A TOTAL DISASTER IN EVERY WAY

[Kody]

I was chatting to a professional trailer manufacturer today about the RHS sections to use for the frame of a TD. He told me about a new TD bought in Melbourne (1800 miles south) and towed up here. When the owners arrived in Rockhampton, the "A" frame of their TD had snapped in half. The frame had been made using Chinese manufactured steel (I think it was an import) and the RHS used was only 1.2 mm (0.047") in wall thickness. He stiffened the frame up, made a new "A" frame and welded it onto the lugs that hold the springs. The TD traveled another 250 miles and the rear section also broke. What a horrible way to start a touring holiday. There was no indication by looking at it, that the steel was inferior in strength or that a woeful choice in the section had been made. It very obviously had been made as cheaply as possible. It boggles the mind as to what could have happened if the TD had smashed into some innocent person on the highway.
I talked at length with the manufacturer about what RHS sections I should use to make the frame of my own TD. He said that I should use the original sections that I had first chosen when I began my original design. I came home, fired up the CAD and went to work on an entire new design for the frame. At the end, I had a design that weighed 6 kg lighter than my other design. I will now be using 3" x 2" x 1/8" RHS for the main frame and the "A" frame. To support the floor, I will be using 2 x 2 x 1/8 angle. I have also been asked to do some CAD work for the guy and he will pay me with the new parts I need for the undercarriage, ie, the springs, axle, hubs etc that I need to complete the frame. How many and what parts will depend on how much CAD work he wants done. I will be ordering the steel this coming Monday and I can then start cutting it up. I should have some photos for you fellas by next weekend. From my own experience of travelling around this great country, the (pathetic!) roads here, demand the very best in design and construction of trailers and gear. Anything less becomes an accident or a tragedy waiting to happen.

Kody

[bobhenry]

I have witnessed the angst and aggrivation of others arriving at a gathering with horror stories of broken tongues in route. This single thing scares the hell out of me. Safety chains do no good if you have pulled the tongue out of the trailer. All you can do is watch as the trailer takes what ever path it will into the side ditch. All the while hopeing no one gets hit by it.

My first teardrop was a modified harbor freight and every time I stepped up on the tongue the flex scared me. I finally added a 2x2 x 3/16 square tube from front to rear and added 18" in length. This ties all the cross members to the tongue and reinforced the right and left angled members of the tongue. I no longer worry about tongue failure.

[Vedette]

Painted the tongue on "Miss Piggy last night!

[Shadow Catcher]

I spent my industrial working career in non destructive testing X ray, GAMA-ray, ultrasound, magnetic particle testing, penetrant testing and eddy-current. I have x-rays I did on the space shuttle and remember well high iron inspection on the Orbanco building in Portland Oregon where all external beam to column welds were 100% ultrasonically tested from the 3rd sub basement to the 14th floor.
I was concerned with the tongue flex on Mega Mini #1 and the second owner had a catastrophic complete failure, fortunately at slow speed in town. Ours which is in reality Mega-mini # 7 the final one built, because of the longer tongue was bending and flexing more than I was comfortable with, (particularly in view of #1 failing) and I had it reinforced.
I am NOT a fan of many of the Chinese imports and would question inherent quality of the raw steel. However even give inferior quality there would likely have not been a failure had it been made with a greater wall thickness. Sounds to me like some one bought something analogous to a Harbor Freight light duty trailer and build something that was not so light duty.
I can if any one wishes go into excruciating detail in ways you can use some techniques i.e. penetrant testing or even spark testing to check welds and some idea of exactly what the grade and the alloy of the steel is. I can tell easily by looking at the spark stream from a grinder what the carbon content is with in five points, and if it contains chrome sulfur and molybdenum.