Who made these?
They appear to the the US Cartool pieces.
you all did it wrong. ill take mine over any pictured in this thread.
you all did it wrong. ill take mine over any pictured in this thread.
I'll bites, so what is superior about yours as opposed to all others.
last one. notice the support from the rocker to the connector? thats the thickest part of the cente rof the cwr as mentioned earlier in this thread.
I don't even understand the debate, other than a response to the borderline rude nature of the commentary.
Tying in the sub-frames to the floor is going to be substantially stronger, than just touching a frame to the other frame.
Whether the lesser works great, doesn't matter. In the case of rigidity and strength, this more is better.
In the end, though, what are you trying to achieve? Sometimes you want flexing to achieve your goal, sometimes you absolutely do not. Sometimes you want less weight, sometimes it doesn't matter.
Don't get a titty twisted over it.
I don't even understand the debate, other than a response to the borderline rude nature of the commentary.
Tying in the sub-frames to the floor is going to be substantially stronger, than just touching a frame to the other frame.
Whether the lesser works great, doesn't matter. In the case of rigidity and strength, this more is better.
In the end, though, what are you trying to achieve? Sometimes you want flexing to achieve your goal, sometimes you absolutely do not. Sometimes you want less weight, sometimes it doesn't matter.
Don't get a titty twisted over it.
glad you asked...any questions?
you all did it wrong. ill take mine over any pictured in this thread.
Blame Sedanman. All his fault for stirring this up again. ;)
Like I said before, until someone does a full stress/strain analysis on a complete chassis and compares the different types of subframe connectors it's all just guessing. Until that happens, saying someone is "doing it wrong" makes assumptions that can't be scientifically justified. All of the "evidence" that anyone has is pretty much anecdotal. The chassis and body structure are too complex to just "wing it".
Heck, even if someone did do a full on computer model with a stress/strain analysis there would still be points to argue, based on the assumptions that have to be made in order to model welded joints in both the original structure and the subframe connectors. It would be much easier to model the tubular subframe connectors, the contoured and welded to the floor type would be a royal PITA to model for analysis. And they way that they get modeled absolutely has an effect on the end results. Or maybe we should compare two cars with different style connectors using dynamic loads in the real world? Consider the lousy quality control when they left the factory, then consider it's 40+ years later. How much hidden damage is there? Who knows. Maybe one of the cars has a couple extra spot welds because it wasn't Friday afternoon. Test 50 cars and maybe you're getting somewhere, but who's going to do that?
All of the different types of subframe connectors out there are better than nothing. Better than each other? Good luck. The Hotchkis Taxi is a full second faster than a 2012 3 series BMW on TireRack's test track with TireRack's driver. Meaning, in a one day test with a 1970 4-door Satellite he beat his own best time in a 2012 3-series BMW that he makes hundreds of laps in. And since I have a set of Hotchkis subframe connectors that I'm currently installing on my Challenger, I can tell you they aren't even the strongest subframe connectors I've seen. The ones I built for my Duster myself at home are stronger, at least comparing subframe connector to subframe connector. But obviously the Hotchkis pieces work, even if they're not the beefiest, or biggest tubes and even if they don't get welded to the floor.
No need for computer models, a torsional test will separate fact from fiction. This type of fixture with attachment points at the wheels is the proper method:
That is one way to test for torsional rigidity, yes. Proper? Again, this is totally misleading. The test shows a weighted lever arm applied to the front suspension, but the rear suspension is constrained and even the front suspension is locked out using fixed rods instead of the usual springs and shocks. Yes, it gives you a torsional rigidity number, and it is a fairly common way to test torsional rigidity because it's pretty simple (ie, easily repeatable). But how that number relates to how the chassis actually behaves going down the road is a different story.
In about two seconds I found this nice post on a Formula SAE board. If you don't know, formula SAE (society of automotive engineers) is a yearly competition for college engineering students where they design and race what amounts to a 2/3 scale formula-1 style car powered by a 600cc motorcycle powerplant. I was a member of a FSAE team the first couple years I was in college. Anyway, it's a nice, simple explanation of the shortcomings of the test you show.
https://www.reddit.com/r/FSAE/comments/39rpow/best_way_to_test_simulation_and_physical_chassis/
My point here isn't to be contrary. My point is that there are dozens of different methods to test something like how subframe connectors will effect the chassis, all with varying degrees of accuracy and relevance to the real world. And even among engineers, you will run into a spectrum of opinions on which tests are most valid. The test you show is just a single method, and in a lot of cases it's just used to compare the results of a computational model to a simple real world test to check the validity of the computer model that was used. If the model lines up with the results of the test then the computational model can be used to determine more relevant loading scenarios.
And even if you accepted that particular test as the standard benchmark way to conduct your tests (which is reasonable, and that test is used as a benchmark for certain applications), all you could really say at the end of it was that in that particular test one type of connector outperformed the other. It's not an end-all, be-all kind of deal, as the short discussion I linked helps to point out.
So, I can help but notice all of the sub-frame connectors that many people build, and do next to nothing for the rigidity of the car.
I have noticed the common thing to do is to weld some form of tube from the front sub-frame to the rear sub-frame with no attachment to the floor pan itself. This method is next to pointless. Im sure Ill fire up some huge differences in opinion here, but it truly comes down to fact and not ones opinion.
Adding tubing from front to rear will keep your car from stretching.... That's about it... As far I I have ever known, its just not an issue! LOL
So to explain this a little better, there are some basics in building strength into anything, whether it be full tube chassis fabrication or shoring up your twisting little a-body.
By welding in the tube and only attaching it at the ends, you have accomplished exactly the same strength as the rocker panels already produce. They are already there, so why add additional weight?
The correct way to do this is with the laser cut sheet metal sub frame connectors that conform to the floor pans and are meant to be fully welded.
With the new material being welded to the floor pan, you have now tied, the floor to a rail, which in turn is tied to the front and read sub frames.
The correct way to build these to the point they actually provide structured support is shown in the pictures below.
Even the pictures which dont have 100% weld along the connector is better than the "floating" connectors.
Though it transfers much of the torque to the area that is not welded. This creates a high stress area in a pretty concentrated area.
The bottom pictures are the type that do next to nothing for the problematic area in these cars which is the nearly flat plane of the floor pans between the sub frame sections from front to rear.
Im sure this will chap a few hides, but I hate to see this mod over and over and done for nearly no gain.
But you seem to be the only one who thinks it's informative. Just cause it's your way doesn't make it the best way.
I would agree that's most likely a superior method described in that paper, thanks for the link. It also looks like it might be an easier method for the serious amateur to use in the home shop.
But whichever method is used, my point was to show that there's a way to move the discussion past the blind speculation on a forum and into the real world with measurable results. I've always been curious how important the welding of the floor pan was to the effectiveness of the frame connector, maybe sometime this year I'll test it out. I do have an A-body parts car that's sitting around...
Why this was resurrected, just to recycle the questions and answers is beyond... As far as the whole 'do I weld it to the floor pans?' how do you even entertain the idea? ...
Have you ever glued paper towel wings to a cardboard tube and expected it to fly?
/thread