Opinions: Gripper Diff

http://www.racecar.co.uk/gripper/

These appear to be popular with Mini folks in England -- appears to be plate based but they mention some stuff about "unique design that gives progressive engagement" or some such other marketyspeak mumbo-jumbo.

John (or others in the know), can you take a peek at the drawings and tell me what I'm looking at?

Might be of interest to the Focus boys as well, they make a BMW Cooper S application which shares it's tranny with the SVT focus.

Thanks, Ted

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Pure mathematics is the enemy of every truly creative man -- Sir Alec



Edited 2 time(s). Last edit at 07/09/2008 07:40PM by Ted Andkilde.

You're looking at the way conventional "Salisbury" (made by GKN in the day) clutch plate diffs always have been but with the finesse of have different and more aggressive on drive, essentially open on over-run locking effect.

see the thing they call "planet driver". well ZF calls it "Pressure ring" and follow along:
Ring gear bolts to the diff case
"planet driver' splined on OD to ID of case
Cross-shafts of planets sit in the notches with now different 'ramp angles' (in the Old Days the angle was on most things 45 degrees and at some point in mid 70s Ford had ZF make them pressure rings with 30 degree ramps which locked up harder)

Now when the pinion turns the ring gear, the ring gear tuns the case and the two "pinion drivers" indide of which are the two side gears--via splines driving the axles and hence wheels.
So planet drivers splined to case (and half the clutch plates too), side gears splined to the other half of the plates.
when the case moves forward, the planet shaft will CRAWL UP the ramp or more correctly as the case moves forward the ramps will be pushed outwards by the cross shaft which doesn't want to turn---and add more pressure to the clutch packs.
More than you have from "Bellville Preload Plate" which is a bellville spring.

On;ly thing different than say my old Saab unit from the 70s is :
More plates for more area (Kaaz carries this to the point of reaching material limits, they break off the "ears" )
and variable ramp angles.

This is particularly nice on tarmac to eliminate the supposed big PUSH that FWD and 4wd cars with stiff front diffs suffer from.

It is what replaced the various soooooooper spendy active diffs when active crap was banned for WRC cars, and the seem to work OK.

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

I think I got it, thanks John.

They offer different options on the ramp angles.

"Current ramp angles available are 30/65, 40/65, 45/45"

Would either the 30/65 or 40/65 be OK for an underpowered front driver on gravel?

Thanks, Ted

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Pure mathematics is the enemy of every truly creative man -- Sir Alec

I have one in the gti and am very pleased with it. However i do not have anything to compare to other than a quaife i tried on a street car.

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rally gods would turn in their graves if they ever knew Lada's were now part of EU rallying!!!

Ted Andkilde Wrote:
-------------------------------------------------------
> I think I got it, thanks John.
>
> They offer different options on the ramp angles.
>
> "Current ramp angles available are 30/65, 40/65,
> 45/45"
>
> Would either the 30/65 or 40/65 be OK for an
> underpowered front driver on gravel?


ANYTHING is OK on a GRAVEL car.
What's his name Loriaoux, the rally engineer who was at Subaru said "In some ways gravel is hardest because in some ways it is the easiest to make good results when you have a good driver"
What he was saying is a good driver---and in the context of top 5 at WRC, there's less than 1% different tween them, can "drive around" even serious set up mistakes, and so their feedback on set ups and from that, improvements based on their feedback to make the car even more optimised, is very difficult.

He said it is very much easier to get consistant feedback on asphalt.
He further went on to say that for this reason to an increasing degree as the cars got more and more hi-tech sysytems, the engineer must pay less and less attention to the driver's subjective reports.

In other words---the engineers know better, so they should make all the decisions on set up, and the monkeys just shut up and drive-----very candid admission.
Racecar Engineering a few years ago.
>
> Thanks, Ted
>
> Pure mathematics is the enemy of every truly
> creative man -- Sir Alec

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

I've got one in the Saab, a 40/65.....works just great.

Per

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Per

I had one. Took it apart to replace the crosspieces (Tom from Gripper sent me new ones free of charge, explaining that the ones I'd gotten with the diff had been made of the wrong metal). They arrived slighly rusty, but I cleaned them up and put them in anyway. I didn't end up using it because I didn't like the construction or the fitment. It didn't quite fit - the distance needed for the preload was off. Also, the construction seemed cheap. I sold it (and I think Ozgur eventually ended up with it via the Mosers) and went looking for a different diff.

John's description of how it works is spot on.

I ended up with a Quaife. Big mistake. Quaifes are nice diffs, and pretty damn reliable, but not the right thing for gravel. See all the other threads griping about them going open when one wheel has no grip at all. It's true. It knocked me out of two different rallies last year, and cost me seriously.

Although in retrospect I should've taken the Gripper over the the Quaife, ultimately what I'd really like is the KAAZ that's sitting here in a box. Nice clutch-type, and much better built than the Gripper.

-michel

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Self-righteous douche canoe

Yeah, I ended up with that diff. Bought it off the Mosers. I am quite happy with it, thanks...

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rally gods would turn in their graves if they ever knew Lada's were now part of EU rallying!!!