Axle Snapped in Half

[berge75]

I always remove the drive shaft and machine the plastic drivers,as they tend to run out quite a bit. Runout and vibration, no doubt, would have an impact on the life of the shaft. So far, I have 7000mi. on this drive,and keeping my fingers crossed.
I found it a little strange that Mountain claimed the sxrs where knowen for breakage,I have 15000 hard miles on my 2000 sxr700 with orig. drive in it.

 

[ReX]

Is it at all possible that the slow growth fatigue was initiated by a slight runout, maybe caused by a one time impact to a not hard enough to remain straight shaft?

No. The shafts I've seen are very straight close to when they fail (within manufacturing tolerances).

I actually changed the track on one about a week before it failed. I even spun the drive shaft to check to make sure it was straight and it was (within a few thou anyway). We were then riding only on perfectly groomed trails in Northen Quebec when it failed a few days later.

It is simply classic fatigue failure that does these in. They are obviously run with a high enough cyclic stress that is above the "infinite life" stress limit. When you cycle moderately high loads long enough, most parts will eventually develop cracks that slowly propegate through the part.

A lot of it is related to how the sled was ridden. If you take it easy I'm sure the shafts would last forever. On the other hand, if you are always at WOT going from low to high speed while bouncing off stutter bumps and then slamming on the brakes over and over the shafts will fail relatively quickly. Should they be failing at all? That is up for debate (if it was a car, train, plane, etc. the answer would clearly be no - I don't think these should be failing either; especially since I'm riding one...).

The guys who are seeing the failures (including my buddies) are likely running their sleds very hard and doing it for well over 5000 miles.

Have a look at this web page and have a look at the S-N curve plot to get a better understand on how fatigue failure works.

http://en.wikipedia.org/wiki/Fatigue_%28material%29

Every material has a different S-N curve. In order for something to last forever that is made out of the material in that plot, it needs to see a maximum stress of less than roughly 40MPa. On the other hand, it will still handle a single application of 320MPa without bending or breaking suddenly. Our drive shafts are running somewhere in the middle of this graph.

Basically materials behaving per that graph will:

- a stress of below 40MPa -> last forever
- double that load to 80MPa -> last for 2,000,000 cycles
- double that load to 160MPa -> last for 10,000 cycles
- increase that again to 250MPa -> last for 100 cycles

Note that with the material mentioned above it will not bend unless the stress gets above 320MPa.

Although the curve will be different, it will look very similar for the driveshafts on our sled. It takes an aweful lot of load to actually bend the shaft (or ruin it with a single load), but it takes a whole lot less to make it eventually fail through fatigue failure (a crack).

Most likely the only time the stress gets high enough to really start taking away some life expectancy is when the track suddenly gets major grip (like landing off a big bump under power). Take a couple 1000 big stutter bumps at heavy throttle and the shaft's life expectancy will probably go down a lot (possibly fail).

 

[number1kyster]

Now I'm scared, 4500 miles and a slight vibration I my feet. I ride hard and I'm about to leave for a 1k mile trip in Northern Quebec. God I hope it doesn't break.

 

[ReX]

Now I'm scared, 4500 miles and a slight vibration I my feet. I ride hard and I'm about to leave for a 1k mile trip in Northern Quebec. God I hope it doesn't break.

I have over 5000 miles on my 07 RTX.

Which one of us rides harder....(harder on drive shafts that is)

I don't know if this will make you feel any better, but none of my buddies drive shafts failed until over 8500 miles and I've never broken one yet.

 

[number1kyster]

Thanks REX, you are the man! Also I want to thank you for your suspension setup tips. My sled handles great now.

 

[chrisinparts]

call mirco-belmont they make stronger axles. they have something they call mircoloy that is stronger then cromemoly. had one made for a tcat years ago.

 

[Bob Miller]

Just read through! My axle broke on my 04 Warrior at 9800 miles 80 miles away from Real Masse in Quebec

It broke on the chaincase side right on the edge of the Hex Locking collar. I wonder if that collar has anything to do with it?

I have an axle on order and I'm thinking that those collars might not be needed since the drivers are pressed on.

Are most of these breaks taking place at the edge of this locking collar on the chaincase side?

MAYBE THE COLLAR IS CAUSING THE PROBLEM??

 

[mdkuni]

call mirco-belmont they make stronger axles. they have something they call mircoloy that is stronger then cromemoly. had one made for a tcat years ago.

Thank you! I will contact them and let you guys know what I find out. If it is not too expensive it would be worth it for the piece of mind. I really hope I never have to go through the whole 110 miles away from home issue again.

 

[mdkuni]

I called Micro Belmont today and spoke with Gary. A great guy! Website: www.micro-belmont.com

$175 for a drive axle that IS stronger then the stock one. Very straight forward guy. He said it is not likely that you will break this axle, but it is possible. Everything can be broke!


He also sells a socket and tool for the drive axle to remove the top nut.

I will replace my drive axle at the end of the season and hope to put my worries away.

 

[JERSEYJOE]

Axle breakage

WOW all of this scares the hell out of me. My Apex Gt has 4500 miles, no studs, not ridden hard. I am going to Quebec for about a 1200 mile trip and I don't want any trouble. Had a discussion with my dealer regarding the chaincase, axle and front w arm. Must be the dealers are in denial. They have not heard of any problems. My current fleet is:

2001 SRX 7000 miles
2003 Viper 7000 miles
2006 Apex GT 4500 miles

never had a drive shaft break. I do not run studs and I run my track as loose as possible to prevent hyfax wear.

the chaincase issue scared me so much I am having a new cover installed before I go. Might consider a new drive axle. I am going to print the whole thread and show it to my dealer who is in denial. he is not the one that is going to be stuck on the side of the trail broken either.

 

[Bob Miller]

LB made mention of the ICE build up in the tunnel breaking loose and wedging between the tunnel and the front axle.

The day my axle broke, I was going along and a big piece of ice broke loose in my tunnel and went forward into the front axle area and I just kept riding, there where five of us and I did not want to hold up the Posse! Big mistake! I should have stopped and backed up, conveying the block of ice out the back, but I did not! Later on that day we traveled down the St. Lawrence river,some 25 miles, I saw 124 on the DM at one point. We stopped for gas, and about 5 miles further the axle broke! 9800 miles on sled, not to bad, but it's very possible that the ice in the tunnel could have done it!

I am curious if this has happened to anyone that parks there sled in a heated garage

 

[suprfst]

My sled is always in a heated garage,except for back pack trips but none so far this year( I was on the first day of a two day trip when mine snapped 90 miles from home).My axle snapped in half right down the middle 9000 miles.No warning,no vibration.I just passed a group of slower riding sleds was only accelerating half throttle or so.I replaced with new yamaha shaft but I will get the micro belmont one once I get around 5 to 6 thousand miles on this one.This is the first time in four years the sled ever left me stranded but It sucks.the artic cat 600 twin just doesnt compare to my sled with hauk pipes on it.When i was being towed in i fired my sled up just so i could listen to it,insead of the FST towing me

 

[ReX]

LB made mention of the ICE build up in the tunnel breaking loose and wedging between the tunnel and the front axle.

The day my axle broke, I was going along and a big piece of ice broke loose in my tunnel and went forward into the front axle area and I just kept riding, there where five of us and I did not want to hold up the Posse! Big mistake! I should have stopped and backed up, conveying the block of ice out the back, but I did not! Later on that day we traveled down the St. Lawrence river,some 25 miles, I saw 124 on the DM at one point. We stopped for gas, and about 5 miles further the axle broke! 9800 miles on sled, not to bad, but it's very possible that the ice in the tunnel could have done it!

I am curious if this has happened to anyone that parks there sled in a heated garage

Don't kid yourself. Not clearing out the ice did not cause the axle to fail.

Those axles are very, very strong as far as their ultimate strength is concerned. Unless your axle is clearly bent (from some sort of huge sudden load), the failure is most certainly a fatigue failure from many miles worth of hard acceleration and braking. Even then, bending the axle won't cause it to crack right away, but a bent axle probably would crack eventually (and vibrate terribly).

JERSEYJOE, if you don't ride hard your axle is most likely fine. Nothing is an absolute certainty, but we are not seeing posts from people claiming they ride easy with failed axles. I suspect there is a lot more than 4500 miles of life in your axle if you don't ride to hard. Have you broken your front pivot arm yet? Even though it is somewhat different loads on the pivot arm vs the drive shaft, I suspect people are typically going through a couple of pivot arms before the drive axle.

 

[Snomad]

I have never broken a drive shaft. And if you think that this is a problem that requires addressing by Yamaha how about the Doo dealers that are welding the splines on the new drive shafts on those machines??? 0 miles, new machines before going out the door. That sounds like real confidence in 100% failure to me. And how about the first year 900 Polaris Fusions and their drive shafts?? Put it in perspective.

 

[mdkuni]

I have never broken a drive shaft. And if you think that this is a problem that requires addressing by Yamaha how about the Doo dealers that are welding the splines on the new drive shafts on those machines??? 0 miles, new machines before going out the door. That sounds like real confidence in 100% failure to me. And how about the first year 900 Polaris Fusions and their drive shafts?? Put it in perspective.

How many miles have you put on a single sled? Is it possible you have not put enough miles on a sled to fatigue the drive shaft?

Sounds like Doo admitting a problem and taking care of it.

I still would never own one though.