Creation/Fabrication of strut tower bar/brace

[Guest dvlax28]

I am in auto tech and my teacher says he will help me weld a strut tower bar for the back and front. anyone ahve any blueprints or plans for a rear and front bar? i want it to look pretty good, not like a rusted metal bar in my newly redone engine compartment. i want that shiny nice metal to match my valve cover.

 

anyone know what this material is and where to get it for how much? and what is the best setup weld-wise?

 

jason

 

pictures of what the heck im talking about:

 

http://geocities.com/dvlax28/strutbar

 

i could go with either painted or silver....but the whole attaching the bar to the metal circle is crazy

 

Thanks!

[Hugh]

The strut tower piece should be relatively easy. The problem is the cross-bar. The tower mounts are usually steel. The cross bar should be aluminum (like everyone I've ever seen)

 

You don't need a fancy cross bar... you could do it with any properly sized aluminum pipe with a thick wall. You can bend the stuff into shape pretty easily.

 

Seeing that pic of the gold engine bay makes me want to go set fire to my car in the parking lot. Thats absolutely beautiful.

[SSflyer]

CRAPOLA!! How many hours did that engine bay suck up? Excellent work!

[Hugh]

I don't think its his car, its what he wants his to look like. (don't we all)

[DaleMX]

It's not a real expensive item, around 100 bucks at MSA.

[johnc]

The cross bar should be aluminum

 

Why? I'm thinking thin wall 4130 is a better choice for lightness and strength:

 

 

[Hugh]

I'm just trying to help him make one that looks like the picture.

 

You can use whatever material you like.

[johnc]

That's great and the pictured strut tower bar looks cool. If the car's being built as a street car that type of strut tower bar works fine.

 

I just wanted to point out that bending an aluminum tube severly weakens it. If you start with a 6061-T6 tube and put a bend in it, you've reduced that bar's material strength from 45ksi to, at best, its yield limit of 40ksi with less then 12% elongation. Conversly, if you take a 4130 tube and bend it the material strength goes from 80ksi down to, at best, its yield of 56ksi with 28% elongation, so you still end up with something that's stronger (at least in materials), and more ductile (meaning it can take some additional flexing before failure) then what you started with in 6061.

[Drax240z]

For 90% of the road going public, good old low carbon (1020) mild steel will work just fine. It's easy to work with, relatively stiff, strong and can be finished many ways.

 

Here are a couple of steel ones I've made in the past month or so. Very simple and easy to make.

 

The first one is on a 510 and allows a straight bar between the towers. (on an non-L20B engined car) The cross bar is 0.065" wall 1" mild steel tubing.

 

 

The second one I did on my own car more for an experiment than anything, to see just how much difference it made triangulating the strut bar to the firewall. The results: the gains from triangulating to the fire wall over the previous straight bar, were MUCH greater than the gains from going from nothing to a straight bar... Again using my old stand by, 1" 0.065" wall mild steel tubing. I use this stuff all the time.

 

 

Anyway, the 2nd one is kinda hacked together, it is just a prototype.

[BillZ260]

do what john said and then put your aluminum around the steel for the look you want...

 

Drax how much time / $$ you got in your experimental bar? What do you use to cut the steel plate. I have a 12" band saw, and a 4" grinder, and can borrow a welder, and was wondering if I could replicate what you have there...

[Mikelly]

Not to mention the fact that a 4130 tube isn't much heavier when compared to the aluminum, and with your bar John, using the aluminum heim joints saved additional weight to get it back down to a reasonable amount of weight.

 

Mike 8)

[johnc]

Another strut brace building tip:

 

If possible, use the strut tower itself to locate and brace the end brackets. In my 240Z example above the brackets were welded to the strut tower and in the example below that I built for an ITS BMW 325is, the 3.065" OD vertical tubes are an interference fit within the top hole of the strut tower. The loads go from the strut tower, through those tubes, to the strut tower brace. The strut studs are just used to hold the end brackets down onto the strut tower.

 

 

That BMW previously had a Bimmerword strut tower brace that used the strut studs as the mount and load path. After installing the brace I made, the owner had to reduce the rear spring rate by 25 lb. in. because the front planted so much better.

 

[BillZ260]

DAMN I LOVE THIS SITE!

 

THanks John, will kee that in mind if i get far along enough in my project to build a bar!

[Drax240z]

Drax how much time / $$ you got in your experimental bar? What do you use to cut the steel plate. I have a 12" band saw, and a 4" grinder, and can borrow a welder, and was wondering if I could replicate what you have there...

 

Uh... 2 hours and $10? Your bandsaw or angle grinder with a zip disc should make a plate for you in no time. I did use a torch to heat the tubing for the bends, but you could do it with a cut/weld technique without any problems.

 

John makes an extremely good point about letting the loads transfer directly to the chassis. It is very important to minimize the slop between your chassis bracing and chasiss. (ie: oval holes aren't the best!)

 

I've not yet driven in any Datsun that hasn't benfitted HUGELY from extra chassis bracing in the strut tower area, front or rear. It makes a really large difference.

[Guest dvlax28]

do what john said and then put your aluminum around the steel for the look you want...

 

put aluminum around steel? i dont get it.

 

so obviously there are 100 ideas and 100 different styles... i kinda want to go with the straight tower to tower connection...no triangles this time.

 

by the way i cant afford 100 bucks to buy a bar and i want to learn how to weld better.

 

so if you look at

 

it has an allen wrench bolt that lets the bar pivot? or is it just holding it down? whats up with that?

[Pop N Wood]

Don't want to answer for the guy who made it, but the allen bolt is probably so the bar can be removed for engine access. You want to mount the bar as rigidly as possible, so the pivoting ends could be replaced with something that bolts solidly to the mount.

 

I have seen strut bars made by simply flatenning the end of a piece of heavy conduit and drilling a bolt hole in it. Not pretty, but it doesn't get much cheaper than that. Just try to keep the bar straight if possible.

 

Also, I think the idea of wrapping the bar in aluminum was just to get the "look" of aluminum but still have the strength of steel.

[Drax240z]

Pop N Wood got it. The biggest issue I have with the bar on my car is that it has to be completely removed from the car in order to do a valve adjustment. Not a big thing really, but a bit of a pain.

 

You won't be able to do a straight bar on a Z with the L6 in there. At a minimum you will need a gentle curve along the whole bar, or one more abrupt curve over the valve cover. (or multiple bends as john's pictures show, a lot can be learned from what he has done there!) My cross bar actually has 3 bends in it, one at each end, and one slight one just over the valve cover. Not optimal at all for stiffnesss.

 

End plates I'd suggest 1/8" mild steel.

Cross bar 1" diamter 0.065" or 0.083" wall mild steel tubing.

 

Removing any flex point is a good idea, but you do have to think about being able to remove the bar easily & access the valve cover, so you might want a more traditional pivoting design. Or you could fab something up that was removable and didn't flex... (which is one of the draws of John's triangulated setup) Fabrication wise it would be a bit more involved though.

[Guest dvlax28]

i was talking to my teacher today and he said that what people use is just plain hollow tubing... and i know it is stronger than i think, i thought since a whole car's flexing is on the bar, it should be solid metal. but he said all bars are hollow. and i know roll cages are hollow too, so it sort of made sense.

 

so Drax... you said

"End plates I'd suggest 1/8" mild steel.

Cross bar 1" diamter 0.065" or 0.083" wall mild steel tubing"

 

my teacher said 1/4" on the circle plates...any thoughts?

 

dumb question.... the .065" is the thickness, right? and that thin of a bar will really have no problems?

 

jason

[Mikelly]

.065 is the tubing "Wall" thickness. The 1inch diameter is perfect... Hell the unit I bought years ago from MSA was made of 3/4 inch diameter stuff...

 

That information Drax and John C. Gave you is excellent info... Your shop teacher might know about automotive repair and fabrication in general, but these two guys are "Z Specific" guys who put their parts to use on the track... I follow their advice regularly and would recommend doing the same!

 

Mike 8)

[Pop N Wood]

1/4 plate will be too thick to allow putting the nuts on the top of the strut isolators.

 

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

 

Hollow vs. solid: the majority of the strength comes from the outer diameter of the bar. If given a chance, you want a larger diameter, hollow tube rather than a small diameter solid one. The solid core just adds weight and not much strength. Look at Cannondale bikes. Use light weight aluminum with a large diameter to retain rigidity.

 

Another case in point. Air craft carriers use propeller shafts that are hollow (well, filled with sand).