DIY C-pillar bar, questions about materials

[Darkness and Light]

I'm trying to make my own C-pillar bar to provide additional bracing on my S13 fastback and use as a camera mount. I'm pretty good with my hands and tools but I don't have very much experience. Then again, this doesn't seem to be rocket science.

My basic plan is to drill two sets of holes in a 0.5" steel pipe. The pipe will be mounted where the upper attachment point of the rear seatbelts. A 10mm x 40mm bolt will washers on each side of the pipe will be used to attach it to the pillar. Spacers made of plastic will be made to support the inside of the pipe where the bolt passes through.

However I'm wondering how I should plan for part failure. Should I just use grade 8 carbon steel bolts, a thick bar and plan for no failure? Or should I make the bolts the point of failure and use grade 2 steel bolts because they are the cheapest and easiest part to replace. Should I use steel or aluminum conduit with thinner walls instead to reduce the stress on the bolts and mounting point? Should I make the holes in the pipe bigger and use the spacer as a bushing instead?

What types of forces are acting on a c-pillar bar anyway, is it torsional, compressive, etc. what kind of chassis flexing is it supposed to prevent?

[Darkness and Light]

For anyone who is interested I've started work on the project.

4' long half inch diameter section of steel pipe about $13. two 10mm 1.25 pitch 1.5" long steel bolts about $34 washers about $25' section half inch diameter pipe insulation about $62 3/8" rubber grommets about $1.501 bolt to attach camera, I'm not sure the size. $0.08Rubber end caps about $4 for 4

I have some steel plate straps at home I'm going to bend and use to make the camera mount.

So far I've measured at began drilling holes in the pipe. Unfortunately I didn't take metal shop in High school and have never tried drilling anything thicker then sheet metal before. After using a center punch to start the hole I began drilling with a 3/8" bit. After drilling most of the way through the bit is getting stuck on two little bits of steel that are sticking out. I'm attempting to grind them down with a rotary tool.

[long shot]

Do you have pics of ur progress yet

[Darkness and Light]

Not much progress to show yet, its a steel bar with two holes in it. I'll take a picture once the hole is large enough to run the bolt through.

[Darkness and Light]

Finally mounted the bar. Turns out I made a mistake with my measurement and my first set of holes was about 3/4" to far in. When i drilled the second set of holes it was about 1/8" too close and about 5-6 degrees off. I spent about 3 hours using and metal file and ruined two grinding stones fixing the problem. It BARELY bolts on. Tomorrow I'm take it off again for pictures and to file the holes a little more. In retrospect, square turbing would have been ALOT easier to work with.

[Darkness and Light]

Alright I finally got around to taking pictures of the results.

http://www.angelfire.com/sd/da....html

I still have to cut and attach the foam coverings, remove the side flaps on the mount which i just flattened out for now. and add rubber bushings to various attachment points.

I shot a few test videos and the mount is very solid, no visible shake. However I am hearing some squeaking from the video so there are probably vibrations being conducted to the camera.

Modified by Darkness and Light at 10:05 PM 11/3/2008

Modified by Darkness and Light at 10:07 PM 11/3/2008
Modified by Darkness and Light at 10:14 PM 11/3/2008