halfshafts

[extreme90]

heres one to ponder over  :lol:
why is it 9/10 always the short shaft that snaps when onne breaks ?

whats your theorys

mine are

1. theres less surface area to flex in the short side vs long so the short one lets go where as the long side flex's

2. more torque gets transmitted down that shaft as its a shorter distance to travel from diff to wheel so less potention energy is lost in the shaft  :?

what are your theorys, as this has nagged me for years so thought id let it nag others  :lol:
dan

[lambert]

Number one is you're most probable cause after that a few will be defective materials, but mostly down to torsional stress over a shorter span.

[Devon-Rover]

The shorter shaft goes as the is less less longitudinal length in which too allow the Shaft to twist and flex under normal stresses. So less allowance for twist over a shorter surface but still an equal force will cause a higher Stress loading (due to the lower area) and so causing it to fail

[clbarclay]

Agh @#!&   dislexia :x  

Trying to put this into words but failing miserably.

 :(mad):

Its not to do with surface area as such, say a given stress puts 1 turn in a shaft for ever 1 meter of length, therefore a shaft 2m long will twist have half the stress of a 1m shaft if twisted the same amount.

Dan, you have an ARB diff if memory serves, so if neither wheel turns as torque is applied to the diff when locked then stress rise in the short shaft will be greater due to it being twisted further relative to its length.





My other theory is the law of sod, the same law that states its only off side rear light clusters that get broken when off road so I have a gouing mound of good spare near side clusters

[Terranosaurus]

As clbarclay says law of sod - if it was the short one you've just changed the odds are greatly increased that it'll be the shiny new one that you break again.

But seroiusly clbarclay has it right. The shaft acts as a sort of spring (torsion bar type) and the load on a longer shaft is more "thinly" distributed so there is less loading at any one point.

[Range Rover Blues]

I think some of you have got that a bit wrong.  An open diff will distribute equal torque to both shafts, irrespective of how far they twist, so the longer shaft will twist further than the shorter, effectively it's a softer spring due to it's length.

Whether it's the law of sod I'm not sure, perhaps the shorter shaft is unable to absorb spiked loadings that often cause failed halfshafts.  Have you checked the longer shaft recently? is that showing signs of damage?

 istripped a 200 TDi axle that had been in Dom's Ibex with lockers and both rear halfshafts were close to going (he did supply me with spares though :) ) by equal amounts, though of course the lockers would have transmitted all the torque to one wheel or the other depending on grip.

I suppose the other thing is are you using the same quality replacements?

[The Ant Hill Mob]

RRB, get off the PC at once!  You are supposed to be fitting the bathroom carpet!

[clbarclay]

RRB, get off the PC at once!  You are supposed to be fitting the bathroom carpet!

 :(biglaugh):

[extreme90]

:lol:
have i started something here  :lol:
i was just wondering, i wont snap a shaft in mine due to having ashcroft shafts and cv's, but out of all the broken shafts i have changed for people and myself  :roll:  :roll:
they have been the shorts
at least i was partly there with my theory  :lol:  :lol:
dan

[clbarclay]

:lol:
have i started something here  :lol:
i was just wondering, i wont snap a shaft in mine due to having ashcroft shafts and cv's, but out of all the broken shafts i have changed for people and myself  :roll:  :roll:
they have been the shorts
at least i was partly there with my theory  :lol:  :lol:
dan

So this is not necisserily with locked diffs then :-k

[Range Rover Blues]

It's a valid question though, after all if you knew it would always be the short one, you'd carry one as a spare.

[extreme90]

:lol:
have i started something here  :lol:
i was just wondering, i wont snap a shaft in mine due to having ashcroft shafts and cv's, but out of all the broken shafts i have changed for people and myself  :roll:  :roll:
they have been the shorts
at least i was partly there with my theory  :lol:  :lol:
dan

So this is not necisserily with locked diffs then :-k

no i snapped my front short shaft at idle rpm in deep mud with my simex

( std diff then aswel as on 10 spline )

in fact, out of all the broken shafts ive changed thers only been 1 long and that broke cos the divvy kept the power on as the front pass wheel cam back down to ground with a crunch  :roll:

dan