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S550 Chassis School

WestRace

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Not to derail the thread, but this info on the M4's weight grabbed my attention. I had heard that the M3/M4 were supposed to lose quite a bit of weight, approaching the 3300 lb range as mentioned above. However, when I check specs now, they seem to be talking more like 3500-3600 lbs.

Here, on the BMW USA website, the weight is reported as:
M3 = 3540 lbs (Manual), 3595 (automatic - assuming this is the dual clutch)
M4 = 3530 lbs (Manaul), 3585 (automatic)

http://www.bmwusa.com/Standard/Cont...Features_and_Specs/M3SedanSpecifications.aspx

To me, this seems quite a bit higher than was mentioned originally. Is this just a matter of different standards used for measurement, or different features, or safety requirements?

No matter the reason, I suspect Ford will have similar difficulties getting weight much below 3500 lbs (and that's my attempt to bring things back on topic).

-T
I believe here in the US the vehicle weight includes a full tank of gas and a driver, whereas in EU the gas tank and driver are not included. Don't know.
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WestRace

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...The cut away pics reveal that the stampings themselves are thin, its the overall shape that makes the structure strong, remember, efficiency of design.
That's it. Like the shape of an egg. Each member supports the other making a tight structure. But I hope that is true. Can't wait to see the final weight figure.
But we have to be realistic. I'd say a reasonable weight for the GT would be 3550 and about 3450 for the EB.
 

IGJoe2192

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If they keep the GT weight in the 3500k range. I will be very satisfied. My 2004 Mach 1 was around that weight. Fun car to drive and throw around.
 

c3po

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Just imagine another 100+ hp!
 
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thePill

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I can't even give a decent estimate, I have never seen a Unibody like this. The current Fusion is similar and has a full size wheelbase, it is as large as a Taurus.... It's heaviest car was 3637lbs, fully loaded.

That's a very good sign...
 

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qwkcoupe

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Let's not get ahead of ourselves folks. We need direct comparables to the S197 for which those force load documents and cutaway images are not (yet?) provided.

That said the S550 looks way better than the 81 and 93 Fox Body mustangs I played with for 15 years. ...

If the unibody structural rigidity turns out to be what we hope for the S550 to be versus the 2011 and later S197..... Well I might need a midlife crisis fix LOL !!!

I plan to read the earlier posts to see if anything catches my attention worth mentioning since unibody rigidity supports everything the mustang is capable of.
 

qwkcoupe

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Amen to that! "Need some input from anyone to be honest."
 

Thed

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There is an interesting crop of vehicles here in the background...

 

WestRace

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Would someone high-light where the S and Y braces in those pics?
 

qwkcoupe

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Would someone high-light where the S and Y braces in those pics?
They are in the CAD drawings in the begining of this thread.

In the rear they are a concept of visualizing the force load path. Obviously forces have to be dealt with relative to a rear-end collision, or for the transfer of power from the IRS to the uni-body. We probably will not call them s/y braces in the rear.

The rear uni body visually looks better than fox body. but that isn't saying much because S197 was a big improvement over the Fox 3/4 platform .

Eventually direct comparisons will be made between the S197 and S550 specifically about chassis force-load path torsional and longitudinal rigidity.
 

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qwkcoupe

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Do you think that the "Lions Foot" type support under the B pillar functions the same as the actual "Lions Foot" under the C?
If I am translating my fox body memory over to this accurately...... then the b-pillar cross-member attachment is much different than the lions foot at the c-pillar.

The lions foot reaches over toward the center line of the car to better couple/triangulate the inboard side of the upper spring perch so the springs forces and the IRS mount forces can transmit directly to the wheel well and c-pillar without twisting on the floor of the trunk as much.

Imagine a letter L, now triangulate that... "L"ions Foot... I guess where the name came from.. who knows??

...the B, which has a mini-foot w/cross member, that is supported by the tranny tunnel... Which is connected to the Sled runners... ITS ALL TIED TOGETHER!!! Like Chassis Weaving!!!
The Front sled runner does not connect to the b-pillar cross-member. It's span is greatly improved, but leaves about 4" of floorboard sheet metal free to isolate crash impacts from damaging the entire unibody front-to-back. Take a look again at the rear floor board from the inside and underside. There is a body plug hole about 4" away from the seat/B-pillar/cross-member, and the sled runner from the bottom picture is about 2" from the hole.

Wait, are you saying the rear of the S550 also has an S and Y braces? I guess it makes sense due to the missing torque box, it would need a similar setup for the rear.

Edit: Does the ILIRS Cradle connect in some way to the B-Pillar foot's cross member?
That is probably one of the most important questions we'd like the pictures to answer. I certainly do not see hard evidence of rear s/y braces in the rear. But that is A-OKAY because all we really care about is that Ford has done what is needed to transfer those similar power forces from the IRS sub-frame, to the unibody, to the engine and transmission.... and for rear end collisions, not to transfer the crash to the front of the car, engine and transmission. crash versus performance is a tough balancing act.. like the front sled runners don't connect to the b-pillar cross-member... so too we expect both greatness for performance and crash reasons.
 

qwkcoupe

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Friends,

Yep, Ford is going to blow the doors off the competition.

Hands down, this thing is great. Even better will be hard data tests, etc.

I keep looking over all the pictures. I now see the rear frame rail area where the IRS mounts.... Seems pretty "solid" back there between the rockers and the rear rails and the b-pillar cross-member. Above the lions foot at the wheel well spring perch c-pillar looks way better than a Fox and a little iffy as far as beams are concerned, but the entire quarter panel attachment has a big job too for a reason. I don't expect much different from this convertible to what the fastback is.

Oh and if there was any doubt about the room you see, please recall a solid axle retrofits under a Ford Focus, I'm calling it now, S550 will find a solid axle up its rear one day too!!
 

jjw

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I really want to see the coupe unibody. Who else remembers this statement made by mrpeabody?


---Originally Posted by UOP Shadow
Please enlighten us with your knowledge. No hatchback? Do you know the reasons why the C pillar is larger?-----


"Correct. Several reasons. Good reasons."
 
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thePill

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Fellow readers,

Looking over the new S550 type Unibody and doing comparisons with similar vehicles within the market, I really don't feel comfortable forecasting how capable and light the platform is. I want to say it's easily a couple hundred pounds lighter than the S197's platform. Not only is it more compact, it's just a far better design.

I can speculate, and speculate hard given my experience and education in this area. The S550 is a Unibody like I have never seen... First of all, there is no torque box... I can't even speculate on how much weight savings that is, nor can I properly discuss the amount of torsional rigidity it has gained. It still is a basic frame within a body type Unibody BUT, the mass has been removed, streamlined and now has two LARGE sled runners. The largest runners I have ever seen on a Unibody coupe... EVER... The rockers are obviously a solid construction, but now, the rockers work with the runners via a Y brace on the engine side and a Y, V or U shaped brace on the others. Like a canoe...

Mechanical Drawing of the S550's platform

Front/Rear

S
|>====<|o+
|=---------| •
|>====<|o+
S

What my crude mechanical drawing depicts is the Firewall/Y Brace/Rocker&Runner/B Pillar cross member/rear U or V Brace/ Monocoque type hole panel (ID'd by the "o") and the ILIRS cradle (+). The S braces are positioned on the outside of the diagram because they actually move through the firewall (under) and B Pillar brace. The center line on the diagram is the driveshaft tunnel and, in the front, the tranny tunnel.

Here's what I'm missing so far...

The rear S brace and Y/V or U brace. I call the rear Y brace a V or a U because it is a totally different design compared to the front Y brace. Now that is cleared up, I need to know if the rear S/V brace distribute load the same way the front S/Y brace do. If the V brace doesn't link directly to the rocker/runners, it would have to attach to either the B Pillar Cross Member OR, the V Brace is part of the Monocoque Type Hole Panel. I think the V brace distributes loads in both the B Pillar Cross Member AND the unique Monocoque Panel.

The panel I refer to as the Monocoque is the strange and seemingly simple floor panel toward the rear of the cabin floor, it's attached to the B Pillar Cross Member. I also call it that because a hole with a reinforcing lip on the edge is the most common type of weight savings/reinforcing method used when building a Monocoque Chassis. It has two large holes engineered into the panel, probably has a rolled or pressed lip around the edge of it. This is how you work harden a hole. It makes the area stronger than a full panel... Believe it or not, this is also a Cross Member.

For a few reasons... First, the reinforced holes... We got that... Next, the panel seems to be positioned at an angle. They raised one side to make a long, TRIANGULAR support/cross member that literally joins the B and C pillar assembly together. This is where the V brace seems to be anchored to, as well as the rocker in the rear. Now, that panel is positioned to transfer force to the opposite end of the car but, it's natural position seems to make kind of a buffer midway. It's a huge crumple zone for a head on front collision which could work from the rear too. However, that angled panel probably adds an unfathomable amount of torsional rigidity.

As Coupe stated above, the B Pillar Cross Member and the C Pillar's Lions Foot have a different design and function but, they both contribute to the evolution of the Unibody. The large sled runners and beefy rockers are most likely the reason a S550 convertible achieved a huge torsional rigidity improvement without any sub frame connectors. Also, the B Pillar Cross Member, the Monocoque Panel, the ILIRS cradle, the Lions Foot and the Sled Runners, Rockers and Transmission/Driveshaft Tunnel all tie together, not sure about the rear S Brace and the V/U brace yet. The front has the S Braces and Y Braces leading to the Runners and Rockers, anchored to the Firewall. The Mustang specifically has a proper Strut Tower Brace, it is a triangular shaped support that connects the strut towers together as well as the center cowl/firewall mount. I am still looking for Cross members in the engine bay. Seems like an additional support near the firewall and another behind the bumper... Or perhaps it is merged into the bumper supports for some extra weight savings....

As soon as I get these questions answered, I will post up my findings.

I can't stress to you guys how different and improved this Unibody type is compared to a traditional platform.

I have a feeling this Mustang lost some weight, at least the chassis did and that's what's really important. The Camaro was plagued by fat sheet metal, you can't pull most of that weight out. This platform was designed specifically for THE Mustang, that will be a huge advantage in the Mustang/Camaro fight. The 6th Gen will need a specifically engineered chassis or it will be another generation of expensive bandaids... The Alpha chassis is lighter sure but, it needs some major reinforcing for Camaro duty. It is also riddled with hinge points, that requires a lot of firewall/rocker reinforcement, especially with a V8. There are also holes stamped into the platform... A collision nightmare...
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