Fusible flanges

thinfourth · Just got MTs Joined: 24 Apr 2005 Odometer: 257

I have a hybrid trialer and a lathe in my garage.

Now so far i have had one diff fail on the hybrid , which meant thats the day over on the trialing front and a few hours and expenses to replace.

It seems diff is the weak point on the landrover drive train along with the CVs.

What i was thinking is would it be practical to get some drive flanges and machine out 25% of the length of the splines to make them the weak point in the drivetrain.

That way the first thing lible to pop is the drive flange which means should one fail you are five bolts to swap it out between courses and you are up and running before the next course.

Also would machining out 25% of the flange make it the weakest part of the drive train?

Is anyone able to calculate this or would it be a case of trial and error

doda456 · Gate Opener Joined: 31 Jul 2008 Odometer: 38

in theory its a good idea as KAM diffs all come with a fusible shaft to protect the diff and drive shafts.

the only problem is the base metal in landrover shafts/flanges maynot break cleanly and metal could enter the diff

scut44 · Guest

I would forget the figure 25%.

Maybe someone from KAM or Ashcroft thats on this Forum might see your post,
or someone like RedLine Mike who used to use the practice of fusable links successfully & maybe still does, will give give you advice.

I would hold off 'touching your shaft' just yet.. Embarassed

& stick with getting your Diff Strong
& driving according to whats currently fitted.
Works out cheaper in the long run.
george

thinfourth · Just got MTs Joined: 24 Apr 2005 Odometer: 257

scut44 · Guest

Very good point & taken on board.

So its down to the events you do
& if you are happy with DNF's
& if you dont mind spending money traveling & entering, but needing to change shafts on site, or if that doesnt spoil you day/weekend.

If your quick at doing it at the side of a section & up for it,
then go for it.

Just maybe find out first from others doing the same how much to machine to give you the fusability you want without being stupidly weak.

Which was really what your post asked. Embarassed

I must never of tried hard enough in a LR, or been lucky!
never ever broken anything,
or maybe thats just down to making sure it was built strong in the first place & up & beyond to the job being asked of it.
george

.

thinfourth · Just got MTs Joined: 24 Apr 2005 Odometer: 257

teamidris · Posted: Sun Oct 31, 2010 6:06 pm Post subject:

Considered it Very Happy

And lets face it, in my crazy brain there isn't much I havn't considered Rolling Eyes

Like a Tractor PTO shaft clutch Idea

I rang GKN tears back to see if they still did those 'clutch' hubs, but no good Sad

And in the same vein, I was thinking 'sheer pin'.
Theory is; you get two flanges, machine the outside off one, the inside off another so they fit together with a step for an internal circlip. Then drill through the two together, to make a hole for a sheer pin Cool

The number, material or diamter of the sheer pins dictates the torque.

james_hillerby · Posted: Sun Oct 31, 2010 8:48 pm Post subject:

If you are machining out some of the splines then you are after the remaining splines to strip and then this would ruin the shaft and the drive flange. You should be machining a ring around the halfshaft to reduce the diameter and cause a week point. This way only the halfhaft would fail.

thinfourth · Just got MTs Joined: 24 Apr 2005 Odometer: 257

mudplugga · Posted: Mon Nov 01, 2010 12:14 am Post subject:

The hardest driver in our club, with possibly the most powerful V8, makes his own fusible shaft.

He only does the short CV shaft on the front as it's the easy one to change and a spare is easily carried.
His reasoning for just doing that shaft is that the weakest point will break first, and if the diff's are all locked ( he uses ARB's front and rear ) he'd rather break that one frequently and change it quickly than miss a days trialing.

The reality is he very rarely breaks the shaft, and like I say, he drives very hard with our club and the AWDC in the Supermod class.

teamidris · Posted: Mon Nov 01, 2010 7:28 am Post subject:

"How you would get the right size of shear pin is the hard bit.
Unless you start small and then work up until they aren't failing as often. "

Probably, but it is easier to work out the shear strength at a given radious on a pin than a shaft spline. Ashcroft rate a standard shaft as a start point.

Circlip was to keep it all in line once the pin went. Then any scuffing during rotation upon failure would be kept to a localised area.

paul_c · Off-Road Guru Joined: 17 May 2009 Odometer: 1378

No need to reinvent the wheel.....

http://www.kamdiffs.com/four_by_four.php?l=Fused_CV&link=Fused_CV242

paul_c · Off-Road Guru Joined: 17 May 2009 Odometer: 1378

Winnet · Posted: Mon Nov 01, 2010 12:49 pm Post subject:

You also have to think on how often you actually have breakages and why the item broke. Do you drive roughly or is it down to the item being old and worn?

Normally it is the halfshaft that goes and if you source decent 2nd hand parts the cost can be kept down.

G.

fixit · Posted: Mon Nov 01, 2010 8:00 pm Post subject:

To be fair when i was trialing i never broke a shaft they are quite good and i broke 2 diffs

I couldn't afford a 4 pin diff or tricked up unit so a chap at our club suggested pegging the next diff which i done and hay presto prob sorted

Ps i think i had also learnt at that point that there is more than 2 positions for a V8 trottle peddle Embarassed

thinfourth · Just got MTs Joined: 24 Apr 2005 Odometer: 257

teamidris · Posted: Tue Nov 02, 2010 7:03 pm Post subject:

Need to make use of that lathe then Very Happy

So where in the diameter are you splitting the two halves Confused

It'll need to have enough left on the inner part to not split wide open with torque from the spline?

There's two 'rubber cap' ones here going spare if your coming through Staffordshire. Slightly drilled to fit 10 spline hub, then replaced with the proper thing after one event.