new 25.00 strut bar

the other day i went looking for some carbon fiber material at my local rice rocket retail store and found a wide selection of strut bars for japanese cars. 25.00 each. i went home and took measurements of my p car to match up to what they had. the accord seemed close. i bought it and modified it alittle and works great. the polished aluminum cross bar looks great too. what do you guys think? heres some pics.

[Wayne 962]

Let me modify your comments slightly here:

Originally posted by joseph herreros
i bought it and modified it alittle and works great.

Should be *looks* great. These types of "strut bars" if you can even call them that do almost nothing. At least this one is straight, so it can offer some tension, but it's made of aluminum, which is not typically used for stiffening steel chassis.

There was a very long discussion on these in the BMW forum, it's actually pretty good reading:

Front Strut Bar

On a side note, the Weltmeister ones are actually pretty good, with a very beefy tie-in mount to the shock towers, and a steel (hmm, I'm hoping I'm right, memory tells me it's steel) bar for added stiffness (see the project in 101 Projects...).

-Wayne

[JackT]

You get what you pay for. A lot of the rice performance stuff is now being sold by Circuit City and Best Buy. It is for looks and not performance.

[juanbenae]

OUCH! hang in there joe.

[SC-targa]

What exactly were you looking to do in carbon fiber? Just a cosmetic overlay or something functional?

I actually think you did good getting a strut brace for $25. It has to help some. I've been thinking of fabbing one up myself over the holidays. The rod ends were more expensive than you paid for the whole strut.

The aluminum tubing is not as stiff as steel, but Porsche used to use aluminum tubes for the frames of their 917's and such.

Good for you,

Jerry Kroeger

[masraum]

Bummer, one of these days I want to test the whole in or out flex theory of front strut towers. Seems you could put some sort of string/wire/whatever (something that is more likely to break than stretch) tightly between the two strut towers and then drive around performing some hard cornering, and then see if you've broken the wire/string/whatever. Seems you could also do something similar to see if they go together by putting something that would bend and deform between the two strut towers, drive around, and then see if the part has been bent.

I suppose if BA is right then the above strut bar will keep the towers from pulling apart as it will be under tension and not compression. I assume al is more likely to bend than compress or stretch, anyone got any info on that?

[cowtown]

This is such a subjective topic, the only way you're going to get any sense of the value of your bar is if you like it well enough to have paid $25.

How about posting a shot of the bar installed on the car? It's difficult to see what you modified, where it anchors, and how it fits.

jeez. tough crowd. will it work? problably. i have too many other things to spend money on right now. i really want an elephant triangler bar. i will post some more pics when i put it on the car.
thanks jerry. it is cosmetic. i removed the heater control and radio. cut out new inserts pieces for the 73 aluminum trim, then put carbon fiber over it. im not sure if i like it yet. does anyone know what types of preasure in#s that the tops exert. i asked around but no one knew.

[Elombard]

Hmm I never disagree with Wayne but seems like if that is bolted to the top of the stru tower with two bolts on each side it is going to reduce flex some?? Also a little safer in an accident god forbid.

[thabaer]

Originally posted by masraum
I assume al is more likely to bend than compress or stretch, anyone got any info on that?

There are in fact some Al alloys with a tensile strength higher than some steels, depends on what steel and what aluminum is compared. Yah'd tink dem aircraft N-gineers might have a clue and dey be using a lot of da stuf! Speaking of aircraft, I'm doing some turbo plumbing with tube from these guys: http://www.aircraftspruce.com/index.php , they have a motorhead racer type catalog full of good stuff.

I did a search and found a pile of data on one site:
http://www.asatlantic.com/Reference.htm

tons more stuff using these keywords: ( elasticity near modulus ) and aluminum and steel

[JTO]

Maybe we could use Steve's idea, modified slightly. Connect strong steel wire to the tops of the strut towers. Connect a load cell to the ends of the wires and set the wire tension to a few pounds. Go for an agressive drive. Most load cell have the ability to hold the peak load. This would tell us how much force is being applied. Load cells are pretty common. We have several at work for use with our destructive testing lab. A few are battery powered. I just don't know if I can escape out the door with one. So, I guess I can't contribute to this fact finding at all.
Troy

[echrisconnor]

The fact that you have a "destructive testing" lab at your work sounds so cool. I want to work with you!

I suspect there are a bunch of ways to test for pressure or quantity of deflection. This brace is only suppoted on one side of the shock. The Weltmeister and others go all the way around. Could you buy two of them, double up the shock tower mounts an make the bracket more secure.

As to the relative stifness of Aluminum vs. Steel, I agree that it must depend on the type of alloy and thickness. In my limited exeperience with both on mountain bikes, steel is generally more flexible than the Aluminum which tends to be more rigid.

[thabaer]

Originally posted by JTO
destructive testing lab

Ook-ook, arr-arr-arr .... destroy

I agree, sounds fun!

Do you have any recommendations on where to look for sensors ? ( or is the price out of range for recreational lunacy )

[Teutonics]

A while back I saw an article where the author had rigged a contraption in the trunk with rulers and sharpie markers (or something like that).... but I can't seem to find the link to it now (of course).

After a hard driving session, what it showed was the amount of deflection of the strut towers as marks on paper by the sharpie marker. It was a fairly good indicator of how much flex actually occurs under hard cornering.

Has anyone else seen this?

[JTO]

Guys,

Radio Shack might have a 4-20 mA recorder such as a HOBO. The load cell (I'm just talking about the pezio electric S-beam type made by Omegadyne, etc.) can be found pretty cheap in an Omega catalog and other sources. Looking at Mitchell Instrument's catalog, a portable load cell/recorder will go for about $1200. Kinda pricey for our little fact finding mission.

Oh well, fun to talk about.
Troy

[Early_S_Man]

No way is that aluminum bar as strong as the 0.125" wall Chrome-Moly tube I made one out of ... and those attachments to the strut towers look pretty weak without any gussets!

An interesting data acquisition experiment would be to epoxy a strain gauge to the bar and both attachment brackets ... and log a couple of hours worth of data during a DE or autocross with one of these DAQ modules attached to an old Windows 98 laptop ...

http://www.measurementcomputing.com/cbicatalog/cbiproduct_new.asp?dept_id=352&pf_id=1535

[Steve W]

There was a long discussion and on the effectiveness of a strut bar in a 911 a while back here:

Strut Braces- What do you think?

Bernd Andritzky did some test measurements using a laser pointer pointed at piece of paper, which was recorded with a camcorder in an autocross. Found some interesting results.

[masraum]

Hmm, a contraption with something like a telescoping leg from a camera tripod or one of those cheap curtain rods could be rigged with something to indicate how much total deflection it had experienced during the drive. I've been dying to do this, just have never gotten around to it.

On the subject of this specific thread, the week point in the setup looks (we all know what *ASSuME*ing can do) like it would be the mounts, not the rod. Again, what do I know, but I would think the two bolts would be enough since the whole thing is only bolted on using 3.

Deflection would be a decent test, but if someone can manage to get ahold of a load cell (assuming it indicates the force applied more than the deflection distance) that would be an even better measurement since it would allow you to properly design a strut bar. Of course I suppose it would be somewhat dependent on the year and model of 911 too.

a quick search online shows the cheapest at the first site to be good for compression or tension and having a range of 1 - 1000 lbs to run $300. More than I am prepared to spend for this little adventure.

PS I'm very excited, I have proven that I have too much free time (or should be doing more work) and less of a life than all but 19 other people on this board, I am now officially in the top 20 posters having knocked "1.2Gees" out of his position earlier today. Yay for me.

[chrisp]

This could go on forever and short of a super-lengthy post I'll convey a couple of thoughts.

1.) Although he asked for input I would say that some of you may have been pretty harsh with joseph herreros. Especially those who are looked up to in a big way around here.

2.) Load straining would be the ultimate. However I also like the idea of the sliding tripod leg idea. It's easy to measure the deflection. Wipe it with grease and measure the drag marks accross the grease. Or, use an o-ring and see how much it slides before and after. This is how I measure bicycle, motorcycle, and auto suspension travel. Compress the shock and the o-ring moves. Once the shock rebounds and stops at the static extension the o-ring will be some distance away from where it was originally located.

3.) I am building my own tower brace because I think they work. I suspect the two towers are flexing away from each other and putting a member that's in tension between the two will reduce outward wheel tower flex by sharing load between them.

[Chuck Moreland]

Couple quick thoughts -

- Load cell not the best solution. The measure of effectiveness is movement, not force.

- You really want to measure movement relative to another point deemed stationary. The towers can move in parrallel, falsely indicating zero movement if the tower is the reference point.

I think the best reference point would be the front suspension cross member. Even the floor will deflect a bit along with the towers.