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Question about fitting subframe connector #2726212
12/22/19 07:12 PM
12/22/19 07:12 PM
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West Plains, MO
DrCharles Offline OP
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I decided to make my own 2x3 x 1/8" subframe connectors for my '72 Dart Swinger after reading this article: https://www.bigblockdart.com/techpages/connectors.shtml

Unfortunately I am going to have to notch the rear footwells (and then to weld the floor pan to the connectors, remove the seats and carpeting). The car in the pictures cleared the box tubing but there is no way mine is going to. Oh well, such are body tolerances (especially since some of the floor was replaced by a previous owner, ditto the spring relocation).

However, the left torsion bar crossmember has a "bump" in the rear-facing side. Looks like it was made that way, not bent in an accident.
But now the 2x6 plate on the end of the connector won't sit flat against the crossmember.

Should I hammer it flat? Cut it out? Or notch the end of my connector so the crossmember doesn't require massaging? work


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Re: Question about fitting subframe connector [Re: DrCharles] #2726239
12/22/19 08:19 PM
12/22/19 08:19 PM
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TJP Offline
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How does the other side compare?? I'd do some measuring to try and find the root of the problem before banging away with a hammer. twocents beer

Re: Question about fitting subframe connector [Re: DrCharles] #2726241
12/22/19 08:22 PM
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Looking at it again, is the bump you're referring to there to angle the e brake cable ?? shruggy

Re: Question about fitting subframe connector [Re: TJP] #2726243
12/22/19 08:25 PM
12/22/19 08:25 PM
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West Plains, MO
DrCharles Offline OP
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The right hand side doesn't have that curved protrusion in the crossmember, and the connector is the same length on both sides shruggy
So it would fit except for the rear footwell interference.

Re: Question about fitting subframe connector [Re: DrCharles] #2726262
12/22/19 09:35 PM
12/22/19 09:35 PM
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central texas
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looks like it was made that way.
i would make the subfraem connector fit the shape, or make the subfraem connector with a bit of an angle so it goes to the left of that bump, but it seems you've already cut that tubing so that might not be an option now...

Re: Question about fitting subframe connector [Re: TJP] #2726269
12/22/19 09:56 PM
12/22/19 09:56 PM
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West Plains, MO
DrCharles Offline OP
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Originally Posted by TJP
Looking at it again, is the bump you're referring to there to angle the e brake cable ?? shruggy


No... there is some distortion in the picture with the closeup setting on my old camera. The e-brake cable hole actually comes straight through the t-bar crossmember, next to the bump.

I'll probably just notch the end of my connector on that side. It only has to sit flush with the bottom of the crossmember - the required notch isn't that big nearer the bottom anyway.
hammer sawzall

I don't feel like taking more of the car apart just now (3rd member is at Dr. Diff) so the connectors can wait a while...

Re: Question about fitting subframe connector [Re: DrCharles] #2726280
12/22/19 11:33 PM
12/22/19 11:33 PM
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oklahoma
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forphorty Offline
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The bulge under the E brake cable is factory. You could put a slice in it, beat it flat and weld it up. On my duster I used 2x3 . At the rear, rather than cut into the rear floor pan, I cut out a 1/2 tall strip lengthwise making it a 1.5x3 in the rear floor area and welded it back together . I cut it with a curve so it made a nice transition at the rear pan. Cardboard templates are your friend with this kind of stuff.

Re: Question about fitting subframe connector [Re: forphorty] #2726285
12/22/19 11:57 PM
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DrCharles Offline OP
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Thanks. That is another option, but I'm already giving up stiffness by mounting the 2x3 tubing horizontally... making part of it 1.5 would be even weaker (although still better than just the unibody).

Also it's easier to cut the sheet metal of the floor pan than the 1/8 wall tubing. I don't own a plasma cutter and using a cutoff wheel has already gotten old wink

What about just lowering the rear of the connector 1/2" so it touches the floor pan but doesn't have to go up through it? work

Re: Question about fitting subframe connector [Re: DrCharles] #2726292
12/23/19 12:52 AM
12/23/19 12:52 AM
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forphorty Offline
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I here ya on the cutoff wheel being tedious. I used the plasma cutter from work. You can just push the connecter up against the floor pan but it will hang down about a 1/2 lower than the rail. I wasn't too worried about the strength of the 1.5 section as most of the old connecters like the MP ones are only 1.5x2. Plus I welded mine to the floor pan where it touched. Originally, I didn't intend on welding to the floor because I wasn't keen on scraping off a bunch of undercoating in the area. In the end, I got carried away and removed all the undercoating off the bottom of the car. Being told that undercoating typically weighs 50 to 100 lbs was my motivation.

Re: Question about fitting subframe connector [Re: forphorty] #2726339
12/23/19 09:38 AM
12/23/19 09:38 AM
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I'ma firm believer that the rail thru the pan welded fully is the stiffest. I cut the bottom out of the rear rail. Drilled the spot welds holding the remaining rail to the floor pan at the front. Then slid the 2x3 into the rear rail "sides". Clamped the the sides to the tube . Then welded it all back up thru the previously drilled spot weld holes. Plug welded the rail sides as well. .This pulls the frame rail sides in about 1/8" but everything fits nice and tight. Cut the slices in the floor narrow and work your way up to size.
Doug

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Re: Question about fitting subframe connector [Re: dvw] #2726397
12/23/19 02:23 PM
12/23/19 02:23 PM
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Stoney Creek, Ontario, Canada
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I agree with dvw that going thru the floor makes it much stronger.
Mine started out as bolt in connectors. But they hung too low in the back (they sat below the rear frame rail).
So I modified them to fit up thru the floor.
This is on a 1971 B-body.

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Re: Question about fitting subframe connector [Re: 76Beeper] #2726406
12/23/19 03:12 PM
12/23/19 03:12 PM
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Yup, into the rear rails and the floor involves more of the structure.
IIRC, 2 x 2 is a nice fit on an early B into the rear rails but not needing the floor cut.
1/2" or so coming up through the floor isn't noticed under the carpet, though, that's how my Duster is.
An alternative to cutting the floor is a slight bend in the tie tube, but straight is arguably stronger than bent.
As for the crossmember bulge, fit the subframe tube & tie plate to it.

Re: Question about fitting subframe connector [Re: dvw] #2726408
12/23/19 03:25 PM
12/23/19 03:25 PM
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Fulton County, PA
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Originally Posted by dvw
I'ma firm believer that the rail thru the pan welded fully is the stiffest. I cut the bottom out of the rear rail.


True. But I'm not quite that invasive on a typical deal, especially if we're keeping the leaf springs. We use a 2x3 and section it into the rear seat floor area so it is half above the floor and half below at the rear rail area. Open up the front of the rail where it joins the floor, half above, half below the floor so the connector will slide into the front of it. The rail can still be drilled up for plug welds if you like. Section the floor so the connector will rotate up and bump into the rear of the torsion bar x-member and just touches the top flange where the floor is spot welded to it. Everything will be above the pinchweld of the rocker this way. "Outriggers" from the connector to the inside of the rocker can be installed to mount the main hoop and diagonals rather than using plates. Makes for a stiff platform.

This will take some time to layout and cut to get the connector in parallel to the CL of the car and keep the fits tight for welding. But the results are worth the time.

Wish I had taken photos of some of this stuff.


If the results don't match the theory, change the theory.
Re: Question about fitting subframe connector [Re: CMcAllister] #2726425
12/23/19 05:49 PM
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West Plains, MO
DrCharles Offline OP
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Nice work! But since my car is now complete except for the connectors, it'll be hard to put on a rotisserie (not only that, I don't have the floor space... or a rotisserie) whistling Not to mention that my welding skills even on a table in-position are mediocre...

The springs are already relocated into the frame rails, and I plan to purchase the appropriate Caltracs (#4209 I think). So even if I lower the rear of the subframe connectors by 1/2" and don't cut the floor, they won't present a problem with ground clearance relative to the Caltrac front plates. Could still weld the connector to the floor pan at some later time also, or add angle iron brackets welded between the connector and the pan. work I didn't put the heavy bench rear seat back in, either.

Last edited by DrCharles; 12/23/19 05:50 PM.
Re: Question about fitting subframe connector [Re: DrCharles] #2726441
12/23/19 07:18 PM
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Not sure what the design goal here is, or the cars intended use. I would Not "roll Over" the 2x3. I would not use 1/8"/11g tubing. 2x2 would solve a lot of issues I suspect. Nobody here in over a decade can clearly delineate what forces the SFC's are exactly resisting, so the thinking "it can't hurt" likely applies. I would weld the 11G? end plates onto the TB crossmember first, and also add a center hole to weld/hold down the center of the plate, and then weld /fit the SFC to that, and weld in place. You may have a tough time welding the top fully, but anything you get on that surface would help.

Here is one of my cars with 2x2, 3 pics starting at pic #8:

https://board.moparts.org/ubbthread...e-62-polara-500-cruiser.html#Post1554319

Last edited by jcc; 12/23/19 07:26 PM.

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Re: Question about fitting subframe connector [Re: jcc] #2726446
12/23/19 07:50 PM
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DrCharles Offline OP
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Originally Posted by jcc
I would Not "roll Over" the 2x3

What does this mean? shruggy

Quote
I would not use 1/8"/11g tubing.

What would you use?

Re: Question about fitting subframe connector [Re: DrCharles] #2726459
12/23/19 08:29 PM
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I like the outrigger if your running a cage. I plate the inner rocker as well. Much easier to remove a section of floor. Trim and reinstall after
Doug

RC21.jpgRC23.jpgRC22.jpgRC24.jpg
Re: Question about fitting subframe connector [Re: DrCharles] #2726562
12/24/19 11:34 AM
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Originally Posted by DrCharles
Originally Posted by jcc
I would Not "roll Over" the 2x3

What does this mean? shruggy

Quote
I would not use 1/8"/11g tubing.

What would you use?


Your attached pic looks like to me like you have the vertical dim as 2" and the horizontal plane 3". That is not a very common orientation, and I described as "rolled over".

I would use 14g in this application, 16g is too light, and 14g is a common available size, it will also be easier to weld up to floor sheet metal, and 11g is overkill unless there is a specific need, IMO.


Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
Re: Question about fitting subframe connector [Re: jcc] #2726666
12/24/19 05:12 PM
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West Plains, MO
DrCharles Offline OP
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Did you read the BBD Tech Pages article I linked in my first post? shruggy
The rear frame rails are a near perfect fit for the ID of a 2x3" 1/8-wall box tube when it's oriented that way. Which is also readily available at both steel places in my area... don't think they had anything but 1/16 and 1/8 anyway.

Although the connector would be stronger in flexion if oriented vertically, much longer floor cuts/welding would be required also.

Anyway I originally just asked whether to flatten the curved protrusion on the left T-bar crossmember or to notch the plate/connector whistling
But this is one of the topics (like 8-3/4 vs. Dana) which is guaranteed to start a lively discussion popcorn


Re: Question about fitting subframe connector [Re: DrCharles] #2726672
12/24/19 05:45 PM
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Before all this, I would start by 'reconnecting' the floorboards to the crossmember again (since someone replaced the floorboards but 'forgot' to weld them properly).

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