Frame material for DIY job?

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Frame material for DIY job?

Postby shoeman » Fri Sep 28, 2007 12:44 pm

OK, I'm fed up with chasing used frame options and have decided on building my own. I've searched and scanned the forums and read the trailer tutorial. What I can't decide is what material to use...square tube or angle? I can't seem to find a consensus on that issue here. I know that both will work, I'm just looking for pros and cons to help me decide.
So let's here some thoughts please!
What did you use?
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Postby Podunkfla » Fri Sep 28, 2007 1:26 pm

Hmmm... Angle steel is lighter. Square tubing is stronger. Both will work fine for you average small teardrop with a 3/4" plywood floor. Even a 1/2" floor is prolly ok with some 1 x 2" framing. when the whole box is assembled it adds quite a bit of strength so the frame doesn't have to be all that heavy. JMHO ;)
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Postby Chuck Craven » Fri Sep 28, 2007 2:20 pm

Like Brick said!
If you are going off road then square tubing should be considered.
My frame is 2” square tube with angle iron cross members and is welded by a certified welder. It’s meant for off road but not rock hopping. If you are doing rock hopping it needs to be a little heaver. ;)

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Postby brian_bp » Fri Sep 28, 2007 3:57 pm

Podunkfla wrote:Hmmm... Angle steel is lighter. Square tubing is stronger. Both will work fine for you average small teardrop with a 3/4" plywood floor. Even a 1/2" floor is prolly ok with some 1 x 2" framing. when the whole box is assembled it adds quite a bit of strength so the frame doesn't have to be all that heavy. JMHO ;)

Really?
For the same width, height, and thickness, of course angle is half the weight (it's half a box).
For the same strength, a thinner box of the same metal (alloy, heat treatment) will weigh less than the angle alternative, and a C-channel falls somewhere in between, which is one reason why no vehicles other than inexpensive trailers are made with angle iron frames - it's not efficient.

One reason that C-channel is almost universally used for heavy truck frames is that it is practical to bolt together a chassis with heat-treated alloy C-channel, so the material is stronger than the same thickness/weight of mild steel. It can't be flame-cut or welded without weakening it, due to the heat treatment.

The inexpensive bolted trailer frames might be heat-treated, so if I were picking material I would careful not to choose my dimensions based on some example unless I knew the steel I was buying was as strong, in the condition it will be used.
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Postby jeepr » Fri Sep 28, 2007 5:36 pm

I used 2x2 tube for the frame and 4x4 tube for the tongue. I made some stiffeners out of 1/8 plate at the corners and at the tongue. I like the strength of the square tube.
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Postby Chuck Craven » Fri Sep 28, 2007 5:38 pm

Jeepr

looks almost like mine! 8)

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Postby jeepr » Fri Sep 28, 2007 5:41 pm

Chuck, I wish I had put the extra bracing on the tongue. Not that it needs it for support, it just makes it easier to mount the front box.

Nice looking trailer! :thumbsup:
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Postby Chuck Craven » Fri Sep 28, 2007 5:52 pm

Every thing is 3/16” thick streusel steel, the tube for the tongue is 2” by 3” and the stress calculations was just at the 50% over stress point so I added the two angles. My frame has been gone over by a professional engineer and welded bye a certified welder. The PE is a friend so it did not cost me anything for the engineering eval. :twisted:

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Postby Podunkfla » Fri Sep 28, 2007 6:11 pm

For the same strength, a thinner box of the same metal (alloy, heat treatment) will weigh less than the angle alternative, and a C-channel falls somewhere in between, which is one reason why no vehicles other than inexpensive trailers are made with angle iron frames - it's not efficient.

True... And, a thinner wall round tubing would be even stronger yet, although a bit harder to attach to. It is still my openion that a lot of folks overbuild though. Nothing wrong with that if you don't mind the extra weight and expense. But, a well built wooden tear doesn't need a massive frame in most cases. The ones built with the lightweight HF frame seem to hold up well. As far as I know the HF frame is just mild steel, not heat treated... You can file it or drill it easily, so it's pretty soft.
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Postby Chuck Craven » Fri Sep 28, 2007 6:34 pm

The problem using heat-treated steel is if you weld it, you looses it strength or it can be over-hardened. That type of steel needs to be welded then heat-treated. A homebuilder can’t do that very easy. Plus most heat-treating shops will not do the treating with out a welder’s certification. If you look at truck frames the frame is riveted or bolted together. That way the heat-treating is not compromised. Some of the new truck frames are welded but by robot welders in controlled conditions to prevent over-hardening and making the steel brittle. Most racecar builders use crome-moly for cages and such but it is just has heavy as structural steel. And Yes! My frame is way over built but that is what I want. The weight does not bother me. I have a bad habit of boon daggling. (Off road toad chasing) :o

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Postby madjack » Fri Sep 28, 2007 7:09 pm

..the frame material of my current build is 1x2x3/16 forged "C" channel...very strong and at 5x9, it is lighter(and cheaper) than the last one(4x8) made of 2x1/8th tube...I used a piece of 2x1/4 tube 7' long for the tongue with 2 braces made of the 1x2...the tongue is 5' long to accomodate our front box, a Pet Cool and a propane tank...Andrew tells me, it comes(the tongue) damn close to meeting Aussie trailer rules, which are 2r3 times what is required most anywhere else...oh yeah, I also incorporated a receiver hitch on the rear for a cargo tray..........
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Postby len19070 » Fri Sep 28, 2007 7:36 pm

Brick brings up a very important point.

Once the box is on it adds a lot of stregnth. You create what is known as a "Box Beam". If you build a 3/4" solid wall, and bolt it to the side of the frame, you have made it very difficult if not impossible for that frame to flex.

Why, because you have installed 2, 4'X 3/4" beams running front to back.

Same thing with a stick built wall bolting it to the top of the frame.

This frame,
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is built out of 1 1/2X 1 1/2X 1/4 angle.

I've built another one out of "Bed Rail" (6')
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This frame has both the outlookers made from angle and square stock.
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You have to look at your build as an entire unit. Its Not just a frame.

2X2 angle is fine for up to about 1200.bs (I think more on a Tear) as per my father in law the Engineer. But he thought I was just making a frame.

Free Engineers have no imagination.

Happy Trails

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Postby Chuck Craven » Fri Sep 28, 2007 7:41 pm

Madjack
Your forged "C" channel is structural steel, if you would drill holes in it you may find hard spots from the hot rolling process. I have seen some one drill holes in the harbor freight trailer had he found hard spots also. I think the steel in them is cold rolled then heat-treated. That’s why they are holding up so well. :roll:

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Postby doug hodder » Fri Sep 28, 2007 8:42 pm

I've had really good luck with 16ga 2x2 tubing for the frame and 2x3 .120 on the tongue..4'6" x 10' with an extra long tongue, loaded with all the stabilizer jacks, swing away dolly, 205 75 R 15's and a heavy 4" drop axle with springs...weighed in at 290...Right there with the heavier HF frame, and it's got a lot more in the way of axle and suspension than the HF. Andrew engineered it. Doug
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Postby shoeman » Sat Sep 29, 2007 6:50 am

Sounds like all the usual choices will work just fine then. Square tube and C-channel might be easier to fab at the joints than angle would be I suppose. But if you made all the ends 45deg cuts where they mate that would be simple enough. Question then is how to attach a tongue, which would probably be square tube, to a channel frame? It's all easier than the round stuff we used to have to use on the race bikes. Fishmouthing gets old fast. Guess I'll start calling the local steel house and see how costs compare for the various types. Good old 1018 steel works every time.
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