Widening Jag Rear End

stevehaygood · #1 (**permalink**) 01-15-2004, 05:22 PM

I AM IN THE PROCESS OF BUILDING A JAG REAR END FOR MY COBRA. I AM PLANNING FOR ABOUT A 4" OFFSET.
MY QUESTION IS THIS: WHAT SIZE AND TYPE OF SEAMLESS TUBULAR STOCK SHOULD THE NEW "PROP AXLES" BE MADE OUT OF???

I UNDERSTAND THE DRAWING ON E-M'S SIGHT, BUT THERE SEEMS TO BE NO WHERE I CAND FIND THE THICKNESS, TYPE OF STEEL AND THE O.D OF IT! CAN ANYONE HELP ME AND AIM ME IN THE RIGHT DIRECTION
THANKS AHEAD OF TIME!!
STEVE

mickmate · #2 (**permalink**) 01-20-2004, 07:43 AM

Steve, I would use a 1020 DOM seamless tube with an ID a little smaller than the axle OD. Put the axle between centres on a lathe ( centre holes are already there ) and turn down to your next standard tube ID. Calculating the CSA ( cross sectional area )of the shaft backfigure to the required OD for equivalent CSA of tube. This will be more than adequate as you have the advantage of the increase in circumference for torque transmission. I would plug weld tube to the shaft as well as welding round the ends. ERA has some good info on their site also. Interesting you're widening not narrowing, do you have an E type rear? I'd be interested in talking to you more if you need help as I have some Jag axles and a lathe just waiting to meet each other! Good luck.

stevehaygood · #3 (**permalink**) 01-27-2004, 10:56 PM

Hey mickmate!
sorry I haven't replied earlier, but the flu had me down and out for a few days.
Apologies for the typo. I am narrowing the rear end. Don't know where my head was when I wrote that.!!... Not sure I want to know! Anyway, What about the gauge/thickness of the of the tube you suggest?? Also, do I leave the existing axle shaft in place? I mean I understand the outboard end is turned down, but If I leave the axle shaft in place, would that not create a "whiplash" movement inside the new tube? So, if I cut the axle off, should I weigh each axle end to an exact weight/balance so both sides would be equal in weight etc?

Thanks for the info!

mickmate · #4 (**permalink**) 01-28-2004, 07:44 AM

I'm sure you've heard the horror stories of what happens to a broken axle on a jag rear end. The axles are working in torsion and compression. If you're going to modify them make them failsafe by having the shaft tight inside the tube, see http://www.erareplicas.com/427/shorten.htm
That way if it breaks the welds it will spin and not come apart.
The ends of the axle should be the same length and weight so you can't put them in backwards. Make sure it is turned to diameter first! You can't do that afterwards unless you build some fancy yoke fixture. The tube area should equal the axle area. I'll measure some bits when I get home. Now for the dogbones...........( lower arms)...

stevehaygood · #5 (**permalink**) 01-28-2004, 08:28 AM

That's great mickmate!! thanks very much, you clarified it just fine with me. Do you know anything a front end indie system with Jag xj unequal wishbone set up??? This one has me pretty stumped. I am reading the "Chassis Building by Herb Adams for about the umpteenth time. I lioved in the UK(London) for 6 yrs and almost every cobra replica mfg uses a modified Jaguar XJ sedan, series 2 or 3. They are a dime a dozen over there and are popular much like the Mustang II is here in the US.
I am attempting to figure if I can just transfer all measurements, (camber, castor, toe etc.) to my cobra but narrow the track to the cobra's track which will be about 55-56 inches. Any ideas? I am worried about some of the real technical aspects ie., scrub radius, c of g moment etc....
Thanks again

Steve

mickmate · #6 (**permalink**) 01-28-2004, 08:26 PM

Steve, the rear axles measure 1 5/16" dia rough so they'll clean up good at 1 1/4". Same area weight etc would be a 1 3/4" OD 1/4" wall which would be a good stout tube. I get my tube like that from Marmon Keystone. If you are narrowing a front end and duplicating geometry you could shorten arms equal amounts and sacrifice suspension travel, ride quality, increase camber change and bump steer or narrow the rack and move everything in further. Drawing it all out full scale per Heidts, Steve Smith, Herb etc is a good idea. I have a corner of my workbench laid out with nails for pivot points and wire at control arm lengths to make a working model of it before even building it. You can measure camber change and any other dimensions right off it. Yes I should put CAD on my computer but I'd spend even more time playing on the computer instead of working on my toy or other projects. Let me know if I can help with the axles.
Cheers Nick