carbon fibre prop-shaft

[Marius]

Am I the first to think about this ???? Don´t know about costs but even a bulk buy would show still huuuge prices I guess.

 

On the other side: 50% weight saving on the prop-shaft would be more in terms of overall weight saving than fitting all the other cf body parts as wings & nose.

 

Anyone more experienced in this topic ??

 

See here:

 

http://www.ctgltd.co.uk/technology.php?id=17&title=Propshafts+and+Driveshafts

 

Marius

[scooby dooby doo]

there's a lot more to be saved in the half shafts - they're REALLY heavy.

 

I do have a spare (knackered UJ) propshaft that would be available for test purposes.

 

I think Miraz started looking into it as well...

 

HOOPY 500 kg R706KGU

[V7 SLR]

But it's not the half shafts is it? I understood the weight was in the CV joints. Correct me if wrong but hasn't Miraz had problems with his newer lighter half shafts, resulting in Caterham replacing them for the original versions which don't fail?

 

I'm sceptical that a CF propshaft would last. I know they are in existence in other industries but I'd have to see it to believe it. Better to invest in a CF bonnet and scuttle IMO. No stress analysis needed and good potential for weight saving (although not rotational mass).

 

Also, ISTR the front hubs weigh a ton. I'm interested in a lighter hub and brake assy without compromising brake efficiency (admitting that these wouldn't be CF, but commenting on weight loss in general).

 

I could also go on a diet but that's totally unbelievable.

 

Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours

 

[scooby dooby doo]

the disks themselves are rogeringly heavy as well. but i guess we need to wait for the Ferrari Enzo / Porsche Turbo / AMG SL55 technology to trickle down a bit...

 

HOOPY 500 kg R706KGU

[Peter T]

Lose the disksand brake calipers, and manufacture one carbon ANCHOR!

 

C7 PWT X-Flow all Steel

 

[JAG]

W*******d make a cast Aluminium upright for their cars, it's a direct replacement for the cast Iron Cortina item. Perhaps someone could investigate something similar for the Caterham??

 

Lotus used an Aluminium Metal Matrix Composite material (cast Aluminium with small ceramic particles) for the discs on the very first few Elise. They withdrew it shortly after, presumably it couldn't cope with the duty cycle imposed upon it in the real world. It did however pass all the durability testing that the Elise did prior to production.

 

JAG

[Morls]

Sounds a good idea, but...

 

Isn't the heavy bit on a prop the cast / machined solid bits at the end, rather than the tube 🤔

 

I know these cause problems on some BECs when the flanges either side of the rev box / centre bearing fall into phase (after rev box use) and try and throw it out of the car.

 

With my limited knowledge of materials and their use, I know that while CF is ideal for large hollow structures where a surface needs to be supported (motorcycle seat units, monocoque chassis etc. I didn't think CF was ideal for small dense things largely subject to compressive forces (like UJs / prop flanges).

 

Maybe thinking more laterally than simply assuming the use of traditional UJs is the way to go.

 

Although Elan, Spitfire and Early Mini owners would probably love to have traditional UJs rather than funny rubber things.

 

I need to buy a split prop soon so If someone can come up with a realistically priced alternative to the heavy normal method, i'd be interested.

 

Also...

 

Wouldn't CF be absoloutly perfect for a lighter LA axle case to take stronger (and cheaper) Ford bits.

 

The braced standard thing weighs plenty and yet is used on cars built to be light (blades etc.).

 

I know most of the people who spend plenty on bits are now running De-Dion chassis, but this would definately help get things like Dave Edmands' LA car even lighter.

 

So... CF experts... am I barking up the wrong tree 🤔

 

 

Mark

 

☹️ My Caterham Silver Jubilee No. 7 is for sale ☹️

[scooby dooby doo]

The half shaft id still a foot long cyclinder of solid steel 30mm in diameter. Thats heavy.

 

quick back of the envelope calculation reckons 6.7 kg EACH for the shaft itself.

 

M = rho PI r r h

M = 8000 3 0.03 0.03 0.3

M = 25000 0.00027

M = 6.75 kg

 

HOOPY 500 kg R706KGU

[edmandsd]

I was very keen to save as much weight as possible in the drive train and have managed to get my complete strengthened English axle with halfshafts, diff unit, brake discs and calipers all fitted down to only 37kgs from circa 50kgs.

 

Weight savings came from the following:

Box section strengthening as opposed to solid bar on Ital.

Alloy diff nose with Anglia flange - saved 3kgs

Steel spool - saved 3.5kgs (Not applicable to most I accept)

Gundrilled Grp 4 Atlas half shafts - saved 2.5 kgs (5/8th inch hole actually makes them stronger)

Lightened flanges - saved 1 kg

240mm Motorbike rotors on alloy bells - saved 4 kgs

 

I was also interested in carbon props as I know a lot of tuned Nissan Skyline's use them. However I opted for a steel Reco Prop with Anglia flanges to suit a standard 1600 x/flow Caterham. Although i've got a fair bit more power than a x/flow from my 2 lt BD the overall weight of the car (410kgs) means I didn't have to use a heavy duty prop.

 

 

 

Home of BDR700

 

 

 

 

Edited by - edmandsd on 6 Nov 2002 12:07:41

[Graham Sewell]

Hoopy,

 

I hate to nit-pick but area of a circle is pi*r*r or 0.25*pi*r*r - so for a bar of 30mm diameter....

 

8000kg/m^3 *pi*0.3m *0.03m*0.03m/4

1.6964600329384883487698274269709kg for mathematicians

1.7kg for scientists

1*10^0kg for engineers

 

 

Low tech luddite - xflow and proud!

[WILL FLY]

James whiting does Ali hubs for the Blackbird 7 which I expect would fit a normal car. They're a lot lighter than the standard hubs.

 

I don't hink a carbon bonnet would be much lighter. I remember picking up Graham Finlaysons and it felt heavier than my Ali one.

 

Will Fly

 

See willfly.net for more info.

If you don't spin you ain't trying

 

[Joe 90]

I believe CF propshafts have been tried on trucks, so it's realistic for a seven. It reduces rotational inertia, so you get a double benefit. Who will do the stress and vibration calculations though? I've been thinking that box section strengthening has got to be the way to go on the ital axle, so I'm glad someone has tried it (successfully I trust).

 

An alloy front upright might not be that much lighter than a steel one by the time you have beefed it up, and you really don't want them to fail. ❗

 

Lotus dropped the alloy discs from the Elise because the supplier went bust, not for any technical reasons.

 

Alloy hubs and brake calipers would be my first step.

 

 

99,000 miles so far

[scooby dooby doo]

ooops ❗

Area = PI x radius x radius or...

Area = PI x diameter x diamter x 0.25.

 

I though 7 kg seemed too big

 

So its 1.7kg on each side. 3.4 kg in total.

 

HOOPY 500 kg R706KGU

[edmandsd]

I'd be interested how an equivalent de dion set up compares with my 37kg fully assembled axle so I could roughly determine how heavy my car would have been if i'd gone the de dion route.

 

I've obviously excluded the A frame and axle bars for these purposes as the de dion will no doubt have an equivalent, plus I understand the bare de dion chassis is heavier to start with.

 

Home of BDR700

[Peter Carmichael]

I saw an Elise shed an MMC brake disc at a track day at Llandow.

 

Investment cast titanium uprights seem to be popular on Formula cars... and guess who received an email this morning saying:

 

I've been thinking about your car. There are some fairly wacky far out F1 type things we could do to it, if and when you fancy taking things further. For example inboard shocks, with carbon pushrods, carbon wishbones, small bore shocks and ceramic wheel bearings.

 

[edmandsd]

I thought very carefully before going the bike discs on the rear route and deliberately made them floating (as opposed to fixed). In addition I chose the 6mm thick centrifugally spun iron ones from PFM as opposed to the 4.5mm thick steel ones fitted to most production bikes today.

 

Home of BDR700

[V7 SLR]

Bloody hell, that sounds fun. If they could prove the longevity over the next 12 months, I'll have enough cash to have a go too.

 

Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours

 

[mr_ed]

Mr Edmands!

 

Reading about your weight savings is very interesting, I saw your 410kgs earlier in the week and was stupified!

 

I've got a fireblade engined car that weighs about the same as that, but am hoping to just dip below 400kgs over the winter.

 

Would you care to share any other of your weight savings? ...as its all very interesting.

 

Any idea what your car weighs without the engine and gearbox? (given that a fireblade engine weighs 55kgs)

 

I take it your car is non-road legal, and so has no lights, no handbrake etc?

 

Cheers,

 

Ed

 

[murph7355]

Anyone know where you can get carbon bonnets and scuttles from...I doubt they'd be much lighter, and should drunken herbert fall on it it could be upsetting, but there's an aesthetic angle I'm thinking of here...

 

 

 

[EFA]

They would be v.expensive to make, and the product liability insurance would probaly cots more than the product!

 

Fat Arn

Visit the K2 RUM website

See the Lotus Seven Club 4 Counties Area Website here

 

[R2D2]

Metal Matrix Composite discs seem a bit crazy. I did some work a few years ago with Aluminium reinforced with BorSiC fibres and we looked quite carefully at "high" temperature properties.

 

Typical maximum operating temperatures are likely to be in the 300-325 deg C area. Any higher than this and the matrix will fail. Something to do with grain boundary strength I think.

 

AEA at Risley have made quite a few CF propshafts for Panos Lemans cars and other race vehicles.

 

They used Aluminium Alloy UJ housings which were pressed and bonded into the CF tubes.

 

I have also seen them used on F1 engine dynos.

 

The biggest problem seems to be that torsional vibrations tend to loosen the adhesive joint after some time and then the vibration levels become huge.

 

The Subaru WRC cars use Titanium props that are EB welded by a company in Milton Keynes.

 

I would have thought that the best solution for a BEC would be to use a flexible disc coupling between the bike gearbox and the reversing unit.

 

A light weight disc coupling would have less overhung weight than a carden shaft and this must help bearing life for the gearbox shafts.

[edmandsd]

To Mr Ed

 

You're right the car isn't road legal and has no lights/handbrake etc.

 

My all alloy 2lt BDX (with all ancillaries) and alloy 5 speed sequential gear box weigh 110kgs combined (I'd read somewhere that a Fireblade weighs 66kgs incl box and that a Hyabusa was about 20kgs heavier than this)

 

It obviously helped building a car up from a bare chassis so as to minimise weight wherever possible.

 

HTR made me a one off wide track front suspension set up that saved about 3 kgs over the standard live axle front end.

 

I also fitted 10.5 inch F3 solid rotors on the front that saved another 3 kgs.

 

Normal 4 pot front, 2 pot rear Caterham alloy calipers.

 

Wiring loom weighed 3 kgs.

 

It's got all the usual carbon bits and MBR mag split rims with crossply ACB10'S.

 

Single aeroscreen.

 

Battery weighs 5 kg

 

HTR also made me a l'weight rollbar - Not quite as light as the standard live axle bar but at least one that would protect me if the car turned over !

 

Removed runners from single carbon seat etc etc

 

From Mr Ed

 

Home of BDR700

[mr_ed]

>My all alloy 2lt BDX (with all ancillaries) and alloy 5 speed sequential gear box weigh 110kgs >combined (I'd read somewhere that a Fireblade weighs 66kgs incl box and that a Hyabusa was >about 20kgs heavier than this)

 

110kgs, blimey (thats light!). So 300 with no engine, 360 with a blade engine. Being as EVO bloke says his caterblade is 370kgs (I think Road Legal) then that ties up quite nicely.

 

Claims for the fireblade range between 55 and 65kgs aye. The busa and blackbird are both 83kgs.

I think being as I could lift my blade lump easily I'd say it was the lower end of that scale. Bit weedy me.

 

To have the weight of a bike engined car with the power and torque of a car engine sounds like having cake and munching away big time!

 

My blade is a road legal (cough) Westy, with the lighter freelander diff, no reverse box (electric), mike barnby wheels and ACB10s (6inchers). Its 410kgs, but still has the standard M16/Sierra brakes all round. Will probably put HiSpec ultralight 4's on it, with the ali belled disks on it over the winter.

 

Seeing cars like yours, and the SBD westfields with startlingly light weights gives me hope theres more to come off mine ;) Although deciding to make my car non-road legal would be a big step.

 

Cheers,

Ed

 

[Blatman]

Mr (Westfield) ed....

The biggest obstacle you'll face is the weight of the bodywork unless you already have Westfields lightweight "race" bodywork...........

[scooby dooby doo]

I weighed my car against a megabird a couple of days ago. once fuel was taken into account he was only 10 kg lighter than my K. both of us are aeroscreened, but he's also missing doors and boot.

 

blatman - how much lighter is the race bodywork - that was the only reason we could think of for the extra weight (although IRS weighs more than a dedion so will account for some of it)

 

HOOPY 500 kg R706KGU