Frame built from sheetmetal instead of $teel tubing??? Pros? Cons?

Hello.

I stumbled across these T bucket plans the other day. They advocate building a frame out of 8 gauge steel instead of square tubing.

From the website:
"Here’s what the Bird T-Bucket plans include:
How to scratch-build your T-Bucket frame using inexpensive 8 gauge sheet steel, rather than rectangular steel tubing."
http://www.tbucketplans.com/the-bird-t-bucket-hot-rod-roadster-plans/

I had planned on using round tubing but this got me thinking. With sheet metal, you could have a little more flexibility and creativity in your frame design.

For instance, you could:
Have a taper in the rails between the firewall and the front.
Make the rails wider/narrower in various areas of high/low stress.
Angle the visible edge of the frame in at an eye-pleasing angle under the body instead of the usual 90 degrees. That would make the body look lower without sacrificing room.

So, the big questions are, how does a frame made out of 8 gauge steel compare to a square tube frame in strength? Crash protection? Weight? Price? Difficulty to make in my garage without special tools? Anyone done it?

 

8 gauge isnt sheet metal, its .164" thick, thicker than most people run for wall thickness on their tubing.

It does make it pretty open for designs. You can water jet, laser, or plasma cut the rails in whatever shape/design you'd like. It will just make for a whole lot of welding and you need a good jig to build the chassis on to keep everything square.

 

Most of that depends on your welding equipment and your welding & fitting abilities. More to that than just laying a nice bead, welding it up with out warping & twisting it.
Next would be your cutting equipment and abilities.
Id have those two worked out or hired out before thinking further.

Then your design and imagination should be in top form to take advantage of all the extra work.

Square tubing can be tapered, bent, or rolled, blended to different sizes, and some plate work can be added for those parts where tube can't be useful.

There are two great tech articles on here where guys made their own 32 style frames. One used plate steel and the other used square tube.

 

If you have access and expertise with a Finite Element Analysis 3D modelling CAD package, and have an ability to assess the likely loads that will be transmitted through the chassis and apply them to an accurate design, then go right ahead and think about it. It's way thicker than Detroit uses for their current unibody designs.
Similarly, are you able to determine how much weld, and where to place it?
Mass really only matters if you're going racing, but for the road, a little bit of conservatism isn't a really bad thing - better than finding you fucked up in your assessment of loads when you're turning hard left in front of an 18 wheeler and something breaks.
....................... but hey, why bother worrying about safety? - go for it!!! Life's cheap - especially when it's someone else's.
Enjoy.

 

Why not just go with 2X4 tubing, Faster, cheaper if you count you labor into the cost and safer.

Nothing like your frame coming apart at 60 MPH. I bet that there would be people out there trying to weld it with a 110 mig or wire feed welder.

 

tubing is alot faster and maybe cheaper but it limits you to sweeps and styling details such as a 32. if your frame wont be seen id go with tube but if its exposed it would be nice to see some styling that you could achieve with thick plate....like the guys above said just make sure you have a good welder or take it to a certified welder to do the safest job for you.

 

I had one of those cars. Had to box in a lot of areas for mounting things.

 

There is a thread here on the HAMB (from a couple years ago) about a 32 frame built from steel sheet as you are referring to. The guy did an excellent job of going through the process step by step (and building the thing, for that matter!), but it was a LOT of very precise fitting and careful welding. If you are up for that, I say go for it. Getting in a hurry with fit-up or welding could have disastrous results...

 

It would allow for designs that would be hard to do with tubing but one would be trading a lot of hours of work for that.

As far as welding and safety, suspect welding is suspect welding no matter if it is welding a crossmember in, welding up a tube frame or welding up a complete frame from strips of metal. I've seen some pretty scary tube frames over the years that were built out of tubing that was too small or had welding that didn't look like it would stand up to the stress that driving the car would put on it.