CMC sub-chassis design

As part of my mould building project, I am looking at the CMC sub-chassis with an eye to redesign any flaws and incorporate improvements. This sub-frame is mounted on a custom tube chassis, retaining the VW VIN number and front and rear pan bulkheads for body mounting.

I am aware of the saggy bum problem and work done by Jogyver to address this issue, and just sent him an email.

It looks pretty hokey how the rear engine frame rails are done by scabbing 2 bits of 2x2 together and surely this could be done a bit nicer.

The only other issue that I am aware of is the offset steering wheel and I intend to simply move the steering wheel brace inboard.

Are there any other mods and improvements you would do given a blank sheet of paper?

a bit more protection. it would not be hard to weld a mini-cage into the existing frame/body lines.

joe=no image there.

I know you asked about frame questions but here are a few others too:

1 .I would "tie" the perimeter box/frame to the pan or frame a little more completely along the fwd and aft firewall areas.

1a. add uprights at the fwd firewall at outer corners and then tie them from the top of those to the forward most corners of your frame/suspension. Similar to what Joe did for the rear but in the front.

1b. quite a few of these cars have been put together without anything supports the front half of the body. People have left out the support between body and frame head. Since I think you aren't going to have this front end don't forget to support the fwd half of the body to the frame. like:
http://i124.photobucket.com/albums/p25/h2fzr/IMG_1515.jpg

2. I would duct a fresh ir supply for the engine fan intake sealed off from the engine compartment (I think you are using subby power though)

3. I would run steel lines (stainless preferred) from front to back under the side of the frame following the pan shape (4 of them). Have the lines made up with an fittings at each end. Then use flex lines the last foot or two. Two for the fuel (supply/return) and two for a front mounted oil cooler.

4. people seem to care about safety---plan ahead with structural mount points for
lower seat belt mounts and a safe/secure three point attaching mount.

5. I know the bumpers are for show but maybe a stronger tie between bumper mount and frame-transmitting force to a more secure area.

6. under car access to hood and trunk latch for if/when the cables break

You mean an engine cradle like this.
There also is a photo of the front structure.
You know with some cool innovations the Hot Rod industry came up with could apply to some of the ill designed CMC's. I like the idea of welding internal bracing into the channel frame.

Thanks for the input, and please keep them coming

I am working concurrently on both chassis and subframe designs and comments on both are appreciated.

There are 2 design paths. One for my personal car with Suby power and my Buddies with ACVW power so design input for both styles is appropriate.

Have been thinking of a Mini cage as suggested by Paul, but am not personally keen on getting my head knocked again by a roll bar. OTOH mounting points could be designed in for those that want it. Incorporating other safety components is prudent given the constraints of the body.

Will post a drawing of the final designs in the next couple of weeks

Robert

Joe

Can you email me your design for the saggy bum. The jpeg posted on this site is not very clear. I have the basic idea but would like to see clearly how you did it

Supporting the entire rear end with fiberglass inner fenderwells secured by pop rivets is not the greatest idea. Another idea would be to use a 2x2 support to the body off the rear 2x2 framework. the subframe is glassed into the body while in the mould so this is easy to do during manufacture.

rgstraghan@yahoo.ca

Thanks