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Still plays with sparks
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Discussion Starter · #1 · (Edited)
mkay...i quick made this up to stop all the rumors about what size box tubing to go with for frame rails.....its kinda self explanitory, ignore the stuff in the middle, just pay attn to the hieght, width, thickness, deflection and weight. The deflection is in inches and the weight is in lbs.

BTW...this is assuming stock dimensions, a 5 foot length, and 1000lbs of force on the beam....
 

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Still plays with sparks
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Discussion Starter · #3 · (Edited)
This chart is only for bending in the vertical direction....But If the beam is square it will bend the same in all directions...If u plan on usin 3" height by 2" width, the beam will bend much more in the horizontal than in the vertical....If thats the plan and u want horizontal bending just look at 2" height by 3" width and that will give u horizontal displacement....

BTW...displacement just means how far in inches the beam will bend.....here is what I mean by 3x2 and 2x3
 

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Still plays with sparks
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Discussion Starter · #4 · (Edited)
Where did you find that chart?
mkay...i quick made this up
damn u quick.......as u guys can see 2x2 even with 1/2 inch wall still has about 2" of bend in it...I wouldnt want that under me....I personaly went with 3"x3"x1/4" wall

if anyone wants it in its excel for just shoot me a pm and I'll email it to ya...
 

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Hell Yeah I Drag!!
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He's not talking about deflection on the frame he is talking about deflection on the new tubing you are going to be using to make the sfbd possible.
 

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Still plays with sparks
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Discussion Starter · #12 ·
Yeah but S-10 frames are C-channeled frames not square. Does this throw off the chart?
2nd gens are boxed in from the radiator support to the back wall of the cab.....not sure about 1st gens......and since under the cab is the only place u would need to use small stuff it works out perfect.....
 

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circa 1996
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500 Posts
Nice chart man, ive been telling people forever that 3x3 1/4 wall is the smallest youd ever want to use for frame rails.They dont seem to understand the concept, or maybe they do but are being blinded cause they think they HAVE to have a stock floor cause its the "cool" thing right now.Stock floor body drops work great on fullsizes cause it requires almost no cutting on the floor and you can get a decent size frame under the truck easily.A mini is WAY smaller , requires a bigger bodydrop usually and you will have to chop the shit out of the floor to be able to get a strong enough frame under it. I see what people are doing with these 2x2 and smaller frame as dangerous or trucks that dont need to be daily driven at all.Trailer queens would be ok i guess but i still wouldnt do it on anything i worked on.The frame is the back bone of the truck, the body isnt meant to hold the truck together and if you try and make it you will start breaking the spot welds on the cab cause the stress from too much frame flex.Oh well i guess actually knowing about structural intergrity is one of the things that separates being a professional from the rest of the ummmm what should i call them? Hacks i guess?Not trying to be a ass but damn it gets old.
 

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Still plays with sparks
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Discussion Starter · #14 ·
Nice chart man
Thanks man....The biggest misconception is that thicker the wall wall the stronger, no matter the size....3x3x1/4 is much stronger than 2x2x1/2. And 3x3 still isnt as strong as factory verticly, but it is stronger horizontaly...so if u use crossmembers correctly u can get a super stiff frame side to side....and close to as srong verticaly.... I see no reason to use 3x2 rather than 3x3 because the stock frame is about 4.5" wide near the firewall and about 2.5-3 inches wide behind the cab.....horizontal space isnt an issue so use 3" wide .....later, Jon
 

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thanks for posting that chart. it helped me out alot to see some actual numbers. im sure everybody else appreciates it too. good work, batman!
 

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Still plays with sparks
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Discussion Starter · #17 ·
compare a 2x4 .188 wall box tube with a 2x8 .125 wall channel frame
yea, no prob....im not on my pc right now tho...i'll have it done for ya on tuesday......and is that 2" tall x 4" wide? or the other way around....
 

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Mad man from michigan
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i would like to know were this info was dug up at. if you look at the deflection #'s 3x2 and 3x3 1/4 wall, you will notice that the #s are not the same,but differ by.255. what this is telling me is that something is not quite right with your formula. your vertical height stated the same, the thickness of the wall stock is the same. it should not matter how wide the piece is do to the fact that we are not measuring a horizontal deflection. last ? why doesn't my Reese hitch bend big time when it put my car trailer on it with a tongue weight of 900lbs. it is only made of 1/4 wall
2 1/2x2 1/2. thanks
ps i have a machinist hand book at work if you have a page # for the formulas.
 

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DFWminis.com
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Your trailer hitch is less than a foot long compared to a 5 foot section that was put into the formula. I also have a Rierson book at my work that I'll lookup & see if they have a similar chart.
 
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