RV/Caravan Bumper Cover Screw Cap (Square profile tube)

Many RV (caravans, campers, trailers) have a bumper made of a heavy steel square tube. If you put a cover on it which is easy to put on and remove, you can store stuff inside the bumper.

These bumpers are usually 6 ft / 2m long, so you can put poles, wood, tools, or even rolled-up mats in there – your imagination is the limit.

This design has two parts: 

• a square cover that slips over the end of the bumper. It has a large threaded hole and it attaches to the bumper with two screws
• a large cap that screws into this square cover

The cover and the screw cap each have a small hole that you can pass a cord through (like paracord 550). Tie a stopper knot on both ends and you'll never lose the cap while it's unscrewed.

Dimensions

This model is for a square bumper with the side of 4 inches / 102 mm. 

I'm uploading the source design in Fusion 360, so you can easily modify the “squareSide” parameter (Command+P) to change the size. Alternatively scale in XY by a factor of your_dimension/102 in your slicer.

Tolerances – the model already includes generous tolerances for the cap/cover thread mating and for the cover to go over the bumper end. If you have the same 4 inch bumper size, you should be able to print without any XY adjustments.

Printing

I printed successfully using the following settings:

This would be exposed to the sun so PLA might soften and the screw cap might jam. Or maybe not! Regardless, I printed in PETG. 

With PETG, be gentle with the speed and the overhangs (on the threads) print without supports.