backbone

[Critterman]

Steve, thank you for the review, glad to know the "seat of the pants" wasn't lying to me So after all the Enginerinng speak I take it you liked the effect?

[Windrestrictor!]

Originally Posted by bryan1969 Dave , I got Saphire out of storage today and installed the backbone. Tristie and I went for a 200 mile drive. All I can say is WOW! This car is sooooo flat through a turn. No body roll at all. I even had the rear end steep out on me a couple of times with no body roll. This will take some playing with to get the feel of it. Great product.

I agree, fantastic product and a wonderful company! We love ours

Stephen

[Dave@ddmworks]

I just wanted to say that it was a pleasure spending the morning with Flash's Owner doing the test and talking about different aspects of the car. Also it was great to get his direct feedback on the backbone, especially after all of the positive feedback we have received on it. I have to admit the roads around that area of Michigan are great for testing chassis bracing, as they are a little on the rough and uneven side of things and really put the suspension and chassis through a workout. In the end I was happy that he wanted to leave it on (as I really did not want to crawl under the car again )and was happy for the information and knowledge I took away from meeting with him. I would have loved to spend a couple more hours talking, but my time was limited that day. In the end it was great meeting with Flash's Owner and look forward to meeting with him again if the opportunity presents, and I hope that the community as a whole benefited from this little test.

Thanks!
Dave

[rob the elder]

I do a weekly comparison of the wife’s Sky with the ProBeam and no backbone (it’s on the bench) and my Sol with both the ProBeam and the backbone. My car also has BC coilovers and is lowered about 1.5 inches. Also, it sits level as opposed to slightly nose down.

Her car tends to front load, the front end loads up and complains first when driven in a spirited manner. My car tends to over steer and can consistently be thrown around the same corners with the same driver at higher speeds with a lot less drama. When driven without lots of power on, it just goes around the corner with little tire squeal unless you are really going. If I am on the power, the rear tires will almost always talk first. If I continue to press it, then both ends will talk and lets you know that you are starting to work the tires. Since the comparison driving happens in town to and from the gas station or the wash rack, I try not to get too out of shape with either car so have not had occasion to push her car to its limits of adhesion. (If we are out of town on the GOOD roads, she is along for the ride and is thus a constraint on testing to the limits.) Mine drives like a slot car, then the back end starts to squawk followed by both ends, then it just goes sideways at the rear much more than at the front. I have never had the front end totally lose it, but then I am old.

Headshake on her car is much more noticeable than on mine. It’s relatively easy to get her hood dancing while mine tends to vibrate slightly when the car is pressed on uneven surfaces.

Her car will lose traction at the rear under hard acceleration more frequently than mine does. You have to work to get mine to really break loose. Its considerably quicker than hers having probably 30 HP more than hers up to mid-range.

Several of the annoying creaking and groaning sounds that my car used to make are now absent. Her Sky never made the same sounds so I cannot compare the two in this respect.

[kwtoxman]

Got the extreme version of the backbone installed yesterday. We managed to do it without having to move the exhaust. Although we did have to lever the exhaust a bit to get the backbone to slide in. No driving notes yet.

[perris]

I have a question for flash's owner or anyone who can explain the two of the terms he used for me

He said he needed to "continue to soak", I guess that's an engineers term or a research term, could someone illucidate for me?

also if someone could explain to me what "shear strenght" means as opposed to the strenght that the backbone enhances, I don't understand that either

thanx in advance

[dengel]

Originally Posted by perris I have a question for flash's owner or anyone who can explain the two of the terms he used for me He said he needed to "continue to soak", I guess that's an engineers term or a research term, could someone illucidate for me? also if someone could explain to me what "shear strenght" means as opposed to the strenght that the backbone enhances, I don't understand that either thanx in advance

good guess on the soak terminology. Yes "soaking" is a form of testing.

Originally Posted by wikipedia Soak testing involves testing a system with a significant load extended over a significant period of time, to discover how the system behaves under sustained use.

Shear Strength involves the manner in which forces are applied to the structure and the manner in which that material or structure would fail. I'm too lazy to look but did someone use the term shear strength in their description of the backbone?

Originally Posted by wikipedia Shear strength in engineering is a term used to describe the strength of a material or component against the type of yield or structural failure where the material or component fails in shear. In structural and mechanical engineering the shear strength of a component is important for designing the dimensions and materials to be used for the manufacture/construction of the component (e.g. beams, plates, or bolts) In a reinforced concrete beam, the main purpose of stirrups is to increase the shear strength.

Originally Posted by wikipedia Shearing in continuum mechanics refers to the occurrence of a shear strain, which is a deformation of a material substance in which parallel internal surfaces slide past one another. It is induced by a shear stress in the material. Shear strain is distinguished from volumetric strain, the change in a material's volume in response to stress. Often, the verb shearing refers more specifically to a mechanical process that causes a plastic shear strain in a material, rather than causing a merely elastic one. A plastic shear strain is a continuous (non-fracturing) deformation that is irreversible, such that the material does not recover its original shape. It occurs when the material is yielding. The process of shearing a material may induce a volumetric strain along with the shear strain.

[Flash's Owner]

Originally Posted by perris I have a question for flash's owner or anyone who can explain the two of the terms he used for me He said he needed to "continue to soak", I guess that's an engineers term or a research term, could someone illucidate for me? also if someone could explain to me what "shear strenght" means as opposed to the strenght that the backbone enhances, I don't understand that either thanx in advance

Well, dengel is pretty much right. To "soak" in something is to drive it normally for a period of time, usually several days to weeks, and let intuitive evaluation happen subconsciously.

Regarding shear, well, you asked an engineer, so you will end up with an engineer's answer. LOL

There are two ways you can load a part.

1) tension/compression. That seems intuitive enough, but if it is not, then this is taking something like a bar, and pulling on the end or pushing the two ends toward each other. The amount of deflection of the bar when you do that is related to Young's modulus of elasticity, which, unintuitively, does NOT change for a given type of material (most alloys are so close as to be considered the same). Steel has a very constant modulus, Aluminum as another, Tungsten carbide its own. This modulus, (roughly speaking) multiplied by how much material is there tells you how stiff the bar actually is. Take three bars, all the same size, out of these three different materials. Steel's modulus is about 200 (mPa, it is a pressure because it is related to force and area), Aluminum about 70 and Tungsten Carbide about 400. The steel bar will be 3X as stiff as the aluminum, but only half as stiff as the Tungsten Carbide one. (you can play games with the density, since Aluminum is less dense than Steel or Tungsten Carbide).

When you BEND a bar, what is really happening is the bar is being loaded in tension/compression, the inside of the bar is under compression, the outside is under tension - no shear going on.

2) you can also load something in shear. Shear is like trying to push two parts with opposite parallel forces. If you take a panel and you grab both sides of it, and try and make it move like a parallelogram, you are shearing the panel.

When you grab both ends of the same bars above, and you TWIST them, you are loading the bar in shear, because each tiny segment of the bar can be treated like a stack of discs, each one trying to "turn" with relation to the other. The greatest amount of shear is the furthest away from the diameter. The stiffness in this case would be according to the SHEAR modulus (aka Modulus of Rigidity), and while related to modulus of elasticity, it is not the same.

This is the principle for how a spring - yes, even a coil spring - works.


Maybe that helps, maybe that made it worse. You be the judge.

[diamoney]

Not to argue with an engineer, but for illucidation in my understanding-

Originally Posted by Flash's Owner When you BEND a bar, what is really happening is the bar is being loaded in tension/compression, the inside of the bar is under compression, the outside is under tension - no shear going on. Isn't the line between the tension force and the compression force a shear line? 2) you can also load something in shear. Shear is like trying to push two parts with opposite parallel forces. If you take a panel and you grab both sides of it, and try and make it move like a parallelogram, you are shearing the panel. I can picture this. I would have thought that testing a panel for shear strength would have been more associated with how much it "parallelograms," causing attaching bolts to shear (like moving a stack of discs perpendicularly to its longitudinal axis. When you grab both ends of the same bars above, and you TWIST them, you are loading the bar in shear, because each tiny segment of the bar can be treated like a stack of discs, each one trying to "turn" with relation to the other. And, see, I thought most "twisting" forces were Torsion, but like earlier comment, I guess there is a shear force in torsion as well... The greatest amount of shear is the furthest away from the diameter. The stiffness in this case would be according to the SHEAR modulus (aka Modulus of Rigidity), and while related to modulus of elasticity, it is not the same. It is amazing that a simple flat piece of metal can be bending twisting, and sliding all at the same time! Maybe that helps, maybe that made it worse. You be the judge.

I learn something new every day I wake up.

[Flash's Owner]

Originally Posted by diamoney ... Isn't the line between the tension force and the compression force a shear line?

No, because the "line" has no area. On one side of the line is compression, the other side is tension, ON the line is no force or shear at all. Since the actual shear force is the modulus of rigidity integrated over the AREA, and the area is zero - no shear.

Originally Posted by diamoney And, see, I thought most "twisting" forces were Torsion, but like earlier comment, I guess there is a shear force in torsion as well...

Twisting effort is torsion. The mechanics of the materials that create the stiffness in that torsion is shear. A coil spring is really a torsion bar that is wrapped around a helix. When you load the ends of a spring, all the small parts of that spring react as if you straightened that coil spring out and twisted it. The actual deflections that create the opposing forces are dependent on the material modulus of rigidity, the diameter of the coils, the actual length of the coil and the diameter of the material used to make the coils.

Remember, there are only two ways to load a chunk of material - either you pull it apart or push on it (where the forces are in line with each other and opposing), or you shear it by loading it with opposing forces are not co-linear. All loadings are combinations of these two conditions. If you look at a stabilizer bar while cornering, parts of it are subjected to bending, parts are subjected to torsion, and parts are subjected to both. Through the magic of calculus, we can transform these properties into torsion and bending stiffness.

[perris]

flash's owner, all this made sense to me but I guess this is where my confusion started

I would think the backbone of our car combats both both tension and compression, but you said shear strength is the big factor for this support area

[Flash's Owner]

Originally Posted by perris flash's owner, all this made sense to me but I guess this is where my confusion started I would think the backbone of our car combats both both tension and compression, but you said shear strength is the big factor for this support area

It helps to think of the panel as the bottom surface of a square tube. The tunnel is like a very large hollow bar. Torsional stiffness is mostly dependent on the shear stiffness of all sides of the tunnel. Very little bending in the panel at all.

Even novice comments about how "flimsy" the stock piece is are based mostly on shear. People pick up the stock piece and try and twist it (which we now know is shear).

What is also important is the plane along which the part is experiencing shear. The way the tunnel belly pan works is primarily by shear created by the two sides of the panel trying to move mostly fore/aft with respect to each other. That is why even though the backbone is so much thicker than the stock piece, it does not stiffen the car to roll cage or even sedan/fixed-roof levels.

In fact, one early concept was a simple eight-place attachment in a diamond-shaped truss, instead of a full closeout panel. The panel is much cheaper to build, but it is possible to make a hollow tubed truss stiffer than even the backbone currently is. The funny thing there is such a piece then relies more on the Young's modulus than the modulus of rigidity, because each part of a truss becomes close to a 2-force member.

[kwtoxman]

Originally Posted by kwtoxman Got the extreme version of the backbone installed yesterday. We managed to do it without having to move the exhaust. Although we did have to lever the exhaust a bit to get the backbone to slide in. No driving notes yet.

I've done some driving on the car and here are my notes from street riding so far....

I tend to agree with Flash's owner in so much as there aren't huge differences..... at all. There are way too many people who say the probeam and/or backbone make a huge difference. Street driving no less.

Nope. Not large differences. But maybe some small differences. The car does seem to absorb bumpy pavement better without as much chassis flex. Not huge amounts, but any improvement is good in my book. Less flex means less rattles. The car feels a little more solid and it is nice to feel. Remember, I have coilovers on the car that make it very sensitive to pavement conditions. The added stiffness of the suspension seems to put more stress on the frame, so the additional bracing is welcome.

The car seems to track hard cornering at the limit a little better, in so much as the limit seems to be a little higher before you overcome the available traction from the tires.

I'm hoping to autocross this weekend and I'll report back on some real testing.....

One note is that my GXP handles the way many street owners lust after. With the suspension/bracing/alignment mods I have been able take 20 mph on-ramps (suggested speeds) at 60 mph. Now I need some decent tires.....

[LatinVenom]

The big difference is on the ProBeam, similar to adding the Z0K part.
I have always said the BackBone makes the car feel more solid and so have others.
The other improvement is the Z0K rear sway bar.
Coil overs is a different subject on it's on.

[off2kill]

My opinion of driving with the back bone is the car feels way heavier! Like it gained a1000 lbs....Feels more like an upscale car like a benz or bmw