strut bar myths

[speed]

i know this. the point of my post is that some strut bars work while others dont. this has been proven on the mk2 and could likely be proven on the mk3 as well.

No No no. It CANT. The suspension geometrys and setups are completely different. Putting a saddle on a horse will make riding it easier, putting a saddle on a cheeta won't help you. IJ has already posted how to correctly stiffen the MK3 chassis. strut bars don't do diddly on our type of suspension.

<edit IJ>

 

[williamb82]

yet no one has proven it either way. all thats been shown is a group a car with a full cage that didnt need a bar as the cage had alreayd stiffened the towers all they needed.

 

[IwantMKIII]

No No no. It CANT. The suspension geometrys and setups are completely different. Putting a saddle on a horse will make riding it easier, putting a saddle on a cheeta won't help you. IJ has already posted how to correctly stiffen the MK3 chassis. strut bars don't do diddly on our type of suspension.
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<edit IJ>

now now, don't jump to conclusions. Not one person has come up with numbers yet. While THEORETICALLY it may not do much......those of us that actually do design and build know how far theory really goes....

 

[IJ.]

To stiffen the Mk3 chassis using a Stb you need to tie the Upper A arm towers together on the front subframe but the motor is in the way.

A diagonal brace from the Rail/subframe mounts to the Firewall could possibly help but again is impractical.

The "beauty" of Stb's is they're "bolt on" anything that will actually work won't be, it'll need some sort of fabrication/welding.

 

[GrimJack]

I like mine, it's pretty. Gives me a place to hold on when bending over the engine bay.

 

[IJ.]

Sounds like the plotline to a b grade Porno Dave

 

[Keros]

So... let me get this straight; the only way to stiffen the chassis is to weld in a full cage?

Strut tower braces, the rear end brace that bolts to the rear seat belts, all that bolt in crap, doesn't do diddly squat? Am I getting this right?

 

[GrimJack]

Hmm... new uses for the strut tower bar start coming to mind...

 

[IJ.]

Bolt in parts need to be bolted in 2>3 different axis to be effective most aren't so just act as hinges.

 

[speed]

Okay, I went out to the garage to try and find my dynamics book and just do the math for you, but half my college stuff is in the storage unit, so I can't find it. Here however, are some diagrams that will hopefully visually get the point across:

Upper/Lower Control arms:

Macpherson Strut:

(taken from http://www.rqriley.com/suspensn.htm - feel free to read it.)

As you can see, the virtual reaction point of a suspension wtih upper and lower arms is determined by... the upper and lower arms. The spring and shock are not even part of the equation. In the Macpherson setup, they are part of the equation because its a structural member of the suspension.


what is the reaction point? its the point in space where forces from the suspension are transmitted to the vehicle's chassis. Again: Note: In the double arm setup, the springs and shocks are NOT included.

and another good article:
http://www.tonyfoale.com/Articles/carstuff/spring.htm



IwantMKIII, I agree, theoretically they don't do diddly. but realistically, in the design.. they don't do diddly either. There are diagrams for you. Feel free to do your own research. As an engineering student, it should be beaten into you by now that if it doesn't work in math, it won't work in the real world.

 

[IJ.]

IwantMKIII, I agree, theoretically they don't do diddly. but realistically, in the design.. they don't do diddly either. There are diagrams for you. Feel free to do your own research. As an engineering student, it should be beaten into you by now that if it doesn't work in math, it won't work in the real world.

This part made me LOL!

I'm quite happy if someone supplies the hardware/strain gauge and amplifier (already have the G sensors in place) to perform any tests required on this one but I won't spend my own $ to prove parts don't work.

 

[buldozr]

I know on my mustang convertible, the frontend was god awful loose when I removed the factory triangulated STB. Any long sweeping turns on the expressway scared me, but I didnt build it to turn. I built it to burn gas, make noise and not win any races. F'd On Race Day

Speed: good read, you have enlightened me with your visual diagrams, my IQ just went up I think.

 

[IwantMKIII]

Okay, I went out to the garage to try and find my dynamics book and just do the math for you, but half my college stuff is in the storage unit, so I can't find it. Here however, are some diagrams that will hopefully visually get the point across:

Upper/Lower Control arms:

Macpherson Strut:

(taken from http://www.rqriley.com/suspensn.htm - feel free to read it.)

As you can see, the virtual reaction point of a suspension wtih upper and lower arms is determined by... the upper and lower arms. The spring and shock are not even part of the equation. In the Macpherson setup, they are part of the equation because its a structural member of the suspension.


what is the reaction point? its the point in space where forces from the suspension are transmitted to the vehicle's chassis. Again: Note: In the double arm setup, the springs and shocks are NOT included.

and another good article:
http://www.tonyfoale.com/Articles/carstuff/spring.htm



IwantMKIII, I agree, theoretically they don't do diddly. but realistically, in the design.. they don't do diddly either. There are diagrams for you. Feel free to do your own research. As an engineering student, it should be beaten into you by now that if it doesn't work in math, it won't work in the real world.

Hey i just had a test on this stuff today, a bit more in depth though of course :biglaugh: . It was terrible lol. 50 min tests are waaaaaay too short of a time period. Past two class test averages were in the 50's, i'd expect this one to be in the 40's as the majority of the class was still there when time ran out :3d_frown:

Thanks for the visuals, i'd still be interested in some numbers though (real numbers i mean)

 

[tsuper92]

I know on my mustang convertible, the frontend was god awful loose when I removed the factory triangulated STB. Any long sweeping turns on the expressway scared me, but I didnt build it to turn. I built it to burn gas, make noise and not win any races. F'd On Race Day

Speed: good read, you have enlightened me with your visual diagrams, my IQ just went up I think.

mustang's have a different suspension then a supra.if you look at the diagram's posted you can see the differance between the two

 

[adampecush]

you are talking about a strain gauge

those are pricey!

heh...not for me.

when my car is back together, if somebody wants proof as to whether the strut bar is useful or not, send me a strut bar and I can get a definitive answer.

 

[NgoFcukinWay]

Cusco did somewhat of a test with their bars. It's probably biased though, but I can't really prove that.

http://www.jdm-option.com/eng/pr_CUSCO/towerbar.html

 

[IJ.]

No mention of a double a arm test car there Alex.

 

[T701jz]

IwantMKIII, I agree, theoretically they don't do diddly. but realistically, in the design.. they don't do diddly either. There are diagrams for you. Feel free to do your own research. As an engineering student, it should be beaten into you by now that if it doesn't work in math, it won't work in the real world.

As a Mechanical, Applied Physics, and Chemical major I won't be too fast to judge others design just because you're a student in Engineering. I have come across many process engineering believe that Theory is the answer for every thing. Until further test is applied to MKIII chassis, opinions and diagrams don't mean diddly.

 

[buldozr]

mustang's have a different suspension then a supra.if you look at the diagram's posted you can see the differance between the two

well aware, just making a statement of how badly the macpherson strut style suspensions need more structural support than a double wishbone setup. My bad if I didnt get the image across.

 

[Facime]

wow, Tim, Im beginning to think you are right, lol.

Good link to the Cusco bar...scroll down half way to the animated GIF's showing the stresses on the strut tower....now pay special attention to what TYPE of suspension that is...see any upper control arms?