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Subframe connector options and opinions
#1161168
01/20/12 02:44 AM
01/20/12 02:44 AM
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Joined: Feb 2010
Posts: 18,493
Granite Bay CA
Kern Dog
OP
Striving for excellence
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OP
Striving for excellence
Joined: Feb 2010
Posts: 18,493
Granite Bay CA
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Being the frugal guy that I have been for years, the last 2 sets of subframe connectors that I have installed have been homemade using 3x3 .120 stock cut to fit. I welded both sets in, both were A body cars. Now I am ready to do this in the Charger. When I painted the car in 2003, I sprayed the underside to match the topside. This means that when I weld whatever connectors into place, My welds will need to be cleaned up and everything will get painted body color.
I have seen all sorts of different types of connectors in Mopars. The 2x3 bolt in type seem to be the least effective but offer the most ground clearance. In theory, I like the look of the XV contour fit units, but they appear to be only 3 sided. How effective can that be? I'll guess that they intend the edges to be welded to the floorpans? I'd bet that their units are thicker than the guage of the floorpans, so what would you recomend as far as welding two sections of metal of different thicknesses?
I spent $44 for 3x3 plus cutting & grinding discs to make the A body connectors. They are welded on 3 sides at the T-bar crossmember and 3 sides at the rear frame rail. My thinking is that being boxed rather that 3 sided, these should be stronger.
I'm interested in seeing pictures and reading about other members connectors. It may help me decide which way to go. Thanks.
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Re: Subframe connector options and opinions
[Re: Kern Dog]
#1161170
01/20/12 11:29 AM
01/20/12 11:29 AM
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Joined: Dec 2003
Posts: 22,732
Bitopia
jcc
If you can't dazzle em with diamonds..
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If you can't dazzle em with diamonds..
Joined: Dec 2003
Posts: 22,732
Bitopia
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The first question should be IMO, could someone describe and BACK UP at least, with sound reasoning, what actual forces sub frame connectors resist? I am not questioning many many positive reports of thier improvements in ride etc. So are they resisting compression as the rear leafs push forward upon acceleration, are they resisting twist individually, if just under tension we can just use a steel cable, are they preventing a bending moment as front of leaf pushes up upon acceleration with a bending moment provided by the front mass of the car, ie engine, etc, are they just straightening out the force path thru 4 right? angle turns from the front hanger to the doorsills back to the TB crossmember, etc?. If we knew what they are resisting, it would be a lot easier to design a solution. I suspect they are doing all the above, but some more then others, but which one? Say if twist was the main force, a large dia tube would be first choice, if bending moment, a tall I beam, yaw? bending, an I beam on its side, etc. My understanding is it needs to be the smallest and lightest shape/size that gets the job done. Anyone can oversize a solution, only a smart designer knows just how much is needed, if you way oversize, you look.....? Years back member AAR? (patent attorney) had a lengthly thread on Subframe connectors, and main conclusion was the larger the crossection of the subframe, the stiffer, wall thickness provides a lot less stiffness then crossection increase gives. The installation advantages are numerous with the contour cut-out connectors, and installation ease IMO is thier only advantage. Performance wise, compared to a full tube they leave a lot on the table. 
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: Subframe connector options and opinions
[Re: domingo]
#1161173
01/20/12 02:53 PM
01/20/12 02:53 PM
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Joined: Jan 2003
Posts: 9,670
Lima, Peru
domingo
EL Master
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EL Master
Joined: Jan 2003
Posts: 9,670
Lima, Peru
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2" x 2" sqare tube 3mm tick wall. i dont go rectangular because it prtrudes too much into the pass compartment, rectangular is for a race car only IMO. On an e body I will only cut the rear floor pans to the point that the portion that prtrudes into the pass compartment can be hidden with padding on the sides and then carpet on. 
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Re: Subframe connector options and opinions
[Re: domingo]
#1161177
01/20/12 10:07 PM
01/20/12 10:07 PM
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Joined: Nov 2008
Posts: 1,491
Lethbridge, AB, Canada
dangina
pro stock
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pro stock
Joined: Nov 2008
Posts: 1,491
Lethbridge, AB, Canada
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Quote:
I go thru the trans cross memeber and weld to the front frame rails...much better than what anybody else offers you out there.
looks great  is it bad to cut through you tranny crossmember? would it be better to run the subframe brace to the transmission crossmember on one side, and then to the frame rail on the other side?
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Re: Subframe connector options and opinions
[Re: dangina]
#1161178
01/20/12 10:17 PM
01/20/12 10:17 PM
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Joined: Feb 2010
Posts: 18,493
Granite Bay CA
Kern Dog
OP
Striving for excellence
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OP
Striving for excellence
Joined: Feb 2010
Posts: 18,493
Granite Bay CA
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Quote:
Quote:
I go thru the trans cross memeber and weld to the front frame rails...much better than what anybody else offers you out there.
looks great is it bad to cut through you tranny crossmember? would it be better to run the subframe brace to the transmission crossmember on one side, and then to the frame rail on the other side?
I was thinking the same thing. Maybe if the car is a bare shell, cutting through the T bar crossmember may not pose a problem. I like the way it looks though.
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Re: Subframe connector options and opinions
[Re: dangina]
#1161180
01/21/12 12:09 AM
01/21/12 12:09 AM
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Joined: Jan 2003
Posts: 9,670
Lima, Peru
domingo
EL Master
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EL Master
Joined: Jan 2003
Posts: 9,670
Lima, Peru
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Quote:
Quote:
I go thru the trans cross memeber and weld to the front frame rails...much better than what anybody else offers you out there.
looks great is it bad to cut through you tranny crossmember? would it be better to run the subframe brace to the transmission crossmember on one side, and then to the frame rail on the other side?
Its MIG welded all around, how could it possibly be weaker???  You can do it either way really, it doesnt matter. as long as you cut and then weld everything, its as strong or stronger than before because now the crossmember has a bigger area (the connector) to spread the forces the torsion bar inflicts on it. Either way you see it is stronger all the way.
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Re: Subframe connector options and opinions
[Re: domingo]
#1161181
01/21/12 12:22 AM
01/21/12 12:22 AM
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Joined: Jun 2008
Posts: 186
Middleton, ID
curleysracecars
member
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member
Joined: Jun 2008
Posts: 186
Middleton, ID
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No worries welding two different thicknesses of metal...they wont be much different anyways. The 3 sided units are probably comparable to a 4 sided tube, but you will pay for them obviously. I REALLY like the idea of going through the Tbar crossmember and tieing them back into the frame rails. I have been thinking about building some as a production product...maybe I can make an option that goes through the crossmember.
By the way, where in Granite Bay are you? Small town...we cant be too far away. LOL.
Kyle Curley
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Re: Subframe connector options and opinions
[Re: Kern Dog]
#1161183
01/21/12 04:03 AM
01/21/12 04:03 AM
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Joined: Jan 2003
Posts: 1,376
NORTHERN CA
HUSTLESTUFF
pro stock
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pro stock
Joined: Jan 2003
Posts: 1,376
NORTHERN CA
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I like the hotchkis style as it kinda does away with the need for torque boxes. It in reality, transfers the "load" from the rear end to the front of the car. It also ends up at the front frame rail vs off to the side. I just made a set for my 74 Petty Clone. I used 1 1/2 x 1 and welded two together so I have 1 1.2 x 2. Probably $35 in materials. Franky, Come on up to Orland if you want to build a set. Mike
"Were in it to win it. Anything less will end up being..... A whole lot of fun doing!!" UNLAWFL
RIP UN
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Re: Subframe connector options and opinions
[Re: jcc]
#1161186
01/21/12 11:38 AM
01/21/12 11:38 AM
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Anonymous
Unregistered
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Anonymous
Unregistered
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Quote:
The first question should be IMO, could someone describe and BACK UP at least, with sound reasoning, what actual forces sub frame connectors resist? I am not questioning many many positive reports of thier improvements in ride etc. So are they resisting compression as the rear leafs push forward upon acceleration, are they resisting twist individually, if just under tension we can just use a steel cable, are they preventing a bending moment as front of leaf pushes up upon acceleration with a bending moment provided by the front mass of the car, ie engine, etc, are they just straightening out the force path thru 4 right? angle turns from the front hanger to the doorsills back to the TB crossmember, etc?.
If we knew what they are resisting, it would be a lot easier to design a solution. I suspect they are doing all the above, but some more then others, but which one? Say if twist was the main force, a large dia tube would be first choice, if bending moment, a tall I beam, yaw? bending, an I beam on its side, etc. My understanding is it needs to be the smallest and lightest shape/size that gets the job done. Anyone can oversize a solution, only a smart designer knows just how much is needed, if you way oversize, you look.....?
Years back member AAR? (patent attorney) had a lengthly thread on Subframe connectors, and main conclusion was the larger the crossection of the subframe, the stiffer, wall thickness provides a lot less stiffness then crossection increase gives. The installation advantages are numerous with the contour cut-out connectors, and installation ease IMO is thier only advantage. Performance wise, compared to a full tube they leave a lot on the table.
Aren't the factory rockers in effect thick gauge sorta-square tubes connecting the front and rear subframes? If so, what do aftermarket subrame connectors do that they don't? Just add strength to the connection because you now have four subrame connectors instead of two? Perform some other function?
And although it might present clearance issues for driveshaft and/or exhaust, wouldn't an X-shaped subframe connector be much more rigid than two straight tubes?
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