Monocoque SN95 chassis

[SlowSVT]

I just got my Cobra back from the body shop and thought I would share what I have been up to which is pretty radical to say the least. It was suppose to be a weekend worth of welding to reinforce the shock towers for coilovers but it morphed into a full blown chassis transformation which require 1000's of hours to complete. What was once a “uni-body” is now a full blown “monocock” chassis.

I am going to state this up-front: I am a little reluctant posting details on what I have been up to having put a lot of hard work and ingenuity into this project based on past experience but I think the majority of people will be very interested in what's been done here. I'm in no mood fending off attacks from people who are just throwing hand grenades who can't comprehend what they are looking at or who just have negative personalities. For those people this is not the thread for you as there is a lot more going on here then meets the eye. Nothing wrong with questioning why things were done the way they were and I can assure you every mod to this chassis was carefully considered. If things get “disrespectful” I won't engage in a pissing match which will just poison the thread and will have the admin shut it down and we can all go back to the usual topics. If people are interested and have questions I will go into more detail. There is some pretty cool stuff taking place here and a lot more to this story with a ton more pictures.

I am so happy I'm largely passed the fabrication stage and now transitioning to the assembly process you have no idea what I've been through to get to this point :nonono: I may start a build thread later on but will keep this one focused on the chassis.

Here is the car as delivered from the body shop on Saturday. When finished this car should look like it just rolled off the assembly line :rockon:

 

[71catruck]

I know there is a lot going on there, but I'm sure i wasn't able to pick out every piece that was added/touched. wish you had pictures from before it was painted. Do you have any clue how much weight it added?

That being said i love that you went to that level, I want to build my chassis one day.

 

[gabe1530]

wow.... thats insane. im curious to see how well it makes a difference.

 

[SlowSVT]

Not to worry, have lots of pictures during the build and will post them later, it was ugly! If anyone attempted to do what I've done here I was say "don't do it!". Once I started there was no going back.

At Monks Racing we had it up on this lift when Scott grabbed the corner of the car and started to rock it back and forth on the lift and him and his employees started to laugh. I said "what's so funny?" Their response was: "a car is not suppose to do that".

 

[94slowbra1]

a few questions:
i assume this was done for chassis rigidty? what not through floor sub frames and a roll bar?
any idea on weight added?
anything done underneath?
i know it hasnt been driven yet but can you tell a difference?

i applaud the time and effort, hope it accomplished what you set out to do

 

[SlowSVT]

a few questions:
i assume this was done for chassis rigidty? what not through floor sub frames and a roll bar?
any idea on weight added?
anything done underneath?
i know it hasnt been driven yet but can you tell a difference?

i applaud the time and effort, hope it accomplished what you set out to do

Thanks man

Yes, chassis rigidity was the #1 reason, #2 was reducing chassis fatigue preserving it's integrity over the long haul, #3 is improving the steering response and #4 was improving the crash worthiness. I did not want a roll bar with all that hard metal tubing in the interior of the chassis and short of a full blow roll cage this was the best option for me as the car will still seat 4 comfortably. Yes there are Hans sub-frame connecters underneath which are actually “integrated into the chassis. All told I estimate between 300 and 400 lbs were added to the car including the Han's which is something I hate but the car has lost a few hundred pounds in the process. The added bonus is the vast majority of the weight is slung “low” and toward the rear which moves the CG to a better place.

Ed Schaider said to me “Russ I hope you realize once you drive this car for the first time nothing will be the same”. I guess that's both good and bad.

 

[98 Saleen Cobra]

Holy shit that is a dream!! Look so great and that's going to stiffen up everything tremendously. That's well beyond the typical seam welding ahahaha. Love it

 

[SlowSVT]

here are the patterns used to make the reinforcement ......... all 698 of them!

All of this is chromolly steel most of it is .050 thk, some as thin as .040and a few pieces at .090 thk. We used about 50 lbs of #30 wire with about a 1/4 of that ending-up on the floor and a good percentage of what was left over being ground away.

Note the window fillets. There was 4 spot weld holding the inner A-pillar to the chassis (actually 3 on the RH side the robot missed). There is a 1/8" chromolly plate running up the inside of the pillar. The welding tightened the car and shrunk it by an 1/8". The good thing is the Mustang body is very tolerant to body slop. Everything was test fitted to make sure it all goes back together.

 

[SlowSVT]

Holy shit that is a dream!! Look so great and that's going to stiffen up everything tremendously. That's well beyond the typical seam welding ahahaha. Love it

I new this was something a road racer would appreciate LOL

If I just seam welded the chassis without adding the bracing the welds would be cracking left and right and would have made a mess of the chassis structure. Believe it or not this was addicting!. Just when you thought you completed a section you kick back with a Budweiser and look at what's been done, suddenly you see new opportunities and out comes the cardboard, scissors and masking tape. There are literally 100's of triangulated boxes all over the place. I had fun with it but I'm glad it's over.

Now comes the "fun" part. I already have the engine wiring harness installed, brake MC, wipers and misc hardware.

Don't think for a minute I never thought to myself "what the F#&K are you doing?". Now that it's over I'm glad I did. There will be assembly issues going forward but I'll work through those as they arise.


2 weeks of nothing but grinding welds :cuss:

 

[01yellercobra]

Monocoque. Just saying.

Cool work though. I'm curious how the car is going to feel now.

 

[RichM1983]

This is a pretty neat project. I hope you put more updates in or do a build thread. Keep up the good work.

 

[SlowSVT]

Monocoque. Just saying.

Cool work though. I'm curious how the car is going to feel now.

True statement

My French is bad plus it's easier for me to pronounce "monocock". Thanks for put'N me wise :read: I'll see if the mod can fix that.


I have a pretty good idea how this car will feel on the road. There is NO rubber in this car, very little body twist and with a solid steering shaft/bushings and a manual rack you will get 100% feedback from the steering wheel. If it's too harsh I can always reinstall the rag joint shaft. In a real hard corner it may lift the inside front wheel like the 911 use to. Jack Roush commented the old fox chassis was the only thing keeping the front when on the ground. I won't be doing that on the street but when I'm done I'm bringing it to Willow Springs and see how hard I can push this thing around a corner. I have the stock Bilstien's on there now but I don't think the rate will be right with this chassis and I may opt for adjustable shocks and struts.

My main motivation is I can't stand a flimsy chassis! :fm: Nothing makes a car feel cheap when it rattles like a gypsy bandwagon every time it hits a bump.

Here is the front shock tower reinforcement

With coilovers all the weight of the car (including the engine and 1/2 of the tranny which was on the K-member) is riding on the shock towers. Being a mechanical engineer this horrified me. This topic came up in Corner Carvers whether the shock towers can carry the load when someone whipped out their slide rule and determined they were "adequate" with one guy stating his wife jumped a curb with coilovers and it punched a hole right in his shock towers. I added a doubler on top and gusseted them as well.

This is the stanchion added to the front fender well which moves the load to the frame rails. Note the holes left by the factory so the spot welder could gain access inside. This metal was only .032" thk. Scott got in there and welded-up what he could before we plugged it with .040 chromolly. There is another void on the inside we managed to plug as well.

Rear shock towers

Here I added gussets in the vertical to spread the load over to the frame rails.

Note the webs added to the rear fender well to clear the factory springs and even connected the void across the shock mounting well. This evectivly is like adding a 2nd frame rail to each side at the rear. The spherical wheel well got gussets as you can see from the radial weld marks which is now structural. No stone was unturned anywhere.

 

[SlowSVT]

This is a pretty neat project. I hope you put more updates in or do a build thread. Keep up the good work.

No better Mustang then a Terminator IMO to get this kind of attention. The wheelbase in our cars is 1" shy of double digits which is incredible for a 4 seat V8 car (a 2 door Honda Civic is longer in the tooth). That's what makes them so fun to drive :rockon: Don't get me wrong this car is "dated" the new ones are a better platform. But ask yourself which one would you rather work on and own long term? The new cars are not made to be screwed with and in 20 years a computer failure in an S550 would scare the hell out of me plus they have a black box After 04 things started to get a lot more complicated. If you enjoy working and modding your car stick with old Fox platform. Mustangs are starting to rival BMW's in complexity, nice when new, not so much when old :nonono:

I will start a build thread separate from this one


Inner frame rail reinforcement (note the filleted corner into the floor pan)

 

[50 Deep]

Sick work brother. Way more than I could ever imagine to do. I have the same rear wilwoood setup. What are you thinking of doing for the e brake

 

[SlowSVT]

Sick work brother. Way more than I could ever imagine to do. I have the same rear wilwoood setup. What are you thinking of doing for the e brake

You have no idea! LOL

I got a set of NOS 93 Cobra aluminum calipers (don't ask me how I found them they are made from "unobtainium"). That get's detailed in the build thread.

 

[P49Y-CY]

wow amazing! congrats on all your hard work and progress :beer:

 

[raym5_0]

sweet workmanship! let me know when you want to trade MS terminators :-D

 

[P49Y-CY]

russ several years ago i remember some suspension companies (griggs was one iirc) offered "through-the-floor" subframe connectors. from what i understood, they were supposed to be one of the best available options for tying the car together, but not a lot of people did them because they required so much work. was that something that you considered with this project?

 

[SVT_Troy]

Russ that looks out of this world. Easy to see where all the hours went. I think most including myself fail to truly comprehend the detail and level of modification you have put into this. I think one would either have to have lots of seatime (RaceBronco comes to mind) in a Cobra or drive a stock car followed by yours to get a true appreciation of the the work you put into it. I can't wait to see your thoughts after getting everything together and put to good use on a track where it looks to belong.

 

[ViperRed91GT]

Wouldn't this classify as semi-moncoque?