Creation/Fabrication of strut tower bar/brace

[Drax240z]

I agree with John, nothing on any street/race car needs to be 1/4" thick than I can think of.

 

1/8" works really well for the plates. It gives you enough thread left on your upper isolators in order to use the stock stud/lock washer/nuts.

 

As far as the cross bar goes, Pop N Wood's info is on the right track though not entirely accurrate. A solid bar (of equal diameter) will be MUCH stiffer and stronger under all loads you'll see in this application, especially if the bar is bent. However, the trade off is a rather large weight gain. In purely torsional loading (ie: prop shafts, any spinning shafting for that matter) the OD of a round object plays a huge role into the stiffness and strength of the shaft, while the ID plays very little role, this is a place you can get away with hollow shafts all the time. (ie: driveshafts)

 

Because of the combined loading experienced by something like a strut tower bar, a larger diameter hollow tubing will be stiffer FOR A GIVEN WEIGHT, than a smaller diameter solid tubing. In most racing/street situations we are concerned about stiffness vs. weight. If weight is of absolutely no concern, you could go crazy and make a 100lbs strut bar that will be stiffer than my 3lbs unit, but I wouldn't recommend it. Also the law of diminishing returns applies, your 100lbs bar might be only slightly stiffer than a 30lbs bar, in which case is it worth the extra 70lbs?

 

In order to find the optimal material size there is a lot of physical testing that can be done to come up with some hard numbers. Or you can take the easy road and listen to the guys that have a pretty good 'gut' instinct about these things. (many, many members of this board)

 

Last word: Pretty much anything you do to tie the strut towers together will be a NOTICEABLE improvement in chassis stiffness. Even some cheezy lightweight bar (a buddy of mine used one that was less than .5lbs all told, aluminum and 16ga end plates) was a noticeable improvement over nothing. Don't wreck yourself trying to design the perfect strut bar for your car unless you are a) racing, or going into production with it.

[Guest dvlax28]

last question....how the crud do i know if the bar is going to fit?

 

one has to worry about clearance with A) the valve cover (not too close in case it vibrates...mine is polished and i dont want it rubbing/hitting) and the hood so you dont dent it!

 

i dont see it possible to raise the bar up off the 1/4 circle plates and run a straight tube, because the hood is shallower near the shock towers, but raised up in the center with the valve cover. so bending seems like the only way to go. how do i know if it is too high, besides guessing and slamming the hood down to see if it dents and hits?

 

j

[Pop N Wood]

Trial and error? Also get some play dough. Put a ball on top of the high points and slowly press the hood shut. Can then cut the mushed play dough to measure your exact hood clearance.

 

Also see how most people attach some type of upright bracket to the strut plate to get the bar ends higher. MSA sold a straight bar that "almost" cleared my L6. They claim it actually works with some cars, so the amount of bend you need may be different then other people.

[johnc]

Besides. John once said nothing on a Z car requires 1/4 steel.

 

Absofrickinglutely! I even question the need for 1/8" anywhere. The thickest piece of steel I've used anywhere on any car I've done fab work on is .1196" (11 gauge) and that was for some roll cage mounting plate boxes on a 3,000lb car. Even then I felt kinda guilty about it...

[Drax240z]

Drive shaft flanges, moustache bar, front & rear hubs, brake rotors, exhaust system flanges, yadda-yadda all should be thicker then 1/8" IMHO, but none thicker than 1/4". It depends greatly on the particular material involved however.

 

Forthe majority of fabrication done by 99% of the Z populace, 1/8" is as thick as you need to go though.

[hanomon]

I've got some picts of a 3/8" T-6 grade aluminum support with GTO type holes drilled and beveled edges, Counter-sunk hex-head bolts with nylock nuts. Don't think the jeweling will stay on. Probably will buff and shine it up to a nice mirror finish. Check it out, just click on the "Photo Album" in the Modules column under Main Menu, scroll down to last additions.

[Guest dvlax28]

dude, Pop you rock, that play dough idea rocks, thanks a lot!

 

well im gonna search around the auto tech yard and try to find some steel plates and tubes to practice with welding.

 

that triangle support looks pretty sweet.

 

thanks again

 

j