Fastback inner rockers

[aslanefe 333]

37 minutes ago, RPM said:

For the average Mustang owner without a lot of cash, equipment, skills or knowledge,  I think if the rear seat brace, export brace and Monte Carlo bar were installed they would have a much stiffer chassis at little cost in time and money. 

Coupe rear seat area structure on a fastback is not feasible in my opinion, coupe has a lot of structure like the shelf etc which carry load. I think cross brace under the car like TCP X-brace and export brace are best bang for the buck with little cost in time and money.

[RPM 1,190]

I understand the energy absorption thing, but wouldn't you want the cabin to stay intact, and let the front and rear structures absorb the impact? Seems to me the early Mustang was deigned with the cabin as the crumple zone. I've been wrong before. 

[fvike 173]

19 minutes ago, aslanefe said:

If a part is not bending and deforming, it is just tranfering the energy, not absorbing it.

True. But in a crash, we are talking about kinetic energy. It will dissipate by taking other forms like heat or sound. It's not like the impact (force) of the crash bounces around like in a pinball machine until it can bend or break something to bleed off energy. Crash force is one thing, it is what it is. The energy in that force is another. But we are getting off topic here. 

[aslanefe 333]

4 minutes ago, RPM said:

I understand the energy absorption thing, but wouldn't you want the cabin to stay intact, and let the front and rear structures absorb the impact? Seems to me the early Mustang was deigned with the cabin as the crumple zone. I've been wrong before. 

Well, on a head on collusion the energy that will go to the rear structure has to pass through the cabin right? People sitting in the cabin will be subject to that. You want the energy absorbed before it reaches the passenger.

[RPM 1,190]

58 minutes ago, fvike said:

 But we are getting off topic here. 

I think we're right on topic of chassis strength. Good stuff. 

[Ridge Runner 1,112]

I can see the floor support attached to the SFC keeping the front from pushing back ,i just cant see it keeping the front from flexing upward ,just not a strong enough piece . I would be willing to bet with a colision like you had it would bend right in front of the SFC. 

[aslanefe 333]

4 hours ago, fvike said:

True. But in a crash, we are talking about kinetic energy. It will dissipate by taking other forms like heat or sound. It's not like the impact (force) of the crash bounces around like in a pinball machine until it can bend or break something to bleed off energy. Crash force is one thing, it is what it is. The energy in that force is another. But we are getting off topic here. 

Did you see the car latoracing posted on this tread? Looks real stiff.  I think that car may bounce like a pinball in a crash if it hits something very heavy.

[Mach1 Driver 560]

On 1/13/2019 at 3:01 PM, fvike said:

That is impressive. My car did not do that. But it's been known for a long time that drag racers prefers the coupe over the fastback due their stronger construction. I'd like to see this on a stock fastback.

My fastback is all stock, a southern California car with 77k on the odometer and no rust. I tried picking it up from the drivers front torque box. The front passenger tire stayed on the ground but the suspension unwound, same with the rear drivers tire. So three down one up. Just out of curiosity I'll have to see what goes on with the coupes construction (behind the rear seat?) that stiffens it up.

I wonder if I could get three in the air if I put in an export brace and a solid plate behind the rear seat. From the torsion test the export brace gives a 25% improvement, and a rear seat divider is 11%. A Monte Carlo bar does 0%- it just keeps the towers separated. Welded-in SFCs without cross bracing give 0%. 

[aslanefe 333]

3 hours ago, Mach1 Driver said:

My fastback is all stock, a southern California car with 77k on the odometer and no rust. I tried picking it up from the drivers front torque box. The front passenger tire stayed on the ground but the suspension unwound, same with the rear drivers tire. So three down one up. Just out of curiosity I'll have to see what goes on with the coupes construction (behind the rear seat?) that stiffens it up.

I wonder if I could get three in the air if I put in an export brace and a solid plate behind the rear seat. From the torsion test the export brace gives a 25% improvement, and a rear seat divider is 11%. A Monte Carlo bar does 0%- it just keeps the towers separated. Welded-in SFCs without cross bracing give 0%. 

Try jacking of up the rear tire. Use the factory jack point on the rocker or the area just front of the leaf spring attach point and let's what happens. You can see where the lift pad is on my car in one of the pictures I posted.

[fvike 173]

15 hours ago, Mach1 Driver said:

Welded-in SFCs without cross bracing give 0%. 

I disagree. LOL :D

[Mach1 Driver 560]

24 minutes ago, fvike said:

I disagree. LOL :D

Yeah, I know- lots of people do, but its not my opinion, its the result of the test ¯\_(ツ)_/¯

[fvike 173]

As I said, I don't have much faith in that test. I do have faith in Multimatic's 4-post chassis rig.

[RPM 1,190]

Hey Terry, I can't remember if you were considering doing the convertible seat riser or not, and I'm too lazy to read the thread again.

Here's a tip of you are going to add the one piece seat riser. All of the one piece risers are 1" taller than the individual seat risers, which limits the head room for some folks. This is why I spliced in the one piece hump onto my stock st risers. It's kind of a pain as the inner seat rails are fighting for the same space, which makes the inner seat belt bolt a tight fit. 

[Mach1 Driver 560]

10 hours ago, RPM said:

Hey Terry, I can't remember if you were considering doing the convertible seat riser or not, and I'm too lazy to read the thread again.

Here's a tip of you are going to add the one piece seat riser. All of the one piece risers are 1" taller than the individual seat risers, which limits the head room for some folks. This is why I spliced in the one piece hump onto my stock st risers. It's kind of a pain as the inner seat rails are fighting for the same space, which makes the inner seat belt bolt a tight fit. 

I've lost 3" since high school, I'm gonna need a bumper seat pretty soon.

[Mach1 Driver 560]

14 hours ago, fvike said:

As I said, I don't have much faith in that test. I do have faith in Multimatic's 4-post chassis rig.

Its pretty hard for a guy in his garage to compete with a business resource wise.  Is any of that test available to the public, and where could we see it?

[fvike 173]

It's all there in the videos I linked. It shows all the development of the suspension packages. The result of the testing was that they used SFCs, rad support bracing and shock tower-to-firewall to improve torsional stiffness.

If the guys with the resources tell you SFCs works, and the guy "without" resources tell you they don't, who are you going with?

[Ridge Runner 1,112]

I am not saying they dont help some ,if you have all the front end bracing they probably do some ,but if you have none of the front bracing especially those who have done a mustang ll type front end ,there is nothing to support the front rails . Every part of a unibody is part of the structure ,the more removed the weaker it gets 

[Ridge Runner 1,112]

I actually helped set up the first TCI subframe connector at Stangaholics in Terabella Cali  .Jim Smart did an article out of it in i believe MustangMonthly . We discussed  what extra strength it would actually ad . It was a lot of fun ,if you have never done one of these shoots there is quite a bit of work involved . We installed and dissassembled at least 3 times before the final bolt up and welding . We also did another shoot on front frame rail bracing ,especially after removing the spring towers 

[aslanefe 333]

3 hours ago, fvike said:

It's all there in the videos I linked. It shows all the development of the suspension packages. The result of the testing was that they used SFCs, rad support bracing and shock tower-to-firewall to improve torsional stiffness.

If the guys with the resources tell you SFCs works, and the guy "without" resources tell you they don't, who are you going with?

If I understood your post right, you said they tested a Mopar and added boxed front radiator support like Mustang (and some other stuff). I do not know what the structural differences and resemblances between the Mustang and Mopar, but if they added boxed front radiator support lke the Mustang has, there must be differences. So, that test does not tell me anything about a 69 or 70 Mustang. It only tells me which additions stiffened that Mopar they tested. If those mods worked for that Mopar, it does not mean those same mods will work the same for a Mustang because structurally they are not the same. If we follow those tests and add everything they added to the Mopar, we have to add a second boxed radiator support to the Mustang. May be one day some manufacturer with resources will test a Mustang on a test jig and show us how their SFCs that only tie front rails to rears increased (or didn't) the rigidity of the Mustang.

[Mach1 Driver 560]

14 hours ago, fvike said:

It's all there in the videos I linked. It shows all the development of the suspension packages. The result of the testing was that they used SFCs, rad support bracing and shock tower-to-firewall to improve torsional stiffness.

If the guys with the resources tell you SFCs works, and the guy "without" resources tell you they don't, who are you going with?

I thought I missed something, but apparently not. I've got to agree with aslanefe. The tests you point to only refer to a Barracuda, not a Mustang. They added some bars, stitch welding, plates on the inner fender aprons, new lower radiator support and boxed the top support, then SFCs welded to the floor. There was no data of how anything helped and no followup test to show the improvement. This is definitely and apples and oranges comparison and in my opinion is of no value to a classic Mustang owner. Yes I would still go with the guy in the garage doing testing on a Mustang because he showed the changes one at a time and what the change did or didn't do, and SFCs did nothing for the Mustang. For that matter, you don't know if the SFCs did anything to the Barracuda either. They made all the changes at once and then took it out to the track and make no mention of retesting at Multimatic. They guessed at what to change based on a model. Its a very good start, but they didn't quantify the changes to verify what worked. Sorry, but its poor practice and half the job.

[fvike 173]

9 hours ago, aslanefe said:

If I understood your post right, you said they tested a Mopar and added boxed front radiator support like Mustang (and some other stuff). I do not know what the structural differences and resemblances between the Mustang and Mopar, but if they added boxed front radiator support lke the Mustang has, there must be differences. So, that test does not tell me anything about a 69 or 70 Mustang. It only tells me which additions stiffened that Mopar they tested. If those mods worked for that Mopar, it does not mean those same mods will work the same for a Mustang because structurally they are not the same. If we follow those tests and add everything they added to the Mopar, we have to add a second boxed radiator support to the Mustang. May be one day some manufacturer with resources will test a Mustang on a test jig and show us how their SFCs that only tie front rails to rears increased (or didn't) the rigidity of the Mustang.

The main difference between the Barracuda and the Mustang, is that the Barracuda uses torsion bars instead of coil springs. So the tower of the Barracuda is a lot smaller, 'cause they only house the dampers. The transmission tunnel support is quite a lot beefier, because it houses the torsion bar housings too. The Barracuda does not have torque boxes, only the Hemi cars had that. My brother's Barracuda does not have torque boxes. 

The XV Motorsport kit that was sold to the public did not have the boxing of the upper rad support shown in the videos. They did have a Monte Carlo/Export brace that was mounted to the inner fenders and fire wall. All in all, I'd say the Barracuda weaker in stock form. I remember driving My brothers car when it was stock. On S-corners with a lot of camber, the fenders would visibly lift and dip. It was very soft in the front. This was with a 340 small block. The rear is quite strong. The Barracuda actually have a roll-over protection bar just over the rear window.

So my experience with both cars is that the Barracuda was a worse starting point, and that the modifications XV did is applicable to the Mustang. 

Sean Hyland made at least a Mustang prototype with the XV suspension. I think it was a '66 Fastback. But the XV stuff was very expensive, so they didn't sell in the volumes they needed to survive. 

[Mach1 Driver 560]

If you notice the "model" used was a basic wire frame. It could tell them where they needed to stiffen the chassis, but not how to do that. They guessed how best to accomplish that. They probably made some good guesses, but without confirming tests its not possible to know what helped.

[fvike 173]

24 minutes ago, Mach1 Driver said:

I thought I missed something, but apparently not. I've got to agree with aslanefe. The tests you point to only refer to a Barracuda, not a Mustang. They added some bars, stitch welding, plates on the inner fender aprons, new lower radiator support and boxed the top support, then SFCs welded to the floor. There was no data of how anything helped and no followup test to show the improvement. This is definitely and apples and oranges comparison and in my opinion is of no value to a classic Mustang owner. Yes I would still go with the guy in the garage doing testing on a Mustang because he showed the changes one at a time and what the change did or didn't do, and SFCs did nothing for the Mustang. For that matter, you don't know if the SFCs did anything to the Barracuda either. They made all the changes at once and then took it out to the track and make no mention of retesting at Multimatic. They guessed at what to change based on a model. Its a very good start, but they didn't quantify the changes to verify what worked. Sorry, but its poor practice and half the job.

Did you see all the videos? There's a playlist with 13 episodes. Ep 9 shows retesting at Multimatic for damper tuning. The Videos show re testing on the 4-post rig, and the Multimatic people at the track for real world testing. The job was done right. No, they do not give away their test results, just as they don't with the spring rates and the damper valving. That way a competitor would get them for free. I'm sure the hours at Multimatic wasn't free. 

I'm telling you, all you have to do is drive a car before and after getting SFCs installed. If you have, we wouldn't have this discussion. It is a night and day experience. 

The Barracuda and the Mustang have differences, but they both are unibodies with separate front and rear framerails. How supposedly one benefits form SFCs and the other don't, you'd have to explain to me. Well, apart from removing the shock towers.

All the testing done in the "garage test" is meaningless according to post #24 on that tread.

[RogerC 136]

SFCs only provide minimal improvement to torsional stiffness but will not eliminate it. By virtue of adding 2 more longitudinal structural members between rocker rails reduces the span of the floor laterally which reduces flexing slightly. Where those members are attached determines the degree to which improvement is seen. I'm currently going through Ansys FEA training at work and could illustrate this if I had the time to set it up but I have a more pressing company project, the reason for training. Having dabbled in FEA with a few different CAD programs it would be easy to see the difference.

[aslanefe 333]

4 hours ago, RogerC said:

Having dabbled in FEA with a few different CAD programs it would be easy to see the difference.

You do not need a model, FEA etc to show the effect of SFC. Just glue 2 pencils to the edges of an 8.5x11 inches card board like rocker panels. Twist it from opposite corners and observe how much force is required.. Then glue 2 more towards the middle like SFCs, then twist again. Then remove the 2 pencils in the middle and glue them in an x pattern like tying right front rocker to left rear, and left front to right rear; twist again. Here is your rudimentary test without using expensive resources.