Supastox axle bending , getting annoyed now !

[Jonathon555]

My first diffed superstox axle from the first batch lasted 8 weeks no problem

I bought a new axle 4 weeks ago and have bent at least 1 new axle every week since, now on to axle number 5 !

The replacement axles seem to be alot softer than the initial batch, always bending at the same point on the diff end

Anyone else finding this ?

[stegger]

I had a slight bend in my original one and picked up a new one last night but haven't run it yet.

[mark christopher]

Originally Posted by Jonathon555

My first diffed superstox axle from the first batch lasted 8 weeks no problem

I bought a new axle 4 weeks ago and have bent at least 1 new axle every week since, now on to axle number 5 !

The replacement axles seem to be alot softer than the initial batch, always bending at the same point on the diff end

Anyone else finding this ?

nothing here, what are you hitting?

[Jonathon555]

Originally Posted by mark christopher

nothing here, what are you hitting?

Next to nothing , thats the problem

[Martyn (Bomber)]

It was nearly one a week for me when I was running a SupaStox and I was TQ & F1 most weeks so was hardly hitting a thing, last season I didn't bend one on my mardave diff axle so there's got to be something wrong somewhere

[mark christopher]

Originally Posted by Jonathon555

Next to nothing , thats the problem

Well I have had some good hits and not done one, though I did buy a spare, sods law buy two and never need the spare

[Martyn (Bomber)]

Originally Posted by mark christopher

Well I have had some good hits and not done one, though I did buy a spare, sods law buy two and never need the spare

You can't be going fast enough

[neallewis]

I've had no trouble with axle bend, until I ran a meeting with a mardave z drive on the non diff side. It bent where the grub screws touched, with no real impact to speak of. Bent back perfectly, and completed the meeting without the mardave part. Since replaced, but I'm of the opinion the z drive grub screws caused the weekness, so back running the Schumacher part.

[mark christopher]

Originally Posted by Martyn (Bomber)

You can't be going fast enough

i dont have slow accidents, all mine are maximum attack

[mark christopher]

Originally Posted by neallewis

I've had no trouble with axle bend, until I ran a meeting with a mardave z drive on the non diff side. It bent where the grub screws touched, with no real impact to speak of. Bent back perfectly, and completed the meeting without the mardave part. Since replaced, but I'm of the opinion the z drive grub screws caused the weekness, so back running the Schumacher part.

i run z drive no problem! but from what i have heard its the diff end

[neallewis]

Originally Posted by mark christopher

i run z drive no problem! but from what i have heard its the diff end

Mine bent where the z drive grub screws touched the axle. It wasn't overtightened, just tight enough. It was a first run diff, and had no bending problems at the diff end.

[neallewis]

Isn't there an alloy shaft option?

[mark christopher]

yup understood which end yours was but the ones i have heard of have been the diff end.
there is an alloy option i believe

[SlowOne]

Mine bent at the non-diff side after a big hit on the barrier where I was sent by an errant back marker - ouch!! It was using the Mardave plastic part and bent exactly where the grub screws go if it had the alloy Z drive part.

The point at which it bends will always be the same regardless of which drive is in use. The weak point on the diff side is where the square is machined on the axle. Where the square meets the main axle the radii are quite sharp. That's a stress-raiser so it's the place where the axle will most likely bend.

On the non-diff side, the axle is solid and will therefore bend a distance away from the bearing - which just happens to be the point where the Z drive grub screws are. As they only deform the axle material, and don't change its section or cause a stress raiser, the positioning is just coincidence, not cause.

The axle will bend on the side it is hit, or the side which hits something. Sometimes it doesn't seem like it takes much, but the force needed to bend it will usually be the same each time.

Material is the biggest factor in how easily the axle bends. This can be compared using their yield strength. This is the force they can withstand without plastic deformation - taking a permanent bend - and below that they have elastic deformation - they bend and spring back to their original shape.

If these are made from simple mild steel, then the yield stress is somewhere around 300 to 450MPa, whereas a high-strength stainless will be almost twice as strong at about 700MPa. Aluminium axle strength will depend entirely on the heat treatment of the alloy. A cheap grade could have a yield stress of about 300MPa, whereas something like a 7075-T561 could be as high as 450MPa. Like the steel one, I can't find a complete spec for the alloy axle, so it's difficult to tell how its strength compares to the steel one. If it has a lower strength it will bend more easily.

If anyone has the actual material specs of both axles, we can look up their yield strength on 'tinterweb and then we'll know! HTH

[mark christopher]

Did you cut any flats in your axle for the z drive?
Do you run a Dave with Schumacher diff or a ss?