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heat to 1300f cool to 1100 /\1200\/700/\1000\/.../\... etc etc
not impossible for smaller parts depending on who you know, i asked and as it turns out a glassblower friend of mine is willing to let me use his (commercial sized, and i mean sheesh this thing is bigger than 2 vws put together) kiln on the weekends if i wanted, big enough for uprights and such. a royal pita to go thru without a hotrod autocontrol system but heck, orville and wilbur didn't have anywhere near the tools and knowledge available today and look what they accomplished. larger parts such as a complete frame would be a bit harder, the paintbooth doesn't get anywhere near warm enough even at the custom rim shop down the street(yep i asked, they can get to and hold about 600f easily).

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"There are times when a broken tool is better than a sound one, or a twisted personality more useful than a whole one.
For instance, a whole beer bottle isn't half the weapon that half a beer bottle is ..." Randall Garrett

Sorry, this is a bit on topic, so please dont hate me...

This is my main roll hoop and frame bars. I plan to use 1.5 OD and a .095 wall. I chose that size becuase the entire cage has to be made of it per NASA/SCCA Regs. I also plan on engineering in a cross bar that will connect the lower front of my cage and the main frame bars as well as from the bottom of the hoop to the frame bars at the rear of my very small tunnel in an attempt to keep the cockpit from flexing too much.



As you can see im CADing the car but have yet to design enough to be able to do any FEA to stress the idea. Everything else will be 1" round .0625 Side Wall to complete this:

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Jon Gandy
-My Automotive Journalism site. Be nice, I've just started my career, and the site: http://www.up-shift.net
-Jon's "High Gear" Middy project: http://locostusa.com/forums/viewtopic.php?f=18&t=7423

Some of the discussion in this thread do seem to fit in "Building your own frame", but I'll leave that up to the moderators.

Regarding the need to pre-heat or post weld heat treat 4130, Richard Finch's book pretty well states "don't bother", but he does discuss the importance of shop temperature being high enough and not allowing any cold drafts at all in the shop.

Two articles I've found online also seem worthy of reading http://www.netwelding.com/Welding%204130.htm#Heat%20Treat%20Finished%20Part and http://ezinearticles.com/?Welding-4130-Steel-Tubing---Tig-Welding-Chromoly-Up-in-Here&id=2537522

Both express discomfort with using stainless filler rod (which I've heard of, but never used myself)... They both advocate ER70S-2. One also states the importance of weld beads being flat or convex, but not concave... I've seen a lot of "too small", or concave welds, which do seem to be desired by some due to their "good looks"..?

good looks? as in die young and leave a pretty corpse? sheesh........

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"There are times when a broken tool is better than a sound one, or a twisted personality more useful than a whole one.
For instance, a whole beer bottle isn't half the weapon that half a beer bottle is ..." Randall Garrett

OK, well a bit of an update:
As I am waiting for one of the set dates where the mill can do the 38.1x2.5mm round for my cage I decided to try and get it as light as possible

After staring at it for may hours I removed some of the "unnecessary" tubing (like ones that weren't even found on the 442E) and have got it down to 2 options now

1) Total weight : 68.2kg
Every tube but the cage (which is the required 38.1x2.5mm) is 25.8x1.6mm


2) Total weight : 90.3kg
Most tubes are 31.75x1.6mm, the diagonals are 25.8x1.6mm and the cage is 38.1x2.5mm


At this stage I am leaning towards the lighter option but am worried that it may not be strong enough

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The New Zealand Constructors Car Club:

http://www.constructorscarclub.org.nz/

I just came across this thread, here is my two cents.

Designing the chassis should come after the suspension design. If you don't know where your pickup points are for the a-arms and springs/shocks and other bits you're starting off at a disadvantage. The chassis needs to be designed to provide triangulated support at these points in particular. I've seen a few otherwise nice looking chassis that have brackets sticking way out to hold the end of a coil over or control arm. Those things need to be short and feed the loads directly into a junction of 3 different tubes, ideally in 2 different planes.

A space frame gets it's strength from all of the loading being in compression or tension, if you have any loading that is "bending" then you need to re-think things. Yes, I know you can find a lot of locost frames that don't follow this. I'm just saying that not doing this "leaves money on the table".

The right approach in my mind is to mock up the big components (drivetrain, wheels at intended track/wheelbase) and work out the suspension design. Then connect the mounts for all of the suspension points, drivetrain mounts and roll bar with a triangulated structure.

And unless you have a lot of experience as a fabricator/welder and understand the metallurgy involved stay away from "chrome molly". Too many people assume it's just magically better. It's magically more expensive and potentially stronger IF you know what you're doing. If you're reading on an internet forum for advice on crmo I'd have to suggest you re-think things.

personally i'd still like to see a bit more triangulation at the forward lower outer corners of the passenger compartment connecting to the spine........

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"There are times when a broken tool is better than a sound one, or a twisted personality more useful than a whole one.
For instance, a whole beer bottle isn't half the weapon that half a beer bottle is ..." Randall Garrett

Do you mean the floor to be triangulated or the area ahead of the driver/passenger's feet?

Because it would be easy to do this, but in my post I was implying that I wasn't sure if the one that uses 25.8x1.6mm for everything would be sufficiently strong

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The New Zealand Constructors Car Club:

http://www.constructorscarclub.org.nz/

ahead of and under the drivers/passengers feet primarily. i keep thinking back to the thesis referenced so many times that shows the advantage of an xbrace crossing thru the frame.

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"There are times when a broken tool is better than a sound one, or a twisted personality more useful than a whole one.
For instance, a whole beer bottle isn't half the weapon that half a beer bottle is ..." Randall Garrett

when you say "xbrace crossing thru the frame" I am assuming that you meant like this:

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The New Zealand Constructors Car Club:

http://www.constructorscarclub.org.nz/

took me a second to focus in on the changes but yes thats what i mean. to my eyes is provides a secondary stress flow path for front corner impacts but it apparently(wasn't my thesis)also greatly improves the frame rigidity.

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"There are times when a broken tool is better than a sound one, or a twisted personality more useful than a whole one.
For instance, a whole beer bottle isn't half the weapon that half a beer bottle is ..." Randall Garrett

Can you get an engine and transmission in and out of there?