Interesting stuff, not a stage car but still some cool things to check out, rear suspension set-up in particular.


http://bmsport.no/Verksted/?vis=artikkel&fid=6721&id=0403200909333113361&magasin=ja

Nice stuff. That diff has a lot of offset on the pinion. Door bars are great, I'd like to see more of those and less of the poorly designed X's. Is the car destined for RallyX or tarmac?

It's a RX car, ERC has "Supercar" which is $x$ turbo like the Fiesta's and then they have a "touring car" class, all cars are 2WD most of these are RWD engines are NA.

I don't think those door bars have any advantage over the standard X and if anything I'd think that arrangement would be "softer" in a side impact..meaning bend in a lot more than a standard X.

And by standard X I mean the current vouge two long tubes bent and touching in the middle, then wrapped with a gusset like this pic....then again, neither of us are structural engineers so it's all opinion.



Edited 1 time(s). Last edit at 04/26/2011 10:44AM by Gravel Spray.

OK, Gene I hain't an Injur-near but I have know a few good ones who were "Stress analysis specialists" for some airplane company round here---the one guy had a Cray Soooooper Computer connected to his keyboard----

The Oafish-al word on a welded junction is "The strength of a welded junction is a function of the linear inches of weld in the joint
So this is how you should analyze the 2 methods, think of as two sides of an equation:
Method A............................................Method B
Shallow V and inverted shallow V......................cut and welded X
long "taco gussets"..........................................long Taco gussets

Long Taco gussets on both "cancel out" each other since they're the same

Method A:
How many inches of weld?
Maybe what? 1.5" on sides, and 2 x the radius of 1.75---which is 1.75"

Method B: Well more than 2 times the circumference of 1.75" which is 5.5" x 2 or 11"---more than the circumference because the junction isn't a circle, it's a big long elipse, but it should be evident that its a unit of measurement called "a shit ton" more weld, maybe 14-16" total.

Method A =~~~5" + tacos
Method B =~14-16" + tacos

Method B is "a shit ton" stronger joint.

John,
Just asking here - but by that logic wouldn't it be even stronger to have the X made out of four pieces that were welded together at a single central point?
Isn't there some strength that comes out of the bars remaining intact and not joined?

Well, that's the analysis of the welded junction, so it's only a function of the weld, from what I'm seeing.

It's missing the strength from bars being cut or not, and the strength added by a taco, if any, and the welding of the different taco designs. For instance, if you have a very long taco gusset, or a very short one, as those would add more inches of weld.

The way I see it, if the A method broke, you would have two fully intact tubes bending inwards. If the B method broke, you would have 1 fully intact and 2 short pieces bending inward. The little pieces can be pokey, like a spear. That said, I have the B method in my car. I figure if my door bars are breaking from being hit that much, I'll probably have bigger problems.

I think the best design I've ever seen was possibly on a vermont car, it was a mix of the A method, and the car linked to. It was two continuous bars that instead of one bend, had two. In the center where they joined, there was an 8-10 in section of flat, parallel tubes. That was welded, and that was gusseted. That would be ~16-20" of weld, not counting the side of the tube you have to go around. So, you get the best of both worlds.

Quote
Dazed_Driver
I think the best design I've ever seen was possibly on a vermont car, it was a mix of the A method, and the car linked to. It was two continuous bars that instead of one bend, had two. In the center where they joined, there was an 8-10 in section of flat, parallel tubes. That was welded, and that was gusseted. That would be ~16-20" of weld, not counting the side of the tube you have to go around. So, you get the best of both worlds.

I'm guessing you didn't look at the link then ... isn't this basically what you're saying?


WE also have to consider that cages can be too strong and that bending at a certain loading is almost certainly part of the design consideration.

The problem with many of the current X bars is the friggin things are
A: too high in their location on the main legs and

B: feature one solid tube and two split tubes resulting in pretty much one tube in the middle of the door.


and yup that is just my personal perception. The X like Pete mentions with 2 solid bars is great if installed properly.

No, saw the link. I'm thinking of a shorter middle section. It seems to have more "coverage" IMO

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heymagic
The problem with many of the current X bars is the friggin things are
A: too high in their location on the main legs and

B: feature one solid tube and two split tubes resulting in pretty much one tube in the middle of the door.


and yup that is just my personal perception. The X like Pete mentions with 2 solid bars is great if installed properly.

Gene, you are correct, standard "old school" X, with gussets or without, there is only one tube section at the junction, see pic attached. (EDIT TO NOTE, pic attached is a Homologated T-45 cage, the main tubes, hoop A-piller, brow bar are .065" all other tubes are .050" wall...including the door bars)

We've seen both styles result in injury, Mark Adkins in I think Ojibwe had a standard X no gussets and the long tube broke resulting in a core sample being taken from his thigh.

Dan "the dazzling urbanite" Spongl at STPR, door bars similar to the picture Keith posted above. Nothing broke but they bent in far enough to pin him against the tunnel and I think he was hurt pretty bad.

Bottom line is you can argue cage design neuances till your blue in the face, make fancy cartoons and debate it forever nothing is going to alter physics...3000# car at 50mpg into ilmoble object and somebodies going to have a speach impediment or die. The best cages are the ones that fit the car like a glove and are installed with good craftsmenship/welding quality.



Edited 1 time(s). Last edit at 04/26/2011 02:53PM by Gravel Spray.

And that's why I'm going with a single door bar and a sill bar in my next cage. No X to worry about what's the best design, no gussets or cutting of a-pillar support bar, and easier to get into and out of.

Quote
heymagic
Nice stuff. That diff has a lot of offset on the pinion. Door bars are great, I'd like to see more of those and less of the poorly designed X's. Is the car destined for RallyX or tarmac?

like this?



that's my cage....although, I wish we angled the A-pillar support a little farther forward. we used 1.75" on the door bars too....its beefy.

^^^^

That's the kind of door bars I like a lot.

Yup like Jon's bars. Nice job. The pic Pete posted with the old school X is perfect, one lousy tube thick in the middle, not good. We are in 100% agreement.

Engineers and cages....not to sure about this one. I know what works and what doesn't. I've been racing and building cages for almost 40 years. The common sense engineering degree has some merit.

I had a cage come into tech a few years back. The backstays were bent about 50* or so similar to many old Jeep cages. No fricking reason just someones wet dream. I told the owner to change them. He dug out a piece of paper from a certified edumacated engineer saying the design was ok. I told him to change them anyway....any hit on the A pillar would result in the hole cage going backward and the prebent backstays would last about that long. Engineers...bah.

Quote
heymagic
Yup like Jon's bars. Nice job. The pic Pete posted with the old school X is perfect, one lousy tube thick in the middle, not good. We are in 100% agreement.

Engineers and cages....not to sure about this one. I know what works and what doesn't. I've been racing and building cages for almost 40 years. The common sense engineering degree has some merit.

I had a cage come into tech a few years back. The backstays were bent about 50* or so similar to many old Jeep cages. No fricking reason just someones wet dream. I told the owner to change them. He dug out a piece of paper from a certified edumacated engineer saying the design was ok. I told him to change them anyway....any hit on the A pillar would result in the hole cage going backward and the prebent backstays would last about that long. Engineers...bah.

I don't call them "injur-nears" for nothin.
Only thing I was even slightly referencing is the concept of "linear inches of weld" which, if I had paid attention to the book part of when I did re-training at Arbetsmarknad Utbildning Centrum in Liljeholm, Sweden in 1976 instead of learning to play poker in French and whist in German while we were supposed to be welding I should have learned in my welder training., is a nice concise concept.

The whole thing with tube structures---which I have used and worked on since oh 1968--- is that just a bit of visualisation of the forces involved may not garautee a perfect idea but it sure as hell should expose a dumb idea.
I say to guys---being a dino---photocopy a piccie of the car, draw in the cage then LOOK AT IT and draw arrows representing force---vectors to see where force goes or "is resolved".
It's like first week of "injur-nearing 101" in college (which we know is like 10th grade level for us old dinos.)