What size lumber for plywood rack

I want to build a plywood rack that will sit on four 4" wheels and tuck next to the side wall of my shop. The rack would have a base of 16 inches by 8 feet. It will be constructed with two rails at the base that will be 8 feet long dimensional yellow pine. I'm thinking about using 2x6s. Would this be sufficient? The rails would be bridged by 1" dowels located every 4" with 1" wide by 1" Sch 40 PVC sleeves over them to act as rollers (20 pieces of dowel connecting the two rails).
My rough calculations show 490 lb load applied to each rail, evenly distributed across the entire length (assume 13 sheets of 3/4" plywood at 75 lb each).
Bob
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B B B But, then it won't be a plywood rack
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Having built a plywood rack a few months ago and not getting it perfectly correct..
Mine is about 10" wide, not wide enough to be safe for much plywood in there! I tried placing a 100lb piece of 1" MDF, VERY unsafe.
My casters are 5", I got two fixed and two steer, I would buy 4 steer when making the next one. I will also get smaller casters to lower the center of gravity.
I will not worry about capacity inside and will put some vertical ledges to keep sheets from flopping over in unison.
I will try to put the wheels out wider than the box itself for my stability. I will also plan on dropping the rack itself lower between the wheels. This drops the center of gravity a few inches, when a 4' pieces moves, a few inches can make a huge difference.
You might get away with 2x4 sandwich frame. My frame was strengthed with a 2x2 in the middle, but still get a bit of sag. It does not run full lengh. The plywood was cheap 3/4"
Alan
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Where did you mount the casters? If they are on the corners, move them.
Put the two fixed at the mid-point, as far to the outer edge as you can. Put the two swivels at the ends, in the center. This makes a sort of diamond layout. You can steer it very easily that way and pivot the entire rack about the centerpoint. _________________________ | F | |S S | |___________F____________|
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You make an excellent set of points. Mine will sit next to the wall, except to swivel out a few inches to roll out a sheet when I need it. I view it like moving a drill press on rollers - something to be done very carefully. I realized today that the design I have in mind is going to be very strong without having to dwell on the size of the supporting cross beams. I'm building each side out of 2x4s with five vertical members, all joined with Mortise and Tenon joints. I decided the 2x6 rails at the bottom will be amply strong, given the supporting framework of the side. I'll consider putting a few thin vertical rails in the middle to prevent tipping as you pointed out. Mine is so narrow because I only have the side next to the car in which to store sheet goods. I'm going to think about some kind of retractable "out-rigger" for added stability. It wouldn't take much to add a hinged swing-out trianble shaped outrigger with an extra caster that could lock into place. It would make a huge difference in stability.
Bob
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