Question about fitting subframe connector
#2726212
12/22/19 07:12 PM
12/22/19 07:12 PM
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Joined: Apr 2006
Posts: 4,220 West Plains, MO
DrCharles
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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.shtmlUnfortunately 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?
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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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Posts: 4,220 West Plains, MO
DrCharles
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Looking at it again, is the bump you're referring to there to angle the e brake cable ?? 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. 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...
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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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Joined: Dec 2005
Posts: 11,551 Fulton County, PA
CMcAllister
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Fulton County, PA
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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. 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.
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Re: Question about fitting subframe connector
[Re: CMcAllister]
#2726425
12/23/19 05:49 PM
12/23/19 05:49 PM
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Posts: 4,220 West Plains, MO
DrCharles
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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) 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. I didn't put the heavy bench rear seat back in, either.
Last edited by DrCharles; 12/23/19 05:50 PM.
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Re: Question about fitting subframe connector
[Re: DrCharles]
#2726441
12/23/19 07:18 PM
12/23/19 07:18 PM
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Joined: Dec 2003
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jcc
If you can't dazzle em with diamonds..
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If you can't dazzle em with diamonds..
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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.
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
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Re: Question about fitting subframe connector
[Re: jcc]
#2726446
12/23/19 07:50 PM
12/23/19 07:50 PM
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DrCharles
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I would Not "roll Over" the 2x3 What does this mean? I would not use 1/8"/11g tubing. What would you use?
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Re: Question about fitting subframe connector
[Re: DrCharles]
#2726562
12/24/19 11:34 AM
12/24/19 11:34 AM
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Posts: 22,696 Bitopia
jcc
If you can't dazzle em with diamonds..
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If you can't dazzle em with diamonds..
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Posts: 22,696
Bitopia
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I would Not "roll Over" the 2x3 What does this mean? 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.
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Re: Question about fitting subframe connector
[Re: jcc]
#2726666
12/24/19 05:12 PM
12/24/19 05:12 PM
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Joined: Apr 2006
Posts: 4,220 West Plains, MO
DrCharles
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Did you read the BBD Tech Pages article I linked in my first post? 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 But this is one of the topics (like 8-3/4 vs. Dana) which is guaranteed to start a lively discussion
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