trek's new carbon dh bike

General Composites Discussions Composites Talk
#1

Here’s an interesting link to Trek’s new Session 9.9 carbon dh bike. Whats interesting from a composites perspective is about half way down there is a cutaway section of the seattube: It states about the problems associated with bladder inflation round tight areas, instead what is used is a ‘proprietary low-density, ultra-stiff material inside the frame to evenly pressurize these areas from within’.

Any ideas how this foam is integrated within the bladder? (aiming to see around Trek’s usual marketing malarky) Presumably some sort of expanding foam…

http://www.pinkbike.com/news/trek-session-carbon-9.9.html

#2

I wonder if that stuff is like Expancel foam which expands when heated. That used in conjunction with bladders makes sense to me.

see this thread: http://www.compositescentral.com/showthread.php?t=5872

#3

Maybe Divinycell? http://www.diabgroup.com/europe/products/e_prods_2.html

#4

Interesting isnt it - I was thinking it was something like expancel but that could potentially be very tricky to integrate with bladders: particularly at the bladder/foam interface. Also, cant see why they wouldnt use the foam throughout the whole frame anyway - would surely reduce the overall weight and possibly layup complexities by laying up fibres over a solid foam as opposed to a floppy bladder!

Rotorage, are those DIAB products not just standard structural cores?

#5

They probably just need some additional strength around the pivot point of the rocker-arm suspension. That pivot point bearing looks to be pressed directly into the carbon.

#6

Findhan - Yes they come in standard sizes, but you can also get anything your budget can pay for. Just like Airtech, they sell standard bags but if you need something unique for your application they can make it up as long as your pocket is deep enough.

#7

I think its great to see companies opening up like this and showcasing cut-ups and sectioned parts! sent expancell guys an email to see what they can offer and will also drop the DIAB guys one. thanks for those links.
In the next 6 months, would like to try expanding foams as a pressurisation media for internal bagging of structures, sounds way better to me than bladder bagging.

#8

Findhan, could you give us an update on the expanding foams? Have you gained any experience in using Expancel?

I am about to embark on the same exercise, so any comments would be appreciated. Always easier to learn from someone else’s mistakes!

#9

Could also be high density epoxy foam. (PB600 from Sicomin)

Expancel needs to be mixed with a matrix of some sort to gain any stiffness. In fact, to reinforce a carbon tube you would like to see something with high compression strength / high density.

#10

I ashamedly havent tried them yet-I have three variants sitting on my desk and havent tried any of them! A-nobel are very helpful though and would be happy to send you samples.

#11

Rohacell (or any PMI foam) also expands when heated. I dont understand how Expancel can become a core for your product if you have to place the powder within a stretchlon sausage (as bladerunner described it). It seems like this means that any good flex would make the foam “core” separate from the composite facings. Can an expanding foam (like 2-part PU foams) be injected into a layup and compact a wet layup from within? Or would the fact that the foam and fabric are both wet cause a problem?

#12

Hi guys…my first post.
I agree with Herman. I haven’t use that product…but I have used SP gurit F230… expanding epoxy making solid core glider wing for dynamic soaring.
I do think it is PB250…

http://translate.google.com.au/translate?hl=en&sl=fr&u=http://www.sicomin.com/&ei=NyoUTqiNLMSImQWW37yZDg&sa=X&oi=translate&ct=result&resnum=1&ved=0CCkQ7gEwAA&prev=/search%3Fq%3Dsicomin%26hl%3Den%26sa%3DX%26biw%3D981%26bih%3D661%26tbas%3D0%26prmdo%3D1%26prmd%3Divns