School me on square/rectangular steel tube!

[jarheadk5]

A little background:
I've got major repairs needed to the cargo floor/tailpan/tailgate hinge/rear bodymounts area on my '87 K5, and I'm thinking about a bit of a subframe under the LMC replacement sheetmetal for some reinforcement. After reviewing the tailgate hinge writeup in Tech Articles, I was thinking 2x3 tube at the tailpan area (2" side vertical), and 2x3 tube in front where the cargo floor drops down (3" side vertical), connected by 1x2 tube in an "H" with the long legs going front-to-rear to the 2x3's, and the crosspiece at the mid-floor bodymounts. The truck is gonna be more of a utility truck than a 'wheeler - my priorities have drastically changed.

A sketch will be coming shortly, once I clean it up, scan, and upload it.


Sooo, here's my tube questions:
- In general, what are the common wall thicknesses of 1x2 and 2x3 tubing?
- What's the weight-per-foot like on the various sizes? I know there's info and/or links about this in someone's posts, and I used to have a bunch bookmarked (they went bye-bye some time ago with the forum software change ), but you try searching for "tubing", "tube", "rectangular", etc. - you get a million hits, and I just don't have the time & patience to sift through them all.
- Is .250 wall thickness overkill on the 2x3's in the scenario above? Seems like it to me, but that's why I'm asking...
- When I call a supplier for prices, what specifically do I ask for so I don't get the "This guy's clueless so let's double the price" treatment?

 

[dremu]

I think 2x3 is bloody overkill. Unless you're carrying GIANT loads on the bed, 1x2 would be overkill too. I mean, look at what the factory put there! 1x1 is prolly fine.

.250 wall is also HUGE. I used 2x3 .250 wall for my sliders on my '74, but they're intended to support the weight of the truck when it bangs on rocks.

-- A

 

[6.2Blazer]

1x2 tube is typically maybe 1/8" wall, while the 2x3 is commonly around 1/8" to 1/4" wall........I'm sure they make all different wall thickness pieces but the local welding shop usually has the stuff I mentioned.

My sliders are 3x3 3/16" wall and I can jack the whole side of the truck up by them with no noticable deformation. My front bumper is 2x3 3/16 and my rear bumper is 2x4 3/16 and have held up with no issues.

Basically I would think that small 1/8" wall tube would be more than sufficient for a subframe for the rear floor/cargo area.

 

[jarheadk5]

I think 2x3 is bloody overkill. Unless you're carrying GIANT loads on the bed, 1x2 would be overkill too. I mean, look at what the factory put there! 1x1 is prolly fine.

I see what the factory put there - sheetmetal. It rusted a bit, and the bodymounts punched through it. Needless to say... I'm not impressed.

My front seatbelt mounts also rusted out and pulled through the interior sheetmetal on the cab sides, because the backside is exposed to crap the rear wheels throw around. GM hasn't shown me anything to trust in when it comes to structural sheetmetal in these trucks...

 

[6.2Blazer]

I see what the factory put there - sheetmetal. It rusted a bit, and the bodymounts punched through it. Needless to say... I'm not impressed.

My front seatbelt mounts also rusted out and pulled through the interior sheetmetal on the cab sides, because the backside is exposed to crap the rear wheels throw around. GM hasn't shown me anything to trust in when it comes to structural sheetmetal in these trucks...

Not sure exactly what you expect, but I'm sure these components are plenty strong when new..........you can't expect manufacturers to compensate for old worn our rusted out parts. That's like saying that Super Swamper tires really suck in the mud, but then mention the fact that they are completely bald.

 

[hack500]

if you put some 1x2 .120" it will be plenty strong enough.... from personal experience as long as it is .80"(14ga) or thicker you will be fine and it'll be quite a bit lighter than .187 or .250 tubing.

for rolled edge welded steel the weight per foot is: stripwidth X thickness X 3.417 = weight, in pounds, per foot - I haven't worked at a steel plant since last year so memory is a bit fuzzy on the last number. but just for an estimation of weight it will work.

 

[dremu]

I see what the factory put there - sheetmetal. It rusted a bit, and the bodymounts punched through it. Needless to say... I'm not impressed.

My front seatbelt mounts also rusted out and pulled through the interior sheetmetal on the cab sides, because the backside is exposed to crap the rear wheels throw around. GM hasn't shown me anything to trust in when it comes to structural sheetmetal in these trucks...

Yeah, but using 2x3 .250 to replace sheetmetal is like replacing 1/4" plywood with 4x6 pressure treat. Sure, it works, but it's expensive and heavy

Point being, you could do well with some tube ... but smaller sizes would be jes' fine.

-- A

 

[jarheadk5]

Whoa, calm down y'all!

OK, OK... let's regain some sanity here.

First, thanks for the opinions and info. Some clarifications:

-The 2x3 at the rear is more for ease of tailgate hinge mounting than strength. It will also be where the rear-most bodymoount supports the body; the stock sheetmetal flange is about 2" or so from the bedfloor. I somehow forgot to mention that little detail...

-The 2x3 at the front (which is just an idea - I'm not married to it) serves a couple purposes; it replaces most of the sheetmetal at the cab/cargo floor step (my sheetmetal there is mostly rust flakes now), and it will be a crossmember of sorts for the new seatbelt mounts I have to come up with. I have to fix the seatbelts - the truck won't pass PA inspection without stock seatbelts. If you've got a better idea on how to fix this area, post it!

-I thought .250 for the 2x3 was overkill in this application, and said so in my initial post - that's why I asked if anyone else thought it was. Question answered - thank you.




Speaking of my initial post - there's still one question unanswered:

- When I call a supplier for prices, what specifically do I ask for so I don't get the "This guy's clueless so let's double the price" treatment?

Just because I am clueless doesn't mean I want to be treated like it...

 

[dremu]

Speaking of my initial post - there's still one question unanswered:

- When I call a supplier for prices, what specifically do I ask for so I don't get the "This guy's clueless so let's double the price" treatment?

Donno. I call it "square tube, 2x3, two-fifty wall" or "quarter-wall", but maybe I get the clueless pricing too

The stuff I used for my sliders I got scrap, actually, so it was described as 100 pounds, or whatever a 12' length of 2x3x.250 weighs. (Freakin' heavy )

-- A

 

[MarcS]

Dude, look around on this site. I think it might answer some questions regarding sizes/guages/DOM and other stuff. I'm in the same boat as you. Seatbelts are useless, tailpan..etc......

I saw these places on ebay. The one will cut metal to any size and shape you want. I'm thinking whole floor sections or something to repair floors/seatbelt and cargo floor step area.

Ebay links http://stores.ebay.com/Cutsmetal-Diamond-Plate-Store and http://stores.ebay.com/ACS-STEEL-COMPANY.


Hope this helps give you some ideas or options.

 

[diesel4me]

suggestions..

I see no reason to use overkill thickness..adds weight,and isn't needed..but you can get rectangular tubing thats thinner that would work fine..

Being a cheap s.o.b.,I do a lot of my projects with used steel,or steel salvaged from other stuff..our local scrapyard always has many piles of nearly perfect metal there for 10 cents a pound..MUCH cheaper than new,and many times its already painted,and only needs a final coat after you weld up what your building..

I've used square metal tubing they call "Uni-Strut"in place of the oem crossmembers of chevy truck beds..its available in standard channel, or with one side with slotted holes punched in it..one side is open in the center,with its edges rolled in..kinda looks like that barn door track the rollers slide in..its very pricey new if you buy it at Graingers,but Home Depot now stocks it..and I bought lots of it cheep when a factory closed nearby,and new owners gutted the building..

I also used pallet racking for many things..its strong,not too thick or heavy,and welds nice..I've made flat beds,cab mounts,bed crossmembers,and many other things out of it,including utility trailers..also used those galvanized street sign square tubing posts with holes punched on all 4 sides,and the "U" channel ones for the same purpose..(some are designed to "break away"upon impact,they are made from hardened and somewhat brittle steel,so be careful which ones you use for load support!)

I built a frame for 10x24' shed out of them many years ago..got all the posts from the scrapyard ,after a blizzard we had,and LOTS of street signs got knocked over!..bought enough to fill my fleetside bed flush to the top of the bedsides for 50 bucks.. ..its been buried with 3' of snow several times,and its been standing since 1992,with no structural problems..

I even used thinner tubing from old treadmills and excersize machines I found junked at the landfill or out on the side of the road with "free" signs to build tool carts for the shop,etc..its not junk until "I" junk it!..then there is NOTHING left but rust!..

 

[13lazer]

i agree with the previous post. the beauty of steel fabrication is that if you can cut and weld, anything is possible. i would find some solid scrap of any kind (cheapest or most abundant) and make it work. the eiffel tower is all angle iron. you might not need tube everywhere, channels and angles can be plenty strong. 1/8" thick material should be more than enough unless you are gonna tow something hooked to it. the reference book with all of the dimensions of structural shapes lb/ft, thickness'... is the AISC Manual of Steel Construction Ninth Edition. (American Institute of Steel Construction) im sure you can find the info you want if you run a search online.
Iron kicks ass
13lazer