DIY Stock Looking Subframe Connectors

[Domino]

With US car&tool over $200 with shipping, I decided to make my own Mopar looking subframe connectors.
Having a local shop bend 2 "U" shaped frame sections for $48.  
Plan is to apply "skyline" templates to the sides (see picture), internal box braces, stock sized holes along the bottom, and cut outs for lines and cables.

Will post updates along the way...

Transferring floor pan to cardboard template using modified square and a long straight edge:

[Hemidog]

Hey, that's clever ! 

[matrout76]

that is EXACTLY what i plan to do, right up to the modified combination square!!!

Because of the depth and the width of the channel, the piece will have to be "W" bent and then flattened unless the shop has some gooseneck press-brake dies that will work. 

My only concern is that i will make these pieces that will fit perfectly to the floor, weld them on, and then they will be holding the car in an arch.  My car is currently on the rotisserie, so i was going to put it on its side to minimize flexing...any thoughts here?

I'm also planning on making my own torque boxes and hope to start that project this week.

Matt

[Domino]

Because of the depth and the width of the channel, the piece will have to be "W" bent and then flattened unless the shop has some gooseneck press-brake dies that will work. 

My only concern is that i will make these pieces that will fit perfectly to the floor, weld them on, and then they will be holding the car in an arch.  My car is currently on the rotisserie, so i was going to put it on its side to minimize flexing...any thoughts here?

Right, I had them bend one side the full 90 and partially bend the other.  More to come on finishing that bend.

As far as prestress arc... IMO, you want to arc the car up, like an empty flatbed trailer.  So put the car upside down and LEVEL to tack them working in stages together.
Upside down will make the undercarriage short and the roof long.  Locking in the connectors while the undercarriage is short will give them tensile preload to resist sagging once you flip the car right side up.

[pipeliner]

Wont that make your door gaps tight at the bottom?

[Domino]

Wont that make your door gaps tight at the bottom?

I doubt it with a bare unibody, it's pretty damn stiff static with no extra weight. 

[Cooter]

That's what i'm talkin' bout Domino...you just saved me $200.00 plus shipping..And I was wondering how long it was gonna take me to trial and error the side panels to get it right....That's a good idea.

[dangina]

  great idea!!

[Domino]

Here's a few pics with the progress on these subframe connectors.  They fit much better than I expected after transferring from cardboard templates.

I found it was easiest to play connect the dots with the square.  Just transferring key points and then finishing up the profile by hand with a ruler.
I installed internal braces, and factory sized holes along the bottom, as well as factory-like weld flaps to join to the Xmember.
Also, pass throughs for the brake line and E-Brake Cable.

[y3chargerrt]

Nice work!

[tan top]

 clever stuff 

[NorwayCharger]

Nice, maybe you can sell cardboard templates

[HPP]

As far as prestress arc... IMO, you want to arc the car up, like an empty flatbed trailer.  So put the car upside down and LEVEL to tack them working in stages together.
Upside down will make the undercarriage short and the roof long.  Locking in the connectors while the undercarriage is short will give them tensile preload to resist sagging once you flip the car right side up.

Curious why you would want to do it this way. The largest, heaviest components in the car are the engine/front suspension and rear axle/suspension. Since these are already at the ends of the car, arching the middle up does nothing to support them. When you solidify the subframe structure via frame supports, sagging no longer is an issue.

If your car is all apart, you want to make sure it is all square, plumb, and level with no pre-load on it anywhere. This is why race cars are built on a surface plate instead of in the air. Adding preload creates wedge which can alter suspension performace from one side to the other.

If you car is together, support it on the suspension points while in the air to maintain panel alignment. Will this lock in some mis-aligned uni-body issues, potentially yes. But if your car is already together, driving, aligned, and set up with them, it won't make a big difference in performance and you likely will never notice.

[Domino]

Well, I'm philosophically opposed to overhead welding on a rotiss'd car 
So, skipping additional technical analysis, I'll just stick by my original opinion  

[AirborneSilva]

This is a great idea, thank you for sharing it 

[matrout76]

What thickness (gauge) material did you end up using?

it also looks like you are planning on making some torque boxes...what are your thoughts for those?

Looks great!

[Domino]

What thickness (gauge) material did you end up using?

it also looks like you are planning on making some torque boxes...what are your thoughts for those?

Looks great!

On the subframes, I'm using cold rolled 16 ga. ~0.060" which is thinner than the UStool ones, this is why I added the box beam braces like chrysler did.

For the torque boxes: IMO 1/8" is too thick, looking at ~0.090"-0.095" CR.

[RallyeMike]

By the time you factor in cutting tools, gas, and everything else though, I'm not sure it's worth the savings, but it sure is fun to do it yourself! Nice job.

[AirborneSilva]

By the time you factor in cutting tools, gas, and everything else though, I'm not sure it's worth the savings, but it sure is fun to do it yourself! Nice job.

Who makes subframe connectors that follow the floor pan contour, for the third gen?

[matrout76]

For the torque boxes: IMO 1/8" is too thick, looking at ~0.090"-0.095" CR.

14 gauge is 0.075" and 12 gauge is 0.105" and both are commonly available...i'd go 12 gauge.

[dkn1997]

By the time you factor in cutting tools, gas, and everything else though, I'm not sure it's worth the savings, but it sure is fun to do it yourself! Nice job.

I'm not sure about that.  I had US cartool subs put in my charger and while they fit well, you still have to a lot of trial fitting, cut here, grind there.... If I had the skills, I'd like the "fun" factor of doing it myself

[HPP]

By the time you factor in cutting tools, gas, and everything else though, I'm not sure it's worth the savings, but it sure is fun to do it yourself! Nice job.

Who makes subframe connectors that follow the floor pan contour, for the third gen?

No one.

By the time you factor in cutting tools, gas, and everything else though, I'm not sure it's worth the savings, but it sure is fun to do it yourself! Nice job.

If you are a regular fabriacator, you likely have all of these around already. Then its just time to satisfaction vs availability ratio to consider.

[Domino]

For the torque boxes: IMO 1/8" is too thick, looking at ~0.090"-0.095" CR.

14 gauge is 0.075" and 12 gauge is 0.105" and both are commonly available...i'd go 12 gauge.

The latest 12 ga I measured was ~0.093", but that's also been cold rolled. 
It seems sheet steel is rated at gauge as mild steel and then rolled a bit thinner.

[Domino]

Some tips/observations regarding the subframes:
It's kinda tricky to set the templates correctly on both opposite sides of the "U", I found the notch for the pan "lip" a handy reference point.
Don't cut the cardboard along the straight line cause the template gets flimsy, just cut out a few square holes to align it to the bottom of the "U".
Ace hardware metal jigsaw blades are much much better than the red "do it best" brand blades.  Night and day.

I ended up finding some 12 gauge that measured in at 0.105" (for the torque boxes).

[Domino]

Pic of the rear box and subframe welded in.  Working on the front boxes next...

[AirborneSilva]

Looking good! 

[tan top]

Pic of the rear box and subframe welded in.  Working on the front boxes next...

   

[Domino]

Front boxes complete (minus a drain hole in each)  
Plus some additional work blending the rear boxes into the existing structure.

[tan top]

nice    sure makes it easier than sitting cross legged  under the charger shell on 4 foot jack stands !! with mig splatters going down your neck & in your ear  !!    don't ask how i know

[TexasStroker]

Very nice work!  Too bad I've got my MP ones bought back in 99 just waiting to be installed, lol.

[RIDGERACER383]

Nice work..Thats the way I plan on doing mine later on down the road.

[Steve P.]

Very nice job... 

[matrout76]

Domino,

Can you please post some more detailed photos of your front torque boxes?

I'm designing my subframe connectors this weekend so i can have a local laser-cutting shop cut and bend them.  I'm also going to have them cut out and bend the front and rear torque boxes and want to see how you did the fronts.

How wide did your subframe connector end up being?  Since the rear frame section is tapered, i can't decide how wide to make them.  At first, i was planning in 2" wide, but now i'm thinking that will look too narrow...

Also, what is your plan for installing you fuel and brake lines that wiil run thru the big slot in the front of the subframe connectors?  i'm trying to figue out how to get tem in there without destroying the line and haven't come up with anything yet.  i don't want to have to cut slots in the connectors and then weld the pieces back in to get the lines installed after everything has been painted and undercoated.

Thanks!
Matt

[Domino]

The front TBs are made from two trapezoid pieces. The larger piece needs a diagonal bend to fit correctly. It has two cut outs for the fender hardware. I notched mine at the front inner corner to fit around the stock torque box and mate flush with the frame rail.
The small piece ties the floor pan to the large piece and the inner rocker to the frame rail. The DVR side needs a hole for the E-brake cable. This piece does not follow the floor pan contour all the way to the inner rocker.
I made these from cardstock templates. Cut with jigsaw, holesaw for the notches...Bent on edge of bench with clamps and big hammer with block of wood.



I don't recall the measurement, but use the bottom width of the frame rail and tap the "U" over it, spreading the flaps...haha. I'll drink to that!

There's a long slot where it mates to the x-member. ( like US tool)that allows the lines to feed through if you put a gradual bend in the line. So I'm told and hope is true.

[nvrbdn]

nice work. thanks for detailing