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Material for drive shafts.

Material for drive shafts.

(OP)
What is the best material to use for making hollow/gun drilled CV type drive shafts, for use with a 180 hp vehicle weighing under 500kg/1100lb? Thanks.

RE: Material for drive shafts.

Professional racing teams are using maraging steels like AerMet from Carpenter.  If you only require small quantities, then a more common alloy steel like SAE 4340 would be more suitable.

RE: Material for drive shafts.

4130 Chromoly would work too...just be sure you keep your required Inertia (Moment of Inertia) less that the Inertia of the material you want to use.  And keep in mind the torque too!

Jack

RE: Material for drive shafts.

How is a drive shaft usually protected from torsional resonance loads?
Terr

RE: Material for drive shafts.

You increase its size until it stops breaking. Honest!

Cheers

Greg Locock

RE: Material for drive shafts.

My reference (Carroll Smith Engineer To Win) recommends 4340 for drive shafts.

He does NOT recommend 4130. This is due to poor deep heat treatment and its dislike of varying cross sections.

John

RE: Material for drive shafts.

I've been using a Mark Williams SAE 4130 driveshaft with 4340 yokes for the last two race seasons. The car turns very consistent 8.9 second 1/4 mile times at approximately 157 mph. I've broken numerous parts over the past two years but this driveshaft seems to be working very well (knock on wood).
As for materials used with some success, the 4130 seems to work well as does aluminum in lower hp applications. Inland Empire builds a carbon fiber unit that's been used with much success in the Pro Stock truck as well as other race venues. A costly piece though.
For a high output street engine my choice, bang-for-the-buck, would be aluminum.

Best of luck.  

RE: Material for drive shafts.

Progressive Racing,

Cadastrophe is refering to drive shafts as in the ones from the differential to the wheel hubs. 4130 would be suitable for what we Brits call a propshaft (gearbox to axle)

John

RE: Material for drive shafts.

My apologies, I failed to read the previous responses/questions thoroughly. Thanks for the correction.

Alan

RE: Material for drive shafts.

cadastrophe:

An 1100 lb vehicle with 180 hp likely won't put much stress into the driveline. Make the axle diameter as large as practical. That will keep it's natural frequency high. Generally your shaft maximum diameter will be slightly less than the CV spline minor diameter. Drive shafts are generally designed with a "waisted" center portion, to help equalize stress.

If cost is no object, weight saving is paramount, and limited fatigue life is acceptable, then use 6Al-4V titanium, in a solution heat treated/aged condition (watch out for nicks though). If you have a more modest budget, use SAE 4140 or 4142 alloy steel(or even 4340, which is a little tougher). It's readily available and fairly inexpensive. You can heat treat it to about Rc46 (147 ksi) and still be able to cut the CV spline into it, without too much trouble. Stay away from 4130 unless there is some welding involved.

Finally, the best steel alloy for an axle shaft (which is subject to load reversals) is a vacuum melt 300M (4340 modified). As for gun drilling, it can be expensive. So make sure the unsprung weight reduction is worth it.

Regards,
Terry

RE: Material for drive shafts.

don't get too complicated... call a manufacturer. Aluminum would probably work fine. 180 hp isn't much to worry about.

RE: Material for drive shafts.

I've never seen an aluminium halfshaft on a 180 hp car. Have you? It would have an astonishingly large diameter. (rough guess about 3-4inches)

Cheers

Greg Locock

RE: Material for drive shafts.

It would be tricky to fit in amongst the suspension, for a start, and I can't see a neat way of getting the torque capacity for the wheel end CV joint.

Still, if you are telling me it has been done then I'll believe it, it's just that the usual ones I see are 37 mm of good steel, which fail by yielding gently under torque. Aluminium tubes don't fail gracefully in that manner.

Note that we are talking about halfshafts (diff to wheel) not propshafts (trans to diff).

The design requirements are quite different.

Cheers

Greg Locock

RE: Material for drive shafts.

(OP)
Actually, there are a couple of outfits in the US who make aluminium axles for quads (4 wheel bikes), for racing purposes. They are normally only hooked up to a motor producing less than 70 bhp. However, I saw in a magazine recently, where they were used for sand drag racing, in quads with street bike motors producing almost 200bhp.
Granted, they are only running on sand, with huge paddle tyres, but they are splined both ends, and in the centre.
They're not more than about 1000mm long, 40mm dia in the centre, tapering to about 28mm at the hubs.
I don't know which grade of aluminium they're made from though, which brings me back to my original query!

RE: Material for drive shafts.

Just a thought, shoot me down if I'm wrong but would there be any advantage in epoxy bonding carbon fibre around an ordinary steel drive shaft or half shaft? It just strikes me as a good way to push up the torque limit without catastrophic failure modes.

There are probably plenty of composite bits out there, but this may be an inexpensive way to keep inertia and wind up down. Maybe the shaft could be machined down first, as long as you do the stress calcs to put back enough carbon fibre.

Mart

RE: Material for drive shafts.

BTDT, for propshafts at least. It is a lousy idea, the difference in stiffness between the aluminum tube and the graphite cloth means that the aluminium is almost parasitic, certainly on a weight for weight basis.

Why not just make the aluminium or steel thicker?

Cheers

Greg Locock

RE: Material for drive shafts.

(OP)
Asuming I could actually settle on which material to use for the hollow shafts, would it not be more beneficial to use hollow bar, rather than drilling out the centre of an axle? I'm thinking in terms of the grain being aligned with the hollow bore, as opposed to cutting accross the grain during the drilling process.
How would one arrive at a safe diameter of bore in hollow bar, or percentage of material to remove? As I understand it, a fair amount of the centre of an axle can be absent without reducing its strength.
Would it be possible, or more importantly, would it work, if splined ends were welded into a thin wall tube, similar to a prop shaft? What sort of proporions would the tube have to be?
I recently found some details of the custom ATV axles. One brand is made from 6061 Al, another from Titanium, and another from 7 series Al. The 7 series is hollow.

RE: Material for drive shafts.

(OP)
Problem solved! There's a firm in the US who supply race teams, and they make gundrilled axles from 4340, to exactly the specs I require. If it's good enough for them it might just do me!

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