Rex2342

I am thinking about designing a chassis and a few other peices for my RS4 3 SS.I want to use 3mm thick carbon fiber for the chassis(http://www.arts-hobby.com/store/item...pid=1&pcatid=0).I am wondering what to cut this with so I can get a nice clean edge's and nice straight cuts and will 3mm be stiff enough?If anybody has any hints or tips I could use them.I don't want to screw this up if I try this.

*Crash*Johnson*

My Feedback: (7)

either a dremel and router attachment or roto tool thingey with one.
Clamp down the carbon fiber to some pressboard or scrap and router it out.
Use a straight router bit and your piece will be straight.

My $.02

shoehead

3mil. is what most radio plates are made from so
that will deffinatly work. But most chassis are thicker.
In addition, the bottom of chassis get tons of abuse.
The carbon wont hold up very long to that without
de-laminating. I would stick to aluminum for the bottom
pan. I recoment a rotary tool like a router or dremel.
Harbor Freight has small routers for twenty buck I think.
Arts sells dimond and carbide bits for them. Again must
be hard and sharp to avoid de-lamination. Anything
you would be able to cut the carbon with would also
be able to cut aluminum so why not go for a carbon
radio tray and an aluminum chassis plate...

They say that you should run cyno. around the edge
of the carbon to keep it from unraveling when you are done.

Rex2342

I was gonna use that stuff they put on the bottom of ski's to protect it when I was finished so it wouldn't get beat up to bad.The aluminum Super chassis HPI sells is only 3.1mm and it's 70$$ so I figured 3mm would be fine for a chassis and it only costs 37$$ and it should be just enough for the chassis with a few scraps left over to make some small things plus the carbon is lighter.I'm just kicking around some ideas i've had and wanted some input on them.I already have a carbon radio tray and wanted to know if the 3mm carbon would even be stiff enough for the chassis.The alloy one they sell has holes cut out to save weight but since the carbon is lighter I can keep them their so I don't sacrifice rigidity the weight.


I gotta go to work keep the info coming i'll check back later thanks.

spadworld

To protect the carbon you can use a little extra epoxy on the bottom. this will also help thicken it some. Keep and eye on it and when you gouge it or scrapi it down just sand it and add a little to the thin spots. It'll just act as a wear spot so it won't really add to the strength.

NitroHolmes

Another alternative would be JB Weld. That stuff it super tough and it's got enough rigidity to add some strength to the chassis.

I agree with shoehead though, you'd be better off with an aluminum bottom pan. Once the carbon fiber gets a nick in it, it's strength drops dramatically. If you want something that has the best of both worlds, you'll have to make it.

packfan88

My Feedback: (2)

watch when your cutting carbon fiber.
its makes small slivers of stuff that can get in your skin or in your eyes and throat. make sure you follow usual saftey precautions like gogles and ventilation.

i email this guy about prices on sheets of carbon fiber. ill let you kow what he says.

shoehead

Another idea I just had is to add a thin .010 sheet of
aluminum under the carbon?

I like the jb weld idea though... That stuff is cool and you
could sand it pretty smooth.

NitroHolmes

Great idea with the .010 aluminum sheet! You could increase the stiffness even more if you put a thin honeycomb layer between the two.....I'll explain what I mean later, I've got to go to school right now and I'm a little late....

GALAXY

Know what a CNC is?I might be able to mill it for you but writing the program takes time and I'd need a CAD drawing.Just an idea.

shoehead

You have a CNC? I got one of those blue plates of carbon
and I wanna make a radio plate for my mtx-3 out of it. I was
going to rout it by hand but If I give you a cad drawing of it
would you cut it for me?

NitroHolmes

Okay, so the honeycomb deal....

The honeycomb can be made out of anything. For this application I'd suggest using an aramid honeycomb. The basic idea is like what you see in cardboard. Two pieces of thick paper aren't very strong, but when you sandwich a piece of honeycomb between them, you gain rigidity from the geometry of the center piece. Here's a link that talks about some of the different types of honeycomb out there:

http://www.ultracorinc.com/papers/NewDevelopments.pdf

NitroHolmes

pic

Rex2342

How thick is the honey comb?I can just sandwich it between two piece's of thinner carbon fiber and still get the same rigidity as if I used the thicker stuff.

NitroHolmes

It comes in different dimensions (thickness and size of the honeycomb). I would imagine you'd probably use something on the order of a few(2-5) millimeters if you can find it that thin. Yeah, you glue it between two pieces of carbon fiber. You should probably use an epoxy that is designed for the carbon fiber. I've seen the carbon fiber "sandwich" used in RC rocket wing design and in RC boats. Maybe check some of those message boards and see if those guys can give you more info.

NitroHolmes

But i wouldn't necessarily go with thinner CF. Stay with what you've got and it'll be that much stronger.

shoehead

You need to still keep in mind that the thicker you make
the bottom plate the more you are raising motor,feul and
batt. If you use a 3mil sheet with a 2mil honeycomb and
another 3mil that is raising everything pretty high and is
probaby still lighter that the 3 mil aluminum. These cars
have tons of power and the last thing you want to do
is raise the center of gravity. A little extra weight on the
bottom should be welcomed (within reason). not to mention
that you need to look at weather your a-arms bolt to the top
or bottom of the chassis plate. Mine bolt to the top. which means
that thickening my bottom plate = lowering my ground clearence.
Right now I have a 3mil plate and 4 mil. of ground clearence,
and that is not much. But if I had an 8mil thick pan I would have
to raise the car quite a bit... Not trying to be negative. I am
ALL for homebuilt mods. It can certinly be done. Maby some
suspension relocation and if you cut holes for the tank, batt
and motor to sit lower...

GALAXY

I work at a machine shop and I might be able to do it for you,I'll have to see.If all the holes were marked it would be a lil faster but setting the arcs and blends on the edges are the slower part.I bet that blue carbon fiber looks sweet,did it come with machining or cutting info or anything?Be cool to know how fast to set the RPMs...I've never worked with CF yet but I was thinkin about it.The unraveling of edges part kinda scares me and I don't know what an end mill would do to it.Let me know,even if you cut it I'd be interested to see how and what it looked like when it got done.

packfan88

My Feedback: (2)

hey i contacted this guy who sells sheets of carbon fiber.

he sells 2mm thick stuff, in a lot of different sizes.

this was his response to a question i asked him on what sizes does he have.

"Smaller pieces are a little more expensive per square foot because we have
to cut sheets. 1 x 1=$60 2 x 2= $140 and 3 x 3=$190.Thanks CARBONTRIX"

shoehead

All they szaid was to use a carbide or diamond bit.
I am REALLY not sure how CNC works but dosnt the
CAD file tell the machine about the holes and arcs?
I'll ask them about RPM and let you know.

I am planning to take a class called Rapid Prototyping
at art center
http://www2.artcenter.edu/atnight/co...d=2677&loc=PAS
Hopefulli I can use thire machines and stuff...

GALAXY

wow,that'd be a cool class.The CNC has to be programmed by giving it the X,Y,Z points for each different function.unfortunatly it won't read an Autocad dwg. file so I'd have to sit and enter all that info onto the CNC.Once thats done though,it'd be just as easy to do 100 of 'em in as long as it took to program it.I'd use probably a 3/8 carbide end mill for the edges and a 1/8 for the slots.Would there be any countersinking or anything?what would that do to the fibers?I'll look for info Tuesday at work and see what I can find

shoehead

I asked the carbon supplier and he said:

"It depends on the type of tool, size of the tool and depth of the
cut. All
I can say is to experiment and find a speed and feed that matches the
tool
and finished desired."

Not that helpfull.

I can counter sinc the holes easliy enough. So that isnt a prob.
It's getting nice looking cuts and doing precise holes like the
one for the throttle servo that concern me.

That class does look sweet! I hope they let me waiv the pre-rec
class though.