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Broke another driveshaft..
https://www.ausmini.com/forums/viewtopic.php?f=23&t=46814		 Page 1 of 3
Author:  Mini Mad [ Sun Oct 19, 2008 8:07 pm ]
Post subject:  Broke another driveshaft..
This time the other side :lol: (i replaced both last time with new billet ones)

GR tested these for hardness and they were 37 Rockwell. (Could have been harder but were OK) The first ones that broke were 55 Rockwell. (too hard and brittle.)

I was doing my third run at the drags and had it up ready to launch at 4000rpm and the new shaft just sheared completely at the inner circlip as i sat there on the start line. The shaft diameter needs to be smaller than the spline so the torque is transfered here and the shaft twists.

I took the shaft out from the otherside too (the short one broke this time) and the spline is already twisted on that side too. Nasty stuff!

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Author:  Blokeinamoke [ Sun Oct 19, 2008 8:18 pm ]
Post subject: 
are you running an lsd? If you are maybe a greater slip may help - wouldnt be as good at the drags though
Author:  Mini Mad [ Sun Oct 19, 2008 8:24 pm ]
Post subject: 
Yea that's partly why i'm breaking them with the extra grip, that and the button clutch is a killer on the launch. I'm using a quaife ATB (worm gear) diff so it's not adjustable.
Author:  Archangel007 [ Sun Oct 19, 2008 8:25 pm ]
Post subject: 
Bad luck Josh!

Maybe now is the time to move to 4340 CrMo shafts now!

Any feedback from the manufacturer as to why? I have ordered these same set of shafts as well so I am interested to find out the reason why!

Chin up!

Cheers,
Tricky
Author:  Mini Mad [ Sun Oct 19, 2008 8:31 pm ]
Post subject: 
Cheers Tricky, sorry they did last a while, i hope they work for you!

I am pretty hard on them though..and they did last 6 4-5000rpm launches with a button clutch, LSD, semi slicks.

I talk to anthony and see what he says, but i have been told by GR that is because the shaft is too thick and transfers all the load to the spline which is the weakest point where the circlip is.
Author:  JC [ Sun Oct 19, 2008 8:33 pm ]
Post subject: 
Not sure what effect loosening the LSD would have Bloke? The shafts would still break at the same rate as there is the same amount of power....just not being distributed evenly.
Author:  Super-mini [ Sun Oct 19, 2008 8:34 pm ]
Post subject: 
slow minis are fun too ya know :lol:

hope you can sort it out soon. :)
Author:  Betty [ Sun Oct 19, 2008 8:37 pm ]
Post subject: 
stop breaking shafts and spend some money on your girl :P
Author:  1018cc [ Sun Oct 19, 2008 8:40 pm ]
Post subject: 
Betty wrote:
stop breaking shafts and spend some money on your girl :P


Shhhhh.....she might be reading this. You don't want to put idea's in her head :lol: :mrgreen:
Author:  Mini Mad [ Sun Oct 19, 2008 8:48 pm ]
Post subject: 
Sir Spamalot wrote:
Betty wrote:
stop breaking shafts and spend some money on your girl :P


Shhhhh.....she might be reading this. You don't want to put idea's in her head :lol: :mrgreen:


Too late, she came up with the idea herself ;)
Author:  CJ_DT [ Sun Oct 19, 2008 8:58 pm ]
Post subject: 
The body of the shaft is too thick, it means that when you load up power, instead of the shaft twisting, it twists at the spline, this also locks it into the CV and can do weird things when suspension moves. All off road style race shafts have the shaft considerable thinner than the spline (usually thinner than the thickness of the splined section at the trough of the spline) this allows them to act a little like a torsion bar, and wind up a bit, reducing snatching loads.
Author:  pubudug [ Sun Oct 19, 2008 11:05 pm ]
Post subject: 
yep.. right on.. my shafts are 4340 steel with the shaft diameter smaller than the spline diameter.. thats the way to go...

Mini Mad, are you running standard mini CV's or morris items?
Author:  cush [ Mon Oct 20, 2008 1:07 am ]
Post subject: 
noting wrong with helical cut splines...

would be quieter... :)
Author:  Blokeinamoke [ Mon Oct 20, 2008 6:16 am ]
Post subject: 
JC wrote:
Not sure what effect loosening the LSD would have Bloke? The shafts would still break at the same rate as there is the same amount of power....just not being distributed evenly.


slacker clutches in the diff mean the power is fed a few millisecs slower. Also with a tight lsd and sticky tyres the power has one way to go (which is the aim). If the power discovers a week point before putting the down something will break. A looser diff will absorb more power than a tight one.

Also the thicker thed rive shaft the higher outer velocoity and greater the inertia all of which has big effects at high revs.
Author:  drmini in aust [ Mon Oct 20, 2008 6:46 am ]
Post subject: 
Mini Mad wrote:
Cheers Tricky, sorry they did last a while, i hope they work for you!

I am pretty hard on them though..and they did last 6 4-5000rpm launches with a button clutch, LSD, semi slicks.

I talk to anthony and see what he says, but i have been told by GR that is because the shaft is too thick and transfers all the load to the spline which is the weakest point where the circlip is.

So is GR going to make you up some unbreakable ones like he showed me on Friday? 8)
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