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Old 11-15-2002, 07:56 AM
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Question Build your own frame? Any basic thoughts?

OK guys, lets try this one. I am a fan of entire frame swaps on the projects that I have done up too this point. I basically take a frame that is close to the configuration I want and make the tin fit.
I now am in a new area. I am wanting a frame similar to '34 Ford idea, but there doesn't need to be a bow in the rail. It will be a full fender vehicle, so I am going with a Chrysler K member from a 76 Dodge Aspen Wagon. The power plant will be small block or even 300-6. This will be more show than go.
QUESTION: Being straight rails, why can't I go with either a heavy "C" channel or box tubing? I was thinking 2X4 .120 wall steel. The basic configuration would not be rectangular, but rather a quadrangle, wider at the rear I suspect (Like my first wife)

Anyone done this or have working knowledge of this? Seems I have seen this in ancient Car mags back when they were good.

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Old 11-15-2002, 08:50 AM
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I wouldn't use the C-channel only because the stuff commonly available (here anyway) is too heavy, even the schedule 40 stuff is over 0.100" thick. I would go with the 2X4 mechanical tubing in a thinner profile than what you suggest, something like 0.075" is plenty strong enough. I don't have my Machinist handbook here (at work) so I don't have actual dimensions or accurate thicknesses to give you. If you can wait till Monday I can search it out for you or maybe someone else on the site has the data for you.
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Old 11-15-2002, 08:57 AM
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I had one of the engineers here tell me his opinion was to go with 1 1/2 X 3" at .120 wall. I will gladly wait until you can check your secret log book, Capt.
This is the reserch part of this project. Like I said, it's not going to be a wheel stander, just a fun ride.
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Old 11-15-2002, 09:11 AM
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That size of tubing is really hard to find here unless you buy a truck load although it would be an elegant option. Still kinda heavy a wall for my taste but them I do like a light chassis, I would triangulate for stiffness not use a heavy wall (just me!). I'll get back to ya if someone else doesn't beat me to it Madd.
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Old 11-17-2002, 08:26 PM
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For a larger, heavy full fender street vehicle I actually would use a thicker box tube, 2 x 3 inch mild steel .125 (1/8 inch) or .188 wall thick. For a street vehicle the increased weight in very negligible. The thicker box tube is very strong and is very easy for welding brackets, suspension, etc. This is very important for a high horsepower, high torque street car. Also the thicker the wall of the box tube, the more corner radius it will have (will be more curved on the corners), this has a more pleasing visual appearance. Good luck on your project.
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Old 11-18-2002, 12:06 AM
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4 jaw wouldn't doing all that trianglulating add up to more weight then just using a good solid metal or somewhere similar... Depending on the tubing and the amount needed to triangulate it could be stronger and lighter but it may not even be worth it....

I dunno just a thought... personally when I do a car from scratch (next on the list, I will probably start when I am 20) I am going to use a fairly heavy metal and make up by putting a fiberglass body on...
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Old 11-18-2002, 03:45 AM
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You gain stiffness by triangulation, heavier material won't get you the same increase in stiffness pound for pound. Have a look at the SCCA handbook online, they have some requirements that are well engineered for any application.

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<a href="http://www.wcma.ca/wracerul.htm" target="_blank">SCCA Race regulations</a>
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Old 11-28-2002, 05:42 PM
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I'm just finishing a similar project ,I made my own frame for my 32 chevy truck and I used 2x4x1/8wall ,I was going to use 3/16 but when I went to buy and looked and felt the weight of it .It was much to heavy so I went with 1/8 which was very close to the same thickness of the old C-channel only boxed ,I then used a m-2 ifs for a 42-52 f100, my frame is 32in. wide on the od straight back and stepped up 4in. for the bed and rearend.hope this helps.
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Old 11-28-2002, 08:41 PM
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Dorsey; Good choice - as 4-jaw says, strength comes from the closed section shape, not particularly from the weight of the material.
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Old 11-28-2002, 09:00 PM
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I just finished the frame for my s-10 a couple months ago so I have worked will this stuff. If you are planning on a full frame with no cage, you definately need to use the .120 box or heavier. I used the .080 and before cage support it was very flimsy. As stated earlier, bracing is key. Use triagular bracing. Simple straight crossmembers will not cut it.

Also, it is very important to make some sort of perfectly level jig to build the frame on. I went to the steel scrap yard and picked up a 13 foot I Beam and some C channel and built a jig for less than $100. I built levelers out of 3/4 bolts and nuts for each leg and leveled the jig before ever starting work. If you dont build a jig, you ar just asking for a crooked frame. The slab in your shop will not cut it if you want it to be perfect.

Chris

[ November 28, 2002: Message edited by: TurboS10 ]</p>
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