making a bed slide

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I have seen models costing upwards of 1,000-1,500 dollars. I personally can make my own but I need to first understand this chart as for the safe loading characteristics of I beam or C channel aluminum. The bed will slide out 80% from a distance of 6 - 8 feet if its a single slide. The bed width will be abut 3 feet.  If the construction is a Double slide, it will slide out 100%. The weight the bed will hold from 500 - 700 bls. I am having trouble understanding this chart. http://www.sapagroup.com/pages/52251...Properties.pdfI am also having issues trying to find plans online else, I have a pretty good idea how they are constructed. www.bedslide.com is one example of construction. I will look into ordering bearings from mcmaster.
Reply:I didn't scroll through all of the pages in the link you provided.   What I can tell you the first two pages with the section depth and spans, isn't what you need to create a bed slide.  The reason being the note on the charts stating these are for simply supported beams and what you are trying to do would be a cantilevered beam which would be a totally different chart if there is one.
Reply:I was looking for cantilevered beam charts for steel, and was unable to fine any.  You probably also want to look at max deflection in addition to just absolute strength.  Also, the max stress for a cantilevered beam is where it is supported, so you will need to be careful about how the beams supporting the load are attached to the truck - it is at the attachment point where the stress is the highest.Here is a calculator that I found for computing the deflection and stress on a cantilevered beam.  This only handles loading at the _end_ of the beam.  If you engineer this to handle the max load at the end, it will support much more evenly distributed.http://www.engineersedge.com/beam_be...m_bending9.htmYou are probably also interested in the uniformly loaded case, which I was not able to find a calculator that I understood.  Here is one for the uniformly loaded case (I think), but the output was not clear to me.http://www.engineeringcalculator.net...alculator.htmlI'm not an engineer, so I'm no expert on this.  I am using rectangular tubing, which makes some things easier, as the "Distance from neutral axis" to the extreme fiber is 1/2 the thickness of the beam in the direction it is being stressed.  A non-symmetrical beam (angle bracket, channel in the flat position) will be different.Roy
Reply:I think you're over thinking this.  My dad had a roll out bed in his pickup.  It was built by a local shop I think and was nothing more than a few pieces of angle iron, some skateboard wheels, and a sheet of 3/4" plywood.  He used it regularly delivering booze to bars.  I remember seeing the whole thing stacked like 2 or three cases high.  So you know it had some weight on it.  His set up could prolly be built for $100 or a bit more.My name's not Jim....