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Author: Subject: Fitting a Quaife ATB to a Sierra 7" diff assembly
hornetV2

posted on 10/1/10 at 05:54 PM Reply With Quote
Fitting a Quaife ATB to a Sierra 7" diff assembly

After a much consideration, I am looking at fitting a Quaife ATB to the Hornet. I have problems with the inside rear wheel spinning at both Mallory and Croft hairpins and also at Ireland and Abbey on the Silverstone International circuit. The car is also quite a handfull in the wet during power application.

I want to fit a LSD but have a couple of problems with this modification:

1. The quaife ATB becomes ineffective if one of the wheels leaves the ground or fails to have any significant load on it, however as the Hornet is low and light I cant see this situation arising. Does anyone in a BEC have any experience of ATBs?

2. If I fit an ATB what is the procedure for setting the pinion/crownwheel backlash? and what is the torque figure for the differential bearing carriers?

3. Although I dont envisage having to do anything to the pinion as it is all working fine at the moment, what is the procedure and values for setting the pinion preload.

Please onlly give me facts specific to the Sierra diff. Also I am always wary of steel items supported by tapered bearings in an alloy casing due to the possibility of increasing clearances as the housing heats up in use, so any information on the best side to work to of any tolerances would also be appreciated.

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zilspeed

posted on 10/1/10 at 06:55 PM Reply With Quote
Hi
I can only comment on the use of the Quaife and leave the rest regarding setup to those with more knowledge.
A pal of mine built a Fisher Fury Hayabusa with Quaife ATB in a Freelander housing.
As he previously competed with a Blackbird powered Clan Crusader, conventional wisdom was that the Fisher would never in its wildest dreams beat the traction off the line and out of the slow corners which the Clan had due to being completely 100% rear engined.

Conventional wisdom was wrong.
I've had one very memorable go in the car and it has no problems with traction.
It did prove to be a bit lively in the corners and didn't feel as planted as he wanted, but the fitting of an ARB to the rear seems to have brought that into line.
So, the characterstic of the ATB picking up a wheel and losing all traction certainly isn't an issue in this instance.

P.S. Where do I find out more regarding the Fletcher Hornet ?

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Bob C

posted on 10/1/10 at 08:32 PM Reply With Quote
I did this modification to a 7" sierra diff a few years ago, so my memory might be a bit hazy now...
1) in order to get the ATB into the housing I had to file a small chamfer to the inside back of the left driveshaft hole in the casing - there's a picture on my website I think - yes
http://i543.photobucket.com/albums/gg471/bobc0/webpageimages/Diff5.jpg
2) setting backlash - you'll note that this being real life the backlash varies ever so slightly as the prop (& therefore crownwheel) turns. Basically aim for zero lash at its tightest point
3) bearing preload - I was told 44 ft lbs on those castleated nut thingies.
I also hoped not to have to touch the pinion, and so it proved - so I've no idea how to adjust that....

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Wadders

posted on 10/1/10 at 09:31 PM Reply With Quote
I've got one in my ZX9 ST and am very happy with it. Seems to work really well compared to the viscous lsd i had before.

The lad i bought it off had swapped to a Tran X because of the problem you mention. This was in an autograss R1 mini so slightly different playing field.

Can't help with the fitting, i chickened out and paid someone to fit it, along with a 3.14 CW&P

Al.






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hornetV2

posted on 11/1/10 at 07:51 AM Reply With Quote
Thanks for the replies so far. Although I was advised against fitting an ATB due to its inherrent problem when lifting a wheel, I imagined it would be OK in a car with a low CofG and your comments seem to confirm this.

Thanks for info on setting up the diff, but can I just confirm that zero lash (on the crownwheel highspot) is what you are aiming for when setting the position of the bearing carriers (castellated thingys) and ALSO when the carriers are torqued up? or is there a different value when they are torqued up?

Zilspeed, the Fletcher Hornet is a sevenesque car I designed and built in the late eighties. Four were built for crossflows (1x Mk1 and three x Mk2), one for a Rover V8 (Mk 3) and the current Mk4 is one of the Mk2 kits that never got built up, so I bought it back fitted a Suzuki TLR V-twin, sidepods and full width front. If you need any more info I have sent you a U2U with my contact details.r

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aitch

posted on 11/1/10 at 02:41 PM Reply With Quote
whats an ATB ??
i hate acronims

aitch

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dan__wright

posted on 11/1/10 at 02:55 PM Reply With Quote
google is your friend.....

but its automatic torque bias, moves power to wherever has more grip





FREE THE ROADSTER ONE…!!

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zilspeed

posted on 11/1/10 at 05:18 PM Reply With Quote
quote:
Originally posted by hornetV2
Thanks for the replies so far. Although I was advised against fitting an ATB due to its inherrent problem when lifting a wheel, I imagined it would be OK in a car with a low CofG and your comments seem to confirm this.

Thanks for info on setting up the diff, but can I just confirm that zero lash (on the crownwheel highspot) is what you are aiming for when setting the position of the bearing carriers (castellated thingys) and ALSO when the carriers are torqued up? or is there a different value when they are torqued up?

Zilspeed, the Fletcher Hornet is a sevenesque car I designed and built in the late eighties. Four were built for crossflows (1x Mk1 and three x Mk2), one for a Rover V8 (Mk 3) and the current Mk4 is one of the Mk2 kits that never got built up, so I bought it back fitted a Suzuki TLR V-twin, sidepods and full width front. If you need any more info I have sent you a U2U with my contact details.r


Thanks for all of the info. It's really appreciated.
Would the Hornet in your avatar have been one of the cars on kit car crisis ?

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hornetV2

posted on 11/1/10 at 05:49 PM Reply With Quote
Hi Zilspeed
Yes thats the one.

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CNHSS1

posted on 12/1/10 at 09:48 AM Reply With Quote
Hi Hornet,
we have a mutual friend, 'Razza' who races a scimitar in your championship?
anyway, i run a similar car to him which also uses the 7" diff. I have used the Ford OEM viscous and quaife diffs extensively for sprints/hillclimbs. The viscous vary due to wear of the fluid in the cartridge, which can give varying results. Generally a really good one from a ford, can be a little tight in action for a small light car, although to be fair we have a lot more torque than a BEC, so thats a factor.
In usage, the viscous is consistent, tends to leave two nice thick black lines off the start if you are over-zealous but the 'action' is the same tension throughout its usage. Can lead to a little understeer if gentle with the throttle on corner exit (car setup dependant of course) but is good on the brakes if theres good grip (dry). It doesnt vary the torque to each wheel in the same way as an ATB, feels more like a constant, non-varying preload across the axle.
The quaife is what im currently running. It feels totally like an open diff when underway, no clunks like a plated diff, and no 'fight' or tension across the axle like a viscous at low speed/low grip. in changeable conditions, especially the wet i have to say its pretty viceless even on slicks in pouring rain! its pretty much all things to all men.
the downsides of the ATB are as mentioned the need for some torque to each wheel or it becomes 'open' and spins a wheel. On hillclimbs due to the often tight, and cambered nature of corners it can be frustrating but ultimately (and according to datalogger) the time lost is minimal. Even this vice is pretty gentle as unlike a viscous or plated when one wheels in the air, it doesnt pitch the car in a lurid turn towards summat immovable, its very docile. Personally i think designing your suspension setup around this 'problem' will alleviate it. A little more droop at the rear and maybe softer in general at the rear, will reduce the one wheel spinning issue and help with traction anyway, a case of playing to its strengths to minimise the weaknesses.
The other issue is an odd one and only rears its head occasionally. Basically when the grips pretty good and you have lots of grunt (mines 280+hp and on 10" hillclimb slicks) you can get a cyclical tramping off a really hard launch (essence of hilllcimbing of course). Both rear wheels in turn grip, so more torque is fed to wheel with most grip until the engine power overcomes the tyres ability, and spins, then the diff feeds the torque across the axle to the wheel thats gripping rather than spinning, so you get a pair of dotted black lines off the start rather than the tradiitional two solid wheel spin lines. Does that make sense? (does in my head...). feels like axle tramp from beihind the wheel, in fact i spent 12 months playing with spring and damper rates and anti-squat to eliminate it, only to eventually find it wasnt the suspension but the diff.

In conclusion, the ATBs dont use the sun/planet gears which are the weakpoint on high power cossies and rally cars so are stronger. They are maintenance free and their action doesnt change or vary with age, but in my opinion you will need to tweak the suspension setup to make best of it.
I think they are better than the viscous in light cars, the viscous is a bit of a blunt instrument compared on a race car.

I intend to try a plated diff one of these days, but info on pre-load and ramp angles are so contradictory that it looks a minefield!

Hope that helps
Craig

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hornetV2

posted on 12/1/10 at 12:24 PM Reply With Quote
Thanks Craig for your valued comments.
I think that pretty much confirms what I was thinking. I want to improve my drive out of tight and lower speed bends, but dont want to impair the already mediocre wet weather handling. It seems the ATB will allow that and may also actually improve the wet weather handling.

Although I run restricted droop at the front, there is plenty of droop at the back and the rear end is set up quite soft already, so with such a low CofG I dont exect much of a problem with a lifting or very lightly loaded rear wheel.

Like the sound of your car, you will have to came and play with us at Barkston some time. You can even join in our sweepstake on when RAZ will get his car finished - LOL

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hornetV2

posted on 12/1/10 at 12:27 PM Reply With Quote
Thanks for your comments, I am now happy that an ATB is the right choice for me.

However, I could do with some more information or confirmation of how to fit one, can anyone out there help?

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CNHSS1

posted on 12/1/10 at 12:32 PM Reply With Quote
sorry, i didnt fit mine into the case, just sent quaife an open diff and payed them to do it. The post re the backlash is spot on. Denis Osborne of DOME transmissions (renowned race/rally trans experts in Bromsgrove) built up my viscous and said that when they built rally car diffs up for Grp N where they had to use the 7" diff, running zero backlash hugely reduced breaking of the CWPs. It was noisy on the overrun back to the paddock for a couple of hillclimbs, but after that it was quiet as a mouse.

from the sounds of your setup it should suit the ATB then. Generally when an ATBs spinning a wheel, a viscous or plated would be drving one wheel furiously, but not necessarily wheer you want to go lol

As for Raz, i reckon fossil fuels may well be in short supply when he gets his sorted (hope he doesnt get on here much--tee hee)

[Edited on 12/1/10 by CNHSS1]

[Edited on 12/1/10 by CNHSS1]





"Racing is life, everything else, before or after, is just waiting"---Steve McQueen

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CNHSS1

posted on 12/1/10 at 12:39 PM Reply With Quote
as for mine, i bent it properly in september at a hillclimb so its stripped for rebuild and further development and aero work, but this is what it looked like.



Maybe will have to do a Barkston sprint when the cars rebuilt
cheers
Craig





"Racing is life, everything else, before or after, is just waiting"---Steve McQueen

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hornetV2

posted on 12/1/10 at 01:10 PM Reply With Quote
Hope yours is fixed soon, unfortunately cant see pics on my work 'pooter, will have a look tonight at home. The SS1 is quite an underated car and Raz's has certainly given quite a few people on the tracks a surprise (when its not in a hundred pieces scattered around the paddock), so I cant wait to see his back out again in 2010.
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hornetV2

posted on 12/1/10 at 07:11 PM Reply With Quote
JUst looked at your photo on my home 'pooter - very nice. Love the way the revised bodywork reflects the original styling details. Except on your car they actually look right.
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procomp

posted on 12/1/10 at 08:47 PM Reply With Quote
Hi

ATB is the way to go for sure. BUT you have to make sure that the damper has enough droop travel other wise as you already know is reverts back to an open diff as such. Many many people do not pay attention to the droop travel and spend much time wondering why the ATB is not as good as some say.

Cheers Matt






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hornetV2

posted on 13/1/10 at 09:06 AM Reply With Quote
Thanks Matt

Thankfully the Hornet design has loads of droop at the back, enough to cater for all the static weight on the rear wheels plus some extra for roll.

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CNHSS1

posted on 13/1/10 at 11:03 AM Reply With Quote
Hornetv2
have you pics of your rear suspension design? id be interested to see what youve done for a future proj of mine, dimensions arent necessary just an overall idea.
could you email me some if you have them and dont mind sharing?

Raz has often raved about your car BTW
Cheers
Craig





"Racing is life, everything else, before or after, is just waiting"---Steve McQueen

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hornetV2

posted on 13/1/10 at 04:03 PM Reply With Quote
Hi Craig

Just been looking through my phots and I dont have any digital ones for the rear suspension. However, I do have some printed ones which I can scan. If you PM me your e-mail address I will sort some out and send them to you. Probably wont be for several days though as I am busy finishing off the regs, entry forms etc for the RAFMSA sprints and races.

Raz is probably just being kind because of all the time I have spent under his bonnet wrestling with his apology for a wiring loom - LOL

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CNHSS1

posted on 13/1/10 at 04:31 PM Reply With Quote
No rush at all.

i think we ought to buy Raz a new tin of 'Lucas smoke' for his wiring, as im sure by now all of his has escaped

Given his occupation, i hope he doesnt have to wire them up, just bolt them on

Craig





"Racing is life, everything else, before or after, is just waiting"---Steve McQueen

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