Jack shaft sheared off behind chain case?

Octanee · Apr 8, 2017

Hey guys, I got a 2012 pro rmk with about 900k km on it. And today during my ride, luckily on the way home, the shaft sheared off! I was cruising, then stopped then started moving and after 30 feet into my light acceleration it rev'd up and went nowhere, I heard a grinding noise... And let it idle, popped open my side panel to see the issue. Wtf! Any reasons why it broke? Did polaris of that year/s have a design flaw? Went too light? I don't know of other sleds having such a issue. Thanks!

LoudHandle · Apr 9, 2017

Shaft Observations

Just some observations from shafts I've collected for my builds.
The pre-'13 shafts are as turned (can see the tooling lines).
The '13 to current shafts are ground after turning (very smooth).

The other difference is the pre-'13 shafts when turned used a 0R tooling (square / sharp corner; which leads to the problem you experienced, fatigue or stress fracturing at the root of the shoulder).
The '13 to present use at least a 2R radius on the tooling which is 1/32" R. While it may not seem like much of a difference, it makes a huge difference in how the stresses are distributed thru the shaft.

P.S. PM me, I still have a few of the chain case style shafts I'd like to part with.

Octanee · Apr 11, 2017

LoudHandle said:
Just some observations from shafts I've collected for my builds.
The pre-'13 shafts are as turned (can see the tooling lines).
The '13 to current shafts are ground after turning (very smooth).

The other difference is the pre-'13 shafts when turned used a 0R tooling (square / sharp corner; which leads to the problem you experienced, fatigue or stress fracturing at the root of the shoulder).
The '13 to present use at least a 2R radius on the tooling which is 1/32" R. While it may not seem like much of a difference, it makes a huge difference in how the stresses are distributed thru the shaft.

P.S. PM me, I still have a few of the chain case style shafts I'd like to part with.

\
much appreciate the info!, I got a shaft in my hands now, I talked to a local machine shop, he figures just polishing the shaft would give the same result as the 2r? If I spin the shaft up on a lathe or something and use some fine emery cloth to kinda smoothen down the ridges It should do the trick? Thanks!

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Jack shaft sheared off behind chain case?

Octanee

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LoudHandle

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Octanee

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