[Closed] Why are there no carbon stanchion forks?

I'm obviouly not 100% sure, but I'm unaware of any inner liner fitted to Lefty Carbon fork(s), so supposedly yes it can cope with suspension oil... or at least, it can be laquered to resist it.

crazy, eh? and why no carbon tyres?

GW - Member
crazy, eh? and why no carbon tyres?

[i]Can carbon fibre cope with suspension oils? [/i]

yep, see all pace and dt-swiss forks - the lowers have lots of carbon.

I thonk it's getting the surface finish and durability needed for sealing that's the issue - even 'smooth' carbon is pretty bumpy.

crazy, eh? and why no carbon tyres?

you say that like Im missing something obvious. Care to enlighten?

I thonk it's getting the surface finish and durability needed for sealing that's the issue - even 'smooth' carbon is pretty bumpy.

fixed with "[i]carbon stanchion with ultra durable resin coat, milled and polished?[/i]"

yep, see all pace and dt-swiss forks - the lowers have lots of carbon

knew that. But was wondering if there was a metal tank in the lower to deal with the fluids.

even 'smooth' carbon is pretty bumpy.

cant be too tricky to lay up a CF tube in a thick outer resin coat that is then machined back perfectly cylindrically.

cant be too tricky to lay up a CF tube in a thick outer resin coat that is then machined back perfectly cylindrically.

Technically that is quite a challenge - vac bagging during cure will try and minimise the resin thickness, to somehow have a thick outer layer, but still have a high volume fraction for the tube is going to be hard in one operation. Post-fab machining will have its problems as well.

Sure it could be done, but can't see how it will be cheaper than a metal tube.

[i]But was wondering if there was a metal tank in the lower to deal with the fluids.[/i]

no, it just sloshes about.

precast resin cylinder, internally coated with wet resin, then laid.

🙂

I wont be beaten by complications....

Machining carbon....gotta love that!

Sure it could be done, but can't see how it will be [b]cheaper[/b] than a metal tube.

Why would it have to be cheaper?

wwaswas - are the bushings still interference fit in the inner face of the CF or is a bushing sleeve resined into the lower and replaceable buhsing inserted into that?

who mentioned machining carbon?

Machining carbon

Silly inkblot.

precast resin cyclinder, internally coated with wet resin, then laid.

I wont be beaten by complications....

You will be beaten on cost 😉

Why would it have to be cheaper?

You have seen the cost of decent forks as it, yes?

My mate's carbon seat post looks a scratched mess after just a few raisings and lowerings...

there must be an uber resin out there.

Also, seat tubes and seat post clamps arent known for their low-friction surfaces.

A top quality hard resin, polished to within a micron of it's life, running in lubed foam rings and teflon coated bushings. Knock out! 🙂

A top quality hard resin, polished to within a micron of it's life,

Moon-on-a-stick at the moment, for a thermoplstic polymeric resin, AFAIK...... if you want to get uber-bling, then metal matrix composites would be the way to go to get a stiff tube and hard outer surface, but they are even more outrageous cost-wise

there must be an uber resin out there.

Moon-on-a-stick at the moment

defeat conceded 🙁

ALso, why do Fox make such a noise about the corrosion resistance of their kashima coating? When was the last time anyone saw rusty fork stanchions? How about making them more resiliant to abbrasion instead! 🙂

just a push fit from memory when I had a peer inside.

Why?

because thats what men in lab coats are paid millions of pounds and given ferraris and prostitutes to invent.

Prob because an aluminium metal tube will do the job more cheaply, better for longer. You may also lose internal oil volume if the leg wall thickness has to be increased for CF, hence existing damping kit wouldn't fit in there.

I struggle with long sentences but resin's never going to be as "hard" as anodized aluminium.

Stoner: how about diamond coated carbon stanchions? 😛

couldnt afford the CNC milling bits needed to machine it.

Stupid idea.

may also lose internal oil volume if the leg wall thickness has to be increased for CF, hence existing damping kit wouldn't fit in there.

45mm stanchions then 😉

may also lose internal oil volume if the leg wall thickness has to be increased for CF, hence existing damping kit wouldn't fit in there.

Unlikely - purely from a stiffness point of view, the wall thickness of a CF leg could be thinner for the same OD and as the modulus of CF is a lot higher than aluminium alloys. I accept it is more complicated than that (strength, manufacturability, impact resistance blar-de-blar-de-blar....), but that would be the theory.

because thats what men in lab coats are paid millions of pounds and given ferraris and prostitutes to invent.

Stoner - Member

may also lose internal oil volume if the leg wall thickness has to be increased for CF, hence existing damping kit wouldn't fit in there.

45mm stanchions then

Too much friction. See ZZYZX for further info 🙂

where's scientific altruism when it's needed eh?

ZZYZX

Is that sleepy physics?

Stoner - Member

ZZYZX

Is that sleepy physics?

In my house it is the tool of choice for owning:

[img] [/img]

Alas due to the friction from the massive stanchions it was rubbish as a suspension fork.

You need a word with your plumber. The drains arent supposed to come out of the lawn like that.

where's scientific altruism when it's needed eh?

A carbon tube with a thin, kashima-coated aluminium tube around it.

And then another thin aluminium tube inside it to allow the piston/damper to seal?

So we're replaceing one thin aluminium tube with 2 thin tubes and some CF inbetween them, which were not quite sure how we're going to get in there?

There are stronger/harder aluminiums we could use and don't, so I'm guessing we've reached the point where the need for stiffness and strength are equaled by a certain material and trying to go any lighter/stronger results in less stiffness, a bit like trying to use 953 in MTB's.

I was joking about the aluminium tube.

<Yoda mode> Truth in that, there is...hmmmmm </Yoda mode>

Why are there no carbon stanchion forks?

I'm sure Al could bodge something together for you. 😉

Getting the chemical resistance would be no issue. Maybe a vinyl ester resin or an epoxy novolac.

You could even polish them smooth but I think you'd be replacing them every ride as I don't think they would be resistant to the wear.

Maybe you could try some nano aluminium oxide in there and a good post cure regime. Still not convinced.

Does carbon composite get used on any other similar contact surfaces?

How about still having a coated alu stanchion but much thinner so it is basically a surface for sliding. The stanchion tubes can then be internally coated on carbon. I'm not sure how but I imagine you could pre-make a CF weave tube and then a bladder could be put down the middle,resin added and bladder inflated. The resin is then cured, bladder deflated and removed and you have stiffer and lighter stanchions.
Or maybe the outer alu sleeve could be header up then pressed over a carbon core before cooling?

A lot of forks use the internal surface of the stanchions for the air/oil seals to work on so you'd need to do the insides too.

same reason they arnt made of Ti - carbon is flexy. that is the whole point of it