IRS vs Live Axle

ian.stewart · Post by **ian.stewart** » Thu Dec 17, 2009 12:21 am

its structural, break a shaft and the wheel falls over

topcatcustom · Post by **topcatcustom** » Thu Dec 17, 2009 10:19 am

How is the Jag IRS so strong when there is no top wishbone? There must be a lot more stress on the UJ's as well as they make up part of the structure of the unit.

What about run what u brung quarters- do the same rules apply?

stevieturbo · Post by **stevieturbo** » Thu Dec 17, 2009 5:10 pm

ian.stewart wrote:its structural, break a shaft and the wheel falls over

That could pose a little problem.

But then, most live axles in the US are similar. I think its sub 11s cars require c-clip eliminators so the same scenario doesnt happen with live axles on the American rules.

Ive never really looked at a Jag rear end. How can a moving shaft on an IRS be structural ?

kiwicar · Post by **kiwicar** » Thu Dec 17, 2009 7:46 pm

"Ive never really looked at a Jag rear end. How can a moving shaft on an IRS be structural "

like on the early corvette rear end, the drive shaft provides lateral location with a trailing link providing the longditudinal location, the inner end takes the lateral loads via the diff case into the chassis via the cage, the outer end of the shaft locates the hub in side to side. The shaft has no sliding joint, it has UJ s to provide for changes in angle. I supose a bit like a beetle rear end swing axel shaft but with a UJ at both ends and a second lateral locating arm below with another trailing link from the chassis. You end up with two semi trailing "A" arms but one of the lateral links is the drive shaft. (Yes I probably have repeated myself but there you go

)
Mike

topcatcustom · Post by **topcatcustom** » Thu Dec 17, 2009 8:08 pm

Here ya go

Its a bit of a shame seeings it has a renowned strength quality. Having looked at John Sleaths website I feel a bit put down by the XJS on there!!! It would be a major project getting mine like that- its a spaceframe with live rear axle and a BBC. I guess its either copy that or just go ahead and do the engine swap for a BBF and leave the rest pretty standard. Oh decisions decisions!!!

stevieturbo · Post by **stevieturbo** » Thu Dec 17, 2009 8:27 pm

Strange setup !!

It all depends what you are trying to do. The one on Sleaths website is obviously an out and out drag build. Is that what you're aiming for ?

Or are you just building a fast, fun toy ? Do you intend actually racing it ? or just RWYB for fun ?

kiwicar · Post by **kiwicar** » Fri Dec 18, 2009 10:16 am

Hi Tom,
may I suggest, year 1 stick the BBF and an auto in it, stick in a good strong cage in it, stitched into the A,B and C pillers so it is good and stiff and forms the basis for later modifications. Use the jag rear end but make sure it is very strongly mounted and tub the boot floor so you can put decent tyres on it. Use it for a year or two like that to learn how to launch, when to shift gear, how to tune the engine for conditions on the day etc (and how to keep it straight at 140mph whilst trying to stop

). Then over the first or second winter you should have a better idea of where you want to go with it, if it is to be a pure track car then you will have to decide on a class and build it to that spec, if it is to be a RYYB car and the skurge of McDonalds then that spec is different and build it to match. Apart from anything else if you change engine, gearbox and rear axel I am pretty sure you will find it needs the new version of the SVA and will cost you £500 for the paperwork!
Mike

topcatcustom · Post by **topcatcustom** » Fri Dec 18, 2009 2:12 pm

Well as with ANYTHING, competing properly costs a bomb- and a lot of time and dedication and I'm honestly not sure if I can commit completely. It would really be for a toy and RWYB, so I think it'll be IRS. LSD as standard, right ratios etc available for peanuts.

Slightly of topic but what do you think about the front end? Keep front subframe or make up spaceframe and new wishbones etc?? I'm thinking keep subframe but integrate a semi spaceframe and full rollcage in the car, then if I decide to do the odd trackday it may be more useful than a drag dedicated car.

kiwicar · Post by **kiwicar** » Fri Dec 18, 2009 10:21 pm

It's your topic. . .

What you propose sounds reasonable to me. I would take out all rubber mountings from the sub frame and replace them with ally, road noise will go up but I doubt you will care about that (young uns

) a space frame is for later I would think.
Yes tie the cage into every mount you can. Personally i like to see a cage tight to the roof pillers and joined in to the steel of the body. I would put x bars inside the doors as they really stiffen the chassis and tie in the floor pan should anything unplanned happen. I bet it ends up a full race car though I think you will find big blocks adictive

.
Mike

topcatcustom · Post by **topcatcustom** » Sat Dec 19, 2009 10:59 am

Maybe I can plan the cage around provision for adding a 5 link rear axle in the future then, and as nice as a full on space frame would be I think it rules out practical use as its not exactly weather proof etc without loads of work and small panels so you can still lift the body off etc. Chopping the front end out sounds good though- then theres loads of space for exhausts and err, turbos?!

think I've already gone too far for now

JJMclure · Post by **JJMclure** » Sat Dec 19, 2009 5:24 pm

ha ha YES twin turbos on a big block, you'll need a doctor to remove the grin from your face
http://www.performancerestorations.com/ ... G_0216.jpg

[/img]

topcatcustom · Post by **topcatcustom** » Sun Dec 20, 2009 4:26 pm

JJMclure wrote:ha ha YES twin turbos on a big block, you'll need a doctor to remove the grin from your face
http://www.performancerestorations.com/ ... G_0216.jpg

[/img]

That is F ING obscene!!!!! How much for the turbos?!?!