Underbuilt.

[Forrest747]

Stupid question time......

Has anyone seen a trailer just fall apart. we build alot of solid built trailers and alot (mine included) overbuilt.

Im not talking from an accident, or weathering, just a poor built trailer. On the maiden voyage falls apart.

IN college we had a bridge building contest. 1/4 inch square balsa wood size restriction couldnt weigh more than 40 grams span 25 cm. well mine held 215 pounds. one guy puts his on and teh test assembly placed on it about 2 pounds and his bridge was done. total failure after 2 pounds.

[S. Heisley]

If you look above, under Design Resources, in the Design Library, Andrew posts a picture of a broken tongue. It is next to the trailer balance one.

[Shadow Catcher]

The first Mega-Mini which we owned failed at where the tongue goes under the body of the trailer with the second owner. I had been concerned by the amount of bounce/frame flex knowing that aluminum has a limited modulus of elasticity, it will break if flexed too often/much.
However there are still DC3/C47's flying around before WWII.
I had the current tongue reinforced on what is MM #7 and certainly it was tested in the thousands of miles we drove over the last month.
The question really needs to be what can be very light weight i.e. the cabin frame on Compass Rose is 1 X 1.5 X .060 aluminum and withstood being put on its side very well, and what needs to be a bit heavier i.e. the trailer tongue which has a good bit of flex.
When I was looking for what fails in trailers it is wood rot and rust almost never do you see structural failures.

[angib]

If you look above, under Design Resources, in the Design Library, Andrew posts a picture of a broken tongue. It is next to the trailer balance one.

Daved Nathanson who kindly donated that photo also donated the conditions under which it (eventually) broke - he was driving fast on washboard roads with the trailer frequently bouncing into the air. And he had a hole through the tongue where it went into the receiver tube for the locking pin and it was at that hole where the tongue eventually cracked and collapsed. I would say that was fatigue failure, though I haven't seen the pieces to be sure.

Incidentally, seeing as I've just posted on another thread about tongue strength, the European standard makes very clear that all they are concerned about is fatigue strength. So it's not the ultimate strength of the tongue under one huge load/bump, but its ability to resist hundreds of thousands of jiggles. Indeed, if you can't do a simple design calculation, they allow a physical fatigue test of 2 million cycles.

Tongues do fail sometimes, but I don't think I have never heard of any trailer failing anywhere else but at the tongue - in my opinion, the tongue is the only part that is strength critical. If we were building car- or machinery-hauling flat-bed trailers, that might be different, but for a teardrop (or small baggage trailer), the tongue is all that matters.