How can I fix wood to some metal in a neither destructive nor permanent way

Question

I sadly have no additional space for a real/standalone workbench, but what i do have is a powerrack (a cage made of steel used for weightlifting). Looking at one half ot it, it looks like this:

I have a piece of wood that i can lay over those bars and use it as a simple Desk, but this alone is too shaky for using it as a workbench.

I am looking for ideas how I can put the piece of wood on there really tight. I don't want to modify anything on the metal side, and once finished attaching/detaching the wood should not take more than a few minutes.

My only idea is using something like hose clamps to fix the wood to the bars. Do you have other/better ideas how i can do this?

Edit:

I like the ideas so far, and in fact I already have something like Jason suggested in place (only on the insides). This works fine for using it as a desk, as it cant move left to right.

But for using it for woodworking, i am planning on putting a vice on it. If i then put force on the workpiece in the vice in direction of the bars, I fear the whole thing will tilt in that direction as it only relies on gravity.

Viewing from the side, black is the rack&bar, blue is the wood, green is the vice, brown the workpiece. If force is applied in direction of the red arrow, it will probably tilt like the orange arrow indicates.

Answer 1

I'd add four simple blocks of wood to the underside of your work surface. I made this out of 2x4x6" long scrap. Drill hole in center with fostner bit, then use jig saw to cut access groove. With deep groove, this one isn't going anywhere. You simply drop the worksurface onto the bars. Obviously this picture is upside down. You should use some flush mount screws to hold this block to your work surface. Quick, easy, cheap, use all three!

Note, I'm assuming you have very little overhang at the ends of your table top. You don't want to have the table flip up because someone placed a heavy load at the cantilevered end of the table. You always want the heavy loads to be between the steel supports.

Update to match the restatement of the original issue above. 9PM PST, 27 Feb 2016:
Okay, lets use the same basic design, but we'll change things up a tiny bit. We're not going to be cutting a deep groove, instead we'll flip the whole wood piece around, drill two 7/16" holes. (i.e. 3/8" plus clearance!) Now you are going to have to drill eight 3/8" countersink holes in your work top. You will need eight standard countersink bolts, eight washers and eight wingnuts. Obviously you will be bolting the bars tight at the hold down in each corner of the worktop. Does this make sense? It's still pretty easy to make; it will take a few minutes to tighten up eight wingnuts, but for the actual tabletop install, no tools are required.

The block of wood will rest on the bottom of the bar. 3/8"-16 bolts will keep things way tight.

This is similar in concept to the design from Daniel B, but I'm thinking this is pretty easy to make. Oh.. note on safety. Its okay to drill a hole in an edge like that if you are using a Forstner bit on a drill press. If you don't have those tools, you can use a spade bit in the center of a WIDE block, then cut the block narrow after you've drilled the hole. Trying to drill a hole in the edge of a piece of wood with a spade bit is much too dangerous. Be careful out there! If you don't have a table saw, you can easily use a hand saw to safely do the post drilling cuts.

Answer 2

Conceptually similar to zipzit's answer, another thing you can do is just mount some 1x2 strips or whatever to the underside of your surface, hugging the bars (you may want to mount one, then place it on the bar and hold the other one in place for a tight fit), e.g. (not to any sort of scale):

You may even be able to get away without the inner set, or without the outer set, or without one of the pairs.

Either screw through the top through countersunk holes, or you could do pocket holes from the bottom if you have the setup to make them, or deep counterbored holes from the bottom.

To keep it from slipping along the axis of the bars you could just stick a wedge in the side, like a door stop or something.

If the table wobbles or chatters a little, a rubber strip or perhaps a strip of that stick-on insulation foam you'd use on drafty windows could do the trick; stuck to the underside of the table along the length of the bar.

If you want to go really simple, just mount one of the strips, then attach it to the nearest bar with a c-clamp (or quick clamp) or two. That'll guarantee a snug grip (sorry, didn't feel like drawing clamps):

Use some clamps with rubber feet to avoid marring your bars.

Answer 3

You appear to be concerned about pressure causing your device to tip off the bars. Following from zipzit's solution ... I don't have access to drawing tools at the moment so I will try to be descriptive.

Take the shoe he has suggested and make another strip or plug or ... basically anything that fits in the slot and sticks out. Additionally, cut a groove perpendicular to the pipe groove on the side which mounts tot he table top. Put a ratchet strap through this groove. When you place the table over your bars, put the "plug" into the remaining opening of the shoe and wrap the strap around it. Ratchet the plug tight against the bar. This will help secure against lateral movement as well as prevent the table from flipping.

Alternatively, and perhaps better, would be to have the shoe not fully enclose the bar. The strap would just press directly against the bar to secure the table.

yet another option would be to use clevis pin held in place by a split pin (https://en.wikipedia.org/wiki/Clevis_fastener)

Here is a crappy picture which I hope explains my thinking.

Answer 4

In the theme of your own idea, you can use a hose clamp to fasten a short length of 2x4, parallel to the uprights, on the "inside" of the rack. You would then balance your work surface on these boards. There is a risk you might damage the paint/powdercoat on the rack, so you might want to use one piece of wood on either side (with larger hose clamps) to make a "sandwich" around the metal.