Subframe Due - the camper frame

[dzzz]

Rather than messing up the "Subframes decisions" thread, I'll post here about the frame that holds the actual camper.
Since the campers a popup, the top is 3" wider on all sides compared to the bottom. The bottom will sit on a frame, not a flatbed.

I'm thinking about a rub rail that extends around the frame. Stairs would attach at any point to the rub rail. See attached.

What do I use to hold the rub rail out from the frame? Aluminum or steel?

 

[Metcalf]

The easiest thing to use would be to lay some I-beam on its side, but it would most likely trap too much dirt/dust/mud in the top. It would be nice to have the entire outer structure pre-made though with minimal welding. You could have the I-beam modified on a laser tube cutter with large holes every few inches ( through the web ) in order to keep the mud problem down.

Choice two would just be some sections of C-channel or box tubing with the open ends up. Cutting 20-30 of these would take a little time but be very cheap. You would have more time in the welding, and welding the inside seams would be harder than normal depending on the spacing of the rub rail.

How are you mounting your frame to the chassis? Still using a unimog style 3-point mount?

You might consider doing something a little more exotic with the deck to make it more rigid. Squares and rectangles have a lot of single point twist unless you grossly overbuild them.

If it was me I would give SERIOUS though to building the frame out of aluminum. It would be one of the biggest areas to save a LOT of potential weight. Material and welding will cost more however.

 

[dzzz]

What about a steel tube "basket"? Tubing is runs the full width. It is curved past the camera bottom and is finished with a rail. Sorta a giant roof top carrier.

As far as mounting, I'm leaning towards a solid attachment at the rear axel, with a flex mount at the front. This is similar to what unimog has designed for a body mount on the U500. I would then attach the camper with spring mounts.

I'm hesitant to use aluminum with any part that shows, due to dents.

 

[Metcalf]

Draw me up some pictures

Aluminum won't dent if the grade and thickness is correct.

 

[dzzz]

Here's a simpler idea