How to gauge the strength (or stupidity) of a custom car cargo carrier?
We spend summers travelling to music festivals in Fest Van, a 1995 Mazda MPV. One of the larger items—really important with a six-year-old—is our garden cart. It’s steel, very robust, and about 70 pounds empty.
We’d get a basic trailer hitch installed by U-Haul. I can’t link directly to their page, but its description is a “Heavy Duty 1¼" receiver; Max weight 3500 pounds Class 2 hitch.” Other than towing, it will also accept a commercially available cargo carrier (example).
Instead of going that route, we’d like to take the cart to our mechanic (a very good welder and mechanic, but not a structural engineer) to fabricate/weld onto it a male fitting.
Given the age and delicacy of FestVan, we wouldn’t load up the cart with anything extraordinary—we’d likely keep the bulky items in there and the max weight added to the carrier would unlikely be more than a couple hundred pounds (if that).
So assuming that the male end is securely welded and supported on the bottom of the cart and that it fits correctly into the female receiver, how do we gauge the stupidity of this idea? I’d be pretty confident on my own that the mere weight isn’t going to be a problem (again, bulky but not heavy items), but what about torque or other structural issues? Is 1¼" of steel (on the female side) strong enough to resist the cart wobbling as we drive?