Quaife gear set in a 4 speed dog box
The gearbox is used in a Mk1 Escort hillclimb car running on slicks with a NA Cossie (270 bhp)

This is the second time this has happened inside 3 events

Any thoughts welcome

Any metrology experts in the house ?

Im no expert,

But that box of cogs does not seem to be up for the power you are putting through it

JMPW

Yep! agree with Steve. Looking at the way the teeth have been hammered, definately not up to the job. Cheers Ray

Curious - in the first image the cogs on the gear appear to be brittle failed all the way through. I'm no expert but I'd have thought they'd be case hardened not fully hardened. But then the cog to the right of the completely failed one seems to have been "smudged" suggesting a non-hardened surface or the surface was too thin and has been wiped off. I think that would need taking to a lab to investigate, or just buy stronger gears.

I wonder if what's actually happening is the hardening if failing on one or two teeth which allows the contact surface to shift, then allowing a clash rather than a mating? Equally I could see that the cogs fail causing excess load on the remaining one so that's not too clear.

[Edited on 15/6/12 by coyoteboy]

I would be interested to see what Quaife have to say. The box is rated above 270 and it does look like one tooth has failed and then the next one has snapped?

Thanks

Quaife have the box and are going to advise, they are very surprised this has happened as it should be more than man enough for the job
These gears aren't cheap to buy so the decision is to let Quaife have a look and report back

I'm thinking its a metal treatment/metrology issue at the moment but we'll have to wait and see


I'll update when we know more...

UPDATE

As promised an update

Quaife have rebuilt the box and are saying a bent selector fork was causing 3rd gear to not be selected correctly
They rebuilt the box quickly and were helpful throughout and have also asked for feedback after the next event to see if everything is ok

so how do you bend a selector fork? but interesting

Well that might explain it. Mind you, id like to see the mechanism by which a dodgy selection rips teeth off a pre-engaged gear (genuinely, I'll have to dig out some diagrams)?

As has been said above, looks like one tooth hasn't been hardened properly, been chewed into and then it's broken the adjacent teeth off because they're not going into mesh properly. With a pre-engaged gear set....bent selector my bottom!.

If the new gear/s have been hardened properly it'll be fine and that's what really matters

Ian

Thanks for the comments, must be honest i thought heat treatment issue when i first saw the problem

To be fair my mate is just glad to get the box back and ready for the next event in a couple of weeks

Now Quaife themselves have rebuilt it i would hope they will stand by it should anything go wrong...