[Closed] Anyone do a carbon fibre pannier rack?

Don't think so, not the ideal material.

You're welcome.

nichomatic.

(edit - that's not a valid answer to your question, by the way 🙂 )

Never seen one. Tubus do one in Titanium if that helps.

As others, I can offer no answer.

But I do want to know why you want one? Have you got some matching carbon fibre pannier bags?

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I reckon that'd be pretty cool. They'd have to be pretty aero-styled, and have huge stickers though.

Carbon fibre is cool!
and more importantly, light n strong.

If it's good enough for a bike frame, why not a rack?

It kind of links with one of my previous threads, "what panniers for jumping?"

Are you any good at knitting or crochet?
You could crochet or knit the fibres together to made one yourself then slap some resin on and job done.

CFRP is OK for strength in tension, but not so good in compression (think rope) Its the plastic that takes the load in compression and the fibres that take the load in tension.

CFRP is OK for strength in tension, but not so good in compression (think rope) Its the plastic that takes the load in compression and the fibres that take the load in tension.

You've just summarised 4 years of my life in one sentence..... 😆

If it's good enough for a bike frame, why not a rack?

Becasue you dont tend to strap stuff to your frame, very tightly, with metal hooks and stuff!

You could crochet or knit the fibres together to made one yourself then slap some resin on and job done

you missed out that the fibres have to be man made polymers, which you burn in a oxygen free atmosphere

Just reinforce the bits that get abrasion
Agree about the weakness in compression, but people sit on CF seatposts do they not?

And after seeing some new tech from my friendly neighbourhood rapid prototype people, there are neat ways to add on useful mounting features.

You're either mad or a pioneer. I'm going with mad, at least until a Bikehut-branded one is on the market.

Its the size of the tubes needed to get the stiffness that is the issue. Easy to get CF to be stiff in a 30mmm diameter tube - much harder with a 3 mm diameter tube.

Go for the tubus titanium one

Presumably, it would be perfectly possible to integrate a rack into the mainframe of a carbon fibre bike, and to then re-design pannier interface to fit.

If you were starting with a blank sheet of paper, say, you'd perhaps extend the top tube aft of the seattube in a single flat bed which cantilevered onto the back of the seat-tube. You could then run a metal rod armature through so that fixing rails for the panniers projected where you needed them. At the chainstay you'd have fins projecting upwards to fix the bottoms of the panniers onto somehow.

I think we'd have to acept we'd be designing one of those tossy concept bikes that also has a docking station for your iPhone, and indicators. 🙂

the monocoque approach would be more successful than trying to make a tubular one.
But CFRP is still not an isotropic material.

Or you could try concrete it is less dense (lighter) than aluminium, but its anisotropic as well.

The real problem is one of distributed loads, or rather not where a standard pannier mount is concerned.

CFRP is very 'strong' (can handle very high stress), is actually very fatigue resistant, despite the common beliefs to the contrary, and can handle loads in both tension and compression, depending on the weave.... very important.

what it cannot do is handle point loads caused by pannier mounts, or attacks by sharp rocks. the material cannot distribute this load to all the fibres easily and hence the eeny teeny weeny littel fibre that it contacts will break as the fibres themselves do not like being loaded in bending.... Carbon Composite is different to carbon fibres.....

you could make a CFRP rack, but it would not look like your traditional tubed jobbla, and the panniers would have to mount through some kind of distributed load interface, or add lugs like you see in any CFRP frame for bottles or mech mounts

CFRP is very adaptable, but is NOT interchangeable with metals, it requires a different design philosopy...it is NOT isotropic, it does not behave the same in all directions of load, and it does not behave linearly with increased load.
CFRP is not all the same,
AFRP (kelvar) is NOT the same as CFRP.. etc etc...

Hope that helps...

I'd go with titanium for the 'springy' properties it posesses.........

what andy said ---^

Oscar Pistorius finds CFRP is a bit springy.

"'springy' properties it posesses......... "
yes a lot of materials do obey Hooke's Law.

How does one get round the problem of fracture toughness with CFRP?
Fracture toughness not to be confused with fatigue.

Yep they are available.
[url= http://www.axiomgear.com/products/gear/racks/rear-racks/streamliner-carbon/ ]Axiom Streamliner Carbon Rack[/url]
Not excatly light though!

Nice find steelfan! As you say though, not exactly light @700g vs 230g for the tubus titanium (I would say you are wrong about using thin carbon tubes TJ, looking at that and from experience)

I appreciate the comments about CF not being like metals, and not isotropic. I know it requires a different approach. Looking at the axiom rack they have to use a lot of metal to attach to the CF, seems like it's not using the material to best effect.

Also thanks for the video, but the process I have seen avoids a lot of the faff with that method, for certain geometry.

Macavity - Hooke's law 🙂 so long as you don't mention mohr's circle we'll be ok.....

Fracture toughness can be handled with different lay-ups and different weave patterns. It is all about spreading the load and avoiding localised bending and stress concentrations. Hard to describe without pictures but I can recommend a very good book on composite design if you are really interested... but it is a long slow read.....I know, I had to.... zzzzzzz

'good' carbon frames will have some impact absorbency to the outer cosmetic layer which reduces damage to the deeper layers. It may use aramid (kevlar) which is 'stretchy' to aid in this. (again trying too avoid to many pure engineering terms for fear of being even more boring)......

interesting that the axiom one has CFRP based legs, but all the interfaces are metal.....

I do like those Spec transitions....

Actually, good point Macavity. A carbon fibre rack designed along different lines would work - some kind of semi-suspended springy thing rather than a traditional rack shape.

That Axion frame is just a standard one with carbon fibre tubes. I don't see the point. If you're going to use CF you should design it with CF in mind, that way you get the 'strength' (not a good word) and stiffness where you need it at minimum mass.

Sweet jesus, that Spesh is about the most hideous bike I've seen.

I thought something like this would work well in carbon
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you could try one of these knitting patterns.

You guys are taking this trolling attempt far too seriously!

I'm imagining something that might resemble the front mudguard of a sports motorbike, but with a flat section. I think some of those are made from Carbon Fibre. I don't know enough about the material to understand if such a thing could be made strong enough to carry a load however. But it would look very nice, and could also act as a mudguard.

surely the carbon fibre would spontaneously explode and shatter into tiny pieces when the bags are loaded onto the pannier

Trolling!
Ha ha this place gets more conservative by the day