Carbon Fiber mold 6

[dipstick]

Tube Construction:
I'm in the process of making a 2.5 inch tube with a gradual 90 degree bend on both ends for the purpose of creating a custom cold air intake for a Miata MX5. This cold air intake has to serve a dual task. One is to reach downward to the air dam and bring in cold air upward to a resevoir blasting across a high flow air filter. This filter takes the cool air to the injection system via the 2.5 inch tube previously described. My problem is that being new to using fiber, I'm accustomed to metal and intended to use aluminum but fiber caught my attention, what should I use for mold material and how can I get the two 90 degree bends and all of this being one piece? Anybody!
Great admirations to those minds in the sky,
Dipstick

 

[patprimmer]

Do you need reinforcement in more than 2 planes. If not, maybe you can filament wind with a single yarn of carbon fibre, but that also,might not give the aesthetic effect you want. From what I can guess from your post, I think you are chasing rainbows.

If you want a woven carbon look, you can't have complex shapes without joins.

Just pretend you are a Tailor or an Upholsterer. Could you get your shape in a suiting fabric or upholstery fabric, without seams. If not, why do you imagine you can get it in a carbon fibre fabric.

Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[ArffinIsht]

Uniformity is what i need.
I dont imagine it, I have a two car parts infront of me now which to the naked eye seem to have no join. Now maybe they have a mechanical method of weaving a knitted jumper style sheet which could be inflated from within, are hand made or an advanced mechanical technique has been used...i do 0's and 1's not nuts and bolts so just dont know.

My frame needs strength in a flexing plane and to a lesser degree in a tortional plane.
It is a recumbent cycle frame therefor the load is my mass from above plus cornering vectors and the tortional is for stability.

I will mail you a stock shot of the advised foam former for this frame as there does not seem to be a way to attach it here. The advised finish is body filler sanded and sprayed but i would like a fine CF finish.

The fillament sounds time consuming but i imagine it to be very neat could you describe the process.

 

[patprimmer]

It is really simple. You gust wind the yarn around the core, so you end up with something looking like a coil spring that is fully compressed

Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[ArffinIsht]

Does it have to be done in multiple planes?
How would i reenforce areas.

i sent an image of the former to your mail does it seem like a realistic process for that shape?

 

[patprimmer]

I just saw my spelling after an early am post "gust wind" for "just winde"

It Will be difficult to wind the filaments through the hole in the centre unless you make a small spool and do it carefully by hand. You do it just like a bandage, but using single yarns. they are wound very close and parallel to get full cover, but can be criss crossed at a wider pitch on the surface to get an aesthetic effect.

The helix angle you use when winding will significantly effect the reinforcement as it will only reinforce along the axis of the yarn.

Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[orkavic]

Hi everybody, I have a question about making a CF part through a mold. My plan is to create an RC airplane with CF. I thought the best way to do this would be with multiple molds, then maybe epoxying the parts together. My problem is that I have never done this before, so if anybody has some time and could write out some detailed instructions on making a mold, and creating parts with CF, I would greatly appreciate it. Also, what kind of materials do I need to buy, and where? I have been looking on the internet, and have some idea about the mold part, but I have no idea where to get Carbon Fiber, or the epoxy. thanks for your help!

 

[MikeHalloran]

Google will bury you in "how I made my CF whatever" sites, many including step by step ad nauseam and photographs.



Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

 

[kognition]

Hi people, this is my first post! Okay, yes i have gone over the issue for CF intercooler piping for my Silvia. Yes you can
do this and here is what i am currently getting ready to do. I purchased 3" I.D. pvc water piping in straight tube and some 90 degree elbows for the moment to get things started. You will go to this site to get your carbon fiber sleaving (or CF Kevlar hybrid sleeving)

http://sollerpaddles.com/composites/

He also sells West epoxy at a very good price. The pvc piping is shapeable after a 30 minute soak in the oven at 200 degrees. Get your misc shapes that you need, split the pipes that you have created, so this will be a 2 piece mold. Now comes the cool part! I found a company that makes sail boat steering wheels this way. You create a plastic bladder that will slide into the the initial 2 or 3 layers of the CF sleeving (prepregged before mold insertion of course) and you will inflate this bladder so it pushes the sleeving against the inside walls of the pvc piping. Hold until it sets up, and remove it from the 2 part tubing mold. Bake for
an hour at about 200 degrees. Now if your first prototype is too thin in the wall, you can always go back and add another
layer of CF sleaving. I do believe this this will work for this application. And i also know that i will maintain a cooler air charge as opposed to alluminum. CF has a lower mass by something like 1.5 compared to alluminum so there is definitely going to be less heat transfer. Good Luck on your projects! Also, the guy that has bubbles in his epoxy after mixing, go to the plastic store and pick up some of that large diameter clear acrylic tube ( the 6 or 8 inch stuff). Make a chamber that your cup of epoxy will fit in, make a sealable lid and attach a vacuum hose (i use a vacuum pump from a scrapped mini fridge : )) and this will suck the bubbles to the top of the cup of epoxy.

 

[kognition]

Okay, this is an addendum to my last post on this subject. I have a better way to do this and i think you will agree. Attached is my email sent to a friend that works at Garrett (the turbo manufacturer). He is also my next door neighbor.
///////////////////////////////////////////////
Yea the tube ends need to be beefed up for sure.
There will be a decent flange on there to prevent
slipoff, but since the clamps have a uniform
force
around the pipe... i might be able to wrap
unidirectional CF at the clamping points. I think
that could prevent crushing forces. But to answer
your question, they are making kayak paddles with
a form that you slide your prepregged CF sleeve
over... then they slide on a low temp heat shrink
to give even pressure and it squeezes out any
excess epoxy. Now applying this to the IC piping
idea: Lay up one sleave layer only and cure it.
Split it to remove off the form, then put the two
halves back together with maybe just epoxy to
fuse
the seams back together. So you have a tube now
in the shape you want that is about 1 mm. thick,
next you prep however many sleaves you plan to
use. Put those sleeves over the tube and then
slide over the low temp heat shrink tubing. Heat
the heat shrink starting at the center to let the
excess epoxy flow outwards to the tube ends. Cure
it and remove the heat shrink. Now you have a
perfect tube. : ) And it will have a super
smooth finish.

 

[coldbluesteel]

Hi, these are all great posts.Right now I,m in the process of designing a cf intake plenum for my car.My question is what would be the best way to connect the cf from the runners to the head and the plenum to the throttle body? Should I use an aluminum plate, and if so whats the best way to join the two materials, or should I go 100% cf with gaskets of course. Thanks in advance for any advice.

 

[kognition]

That sounds like a heavy project. Well running bolts thru any CF material is dicey unless you have at least 1/4 T to work with. Your fiber to epoxy ratio should be 50/50 by weight, so you do need to pre impregnate and lose any excess epoxy that would weaken the structure. As far as bonding CF to metal, just sand the alluminum plate surface with something like a 400 grit wet/dry paper. That will increase the bonding surface
area. For a variety of high temp epoxies, check out JD Lincoln
in Costa Mesa Ca.

http://www.jdlincoln.com/

they also prepreg
for customers large or small. But i think you are one the right track with the plate because it will handle the bolts better.
Mike

 

[doogie48084]

I do plenty of carbon fiber parts for engine covers and also some tubes. I will vacuum infuse the resin into the carbon fiber and in this method I will create as close to a 50 50 ratio as possible. I make a female mold for my tubes, and i also use a modified inner tube from a bicycle with the ends clamped. I pull my sock over the end and insert the tube and sock into the female mold uninflated, then close the mold and inflat the tube till it is slightly expanded. Now I can seal it with a vacuum bag and infuse the resin into the carbon fiber. I have done all my molds in this fashion for 3 years now and I have clear carbonfiber parts all the time.

Check out the latest engine cover parts for clarity of carbon fiber.

http://photos.yafro.com/pics3/i/20050331/14/d/3/9/d39d3106f864b02899bf82f02382c6a30_full.jpg

 

[kognition]

Hi Doogie,
That idea for the innertube came to me a few weeks back when i was racking my brain over a good inflatable bladder for the tube mold. I cut the tube as you describe and was amazed how well the tube worked! I had a flat tire on a bike in my garage so i thought what the heck, and tried it. Great pic of your work BTW. I am making CF mirror covers for the 240SX and working on some other parts as well. My work

http://kognitiondesign.com/mirror_covers_95-98_240SX.html

I am tooling up for the 350Z and Scion right now for parts.

 

[doogie48084]

there are other pictures of parts on that sight incase you didn't look.
Thanks, By the way, how are yur customers reacting to your prices?

 

[kognition]

Hi Doogie, have you done any structural parts projects such as strut tower braces etc? I have some uni carbon and have thought about making a one piece part where the holes for the shocks are just drilled out, and probably beef up the ends with a couple layers of kevlar to handle bolt and nut abrasion/compression. Like an upside down U beam config. The open area facing down towards the engine. Maybe like an overall thickness of 1/8" or even 1/4".
Mike

 

[scapaldo]

This thread is full of great information guys, Thanks.

Ive got some questions about mold construction though.

Kognition- Are you still using pvc? What did you do about imperfections between the straight pieces and the pre-made bends.

Basically, Im trying to find a fairly easy, cheap way to make several different pipe designs. They need to be mandrel bent style and easy to modify and remake.

I was going to use the foam tubing style, but I figured where it bent there would be a crease. Also, how could you shrink it without crushing the foam?

Thanks again

 

[kognition]

No we are making an rtv silicone 2 part mold over existing piping. And going to go with 500 degree rated epoxy. Then insert your CF sleeve with bicycle innertube, expand, and insert into a vacuum bag. The mold is not finished as of yet, but we have chosen to go this route. It provides the best finish over wrapping a pipe with CF.

 

[scapaldo]

Thanks for the quick reply,

What brand did you decide on for the silicon.
Also, did you first mold the part in one piece then split it, or did you make 2 seperate molds? The reason I ask is because Im making pipes that bend on more than one axis and will have to do it in one piece, then carefully split it along the center.

When you say "existing piping" Im assuming you mean factory steel/aluminum pipes. Im trying to find a cheap product that I can build plugs cheaply, without having to fabricate a steel pipe before hand. I liked the idea of pvc, but theres just too many imperfections in it and no real way to repair them.

 

[kognition]

I use the Tin Sil 70-60 2 part rtv available at

http://www.uscomposites.com

good stuff, but its $100 a gallon.

I take a pipe and mount it on a flat plane, build up a layer of modelling clay halfway up. Build a dam around it to hold the rtv when it is poured. I used 1.5" thick sheets of styrofoam available at Home Depot to quickly build dams and adhese them together with silicone caulk. Wax your clayed up surface with car wax paste using the soft sponge pad and dab the surface completely. A couple layers will do. Pour rtv. Let set. Now you need to very carefully flip this whole thing upside down. Carefully remove clay. Wax the new rtv surface and exposed remaining pipe surface very good. Build another dam and repeat the process. From this point to can reinforce the rtv shape integrity by glassing it. Then splitting that. Now you should have a workable shape to make parts from that will have the original surface finish.
Hope this helps.

 

[makaveli200369]

Hi guys I am new to this as well. Its hard for me to imagine what you guys are talking about without anypics showing it. I looked on google for these pics and it always pops up with pics of finished products. No step by step pics. Whenever you make CF pipes are the molds good for only one use like with the aquacore. Can anyone send me some pics so I can get an idea of how the layup looks? Any help is greatly appreciated!

Anthony
makaveli200369@aol.com