S550 Chassis School

[IGJoe2192]

Indeed, his observations definitely sound encouraging. Hopefully we won't have to wait too much longer to find out the facts.

Agreed. Please Pill, find and analyze all of the photos you can get of this new car. I sure hope it is lighter and a better chassis than what GM is going to put the new Camaro on.

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[DiPsTiCk]

Agreed. Please Pill, find and analyze all of the photos you can get of this new car. I sure hope it is lighter and a better chassis than what GM is going to put the new Camaro on.

What he said... exactly.

 

[thePill]

As soon as we get some better photo's, they will be nit picked right here. Now that we have a better look at the rear frame section, I'm very impressed. First off, there is far less frame rail. The S197 used larger rear frame section tubing AND, the kicker here is, there is no kick up what so ever. The S550 has NO hinge points until the V type brace turns to the rocker. There were about a half a dozen hinge points on the S197's kick up. That is a lot of mass removed from the rear, the beams/rails are slimmer and the best part, they are straight... It's even better than an S brace, you just can't get any better than straight.

The Monocoque floor panel (my name for it) has been improved over the S197. This panel has the fuel pump access holes... They are angled in between the B Pilllar Cross Member and the Lions Foot Cross member. The ILIRS cradle is supported by the Lions Foot Cross Member, it does not link the Cross Members together, the Floor panel seems to be seperating the two. It's a very strong area. The Sled Runners are pretty much just long, sturdy Sub-frame connectors that are built into the platform.

The improved platform rigidity was strong enough to net the convertible a 13% increase over the '14 Convertible. That is a pretty big number considering there were no sub frames or additional supports added in. Yes, the convertible is not as rigid as the coupe BUT, it's an increase over the old one without any additional platform R&D or weight/cost added to the Vert. With the roof on, we could be looking at a 20-30% increase in rigidity... That is going to make the Mustang feel like never before.

I know most are tied up in Aluminium panels and they do reduce weight. The Mustang is slowly but surely eliminating steel panels, there really isn't that much weight left to get rid of, maybe 100lbs counting engine bay. The only way to shed weight now is to do what Ford did here, engineer an efficient platform design.

What I see, a much smaller, slimmer and efficient platform over the S197. The powertrains are a wash, front suspension is a wash, rear suspension is very close, within 50lbs maybe less. Interior could be lighter, I know the people that worked on the new F150 and weight savings was number 1. Electronics and Info centers may gain some weight... Tires and wheels are almost a wash. Glass? Less... Doors? Less... Hood? Less... Airbags is a gain for sure...

It's just hard for me to place the S550 anywhere near the S197 in weight seeing the platform now. The Corvette saved 100lbs in platform but gained 190lbs back in new engine, trans, suspension and electronics. That was a 2 seater and 100lbs was lost... With Space frames made of Aluminium, design got them that 100lbs... A larger platform will net a larger loss (see F150). The S550 has lost about 200-300lbs from the platform just judging the mass reduction. I can account for 100lbs in electronics, airbags and rear suspension...

That's pretty much it... If I missed something, let me know...

(Cont)

 

[thePill]

The Alpha Chassis: Oh god, here comes the heat...

I seen the platform, I'm still missing some small visual details but, I got the downlow. First, it's a traditional Unibody. It's built very well as far as structure goes. The holes that litter the structure are a little excessive. I tease about that measure being a weight loss technique and, in reality, it kind of doubles as such. Some of those are alignment holes... They shoot a laser into the hole (an x or +) and if the x or + isn't seen, it's considered straight. That's industry wide... Although, the Alpha has way more holes than normal. If they are using that many points for precision measurement, and the platform is straight, that technique is far better than fewer measuring points... Catch my drift? It is a sign of quality (at least an aggressive attempt) and, it's a sign of great detail. Not great for frame damage analysis, frame straightening or impact resistance. It will transfer collision energy similar to what Fords new Unibody does however, Fords design will resist small impacts while the Alpha will absorb the crash like a sponge. Each of those holes will deform and pretty much total a car...

Looking at the Alpha platform, it is just a traditional Unibody and, it probably uses a torque box like before. This is where some major weight is gained and those hinge points erupt. The Alpha is basically a box with pillars standing on it. Think about it like this... The Fusion has a 112 inch wheelbase, it's a large car. The ATS sits on a 109, I consider it a mid-size sedan, a little on the small side. The base Fusion weighs 3425lbs and the ATS weighs right around that... Ford is literally running circles around GM in this department, technology nabbed while buying and selling other car companies (Volvo). In a sense, they are just as far behind in platform engineering as they are in DOHC development.

The major issue is unavoidable, no matter how much R&D they do. The fact that the 6th Gen Camaro will be built on a hand me down platform. Caddy developed the ATS, they had even said some weight was gained while trying to support AWD, it was rumored the chassis was pushing curb weights up nearing 4000lbs. It's a Cadillac platform... Next, Caddy is re-engineering the Alpha for the larger CTS. I am nearly convinced the Camaro will come from that and here's why. The ATS has a 109in WB, it was developed with an Ecotech 4 and V6 in mind. Look at some of the supports the Alpha is using. The Sled Runners are a small, thin strip of metal. They usually add in another offset runner that's even smaller than the main. The CTS will be engineered to support heavier drivetrains, that 112in WB will also help them with rear seat room. It also puts some space between the Vette and the Camaro as far as classing goes. ATS or CTS doesn't really matter, I can see a ET4 or V6 CTS being 3550-3650lbs. An ATS that has been reinforced to support a V8 will likely gain 50-150lbs of additional support during R&D. Is it possible there is a 3rd wheelbase in the works? Yeah, that would be ideal... but come to think of it, optimal and ideal have been lost once they used a second hand platform. Both the ATS and CTS Alpha's were not developed for the Camaro. In fact, this method of platform sharing will not have any performance advantages. The advantage here is cost... That's it... The team is very limited on what thy can do with another cars platform. It's possible that the CTS is no more than a re-engineered ATS. The compromise began there. Not only is the Alpha kinda dated as far as technology and techniques goes, it has gone through some major compromise getting to the Camaro. In order for the Camaro to evolve and progress to a World Class Sports coupe, it will need a dedicated platform built specifically for Camaro use. After the R&D is finished, THEN the sports coupe chassis can be handed down to others... The S550 is approaching this generation like that. The platform, styling, powertrain... Prett much ALL Mustang exclusive first then handed down. In other words, it no longer feels the compromise of a shared platform.

This is where the Camaro gets left behind again... I know feelings are gonna get hurt and grown men will throw a tantrum... That's just the reality of it. Thy are not ready to move the Camaro up market, it will continue with the traditional Pony Car method of platform sharing.

(Cont.)

 

[Grimace427]

If the 6th gen camaro is slated to be a 2016 model, I find it hard to believe it would still be in the chassis development stage. Even if it were a 2017 model it should have running mules on the streets with 5th gen bodies as camo. Any chance Pill that what you saw was only what GM wanted you to see?

 

[thePill]

If the 6th gen camaro is slated to be a 2016 model, I find it hard to believe it would still be in the chassis development stage. Even if it were a 2017 model it should have running mules on the streets with 5th gen bodies as camo. Any chance Pill that what you saw was only what GM wanted you to see?

The 6th Gens platform should be locked down by now and, if they truly are hiding the 6th under the 5th Gen body, prepare yourselves for another 112in WB Camaro. I seen some bare ATS platform pics, it was part of the Alpha/ATS press release. What they had on display is what they were working on... The ATS started development around mid year 2011 if I remember correctly, the CTS was about a year after that. The 6th Gen platform should have been locked down around Summer '13... I didn't mean to give anyone the impression that it was still under development, it should be done.

I find it hard to believe Chevy won't capitalize on the Camaro's birthday. 50 years would be September 29th 2016. While I am totally against ANY Camaro Anniversary Models or Birthday Packages, I still feel they will either hold the release until then OR, some of this Ignition Switch Recall could push everything back like the Chapter 11.

Although, they could be forced into an early changeover due to falling sales. The refresh sucked and they may not make it another 2 model years.

 

[Dyno]

The mules would be very apparent, even the S197 body fitting over the S550 chassis was spotted easily with all testing equipment around in Aug 2012. It is getting late in the game for Alpha mules to be spotted, but Im sure Chevy is keeping it under tight wraps (if it is indeed a 2016MY) until at least the S550 goes on sale for competitive reasons so no last minute changes can be made before the S550 goes into production.

 

[WestRace]

They took a sh!tload of mass out of the Engine bay, cradle, firewall and cowl. The front frame section on the S550 (S and Y) are much slimmer now compared to the S197's more of a Z and V brace, they could be Hydro-formed. The Firewall's are a HUGE difference. The S197 has a pretty tall Firewall/Cowl, it was also pretty deep meaning, it went all the way to the ground. The S550 has a very tight and compact firewall, it's a proper shear plate now with very little flex... More of a cross member now LOL...

The S550 is lighter, it has to be, that's just looking at mass, the metal that is no longer part of the Mustang. I haven't even thought about materials being lighter... Looking at the S197 and S550's Platforms together, there is A LOT of metal missing in the S550 that the S197 had to lug around.

Hopefully they won't compromise of the structural integrity of the car from the weight saving. I drove a BMW 328i and that thing feels like solid metal ... figuratively. BMW really knows how to build a body shell.

By the way can someone educate me on the S&Y braces vs torque box? Let me see if I get this right.
The S&Y braces leverage the entire body sledges to support the engine so the load and weight are better distributed through out the entire chassis. On the other hand, the torque box uses basically a frame which is attached to the front of the chassis to support the engine? Because of this, more weight is added to the front of the car?

 

[Grimace427]

By the way can someone educate me on the S&Y braces vs torque box? Let me see if I get this right.
The S&Y braces leverage the entire body sledges to support the engine so the load and weight are better distributed through out the entire chassis. On the other hand, the torque box uses basically a frame which is attached to the front of the chassis to support the engine? Because of this, more weight is added to the front of the car?

Torque boxes are points on the chassis where loads are connected, usually control arms or subframes. These areas are reinforced to be able to withstand these loads, and the reinforcements are what contribute to increased weight as performance demands increase.

The S&Y braces can be considered integrated reinforcements, basically distributing the loads over a greater surface area so that less material is required to achieve the same structural rigidity.



This is my crude attempt at visualizing the different concepts as I am still learning as well:

Imagine trying to attach a heavy a/c using to the side of a flat building. You can bolt it straight on the building, but the points where the bolts go in to the concrete could rip out due to the heavy weight. The typical solution would be to reinforce the bolt holes with steel, either plate or anchors. At some point the reinforcements add more weight than they do structural support because the base building wasn't designed to support the weight in that fashion.

The alternate solution would be to cut a notch in the side of the concrete the width of the a/c unit that it can fit inside of. Now the weight of the unit is supported directly by the concrete itself in a compressive force, exactly how concrete was designed. All the bolts need to do now is hold the a/c unit against the building and basically support no weight.

 

[WestRace]

Torque boxes are points on the chassis where loads are connected, usually control arms or subframes. These areas are reinforced to be able to withstand these loads, and the reinforcements are what contribute to increased weight as performance demands increase.

The S&Y braces can be considered integrated reinforcements, basically distributing the loads over a greater surface area so that less material is required to achieve the same structural rigidity.



This is my crude attempt at visualizing the different concepts as I am still learning as well:

Mr. Pill has a point. Looking at the ATS chassis, it does not look like the front cradle as is has enough support for a 6.2L V8, and since not much else could be done to the chassis, the only way to support the V8 is to add more reinforcement to the front frame which will only add more weight to the front, whereas in the S550, the chassis was designed from the ground up to support the V8 so everything is better integrated.
Let's hope all that weight saving does not impact the structural soundness of the S550.
But having read all the reviews of the ATS and CTS, they seem to be very capable, so I think GM guys know what they are doing. Sure the Camaro may gain some weight but GM engineers have done very well tuning the suspension of these cars. The ATS has very good weight distribution so I think the Camaro should be very similar. If they can keep it at around 52/48 or 53/47 then it should be fine. The rest is up to the suspension tuning. I mean given the short coming of the current Camaro chassis, the Z28 has done very well. With the new chassis, I expect the Camaro will even do better. The only real weakness of GM is their engine and transmissions still are not quite there yet, but that can be addressed in eventuality.
I don't think Mustang guys can rest easy.

 

[thePill]

This would be a very accurate definition of the S and Y braces

The S&Y braces can be considered integrated reinforcements, basically distributing the loads over a greater surface area so that less material is required to achieve the same structural rigidity.

Play along with me for a minute... Hold your hand (either one) up. Position it as if you are signaling for someone to "Stop" or "Halt"... Got it? Now, your pinky and thumb represent the rockers on the out most part of the Unibody. Your pointer and ring fingers are the massive sled runners... You middle finger in the driveshaft tunnel. Looking at the back of your hand with thumb and fingers extended up, you can see the L (or backwards L) between your thumb and pointer, another shape between the ring finger and pinky, resemble a V or Y... The skin between your thumb/pointer and ring/pinky is our Y braces. As with the S550, this Y merges and joins the fingers to the hand. The hand being more of a firewall... I hope this isn't getting complicated...

Now, your wrist... That is the S brace, one on each side of the wrist. Traditionally, these beams are large and connect to a torque box.

As you can see, not only is there a vertical hinge point, there are also lateral hinge points... Looking at the Alpha, you will see teensy little sled runners. The runners on a torque box chassis are literally just band aids for that particular platform. They do help, a lot... but, they were almost designed as an afterthought after the platforms main structure was design. The S550 avoids the lateral hinge points altogether... In fact, the S550 uses a strong triangular Y brace to do the job a basic torque box does at a 90 degree angle. The torque box was even forced to add in triangular supports on the outside of the frame rails (pictured above), use a large firewall as a shear plate for additional support AND, they add in multiple sled runners to distribute weight.

Using what seems like a single solid beam, the S550's S brace extends down to the huge sled runners. The hinge points are reduced by 50% (rough math). With a possibility of Hydro-formed, single piece frame rails AND the elimination of very bad lateral hinge points, far less material is used... Balancing the weight of the engine into the main sled runners and rockers also allows this superior Unibody design to lose more weight. I admit, the sled runners and rockers are HUGE on the S550 but that's where you want the weight, in the middle of the car and not at the firewall. Better chance of near 50/50 weight distribution so an even better shot at 25/25/25/25.

The S brace and Y brace together work as a team... The S brace takes a more rearward path where a torque box turns out to the rockers. It displays twice as many hinge points or weak spots. The Y brace does the exact same job a torque box angle does but not, its a triangular support beam.

At the rear of the old diagram above, you will see the rear frame rail section do what we call a "Kick Up". The S197 had a kick up, the S550 does not... That is weight loss so, any weight the solid axle had an advantage is probably washed by the more efficient rear frame rails.

It wouldn't shock me to hear the S550 is far stronger than a traditional torque box Unibody. Comparing it to the S197 or 5th Gen would be silly... Might as well just compare it to the Ford in the diagram...

The S550's front and rear frame sections are almost joined and, they appear to be in line with each other. The diagram above also has its frame sections evened up. It's just the front frame section shoots out to the rockers very early while the S brace dips under the firewall and joins the sled runner. The runner stops just short of where the rear frame section joins the rocker... I am still trying to determine if the rear section still uses a torque box or not. It would have to unless the Lions foot cross member and B pillar cross member some how alleviate that. I'm still working on it...

What I see is a V off shoot from the rear rails that lead to the rockers. It looks a lot like the Y brace in function but, I think it is on the same plane as the rockers. As in, there is only lateral hinge points and no vertical ones.

Edit: What I am thinking is, the B Pillar and Lions Foot Cross Members form a mini midsection frame. This frame not only adds incredible mid-chassis rigidity, it also bears the support that a traditional torque box frame rail needs. Since the rear frame is on the same plane as the rockers, the "V" brace only experiences forces on lateral hinge points. Obviously, a lateral support system is needed and, both those beams along with the B and C pillars (and ILIRS cradle), provide that support. There is also a work hardened shear plate in front of the Monocoque panel (rear seat panel, fuel pump access panel, butt pan). I think it has stamped grooves on the shear plate...

Remember now, all the reinforcement Ford has done to the rear of the S550 would also need to be done if the front was a torque box type platform. Huge cross members, rails, triangular supports, huge firewall... All that is absent here... Efficiency of Design... A lot of components now have two jobs and were design to take out the middle men...


(End)

 

[thePill]

Knowing what we know now, even IF the S550 used a traditional torque box Unibody, JUST ON MASS REDUCTION... The reduction of size alone looks to be 200lbs lighter in platform. Keep in mind, this mass reduction isn't possible on a torque box chassis... There is savings an eye can't see, you can only really judge mass. Less mass usually means less weight...

That doesn't mean Ford won't gain some back elsewhere...

I will say this though, add in some decent materials, use some of those Ford Fusion techniques and Hyrdro-formed panels (can't tell them apart), the platform is easily a few hundred pounds lighter than the S197. 200? 300? maybe 400lbs... It is a very compact platform and believe me, the S197 had the 400lbs to lose.

I have been looking at the bare chassis pics, looking for welds and heat affected zones... I can tell a lot by looking at welds... I don't see any heat affected zones. They would be small, either from nice spot welds, laser welding or, some German glue... Aluminum doesn't display a heat affected zone, nor does it blue or purple when it's cut... Lots of cuts but depends on the cutter... Plasma probably...

 

[thePill]

This is the 5th Gen, you can see they attempt the brace to runner set up but then still use a torque box. The rockers are still supported by a lateral hinge. Also, look at the rear rails, the are kicked up over the rear wheels, this is a huge problem with short-long arm IRS and the bulky cradle needed to support a system. Both the S197 and 5th Gen have vertical and lateral hinge points in the front and rear frame sections. This was an evolution (S197 as well) as the Unibody about 20 years ago, away from the true torque box set up with no runners...The S550 is the Unibody of today.

The Alpha platform inherited these bad characteristic from other GM vehicles... Perhaps the weight lost was merely applying new techniques and lighter materials. Ford chose to rewrite the platform book.

So, whatever we thought we knew about weight loss in automobiles is probably obsolete... At our level, we can know and understand the difference between a 12x12x.120 piece of Aluminum and a 12x12x.120 piece of Steel. This piece weighs this much and that piece weighs this...

We can't look at a newly design angle, know metal thickness, material changes and weight... We just can't...

 

[Grimace427]

I like the front subframe and how straight all the forces look. Out back, that 'brace' looks like a pretzel. I can't really see how that improves anything.

 

[WestRace]

Here is a high resolution shot of the ATS chassis. As Mr. Pill said, there is really no sled runners but seems like the chassis uses the rocker panels on each side as reinforcement. But there are semi-sled runners and a pair of center beams that joint with the side rocker panels and form a main double rails for the engine.

I haven't seen detail of the Mustang chassis but if Mr. Pill is correct, the Mustang uses the rocker panels on the side + the sled runners as the main support for the engine which may have the same weight overall but most of the weight is in the middle and down below. It may still need lateral support upfront for the engine but these should be minor so it will be less weight upfront. This is all we have of the Mustang so far. It seems like a lot of the lateral support is actually the floor pan itself. There might be some lateral support at the firewall but it's hard to tell from this pic. But again if Mr. Pill is correct, seems like the reinforcement is all distributed throughout the chassis which is ideal. I've read that Ford engineers went through hours of chassis optimization on the computer so it all makes sense of what Mr. Pill said and I guess it's no coincidence that they decide to show us this pic. But again, we don't have enough details on the S550 to know for sure.

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