Topic: GM engineer questions backbone

[Uranium-238]

It's possible that the engineering idea of what should and shouldn't be noticeable is flawed...

[lil goat]

I have noticed time and time again on the BB the people who swear this or that don't work have usually never tried it, or in many cases never seen it. They call them a doubting Thomas. I just call them a$$holes. At least the engineer still has an open mind and is willing to test.

[Sol Asylum]

Going back to the aluminum vs steel debate.  Aluminum is quite strong when it comes to bending in fact its much harder to bend aluminum then steel.  I have worked in the aviation industry doing sheet metal repairs in aircraft as well as a lot of auto body work on cars.  Hand forming steel is much easier then aluminum.  The trick is that you have to use the right aluminum alloy for the job.

Now some will say that the aluminum is resistant to bending which means it will break with little or no warning.  Actually this is not true.  The largest structurally member in aircraft is the wing spar, most people don't realize that the wings of a plane flex a great deal especially large aircraft.  The wings on B-52s flexed so much that there is actually a landing gear of sorts out on the wings to keep the wing tips from contacting the ground.  Aircraft wings also don't just bend in an up down direction but fore and aft as well as twisting or torsional loading.  But what are wing spars made of you might ask well in most cases they are all aluminum or some sort of alloy, the other commonly used material is wood.  Thats right the strongest part of the largest of aircraft is aluminum not steel, making a wing spar out of steel that was as strong as an aluminum one would weigh so much that the plane couldn't fly.  Also steel work hardens which means that after so many bending cycles it will become harder and more brittle which will eventually snap when bent one too many times.

The analogy of the coke can is a poor one in that the alloy that the can is made out of is very soft and not structural.  Its that way because it would be a total b!tch to make cans out of structural aluminum, causing the can price to be unnecessarily high.

The point is that your aluminum backbone will never see the bending forces or the number of bend cycles that an aircraft wing must endure.  The steel bolts that hold it in place will fail long before the backbone will (those bolts would also fail before the OEM brace failed too).

Ron just buy the backbone and stop worrying about it!

[G8TR]

The engineer and I had a difference over tunes about 6 months ago and of course he crapped all over everybody's except for GM. When people started asking him about the wastegate mod he kept talking about it voiding the warranty, etc. Eventually he broke down and did the wastegate mod himself and then suggested that people should be real careful and that he didn't advocate it, because of warranty issues. Then he went on to say how much more he was getting out of his car by doing so, because of the no learn down feature on the GMPP tune. He was talking out of both sides of his mouth then and continues to do so now. I ran into him talking to a couple of people at Mecca III and you would have thought he was Bob Lutz, the way people were following him around and hanging on his every word. I moved on after about 15 seconds. (Nothing to see here, time to move on)  

[Ben L]

And whose company is in the crapper? 

That guy's!     

[Uranium-238]

Now some will say that the aluminum is resistant to bending which means it will break with little or no warning.  Actually this is not true.  The largest structurally member in aircraft is the wing spar, most people don't realize that the wings of a plane flex a great deal especially large aircraft.  The wings on B-52s flexed so much that there is actually a landing gear of sorts out on the wings to keep the wing tips from contacting the ground.  Aircraft wings also don't just bend in an up down direction but fore and aft as well as twisting or torsional loading.  But what are wing spars made of you might ask well in most cases they are all aluminum or some sort of alloy, the other commonly used material is wood.  Thats right the strongest part of the largest of aircraft is aluminum not steel, making a wing spar out of steel that was as strong as an aluminum one would weigh so much that the plane couldn't fly.  Also steel work hardens which means that after so many bending cycles it will become harder and more brittle which will eventually snap when bent one too many times.

Ever seen the video of the 747 doing flutter testing in a wind tunnel? You'd think it was a bird the way the wings were moving...

[snaponbob]

Ever seen the video of the 747 doing flutter testing in a wind tunnel? You'd think it was a bird the way the wings were moving...

They damn well BETTER flap !!!!!!!!!!!!!!! Otherwise the 747 would NOT be an AIRplane. Would it? Of course, the back bone is about 2 feet log. And the Sol weighs, oh ...... 3000 pounds with a GVW of MAYBE 3500 pounds. The 747? Max takeoff weight over 800K pounds and the wingspan is 200 feet. Like I said, the wing better flap.

I just love it when people make great sweeping negative generalities (like THIS one) about how (fill in the blank with the negative term) someone, something, or some company is and yet may not be able to do any better. This place is slowly starting to sound like the "other" forums.

238, that was not aimed at you. We might be on the same page on the aluminum issue.

[Duck1313]

Fact: There are 2 ways to spell out Al
Aluminum....or the british (them folks talk funny)....Aluminium

Okay, enough comic relief.....back to the debate

[GXPinKC]

Ron just buy the backbone and stop worrying about it!
[/quote] Sol Asylum

Sol Asylum and DeepBlueGXP, thanks for the good advice.  I needed a push and I appreciate you pushng me over the brink!  I pride myself in being a safe driver now, but it was not always that way.  With my old toy the '95 Firebird Formula, (that I owned for 10 years) and all of it's 280 horses, I used to live on the edge.  Well, I was considerably younger then and could take chances and it was fun.  So, now Sol Asylum, I guess, as an old "fart", I should just forget the past glory and ride off into the sunset quietly.  Uh, not so fast.  Might as well shoot for the moon and take "Miss Red Eagle" to the Summit in Denver, and as they say, go for the gold.  This ain't no Olympics for sure, but now that you have helped me make the decision, I do thank you for that, but now the only choice left is whether to get the "Race" or the "Street"?  I don't plan on racing or track events so probably the "Street Backbone" would work just fine, but the "Race Backbone" would certainly fill the needs better if my wife allows me to get the Lyndon Wester Tune! Ain't it fun to drive Kappa's!

[Sol Asylum]

Ron I always say the best days are ahead of you other wise what have you to look forward to?  By no means would I call you an "old fart."  Being cautious is a good thing it allows you to live long enough to obtain old fat status.  

I don't have a backbone, yet but I too am thinking about it.  I forget what the thickness of the street and race are but when I looked into it I was figuring on going with the race one as I know it will be less flexible then the thinner one and for the small difference in price it seemed a no brainer.  That being said I almost always decide what I need and then get the next one better in fact thats how I ended up with a GXP instead of the NA.

Either part will be a safe improvement over the stamped sheet brace it left the factory with.

Something else to contemplate:  Engineers tend to not like being told that there is a better way to do something then the way they designed it, they like it even less when you prove them wrong.  Is it possible that this engineer is just trying to save face because a couple of "shade trees" (no disrespect intended) bested him?

[Uranium-238]

238, that was not aimed at you. We might be on the same page on the aluminum issue.

Yeah, I think we are too. He mentioned a B-52 and I had to interject with that flutter vid. Besides, for all I know the main structural components in a 747's wings could be titanium...

And FWIW, I'm in the "The DDM brace is a significant improvement" camp. But in Flash'sOwner's defense, there are times when a calculated figure doesn't transfer into how you expect it to be felt. (I read his statement as meaning that GM crunched the numbers on the brace, and didn't test anything like what DDM offers.)

I'm a technician, I see it with some of the engineers I work with from time to time. I'm also an engineering student, and have therefore had it happen to me. Calculations are great, but there's still no substitute for a real, live test, and there never will be. You can quote all the numbers and calculations you want, but it all still boils down to how the test article behaved in the real-world test.

If GM is doing that much designing without a few science experiments to back up their predictions, it's no wonder that they're going down the drain.

EDIT: Oh, and Sol Asylum, your last remark is always a real possibility. FWIW, the engineers, ("my calculations show that A is better than B) usually end up at odds with the technicians. ("you can spout numbers all you want, B still works better than A.) The group that designs stuff will always be at odds with the people who actually use it. Good communication between the groups can overcome all this, but that doesn't happen at my place of work.

[lil goat]

For the Street/Race/Extreme decision process. The difference between the Street and Race is huge compared to the difference between the Race and the Extreme and people are upgrading to the Extreme right and left. The Race has 1/3 the flex of the Street, that is 4mm VS. 14mm The Extreme has 2mm VS. 4mm. Even I doubt you would notice the 2mm difference but if I didn't have a backbone, I would still get the Extreme. The only reason I didn't upgrade to the Extreme is they didn't make it in PINK!

I just had a thought, don't laugh it happens, if there were any disadvantages to the car being stiffer they would appear in the Coupe, if you think a backbone will stiffen a car try a roof!

[Kelu]

Can I ask the backbone which you buy from DDM is made from aluminum or steel? How much weights by approximation?

I made mine out of steel and weights somewhere 22 - 33 lbs, I didn't weight it to be precise.

[lil goat]

It is made of Aluminum and weight 9 lbs, both the race and the extreme, the extreme 1/2 inch is drilled out to keep the weight down, the race is a solid piece 3/8 inch

[Aspenrose]

The engineer and I had a difference over tunes about 6 months ago and of course he crapped all over everybody's except for GM. When people started asking him about the wastegate mod he kept talking about it voiding the warranty, etc. Eventually he broke down and did the wastegate mod himself and then suggested that people should be real careful and that he didn't advocate it, because of warranty issues. Then he went on to say how much more he was getting out of his car by doing so, because of the no learn down feature on the GMPP tune. He was talking out of both sides of his mouth then and continues to do so now. I ran into him talking to a couple of people at Mecca III and you would have thought he was Bob Lutz, the way people were following him around and hanging on his every word. I moved on after about 15 seconds. (Nothing to see here, time to move on)  

Before you all start talking out of the WRONG side of your mouths, Steve is a guy I, and MANY, would go to for opinions on most any after market suspension/drivetrain mod for this platform, hands down. He knows of what he speaks. More so than any shade tree 'mechanic' on this or any other board.

Unbelievable. If he were not on the boards, and he has been for YEARS, there would be virtually ZERO platform presence. Then the whining would be that there is no one who truly knows this platform available.

[DeepBlueGXP]

He is pretty knowledgable but sometimes engineers just need to take of the blinders.  DDM did a measurement of the car on jacks with the stock backbone and removed one jack, did a measurement and then replaced the backbone and did another.  The flex of the body was reduced.  Nuff said....

[kennysabarese]

I thought flash's owner was from michigan, was he at MECCA III?

[snaponbob]

Before you all start talking out of the WRONG side of your mouths, Steve is a guy I, and MANY, would go to for opinions on most any after market suspension/drivetrain mod for this platform, hands down. He knows of what he speaks. More so than any shade tree 'mechanic' on this or any other board.

Unbelievable. If he were not on the boards, and he has been for YEARS, there would be virtually ZERO platform presence. Then the whining would be that there is no one who truly knows this platform available.

Agreed. And the assessment about the "tension" between techs and engineers is SO on target. What is REALLY admirable about Steve is his willingness to discuss his views, learn from us through feedback, and change his mind OUT IN THE OPEN. THAT takes balls !!!!

238, the first time I saw a fuel ladened B52 take off (Kelly AFB) my eyes fell out of my head. And films of B52s in flight in choppy air is absolutely stunning. "Flex" has to redefined for THAT. And this is why I never liked flying on DC9s - their wings are stiffer than Boeing's.

[smartin]

I thought flash's owner was from michigan, was he at MECCA III?

Yes, his name is Steve and he was at Mecca III.

[WWI Flying Ace]

Stupid noobie question...when he says:

"We also did a series of blind evaluations when increasing the rear crossmember stiffness, during the development of the GXP Z0K. The results of stiffening the rear crossmember were so dramatic that we went through the trouble of producing a specific beam for use on the Z0K club racing models. Expert evaluators could consistently, 100% of the time, determine whether a stock or a "stiffened" rear crossmember was in the vehicle. Normal drivers, on one evaluation run, had 11 of 12 able to pick the differences between identical vehicles, WITHOUT cross discussion.  My conclusions from this development work are that it is critical to increase stiffness of the rear crossmember."

...isn't he saying that the backbone is a good idea?  My next mods (which will probably not take place until next year) are going to be to stiften the car using DDM stuff...but am I missing something in the posts?  Or am I confusing the backbone with the ProBeam?  Sorry if so...just want to be sure I get the right thing in the right order for my baby if I get them one at a time.  Since I don't have either one right now they are both conceptual to me instead of actual metal on my car I can look at.  

[elff]

The DDM Probeam is the part that stiffens the rear crossmember

[WWI Flying Ace]

Ok, thanks.  That makes sense.  

[AdamVIP]

The only time where the brace will be noticable will be when the frame is subjected to a vertical force that is not equal across the car.  This is nicely showcased with the DDM jack test.  Essentially they are putting a vertical point load on one side of the car.  It creates a moment which a thicker plate will handle better.

In most driving conditions you will not encounter this scenario.  In 99.9% of driving cases the forces exerted on this piece are going parallel with the brace plane.  On paper the thicker plate will handle this force better as well but youll be spinning well before you you max out the stock piece and notice a significant difference in feel.

All that being said I bought a brace from DDM and haveit installed.  On the .1% chance I get a road irregularity that wil cause the torsion effect Ill be ready.

[elff]

What about Race Track/ AutoX situations with lots of fast slalom side to side movements?

[Uranium-238]

Or sudden dips in the road, uneven driving surfaces, potholes, those odd mounds/folds found in some turns, etc.