TonyEX
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A while back, Dr. Flounder spent a great of time explaining how the front suspension stresses are dealt with and how a strut bar helps. there ought to be a place in TOV to place reference stuff like that
This week, these pictures were posted by IntegraDC5R of his new ITR in Okinawa... the pictures are outstanding, but pay particular attention to how the front strut bar sits.... it is bolted to both struts _and_ to the firewall at two places as well.. this is different as I recall from the GSR... Oddly, the Prelude has not strut bar at all...
these are the ITR pictures:
http://www.vtec.net/forums/one-message?message%5fid=108657
Now compare the strut bar with the RSX-S's
http://www.esporma.com/pictures/strut1.jpg
http://www.esporma.com/pictures/strut2.jpg
Note how the bars seem to be the same? In the old ITR, the strut bar was quite an affair.... square cross section and all, while the GSR's was comparatively a wimpy round section tube.
Oh, btw, the pictures show both engine bays.. ITR and RSX-S.
Now, flounder, why would HMC keep what seems the same bar in the ITR? Do they feel that by bolting it to the firewall it doesn't need to be stronger... By first inpection it would seem like the load transfers are directly from the strut bar to the firewall via a very short rod... and that very little force will be sent side to side....
Last edited by TonyEX on 06-06-2003 11:20
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pat-mtl-itr
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It may be just a spacing issue. Things are tight up there in the engine bay. As far as the material being the same, well the overall rigidity of the RSX over the prev gen Integra is increased 130% therefore having a stronger material may not have much of a benefit in the bar's current place...
Just some points.
Pat
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floundericiousMI
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Most likely one of two things or a combination of both:
1) Shave cost: By having a common strut bar, that is yet another place where they don't have to spend bazillions of dollars to develop a limited-run part
2) No Need: If the dynamics and handling aren't appreciably helped by stiffening the front end... why do it?
actually...
3) How do you know they aren't different? Maybe the diameters of the tube sections are different...maybe the material on the RSXR is different or the wall thickness is different?
I'm willing to bet it's the exACT same thing on each car and that they did it because the cost of improving the stiffness further and repackaging other stuff was ludicrous.
Last edited by floundericiousMI on 06-09-2003 19:45
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TonyEX
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For some reason, I doubt that price considerations would preclude a stiffer bar in the Type R.... in the past, HMC has lavished money on that car... and charged the fawning customers accordingly.
Somehow (2) makes more sense to me....
Dynamics wise... I'd guess then that with a bar like this one, which is bolted in four places, the bar serves not only to transfer motion from the suspension to the firewall, but also stiffen the firewall proper?
If so, how come we haven't seen yet any "firewall stiffening" bars.... like a bar or a slab that is bolted to the front of the firewall, under the windshield?
BTW, per (3) below.... the bars _look_ really much alike... my pictures have been reduced in size..... but when I looked under the hood of my RSX and looked at other pictures, they looked the same size.
floundericiousMI wrote:
Most likely one of two things or a combination of both:
1) Shave cost: By having a common strut bar, that is yet another place where they don't have to spend bazillions of dollars to develop a limited-run part
2) No Need: If the dynamics and handling aren't appreciably helped by stiffening the front end... why do it?
actually...
3) How do you know they aren't different? Maybe the diameters of the tube sections are different...maybe the material on the RSXR is different or the wall thickness is different?
I'm willing to bet it's the exACT same thing on each car and that they did it because the cost of improving the stiffness further and repackaging other stuff was ludicrous.
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jfunk
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I believe Ryan has stated before that it is in fact the same front bar, though the rear bar is larger in the ITR.
I guess the front is adequately stiff for the larger wheels/tires, and they more than likely do not want to induce more understeer by utilizing a larger/stiffer front bar.
JR
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TonyEX
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Hmm.. what rear bar?.... you must mean the rear SWAY bar?... not the front STRUT bar... As I recall the strut bar serves to stiffen the front structure, the sway bars serve to control body roll.
I don't think there's a front sway bar in the RSX.. is there? I got the car today... so I guess I could look under it...
jfunk wrote:
I believe Ryan has stated before that it is in fact the same front bar, though the rear bar is larger in the ITR.
I guess the front is adequately stiff for the larger wheels/tires, and they more than likely do not want to induce more understeer by utilizing a larger/stiffer front bar.
JR
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jfunk
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Sorry, I meant rear sway, as in not rear tower bar. I don't think there is a front sway bar in the RSX-S, though some aftermarket ones are available, Spoon etc..
I have always hear the strut tower bars reduce roll, I could be wrong though. I am pretty sure that with a stiffer front STB that understeer is increased.
JR
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fcd
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TonyE wrote:
Note how the bars seem to be the same? In the old ITR, the strut bar was quite an affair.... square cross section and all, while the GSR's was comparatively a wimpy round section tube.
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Hmm...seems to me a square cross section has a higher weight/second moment of inertia ratio than a circular one. So a circular cross section would be more efficient in bending.
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TonyEX
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(a) I'll take your word that the circular one is more efficient in bending.. On first blush, your point makes sense because of symmetry... but you DON'T want it to bend... in fact, you want it as stiff as possible so the bar absorbs no energy at all and passes the torsional motions on...
(b) Regardless of geometry, the old rectangular cross section ITR bar was much larger than the GSRs.. hence it was stronger regardless of geometry.
fcd wrote:
Hmm...seems to me a square cross section has a higher weight/second moment of inertia ratio than a circular one. So a circular cross section would be more efficient in bending.
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fcd
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TonyE wrote:
(a) I'll take your word that the circular one is more efficient in bending.. On first blush, your point makes sense because of symmetry... but you DON'T want it to bend... in fact, you want it as stiff as possible so the bar absorbs no energy at all and passes the torsional motions on...
(b) Regardless of geometry, the old rectangular cross section ITR bar was much larger than the GSRs.. hence it was stronger regardless of geometry.
fcd wrote:
Hmm...seems to me a square cross section has a higher weight/second moment of inertia ratio than a circular one. So a circular cross section would be more efficient in bending.
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(a) What I meant is it should be stiffer. The second moment of inertia is in the bottom of the bending equation so the bigger it is the smaller the bending moment.
(b) That I have no doubt. I just wonder why its square? Am I missing something? A nice big rectangular bar would be better then a nice big circular bar if there is a preferential bending moment. But I'm assuming the long dimension on the ITR bar is in the plane of the road. It seems to me that you would want the maximum bending performance normal to the road.
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RyanDL
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jfunk wrote:
Sorry, I meant rear sway, as in not rear tower bar. I don't think there is a front sway bar in the RSX-S, though some aftermarket ones are available, Spoon etc..
I have always hear the strut tower bars reduce roll, I could be wrong though. I am pretty sure that with a stiffer front STB that understeer is increased.
JR
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The RSX and RSX-S have both a front and rear sway bar. They also have a front strut tower bar. Sway bars reduce body roll. Strut tower bars reduce chassis flex between strut towers, not body roll. I don't know that a strut tower bar will increae/decrease under/oversteer, but it certainly makes the car feel more "connected" to the road and more precise with regard to turn-in response.
Ryan
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floundericiousMI
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I'd have to see it, personally...
You have to realise something else, also...
Even with all this talk about radii and wall thickness and profile and geometry..you still have to look to the weakest point: the mounting plates. The cross section carries 95% of the way across and then goes to virtually nil where the mounting point comes in...I'm thinking that the old ITR bar might have had a more robust mounting section. The integra shotguns, dash panel, and cowl top were probably nowhere near as stiff as the current RSX architecture. In fact, I'd guarantee it! I think I'll take some hi-res pictures (of my Ford "el Foco", though) and work up an article at some point this summer to help explain some of the structural theories behind body structure and the use of strut tower bars and reinforcement kits.
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TonyEX
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That'd be really cool.... in fact that was something I was hoping you'd do... ;-)
I wish ToV would create some type of archive about the posts and what not that describe the mechanical works of an automobile... engine, suspension, etc... I realize that one could search the forums... but it'd be nice if there was a section dedicted specifically to show such.
If you need help, let me know.
floundericiousMI wrote:
... and work up an article at some point this summer to help explain some of the structural theories behind body structure and the use of strut tower bars and reinforcement kits.
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RyanDL
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That would be an interesting read. When you do that, you should search to find your post regarding chassis theory. Then, create a tech article (rather than a post) and go in-depth. It'd be an interesting article sure to generate some creative buzz.
Ryan
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fcd
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Ok here?s a question. What is the general relative motion between the shock towers? Is the strut really being bent or it being twisted or is it in tension?
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TonyEX
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This is the thread that Ryan and I referred to..... In it, Flounder described at great length how the front suspension loads are transferred and how a strut bar helps.
http://www.vtec.net/forums/one-message?message%5fid=64563
Some of the stuff in this thread really belongs as an article, because our Ford guy.. even though he loves his truck, did do a great job in explaining it... he was prodded all along by a bunch of us... and yet he took the patience to describe it to us Einsteins...
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floundericiousMI
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I'd say its a combination.
The bar on the RSX R, with the mounts up on the dash panel/cowl, would probably be mostly in bending...
Look at how close in the strut towers are with respect to the dash! There's going to be (relatively speaking) very little torsion on that member during a major suspension event or high loading in a fast corner.
On the whole, the major load WILL be bending. Remember, the purpose of the strut tower bar is to not allow the two strut tower panels to walk up and down as much relative to each other. By constraining it, you're pulling some of the bending stress into the bar and keeping your suspension geometry closer to where it should be. This is the truest benefit of strut tower bars: Suspension performance enhancement by ensuring the suspension can do its job.
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