Hi,

I am working with a college project which is trying to produce prototypes for a new remote controlled racing sport. The sport is just an excuse to have a technology demostration testbed, much like formula one. We are using advanced Unmanned Vehicle technology to drive the cars, and want the cars to be as autonomous as possible. Using sensors and remote control to race the cars for four to six hours.

What does this have to do with carbon fiber?

Well, the prototypes that we are working with are made from something called a tetrix robot kit. http://www.tetrixrobotics.com/
This stuff is Heavy and I wanted to try and make mine as light and strong as feasibliy possible. I have always had an intrest in composites, but never had a chance to really get to work with them. After looking at the costs involved, I think that building the parts ourselves will not be any more expensive than buying the tetrix kits, and I think they will be more durable.

I have no doubt that the body work of the cars will be fine as either pure carbon or carbon-kevlar mixes, but I wonder if I will need to use coring material for the chassis, as these cars are being designed to drudge along at 70 MPH \ 112 KPH. Being autonomous, they will crash, and being remotely controlled, they will be badly driven, then crash.

My basic questions are this,

1.) Just how difficult is it to work with coring material?
2.) Is there a place that explains how to take your coring material and fiber and make a finished piece?
3.) Are cored panels really only ment to be straight, or can you mold them at all?
4.) Is carbon strong enough to handle being a Chassis by itself? Could I skip coring altogeather?
4.) and of course, do you guys think i'm barking up the wrong tree by using carbon fiber? (still interested for other projects, motorcycle repair yada yada.)

Thanks,
James

well if your not worried about perfection I think CF is a good base. I think the coreing is a good isdea but not worth it. I would build your cars frame then just make super light 2ply CF body panels.

The Hardest thing I think you may encounter it how to make the mould for a part you dont have? You will spend most of your tie getting the mould.



If Brute Force Isn''''t working your not using enough...

3). Yes, cored panels can have curves in them.

4). Yes carbon fiber is good enough to make a chassis out of it... McLaren F1, Aston Martin 1/77, Pagani Zonda, etc use it as chassis.

5). For example, the car body. You could as well consider Diolen which is less expensive than carbon, almost looks the same, and has "as-good-as" or better impact resistance... badly driven car, you said, huh? You can also use carbon/kevlar as a good impact resistance, but its as expensive as carbon fiber.

Depending the size of your car, i would suggest designing carbon chassis as the lower half part of your car body, so you can bolt mechanical stuff to it. So you save weight with your chassis being a part of the body. i would bolt stuff by pinching carbon fiber chassis plates in aluminium or 4130 flanges, as applying a bolt torque directly on a composite may lead to cracks or fatigue occuring sooner than expected. Using flanges would transfer "bolting clamp force" to a larger area, which would help. And upper body half would be just a skin.

Hope I helped a bit.

 



 


    A $1000 electronic device will always protect a 10 cents fuse

Thanks guys,

As for the molds, no we do not have any, but I plan on cheating a little bit, buying commercially available remote control car bodies (Plastic) to make molds from, if that doesn't pan out, the Phd whose' pet project this is, is trying to get a 3D scanner and printing machine, which would give us blocks to make the molds from.

The coring is more for the cars that get military technology, one of our professors helped design the control systems in the reaper, and they apparently want to use the same extremely high end (But not classified) control technology into these cars. Of course, those would need ALOT of protection.

I like the Idea of using the body as the chassis, I'm just not sure if I'll get away with it, the prof. wants to have these cars use as much automotive technology as possible on top of all the advanced technology buried in them.

Man this project sounds very exciting. I hope u'll post some pics along the build, its always nice to see unusual projects.

 



 


    A $1000 electronic device will always protect a 10 cents fuse

Interesting stuff!

I don't think i'm qualified enough to comment though. What you have to remember about composites is that they can only be made really strong AND really, really light if you know where all the loads would be coming from. If you are expecting a lot of impacts then, yeah cf / kevlar / diolen is super tough, but composites don't yield. They simply split.

Take motorcycle wheels for instance, cf wheels are fantastically light but not overly suited to road use because of potholes and debris and so on. Functioning within design parameters is fine but you can't rule out a sudden, unexpected load in the real world, and nobody wants a suddenly disintegrating wheel! So they tend to be relegated to racetracks.

Extreme example I guess, but its something to consider. I guess if you're doing finite element analysis or something similar you can always build to worst case scenarios. I guess that's the beauty of composites, adding lots of stiffness doesn't have to mean adding lots of weight.

I used to play around with RC cars and those alluminium baseplates were light and plenty tough!

When you say chassis do you mean a box section style chassis or a baseplate? If you're thinking of working with enclosed cores then you might want to check out the links to carbon fibre bicycle frame designs on here, as they typically involving wrapping cloth over a core of ablative PE form or a honeycomb.

That process is very simple, the hardest part is arguably making the core sections from the draft (if you have axis to rapid prototyping or 5 axis milling- no sweat! ). Laying the composites on top can be as simply as wrapping resin soaked fabric around the core and vacuum bagging.

Making curved sections or panels, given the above technology, would be simple. And they'd be able to withstand massive loads.

I love the idea of a curved bodyshell with all the important stuff running inside the panels The only thing I can think of offhand that uses the bodywork as a structural member is a Vespa scooter

Just some ideas. Good luck!

About rc cars, my Team Associated stadium truck had CF base plate and it received a ridiculous amount of abuse. Coming to think of it, the CF base plate was the only part that I didn't break on that thing. In a RC car the wheels / arms tend to take most of the hits. Just my 2 cents...  Just remember the thing about carbon blocking RF signals.