RV Bed Frame Design

[lazylnm]

My wife and I are designing an RV conversion of a Mercedes Sprinter Van. We are planning to use a modified Murphy type bed that pivots up into a vertical position when not in use. I plan to use some sort of pin and sleeve mounted about 9" from one end of the head and foot ends. The opposite ends will be supported by some adjacent cabinetry. See the attached drawing.
I envision using 6061 Aluminum flat bar and angles for the frame and middle support beam. .375"x4" FB w/ 1" x1" x .125 angles around perimeter and a pair of like sized angles for the center support. Everything would be welded.
The mattress is supported by a system of wood slats that span between the side rails and the middle rail with the mattress sitting on top.
Assume DL = 100 lb total; LL =500 lbs - currently weigh a combined 320 lbs
Rather not have much deflection
Assume that we will sit on one end of the bed when entering/getting out of bed. Assume that all 500 LL could be on one side of the middle bar.
Will these members work without a lot of deflection or do I need to increase the size?
Thank you in advance.
LazyLnm

[JAlberts]

lazylnm,

I have not analyzed your design for stength but I suggest you might consider changing your material to 1 1/2 x 1 1/2 x 1/8 steel bar angle (the common material of common bed support side rails) for two reasons.

First, steel is 3x stiffer than aluminum for an equal material shape; and, second, I have made a quick calculation of the relative weight for your bed perimeter fabricated from your combined aluminum bar and angle vs. made from standard 1 1/2 x 1 1/2 x 1/8 steel angle and your alumunum frame will weigh 44 lbs vs 26 1/2 lbs for the steel angle.

An added benfit from the standpoint of time and cost will be the elimination of all of the welding required for your fabricated bar/angle rails.

For reference, if you would like to make your own weight comparison: 1x1x1/8 Al angle weighs .28 lb/ft and 1x1/4 Al bar weighs 1.176 lb/ft for a combined total of 1.46 lb/ft and std 1 1/2 x 1 1/2 x 1/8 stl bar angle weighs 1.23 lb/ft.