Closed chassis

[PeteG]

Hi,
Has anyone had any experience with closed chassis/ bodyless monocoque (ie panels filling in a space frame to give extra rigidity instead of a seperate chassis and body) builds? we're (newcastle uni) looking into doing one for our next car and I was wondering if anyone can give me any tips/ point me in the direction of any info.

thanks a lot,

pete

[PeteG]

Hi,
Has anyone had any experience with closed chassis/ bodyless monocoque (ie panels filling in a space frame to give extra rigidity instead of a seperate chassis and body) builds? we're (newcastle uni) looking into doing one for our next car and I was wondering if anyone can give me any tips/ point me in the direction of any info.

thanks a lot,

pete

[gug]

here is a paper you should try and get through your uni. send me an email if you cant get hold of it.


SAE TECHNICAL
PAPER SERIES 983055
Carbon Fiber Reinforced Steel Spaceframe
Techniques
A. Henningsgaard and C. Yanchar
Department of Mechanical Engineering
University of Minnesota – Twin Cities

[Sam]

the gong boys did that didn't they? have a yearn to them..

[The guru of guru's]

was a thread bout this a while back and the problems with corrosion of the frame with the inbuilt shear pannels...might be worth a look see

[Sparky]

Yeah we did one, carbon skins glued to the frame with structural adhesive, using a honeycomb inbetween, seemed to work pretty well. I dont know about it in alot of detail but drop me an e-mail at ah49@uow.edu.au and I will put you in contact with the guy that did it all.

[Moke]

We done used aluminium panels riveted and bonded in place with some fancy reinforced glue. Not as light a carbon but worked for us.

[Erik C]

The carbon skins on the 2003 University of Minnesota chassis increased the stiffness by nearly 60% with an increase in weight of eleven lbs. We used pre-fabricated carbon panels, cut to fit within the frame. Structural adhesive was then used to create a fillet between the tube and the carbon panel. Carbon tape was then wrapped around the tube and onto the panel; vacuum bagged and allowed to cure. On areas where we wanted the ability to replace/repair and panel, we used welded on flanges, grommets thru the carbon panel and Huck rivets. Aaron and Chris experimented with both of these in their SAE paper with some interesting results.
As far as corrosion issues go. This wasn't a concern unless you plan on using your car for many years, and have minimal margins on your structure. You could also use fiberglass, which would eliminate this. At the cost of stiffness....

[Lyn Labahn UW-Madison]

I noticed a few teams like Wollongong and UTA appear to have a "skin" that is stretched over their tubes, made out of carbon fiber. Is this done with a wet layup and some kind of backing panel to keep the extertior surface smooth? Any comments on how this is done? I would like to try this on the midsection of our car this year because we will not be using our traditional aluminum monocoque, and I don't want to have body work sitting there being dead weight.

[Erik C]

Aircraft fabric
http://www.aircraftspruce.com/menus/cs/dacron.html

[Sparky]

our '03 SAE-A car/'04 SAE car was done as a wet lay up as you described, again not sure on the details but our '04 SAE-A car we made moulds from the chassis and laid it up off the vehicle and then used the structural adhesive to put it on the car. We found this to work better for us as the structural adhesive gives a stronger bond to the frame than the resin, again I dont know all the details, just a humble elec guy here.

[Eddie Martin]

On the 01 and 02 cars we ran "UTA" style aircraft fabric, very light weight.

On the 03 car we ran structural carbon sides that were wet laid up onto the car with foam core stiffeners. Very quick and easy if you know what you are doing with composites. The 04 car had more structural carbon sections with nomex honeycomb stiffeners. Both techniques produced good results.

You can do everything from plain sheets of carbon glued to the frame to carbon sided honeycomb panels glued to the frame. My advice would be to start building test pieces and see how they go. From there you can integrate as much or as little into the design as you want.

[Lyn Labahn UW-Madison]

Eddie,

In regards to the carbon stressed skins,


So did you end up having to vacuum bag the center section of the car in the 03 and 04 years? You mentioned that it was quick and easy, so I assume you had rather simple molds, or none at all?

Sorry for all of the questions, I have done many carbon body panels, made many steel frames, but I have never tried to do structural carbon fiber before and I want to make sure I do it right!

The idea that I had was to make an bent alumnium sheet that fit snugly on the sides. Then wet layup carbon in them and then put then in place securly against the side of the frame, and wrap the ends of the carbon around the top and bottom tubes. Then somehow apply a vacuum bag to the whole thing so it presses against the aluminum and leaves a smooth exterior finish. I hope that all makes sense! Is this similar to how you do it?

I assume since you used honeycomb on the vehicles, you had to have a way to apply the carbon on both sides.

I understand if you want to keep some of it a secret, just trying to save myself some headaches.

[Sparky]

As far as I know there was no vac-bagging involved, certainly not on this years skins anyway. I beleive on the '04 SAE-A car aluminium moulds were made and the carbon fibre was wet laid in the mould and let cure, then put on the chassis with the structural adhesive. Eddie will be able to give you more detail I imagine.