Reinforced IRS sub-frame

[SlowSVT]

I have been reading this since it started and I have to ask why? Is there something i missed that the stock irs cradle is not strong enough? Did you ever get to test the themostat?

If you recall I stated right up front this is not for everyone but there are areas that any Cobra can benefit from. Adding the 2 extra mounting points being one of the more significant ones as it triangulates the sub-frame helping to stiffen the whole back half of the car. Plugging that huge gap on the lower A-arm pivot ear and various other spots the factory didn't weld wouldn't hurt either.

There is quite a bit more to this then just a reinforced sub-frame. This just compliments what it's attached to. Going to this extent on a stock chassis won't be of much benefit other then the items listed above.

I would be difficult to test a thermostat with the IRS in this condition let alone the rest of the car.

 

[zPipes]

Looks like good craftsmanship, I see the logic as well. Im just wondering if its overkill, in theory I get it, but, lets use an analogy to explain.

You can use a grade 8 bolts to hang a tire swing, but when a 5 year old is using said tire swing, grade 2 bolts will work just fine.

So, again, in theory man I get it, and it looks like great work you did. But without any kind of actual testing do we know if its even needed/worth it/beneficial?

 

[03 DSG Snake]

Great looking project with an insane amount of detail. Awesome :beer:

 

[SlowSVT]

Looks like good craftsmanship, I see the logic as well. Im just wondering if its overkill, in theory I get it, but, lets use an analogy to explain.

You can use a grade 8 bolts to hang a tire swing, but when a 5 year old is using said tire swing, grade 2 bolts will work just fine.

So, again, in theory man I get it, and it looks like great work you did. But without any kind of actual testing do we know if its even needed/worth it/beneficial?

"Overkill"

............everything I do is overkill why do you ask? :shrug:

Actually some of the bracing for most cars would be a bit over the top since it would likely be bolted to a wet noodle chassis. All the other mods are relevant to just about Terminator. I don't do anything without careful consideration weighing the benefits against the downsides. In my case the question should be; "why wouldn't you mod the IRS brace".

I just got my diff back from Ed Marlin which I was expecting in December and have turned my attentions to finishing the rear suspension. I'll posts some pics of the progress.

Just my .2 cents worth: I have never regretted "overkilling" ANYTHING! My 5 year old gets nothing but grade 8+ hardware on the swing set. With a Terminator that's good policy :coolman:

 

[zPipes]

Lol, interesting reply. subbed for updates.

 

[THE_EVIL_TW1N]

Looks like good craftsmanship, I see the logic as well. Im just wondering if its overkill, in theory I get it, but, lets use an analogy to explain.

You can use a grade 8 bolts to hang a tire swing, but when a 5 year old is using said tire swing, grade 2 bolts will work just fine.

So, again, in theory man I get it, and it looks like great work you did. But without any kind of actual testing do we know if its even needed/worth it/beneficial?

+1
Some data would be excellent.

 

[SlowSVT]

Update on my progress

Just buttoned-up the diff

The tube is the diff cooler feed which hasn't been welded yet

Here is a photo of the FRP diff cover after sandblasting. I took it to a place where they use high pressure and coarse media to get a rough finish to maximize the surface area for cooling and has the texture of 120 grit sandpaper. I painted it using flat black caliper paint in increase the emissivity of the cover.

Here is the pic showing the faced-off Mark Williams caps, the Torsen T2-R, ARP ring bolts and the studded case which was torqued to 20 ft lbs. Used Kawi bond motorcycle case sealer so I doubt I'm going to have any problems with leaking. I added the 4 fat tabs around the periphery of the cover to provide something to tap it off with a mallet as case sealer is pretty "tenacious" :nonono:

Next thing is to shoehorn this into the IRS cradle and it goes in only one way!

 

[SlowSVT]

+1
Some data would be excellent.

Having an extensive background in environmental testing I'm not sure what kind of test data would be useful in the case of a reinforced sub-frame :shrug: It's just a "component" among many pieces of the puzzle and when you take into account everything that's between both wheels it would be hard to distinguish what impact this has on the rest of the car. My car has been designed and built to take advantage of this and it makes perfect sense for helping to stiffen the rest of the chassis. If you compared this to an unmodified sub-frame I think most people would gain an appreciation for what has been done here. Just looking at it you can tell it will do nothing but compliment the rest of the car :rockon:

 

[SVT_Troy]

Another work of art Russ.

 

[SlowSVT]

I could have updated this thread a couple of months ago but I kept putting it off till now. Here is some of the progress I made.

Managed to finesse the pumpkin into the cradle. With all the bracing and finning I managed to keep things so they can be installed and serviced and was surprised it was fairly easy to install but I'll tell you I took every square inch I could to optimize everything.

The IRS cross brace is waiting for the new chassis mounting brackets to get angle ground to seat flush with the tabs on the IRS frame than I can get them both powder coated. I had to do this twice already due to the weird angle the holes are drilled for the factory live axle upper A-arm attachment points they engage. I kept screwing up the angle. I've devised a way to make it perfect as I don't want to do it a 3rd time :nonono:


The A-arms swing "free & clear". Adding those stainless steel thrust shims to the bushings is going to make these joints work more effectively. It's shimmed for .005" clearance and that's pretty much what I got according to Mr. Feeler Gauge give or take 1 or 2. I don't think you could get better geometry than this coupled with the reinforcement.





Here is where I staked the derin bushings so they will rotate on the crush sleeve and not in the housing. I located them as far from the struts as possible to minimize any loss of the integrity of the A-arm. I ran a 10-24 tap down a blind hole (avoid tapping aluminum with fine threads because they are very prone to damage).

Even the rear IRS support brackets wasn't spared from the welder. I filled the void punched out of the mount and welded in a folded bracket to stiffen the outer spar.

The large curved tab mates with a doubler welded to the wheel well with removes the cantilevering effect of the factory brackets (they haven't been drilled yet).

This IRS is pretty much "married" to my chassis now with the torque box modifications and what it did to the mounting centers on the front. The struts were cut and re-welded to the new position. I guess I won't be selling this thing should I decide to put a solid back there the customer would be pissed :cuss: I won't put the axles in until the IRS is installed in the chassis just to keep the mass down making it less unruly. Other then some odds and ends It's ready to install. I've turned my attentions elsewhere for now but I need to start working on the fuel system and need to get this aspect of the build in the "out" basket.

 

[gabe1530]

amazing job. im happy with just my FTBR setup, i can imagine this would definitely be noticeable.

 

[alexandros]

Good job. I like the unique independent thought used here.

 

[03cobraracer]

You did a great job on this! I thought my FTBR built irs was good! This thing must be stout.

 

[jk_aktion]

I'd like to buy you a beer sir! Awesome work! :beer:

 

[akeohan]

Yes, nice work. I'm interested in your thoughts now that you have some pavement time on it I assume. Anything you would have don’t differently? When do you open up shop for the rest of us?

 

[01Jes]

Amazing work as always, might feel stiffer than a single axle in the rear. Don't come and complain of wheel hop though .
Looks badass!

 

[SlowSVT]

Thanks guys

Golly what timing bumping this thread I'm getting the front diff brace and the auxiliary mounting brackets back from powder coating tonight at Irwindale speedway (anyone going to be there?) which means I can install the IRS . Not only that but the K-member is coming back from the powder coater as well I'm doing the same thing the front suspension as I did with the rear. I will post a new thread on that which should be interesting.

I plan on adding pics of the install


:rockon:

 

[SVT_Troy]

awesome, can't wait to read your updated thread Russ!

 

[pdm]

Adding those upper control arm attachments is genius. I already welded up the subframe, but I'm definitely stealing the UCA idea.

What are you going to use for the links? Adjustable or solid? Heim or bushing?

 

[SlowSVT]

Adding those upper control arm attachments is genius. I already welded up the subframe, but I'm definitely stealing the UCA idea.

What are you going to use for the links? Adjustable or solid? Heim or bushing?

I made brackets instead of heim joints. It's a lot harder to do than heim joints but will allow less movement. This was done mainly to stiffen the back half of the car. The IRS sub-frame can be used as a brace. Attaching it to the upper control arm mounting ears triangulates the mounting points so there will be a lot less movement over than just having 2 mounting points per side.

Just got these parts back from the powder coated yesterday

I take it you seam welded spots the factory missed or did you add braces as well? If you still working on it I can point you to areas where adding brackets will do a lot of good.