

[Going West]

From what I could tell they just recently tested them, like just last day or two ago. A week ago they claimed there was no issue as there were very few claims but now the claims are starting to come in pretty fast so they grabbed a bunch of the shelf and stress tested them.

 

[apex jeff]

Go back a day or two and the actual numbers are given on one of the driveshaft threads. Lords 406 failure shear strength is 1980 psi at 180 degrees F. Making allowances for full stress reversals every revolution and the normal factors of safety, and the allowable working stress came to about 80 psi in shear. Unfortunately, the 2500 psi tension failure strength was accompanied with 30% elongation. Which means that one possible failure condition is that the steel fence post cap can pull out of the aluminum, causing stress concentrations in the aluminum at the corners, before the Lords 406 actually fails completely. It looks like the glue is normally slipping about .035 inches under normal belt tension loads from engine torque alone. Which is a lot. Throw in an "at rest belt tension" and you can add it to those numbers. It would seem that the glue slips, then the cap gets pushed back in, then slips again, then gets pushed back in again, etc. , until the glue just decides that it has had enough of this BS and the bond fails completely on either the aluminum or the steel surface. It looks like bond failure on the aluminum surface.

Thank you for that very well explained post. The better drive axle will most likely end this breakage issue, although only masking the extreme belt tension problem. As you have noted the "at rest belt tension" will place stress on related bearings and shafts. It seems like Polaris was almost there in this design,but stopped halfway. A simple tensioner/idler pulley would have allowed periodic belt adjustments for wear,and also given owners the ability to change gear ratios for track length and profile. Oh Yeah,the lack of a lower belt guard was a true over sight, if I can push the lower panel into the lower gear with my fingers,then imagine a 225 lb rider on a sidehill in heavy snow?