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Kirkham Motorsports

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  • 2 Post By Aussie Mike
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Old 04-08-2014, 01:13 AM
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Default Attaching CVs to driveshafts (US=axles)

Driveshaft - I am referring to the shafts between the diff and the rear wheel hub on IRSs.

On all production vehicles I have observed, the CV is slid over a splined end until it butts up against a shoulder on the shaft. A circlip (C clip) is then attached to locate the CV in position. In this configuration any 'plunge', which is necessary to allow for overall length adjustment when control arms swings through an arc, is an internal function of the CV, i.e. the CV does not slide on the shaft splines.

I require relatively short shafts and to have them made up is quite expensive. I have been alerted to the fact the CVs I will be using (Holden) are a universal item based on 930 Porsche CVs. They are popular in off-road buggies and as well as the CVs there are plenty of after-market driveshafts available at a fraction of the cost quoted to have one-offs made.

The idea is that I could machine a new circlip groove at the distance to suit my application and cut off the excess shaft.What concerns me is that the after-market shafts have no shoulder and I'm worried about the CV moving along the splines.

Is anyone experienced with off-road buggies, or experienced at all with CVs fitted without a locating inner shoulder. Thanks

CV Assembly
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Old 04-08-2014, 02:23 AM
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peter
went & asked the bloke up the road that runs off roaders he said they cut an inner groove then fit an retainer over the circlip to stop the shaft slidding past the spline at full bottom out
hope it helps
rob
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Old 04-08-2014, 02:32 AM
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Rob

Thanks, I saw that as an option but I've not seen any reference to it actually being done. I was worried that the inner circlip groove might create a serious stress concentate but it appears not.

(edit) I'm not the first to be confused on this issue -

http://www.gt40s.com/forum/gt40-tech...ating-not.html
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Old 04-08-2014, 05:32 AM
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It can depend on the design of CV. You will find that a lot of the 6 ball type CV joints like Holden and Porsche axles run have circlips spaced so the CV can slide on the axle shaft. The 3 roller type have plunge inherent in the design but the ball ones don't.


You may find that adapting axles and hubs from another car could do the trick. I cut the roller CV housing off the end of my Ford axles. I then machined them and welded Holden flanges in place.

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Old 04-08-2014, 07:36 PM
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Curiosity got the better of me so I pulled apart a plunge CV and non-plunge CV to have a look.

The first two photos shown the amount of plunge and the others show the difference in design. I didn't even attempt to analyse how it works.
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Old 04-08-2014, 08:02 PM
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Usually one end of the driveshaft assembly is plunge and the other is not. On VE Holden shafts the plunge end is held on with with a large circlip around the outer of the CV housing, removing this circlip allows you to pull the CV housing off then there is another small circlip on the shaft that holds the splined portion onto the shaft.

for the other end there is a snap-ring on the shaft within the housing so that housing can just be tapped off with appropriate soft hammer.

Your idea of machining a slot for an inner circlip sounds like it might work?

round-tube Classic Revivals use custom made shafts which are the same ends as factory VE, the shafts are just 65mm shorter, and they cost about $450 each (ouch).
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Old 04-08-2014, 08:49 PM
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The high performance Holdens have plunge CVs on both ends but I'm not sure why. The shafts I require are relatively short at 350mm. The standard Holden is 510mm. The Classic Revival stafts are still way too long.

Around $500 each is the going price to have shafts made here but you can buy a pair for around $250 in the US and have them posted for around $80. The problem for me is that the shortest they sell are 400mm. I need to be sure if I chop 25mm off each end there is still enough spline remaining.
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Old 04-08-2014, 09:03 PM
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Do you know how long the pre splined shafts are splined for?
With shock removed you should be able to move the rear hub from full compression to full extension, measure the longest and shortest of these distances, and you should be able to work you're answer.
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Old 04-09-2014, 12:14 AM
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Quote:
Originally Posted by boxhead View Post
Do you know how long the pre splined shafts are splined for?...
I have sent polite e-mails to several US suppliers requesting that info but none have replied.

Quote:
Originally Posted by boxhead View Post
...With shock removed you should be able to move the rear hub from full compression to full extension, measure the longest and shortest of these distances, and you should be able to work you're answer.
I've measured that and it's bugger all, 5mm max. I could probably get away with one plunge CV but as plunge and non-plunge have different splines (more machining cost) and the high performance cars use two plunge CVs, I thought it easier to use two.
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Old 04-10-2014, 12:07 AM
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Machining my own axles is something I have been experimenting with. I've been machining splined steering shafts and have been looking at making some axles next. I've been talking with a heat treating company that does a lot of work for the V8 super car teams. I'm looking into finding a source of suitable material. I can get 4130 and 4330 and I've been looking into 300M and Vasco but I reckon 4330 might be the best choice for price versus strength.

I probably won't have anything developed in time to help you with your project but it's something I'm trying to add to the Murphy Engineering arsenal.

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Old 04-11-2014, 06:40 PM
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I've actually found some axles on ebay - 15 5/8" (400mm) - and the good news is the splines are 3' (75mm), so there should be no dramas chopping 25mm off each end and slipping on the 28mm wide CVs. I'm not too sure how to go about creating the new circlip grooves, whether turning with a part-off tool or strapping a die grinder to the toolpost and grinding the groove. Any thoughts?

Mike - Many moons ago I worked in the aircraft industry and I vaguely remember shot-peening shafts to help create a compression layer on the surface to assist resistance to surface cracking. I suspect metallurgy has come a long way since those days and the technique may have been abandoned. Axle suppliers also talk about axles designed to twist like tortion bars (a la VW rear end suspension) so perhaps the shot peening is old hat.

On the subject of torsion bar suspensions, I read that Colin Chapman tried it on a Lotus (the first 72?) and Ronnie Petersen said it was difficult to feel the sensation of braking. The only way he knew the car was decelerating was when the smoke started coming off the front tyres!
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