frame

[MoParMetal]

Has anyone built there own complete frame on their mopar?

a full frame including the trans crossmember and the rear crossmember(?)

i was thinking of making one out of 2"x3"x1/8" square tubing.

would it be better if it was 2" wide by 3" high or 3" wide by 2" high?

would 1/8" be sufficient or should i go 3/16"?

wanna see if anyone has done it or has any suggestions.

i want all opinions.

[Mike DC]

 
If you're really not sure about whether the rectangular rails should have their longer dimension in the horzontal or vertical, then I don't think you're ready to tackle this project yet. 


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If you just wanna give a car a frame at all, then a fabricator could basically just take rectangular steel and copy the stock subframe rail & rocker structure of a given car.  (With professional-level welds, etc.)  That will roughly work.  The off-road truck guys and race car guys have been doing variations of that for decades. 

The main reasons that the factories don't just use raw rectangular tubing for the assembly-line frame rails is because of mass-production stuff like robotic welding tricks and tooling costs for the components.  (And also -- frame rails stamped out of flat sheetmetal can be designed to crumple/buckle very smoothly and controllably in wrecks.  VERY BIG DEAL for the auto companies.)


But you've gotta get smart with the engineering if you want your final result to be any improvement over (or even as good as) the original stock frame was.   




You can learn a lot of specifics by looking at other steel-tubing framed race vehicles.  Trucks, cars, open-wheeled karts . . . the basics aren't that different among a lot of them.  Even the sepecific things like suspension/coilover mountings and sway bars are becoming more and more alike across different types of vehicles. 

But it's not enough to copy what others have done; you've really gotta understand a whole lot about WHY  they did certain things.  It takes a lot of understanding about how things bend in various directions, where different suspension setups direct more of the stresses are, etc.  If you can imagine five possible ways to build a certain car's structure somewhere, you should be able to explain why the factory didn't wanna do any of the other four of them.  Sometimes they're just cutting corners on things but a lot of times they have good reasons for doing what they did. 

Crashworthiness is a big deal too.  You can make a car into a tank and it'll be stiff & strong as hell, but it will also be a deathtrap for anyone riding it or getting hit by it.  (Recently, NASCAR has finally gotten their heads around the idea that there is more to making cars safe than just making their frames into tanks.  But it took Dale Sr's death in 2001 to bring about the change.) 

[MoParMetal]

i gotcha. im still going to do it myself, but not for a while.

im just trying to figure out where i can start looking for cars that have done this.

trying to research all that i can. 

i figured someone on here must have done something like it.


thanks for the reply!

[Mike DC]

No prob.  It's a hot subject of mine.

In a lot of cases even if you wanted to built your own frame, you might still be best working with a local race car chassis shop to do it.  They can build the whole thing on a real flat surface plate and put it together with certified welding skills.



The short answer of crashworthiness is that the frame mainly needs to be stronger in the center of the car than at the ends.  The front & rear clips need to be stiff in terms of vertical stresses but they have to steadily collapse inwards when they're hit horizontally in a wreck. 

And that collapse has to be even.  The pre-COT stock car chassis design had a fair amount of total collapse in front, but it didn't cave inwards evenly enough in Dale Sr's wreck.  The front ends of those cars put up very little resistance at all for the first 15-18 inches, and then suddenly the tube chassis starting at the radiator was like a brick wall. 



   

[MoParMetal]

cool!

since i'm almost out of school i've thinking about working for a company called Agent47.

they road race mustangs  , but one of the main guys is the guy that built "big red"

its a 69 camaro that has held the nevada silver state classic for over 12 years.

so i figured that i will learn everything i can from this person and apply it to my car.

here is his website www.bigredcamaro.com

my car won't get that far into, but i just want to make sure the chassis on my car won't be my weakest link.

[RallyeMike]

I've built several stock cars and a custom front frame on my 60 Plymouth. It's a task that takes a lot of fabrication smarts and experience to do it right. Working at race shop will give you some good insight.

On another note, thanks for posting the link to the Big Red site. I didnt know about it, and it's pretty damn cool!   

[MoParMetal]

yea it is. he is the also the same person that started the Silver State Classic.