Carbon fibre propshaft modifying.

[modifyitmike]

Hi All.
As some of you might be aware, ( SEE MY BUILD PICS ) im building a RWD fiesta mk6, running st170 engine and mazda rx8 gearbox, ( it came with the carbon fibre propshaft as standard ),
i was hoping to use the carbon prop in the fiesta, abit with slight mods. eg new pinion flange to match cosworth rear diff. what im wanting to find out is....
IS IT POSS TO SHORTEN A CARBON FIBRE PROP..
REGARDS
MIKE

[Graham]

a few have dont it, basically teh rear yoke has a spline which is a tight fit inside the carbon prop. so people have just cut the prop down and pressed the yoke back in again

[alladdin]

as above, trig has done it and he is not too far if your stuck. if you sort it you can train me as i need to do same. also someone on facebook is doing adapters - rx8 flange to ford - i think its lee butcher but not sure now.

[modifyitmike]

Thanks Graham / Alladdin.
i havent tried the prop in position yet, so unsure how much shorter it has to be, and i know the diff end flange wont match up. as im still seam welding it all up, next job is cut out and make trans tunnel to suit,
thanks
mike

[wildo105e]

as above, trig has done it and he is not too far if your stuck. if you sort it you can train me as i need to do same. also someone on facebook is doing adapters - rx8 flange to ford - i think its lee butcher but not sure now.

would that be BRE i think it stands for Butcher Race Engineering he seem to be doing rx8 adapter plates etc. to duratec now

Also same as above for shortening and i was also thinking whether an adapter would be easy to make for the flanges.

[modifyitmike]

thanks wildo105e
have just messaged BRE, i await there reply
cheers all

[Turboman]

I have shortened the rx8 prop which I use in my mk2 escort

[scoobymike]

Hi turboman.
How exactly did u go about shortening the rx8 prop.
Cheers
Mike

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[Turboman]

I cut a band around the end of the prop using a hacksaw,until I could feel it touching the metal insert I then put diagonal cuts in the band until I could unwrap the carbon fibre from the insert. Then pushed the insert further into the tube

The end also needs modified to bolt to the English end on diff

[wildo105e]

That’s how I have seen it done before how hard is it to press in. I need to connect an mx5 gearbox to an atlas (did have an rx8 box) so ideally i could trim the gear box end which gives me room to have the spline yoke welded on without heating the carbon then push in and use an adapter on the axle end

Butcher race engineering make and adapter


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[Turboman]

It's a fair amount of pressure to get it to go in.

[modifyitmike]

Hi Turboman.
As you say,, cut around and push it back in, with a fair amount of pressure, so how then dont it spin inside the carbon shaft when you give it the beans, how does it just not rotate inside as you have just pushed it further up into the carbon, ?????? my minds working overtime
regards
mike

[Graham]

it has fine splines which grip the carbon

[Turboman]

Yes as Graham says it has splines on the insert there is no glue etc holding it just the splines pressed into the carbon fibre I have a photo of what the end looks like on the one I cut apart to see how it was made send me a email address and I will send it to you

[Turboman]

Photo sent via email

[wildo105e]

When you look at the prop you see the bulge where the spline is. This is due to i imagine the force it is pushed in and the strength of the carbon fibre clamping it an bulging out. It's like a really strong interference fit.

I think it is hard to comprehend how strong carbon fibre is if used correctly.

[modifyitmike]

Turboman.
One,s again thank you for emails
regards
mike..

[Chris Burns]

I'm about to take this challenge on Was a press needed to insert the yoke further into the shaft? i'm using a BRE flange adapter.

thanks

[jimmy2006]

thats mad that it can take all that power and not slip

[modifyitmike]

I'm about to take this challenge on Was a press needed to insert the yoke further into the shaft? i'm using a BRE flange adapter.

thanks

let us know how you get on with mod. cheers mike

[GavinR]

Have a look at https://www.scimitarweb.co.uk/sgwrs/...4050&start=112
Someone shortening a carbon prop to fit a Scimitar with a Mazda box, not tested yet though
Unfortunately you'll have to register to view the thread

[katana]

thats mad that it can take all that power and not slip

Those splines offer a LOT of surface area not to mention interferance fit! In engineering, a 'good' smooth surface taper slip fit can transmit huge torque.

[wildo105e]

Be nice to know how much pressure is needed to press that in. I assume a lot.

[wildo105e]

Also if it helps, i believe the rx8 prop should also fit the 6 speed mazda mx5 box for duratec installs.

[alladdin]

Be nice to know how much pressure is needed to press that in. I assume a lot.

large sledge hammer worth i beleive

[wildo105e]

large sledge hammer worth i beleive

And some I imagine


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[Mash]

This is on my list of jobs for my Escort estate.

I'll be interested to see how you guys get on.

[modifyitmike]

Hi Everybody.
Can i just ASK.
All this talk of shortening a carbon propshaft , and how to go about it, ( i will need to do this on my project in time ) but nobody has commented on rebalancing it when shortened, as i would think it would need to be. or am i thinking outside the box.
cheers all
stay safe

[wildo105e]

The way i have seen to shorten it is to mark the yoke and prop tube with a line. Trim of some of the lenghth the push back in to allign the marks. As the yoke wasn't removed it should allign and be balanced. So from your picture take off an inch and push in until you get the desired length. This is ok on an escort as i don't think there is a massive amount to shorten by, your project may need more ??

I assume you cn still put weights on the yoke tube if needed.

this is all theory by the way.

[Mash]

Trigg has done it already and there are some good pictures in his thread here:

http://www.turbosport.co.uk/showthre...1076862&page=2

[wildo105e]

Trigg has done it already and there are some good pictures in his thread here:

http://www.turbosport.co.uk/showthre...1076862&page=2

thats where i saw it but couldn't remember who.

[stevieturbo]

it would need balanced, but weights would need to be epoxied or strapped on.

[Turboman]

There was no need to balance as the shaft and the U.J were never parted and you are removing a few grams on a item which weighs a few kilos

[stevieturbo]

There was no need to balance as the shaft and the U.J were never parted and you are removing a few grams on a item which weighs a few kilos

If you are changing the length, of course it needs re-balanced.

That's like saying you do not need to rebalance wheels after fitting new tyres.

[Graham]

If you are changing the length, of course it needs re-balanced.

That's like saying you do not need to rebalance wheels after fitting new tyres.

but you are only taking an inch or so off the prop, which is very little, ive shortened numerous steel props by a couple of inches over the years, never had an issue, and cutting and welding a steel prop is far more drastic the removing a small portion of carbon and pushing the yoke further in. in fact the only time i ever had issues with prop vibration was when i bought a new one from Burtons!

your tyre analogy doesn't really stand up as no one is fitting new parts, if you saying the prop needs rebalancing because its slightly shorter, then your wheels need rebalancing once the tyre tread has worn down

[stevieturbo]

Not quite the same thing though. Although yes if it is only 1" shorter, that is a small amount.

It's also like saying if you change engine components you do not need to rebalance....You should do though.

I have cut and welded steel shafts myself, and they did appear to run smooth, but I'm also in no doubt they should have been rebalanced. But for a cheap runabout at the time, I didn't care.

[Turboman]

Yes I would agree if you were moving the balance pads a vast distance or changing the balance plane, but you simply are not removing enough material to cause a issue. I have done this 5 times now and not had any issues. Sometimes practical engineering is better than speculative engineering

[alladdin]

It's also like saying if you change engine components you do not need to rebalance....You should do though.

why ?

ford etc dont balance every engine as a complete assy. ? ( or didnt ) they rely on accurate repeatability - so swapping even a crank for instance shouldnt make a difference as long as it aligns on pulleys / fw the same as last identical one.

as long as the end yolk is pressed back square to the tube in same alignment i cant see an issue but if one arrises on 1 from 10 then balance later ?

[Mash]

Yes I would agree if you were moving the balance pads a vast distance or changing the balance plane, but you simply are not removing enough material to cause a issue. I have done this 5 times now and not had any issues. Sometimes practical engineering is better than speculative engineering

So how did you press the yoke back in Turboman? Interested as I'll be doing this myself soon.....

[Turboman]

I used a hydraulic jack and welded a jig up on a metal bench