Bolting a trailer and welding?

Just a nit, but "over engineering" would be if you optimized the heck out of it. This is "under engineering" or just brute strength designing (if you can even call it that).

Over engineered would be a aluminum tube space frame, stressed member, composite deck, etc.... to carry your lawnmower.

Never understood why something that was nearly the opposite of engineered was "over engineered".

JW

Is it a bad idea?

Well, I could care less. :)

And you ever notice how often we say 'no' when we mean 'yes'? No, its true!

--Winston

Properly welded you don't need the bolt. Get it welded RIGHT and forget the bolts and associated gadgets. If you don't trust some weld, i.e. the strength of a corner, use bracing across the corners - also welded. Don't forget the plate on the top is going to be some reinforcing for the whole frame.

On Wed, 16 Apr 2008 12:09:32 -0700 (PDT) in rec.crafts.metalworking, jw wrote,

"Over engineered" does not mean too much engineering. It means engineered to meet requirements way "over" the actual real requirements. HTH. HAND.

A bolted joint takes some engineering too. Don't want the bolt just squeezing the tubing. If you can't trust your welding design for a properly bolted trailer and use the weld as a backup, not the other way around If bolting through tubeing, drill your holes big enough to put a pipe with the ID to fit your bolts. Weld the "bushing" into the tube, grind the ends smooth, and bolt it together with washers under head and nut. This way you will not collapse the tube.

Or just use channel. On some channel you need tapered washers on the inside because the "legs" of the channel are tapered.

It's called "over built and under-engineered" East german and russian comes to mind.

stryped, you absolutely need to make a scale drawing of your trailer, an post it here for some comments, before proceeding. I did that and am glad that at least there was somne discussion, before making my trailer. It seems to be holding up fine so far.

drawing here

With 1/4 inch wall tube perhaps it could be drilled and tapped and assembled with cap screws. Then weld the cap screws in so they can't loosen and fall out, and put a couple of good beads in for good measure. That way you can assemble it loosely, square it up, tighten it, and weld it. Gussets can easily be put on then after it it is squared Match drill to tap drill size, remove gusset, tap rail and ream gusset to fit bolt. Bolt on the gusset, and then weld as previously described.

Or lay it all out, drill and tap and assemble with gussets - make sure everything is square, tighten all the cap screws, THEN weld the mitered inner and outer corners and everything you can reach with the gussets on, remove the gusset, weld the rest, grind joint smooth where gusset fits, bolt on the gusset, and then weld the gusse on as well.

Basically your bolted gussets "fixture" the assembly for welding, and the provide a bit of "feel-good" backup. Use half inch UNF cap screws. Just make sure you are not trying to drill and tap the welded seam of the tube!!!!!!

You never just drill through both walls of structural tubing and put a bolt through side to side - that collapses the tubing, and when it is deformed the strength goes away. You need to put a sleeve of pipe or heavy round tubing through the holes and seal weld the sleeve at both ends where it passes through the chassis.

This puts the clamping force of the bolt into the sleeve and not the chassis tubing, and the chassis tubing will retain it's shape and therefore strength.

If you want to attach something bolted, the other acceptable methods are welding on a flat strap stock bracket with a hole, or welding a nut to the rail and attaching with a bolt, or placing the sleeve on the side of the tubing and welding the sides down...

Fort the corners, I would use fishplates along the sides of the tubing to overlap the mating welds, not gussets that cut across the inside of the mating angle.

Fishplates are always cut with a diamond profile on the ends < >

That spreads out the strength along a longer weld path, straight cut ends [ ] just move the stress instead of spreading it out.

Hey Stryped: See if there are any Welding or Metal Fabrication or Industrial Design classes at your local High School Adult Extension, Community College or University Extension, etc. There are SO many little details to doing this right, and we'll all get carpal tunnel from the typing if we try to explain it all.

And if we miss something critical or you don't understand it, you could still end up with a 'two piece trailer'. Which would be bad.

-->--

I have, intentionally, to see how good the weld was. The welding shop at the local high school has a 50 ton press for testing weld samples to destruction. I didn't weld my front end loader's frame until I could make a butt joint with 7018 that could be bend over double. At home you can use a hydraulic jack to stretch a test structure out of shape. Just don't get hit by flying pieces.

Jim Wilkins

The poor man's version of destructive testing, involves a vise and a hammer to bend the pieces.

Also, to the OP, if you add some sides to your trailer, they can increase its strength considerably, without adding too much weight.

Any way I can do this with a floor jack?

That is nice trailer. I have been studying books. I even have the old =93ARC WELDED PROJECTS=94 book Lincoln put out many years ago.

I like how your center tongue almost goes through the entire length of the frame. I have seen that before, I have seen people just use an =93A=94 frame with no center with the A butt welded to the front frame cross piece. I have seen an =93A=94 welded underneath the frame. Underneath the frame is what I was thinking of doing. I would actually prefer the center tongue through the whole thing as in the ignoramous military trailer example, but I don=92t think I have a long enough piece to do that. I was thinking that if I did the A frame underneath, I could bolt for good measure.

Speaking of that someone in this thread mention using =BD inch bolts and threading the holes so the both does not have to go through both sides of the tubing. I like this idea. In the case of a failed weld or a partial failed weld, would this realisticly hold a loaded trailer togther or is it just for =93psycologicla comfort=94? It would help line everything up before final welding.

As a side note, when welding I aways use =93circles=94, basically weaving circles up the joint. Is this a good idea? FWIW I seem to be able to weld eaier with my 6010 rods than 7018. Why would that be? My rods are about 4 years old and have been sitting in a closet inside my house. Are they still ok?

Thanks for your help and time. I am learning a lot. Maybe I could post a sample weld of mine and you could critique it?

I never thought of that. Even the simple angle iron sides?

Yes if there's a tension membrane there to provide shear strength. Heavy gauge sheetmetal or 3/4 CDX Plywood (treated and painted), fastened every three to six inches along the perimeter.

Or build the sidewall frames out of angle iron and place angle iron cross bracing to turn the trailer sides into a big triangular truss. Have the truss rods start at the top at the center upright of the trailer sloping down to the tongue and tail, so they are under tension when the trailer is heavily loaded. The center upright should be roughly over the axle(s) to send the force down.

Oh, and another way to gusset a tubing structure neatly at a 90 or acute angle (trailer A to chassis) is to cut a "Cheese Wedge" out of the same size tubing with the outer wall intact. Then weld it inside the corner after welding and finish grinding the main joint.

Paint the 'inside' areas of frame and gusset with red primer before closing it up, try to keep the rust from starting. Can be sloppy or runny, nobody will /ever/ see it. You hope. ;-)

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Yes, Let's say your trailer's frame looks like this (looking from the side):

#####################

If, instead, you make it look like this by adding a side:

|~~~|~~~|~~~|~~~|~~~| #####################

made from much smaller material, say 1/8" thick 1" square tubing, or even 1" angle, the frame will be a lot stiffer, without too much extra cost. On my trailer, this function is performed by the unibody bed.

I was practicing on 3/16" and 1/4" plate from the school's scrap pile. For 1/8" material you can use a vise like Iggy suggested.

Jim Wilkins