View Full Version : DIY: chassis/body bracing!

the trabe
09-05-2011, 07:56 AM
This was pasted from my club ep3 post.

Hey guys,

This is my first post! I’m a mechanical engineer at a pump fabrication company, so I used a lot of my knowledge of material selection and available shapes to make the following:

Rear lower subframe brace
Rear body joint brace
C-pillar brace

I want to give a brief tutorial, should you want to attempt to make these yourselves. The material costs will be easy for you to calculate. Don’t be astonished….the prices are real. Just a disclaimer: The lengths are approximate….you should obviously measure your car prior to ordering material or drilling holes. Thanks

Rear lower subframe brace:
Material: 1x http://www.speedymetals.com/pc-4767-...el-tubing.aspx 17” long

And 2x http://www.speedymetals.com/pc-3937-...led-steel.aspx 1.5” long

Weld the brackets as shown in the picture. Be sure to grind the layer that forms on extruded steel parts as this will prevent a nice arc from forming. The bracket’s centers should match the distance between bolts on the subframe. http://www.flickr.com/photos/66375159@N07/6041979695/
I machined slots for the bolts, however a 17/32” hole should be perfect, as long as you drill dead nuts to your measurement. The finished product looks like this: http://www.flickr.com/photos/66375159@N07/6041981135/
Paint it when you’re done. I used undercoating:
Btw that's a trailer hitch...i know

C-Pillar brace:
Material: 1x http://www.speedymetals.com/pc-3427-...teel-tube.aspx approx 49”

2x http://www.speedymetals.com/pc-3937-...led-steel.aspx 1” long

2x McMaster Part No: 94640A115
2x McMaster Part No: 60645K241
4x 3/8-24 nuts or jam nuts
2x lock washers and 4x regular washers

Drill the angle bracket. One side should have a 13/32” hole and the other a 17/32” hole. The larger hole goes through the seatbelt bolt. http://www.flickr.com/photos/66375159@N07/6041983511/. Just aim for center and make sure you have clearance for a nut.
Cut the tube to a length that allows a 3/8-24 nut to go on the rod end and lock the overall length in place by tightening against the weld nut. This is a mistake I made and will not show up in the picture.
The weld nut gets welded into the tube (self-explanatory) . I used epoxy rated for 3500 psi. Assuming 1 inch shear area, this ensures 3500 lbs-force per side before rupture. Attach the brackets on top of the seat belt mounts using the existing bolts. Then attach the assembly to the brackets.
Paint it a cool color (and do a better job than my lazy ass). It IS visible through the window

Body joint brace:

Material: 1x http://www.speedymetals.com/pc-3932-...led-steel.aspx 44” approx.

2x 3/8-16 bolt 2” long
3/8 x 3/4” standoff: similar to McMaster Part no: 93320A321
2x nuts
4x washers
2x lock washers ( I forgot these) in pics

Cut the angle to a length that fits in the area just below the hole in the picture. It is difficult to get the bar in there…you have to put one end behind the strut damper and then push on the plastic trim on the opposite side and shimmy it in there. After you test fit the bar, you’re ready to drill the body. You may want to stop reading if you plan to sell your car at auction 20 years from now as “fully original”. Drill out the welded square nut on the back of the body joint with a 13/32” drill: http://www.flickr.com/photos/66375159@N07/6041984165/
http://www.flickr.com/photos/66375159@N07/6041984867/ Be prepared to debur the remainder of the weld nut that didn’t get drilled out. Also DON’T use a damn grocery store bag to catch the chips, since it will melt and you’ll breath in some toxic shit.
Now, remeasure the hole distance, and drill the bar accordingly with a 13/32” hole. Install the bar like so:
The standoff goes between the body and the bar
Finished hatch:

Lmk if you guys have questions. I was kind of vague, but I assume you all have pretty good knowledge of hardware and what not. Sorry I don’t have an international version of this tutorial . Thanks, Marcus
- Marcus

09-05-2011, 10:33 AM
Your links need some updating, otherwise nicely done.

09-13-2011, 02:09 PM
+1 very functional pieces for someone on a budget.

09-21-2011, 11:00 PM
how these suckkers are called http://www.flickr.com/photos/66375159@N07/6041983511/

11-16-2011, 07:03 PM
Nice write up, but those parts (specifically the canter brace) could have been made to look alot nicer and possibly stronger without much extra cost or effort.