Quote:
Originally Posted by PopBeavers
I had a crack at one of the welds for the street side bracket for the swing away hitch. I believe it was because of my experience that the factory made a small change to the way they do the weld. I posted pictures around here somewhere.
My son is a mechanical engineer. He says never drill a hole near the edge. That cost me 50 grand. 
If someone wants his opinion I will be happy to ask him the next time he drops by. Please be specific about where you think you want to drill a hole.
I am paranoid enough about it that when I added a disconnect switch, I chose to use the angle iron that runs horizontally across the front edge of the front of the floor and the batter tray. I did not drill a hole in the frame.
I believe that the forces are rather high on the tongue when driving down the road due to bouncing. Depending on how the floor is attached to the frame, that might make the frame stiffer and therefore weaker in front of the floor.
Imagine where the bend would occur if the TM were connected to the truck and you were standing inside near the front jumping up and down. *THAT*, it seems to me, is a high stress point. |
Your son meant to say "never drill a hole too near the edge."
Welds that are not complete or not done right are always good points of failure. Welds properly done are as strong as the adjoining material.
An engineering analysis of "bouncing" soon has one bouncing into differential equations, and I cheerfully defer to someone who's done it fewer decades ago than me, educated back in the days when men were sent to the moon with equipment designs done on bamboo slide rules to 3 significant figures.
Bouncing on the trailer axle springs is conceptually similar to bouncing on your tow vehicle rear axle (except your rear axle has better shock absorbers and lower tire pressures) (God only knows how these will make your differential equations come out differently, but they will, of course). Regardless, a 1000# tongue weight is a "high" stress point, but still a minor fraction of the loads on the frame that occur at the trailer axle (1000# versus 4000#, in round numbers, assuming the rest of the TM doesn't materially contribute to the TM's structural strength). There are shear loads at the trailer hitch, but minor bending loads. I'm suggesting here that frame failures other than broken welds are probably rare in the RV trailer business in general, and extremely rare among our relatively short TrailManor trailers, except where there might be manufacturer associated design problems.
As someone with one (ahem) experience with a disconnected trailer hitch coupler (NOT the TM, and the story could be on the dumb-things-done thread, but that adventure is really another story), I'd like to report that the safety chains will allow the trailer to skid nicely to a stop behind the tow vehicle, using the easily replaceable jack which can be quite easily and automatically bent into a front trailer skid. In this configuration, it's possible to do fine even going over railroad tracks. The engineering analysis was actually pretty boring, compared to the DW analysis. Fortunately, the WDH makes this particular incident very unlikely to happen because you have both the tongue weight and the spring bars holding the ball and coupler together.
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