Muzz

Hey there
I am looking to produce a nice quality brace for the EK hatch and have plenty of questions.

Firstly though, the reason why I am doing so is:
1. I want to stiffen the rear of my car up significantly for auto cross days.
2. I want something that is going to be more effective than strut braces and tie bars.
3. I want something to help reduce the metal fatiguing due to running high spring rates on a daily basis.
4. I would like to start making a few to sell, i think if the achieve there goal, there will be quite a few potential buyers hee in australia.
5. I don’t want a cage in my street car, I want to be able to remove it at will and reinstall my rear seats, as im sure a lot of other autocrosses are after.
6. help remove the creaking noises coming from the rear.

My idea for the brace came from this product


I would like to do something very simular, but brace the rear strut towers to the seatbelt mounts on the b pillars.
My theory, which is what im hoping other people can confirm or deny for me, is that by bracing like so to the b pillars, the chassis's torsional resistance to twist will increase quite a lot between the b pillars and the rear of the car, much much more than pillar bars and rear strut braces.

Id imagine if you picked the car up, and applied equal and opposite torques at the ends of the chassis, that the twist would cause 1 member to be in compression and one in tension.

Say the torque moment at the rear of the car was twisting the chassis in a way that the drivers side strut tower was being pulled down and the passenger side was being pushed up. I figure the bar between the passenger side strut tower and the drivers side b pillar will be in compression with the other in tension, resisting the rear from twisting quite effectively, and bracing the strut mounts quite alot. What do you think??

Here is what I’m looking at making, something like this.


These are the sort of parts id be using

1. Male clevis’s, to bolt on the centre plate where all four bars mount.
http://www.midwestcontrol.com/...g=227
Choice of chrome moly or stainless steel, which would be more suitable?

2. Crome Moly threaded weld in bungs for the bars.
http://www.midwestcontrol.com/...g=225

3. Chrome moly tubing. What OD and wall thickness would be suitable? I was thinking around 1” with 0.088, what do the people in the know recommend?

4. Threaded eye ends. These will be used at the outer ends of the bars, where they mount to the strut tops and the pillar mount points.
http://www.midwestcontrol.com/...g=170

5. For the pillar mount points, I will use the black mounts from something like this
http://cgi.ebay.com/ebaymotors...sting

And the strut tops ill be getting fabricated at an engineering place, I got that all sorted.
They’ll also be welding the threaded bungs into the tubes.

Anyways, let me know any thoughts you guys might have, im here for your input.
What would be a suitable sized chromolly tube for this application?
Which design do you think would be more effective and why (the two bottom pics on my drawings)?
Any ideas on why this would work effectively
Any ideas on why it won’t work effectively…Any way this could be achieved better?
Any ideas on the linkages/materials being used
Any tech talk on torsional stiffness

Cheers



Modified by Muzz at 1:12 AM 5/5/2007

l2Y4N

cool! i was fabricating one of these in my head today sorry, i don't have any recommendations or input, but good luck with everything, can't wait to see the process and final product.

.john.

the second one looks kind of like the thing i made for my old corolla:



didnt really make any difference, also not really sure if its only for the car with the cage, but obviously its not really going to do anything if the car has a well made rollcage. but those stupid miracle bar things sell for a buttload of money so if you want to market it then just sell it a little under that price and your probably good to go, lol