2x4 steel tube question

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2x4 steel tube question

Postby Thelgord » Tue Sep 13, 2016 9:15 am

I have around 80 linier feet of 2x4x1/8 steel tube to use for my trailer frame. This stuff is heavy. After moving twice in less than a year I am getting ready to start my build. I have a utility trailer that I got off of Craig's List that was build by a farmer (this thing is built like a tank) that is essentially three complete frames, one inside and one on top of a third frame, I will be completely disassembling this trailer to start from scratch. I am not terrible at welding so that really isn't an issue.

Not wanting to over build my frame, would it be a good idea to cut this into angle or c-channel for the frame? I could make 2x4, 2x2 angle, or 2x2, 2x1, 4x1 channel out of it in order to save weight, but in doing that will I weaken it too much?

Thanks for any responses.
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Re: 2x4 steel tube question

Postby MtnDon » Tue Sep 13, 2016 9:36 am

Yeah, that 2 x 4 x 0.125 stuff is heavy!! If that 2 x 4 x 0.125 steel tubing is considerably stronger / heavier than is needed it might be best to buy new thinner wall tubing.

A C-section in the same wall thickness will lose more % of strength strength with one side wall removed than % of weight removed. That is if we are looking at how much vertical force it takes to cause a specific amount of deflection in the vertical direction. And angle stock is weakest of all. The vertical walls of the rectangle tube provide more strength than the horizontal wall when looking at resisting a vertical load as encountered with suspension and loads on the frame. Hope that makes sense.

The online steel tube deflection calculator I used to use has gone bye-bye and I have not found a replacement.
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Re: 2x4 steel tube question

Postby Thelgord » Tue Sep 13, 2016 10:00 am

Thanks for the reply. I can still use the full tube. Like I said, I have three full frames of this stuff all stuck together. Fortunately it's all spot welded together to I just have to cut the weld points to separate out all of the individual pieces, then put it back together at the dimensions I need. Thanks again!
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Re: 2x4 steel tube question

Postby KCStudly » Wed Sep 14, 2016 6:45 am

Do not attempt to cut L's from rectangular tube.

First, it will not likely stay straight as there are internal stresses from how it was manufactured.

Second, it just is not worth the amount of effort that it would take. You will burn up more money in cut-off wheels and grinder discs than the cost of new angle steel.

Channel is more economical to purchase, lb for lb over tube, but tube can be made lighter and can be easier to configure joints; whereas depending on how the channel is arranged you can run into a lot of work coping flanges to fit inside webs. Channel (and L) does have the advantage that you can reach all sides to paint, whereas tube insides rarely ever get protection (but then if they are totally sealed there is only a finite amount of O^2 and moisture to form rust.

You did not say how big your trailer will be, or did I miss it?

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Re: 2x4 steel tube question

Postby Thelgord » Wed Sep 14, 2016 10:41 am

Thanks for the info! I think I will just stay with the full tube, since I have a lot of it to spare should I make a mistake.

The trailer itself need to be five feet wide and at least 80 inches long. My better half says it has to have a queen size mattress LOL! I am still looking at designs to consider, but I will start disassembly of the donor trailer in the next couple of weeks, trying very hard to salvage as much good steel as I can. The trailer will also need to be at least off-road capable, sort of. No rock crawling or the like, but able to go down some trails.

I have been looking at a trailer caller the "T-Van" from Australia. The sleep area is mounted over the wheel wells to get a queen sized bed, and the kitchen slides out from the side with entry from the rear of the trailer. I like the idea and they have a party unique frame I think. It's a 4'X4' box with an 8' V shipped tongue. 7 feet of the trailer is actually on the frame and tongue, with another 12 angled for departure over obstacles. This leaves 5' of open space for the tongue itself. Looks very simple to build, but I am sure it isn't as simple as it seems. Most things rarely are.

So for now, I am just stripping down an old trailer. The donor trailer also has a 4" drop axle that I am fairly certain I won't be able to use if I take it off-road, but I think I can see that for around $100 to recoup some money for the build and get a strait axle.
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Re: 2x4 steel tube question

Postby KCStudly » Thu Sep 15, 2016 6:51 am

For a rock crawler trailer, or longer length I can see where the undercut rear could be useful in gaining departure angle, or if you just like that look, but may not be needed for most two track trails or forest service roads (again, depending on axle placement, size of obstacles, and desired departure angle). Might not be worth the lost space or complication building the lower part of the rear entry door (more importantly, the complication to the door seal).

On bed size, don't forget that you can't accidentally roll out of bed because the side walls will be there to catch you; so you can get away with less than a queen size and still be comfortable sleeping near the edge of the mattress; cozy like a bunk in a boat. Plan on 5 wide for the overall outside width (whatever sheet good size you have available.... or metric equivalent... I didn't catch where you are from) then just plan on cutting down the mattress to suit the inside wall dimension plus a little for tucking the bedding. On my build, a hybrid with relatively thick insulated walls, I went 64 inches wide in order to fit a full queen size mattress and it just isn't necessary; lots of extra material and makes for a wider unit that won't fit down trails that are 4 inches narrower. I mean, if we really want to trail ride we should be doing narrow 4 wides, right?
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Re: 2x4 steel tube question

Postby Thelgord » Thu Sep 15, 2016 3:05 pm

I would love to do a 4' wide, but if I do then I will traveling alone LOL! I have thought about doing something like a small cargo trailer with a roof top tent on top. I have also looked at trailers like this style: http://www.kimberleykampers.com/camper-trailers-range

The whole top folds open like a giant roof top tent. Its an interesting idea to play with. Oh and I am from the states, currently living in Georgia.
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Re: 2x4 steel tube question

Postby Andrew Herrick » Mon Oct 03, 2016 11:07 pm

One thing I have considered is that a teardrop trailer is loaded fundamentally different than a standard utility trailer. In the latter, the load rests in the center of the span. In a teardrop trailer, almost all the weight - walls, roof, even lots of the cabinetry - is borne by the side frame members. So the cross members in a teardrop trailer can be MUCH lighter than in a standard utility trailer. Even cheap angle works great.

Assuming you want a true flat bed, either C-channel or tube steel works best for the side members. Pros and cons to both. You probably around know them :) Good luck!
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