Rods for lumber rack

[LCHIEN]

I've been working on my lumber rack.
I noted in Big Tim's recent post (post #9 in http://www.bt3central.com/showthread...ht=lumber+rack)

that he used 5/8" tubing with 0.065" wall, paid about $100 CDN (right now the CDN and USD dollar are about on a par) for 45 bars 10 to 12", precut.

I figured I needed about 32 to 40 bars of 15" length to withstand as a uniformly distributed cantilever load about 60-100 lbs worst case over 13" length. From the online metal stores it seems like, if I cut them myself, 5/8 x 0.065 would run around $3 each.

My mech engineer friend suggested solid bar. It would be stronger and cheaper. 5/8" round bar or 1018 or 12L14 steel would cost around $1.75 if I cut them myself. Still more than I wanted to pay.

So I played around with EMT Conduit. Now 1/2" EMT conduit comes in 10 ft length for $1.97 which means I could make 8 bars for around $0.25 each.

Two problems, the OD is .710 roughly, a bit bigger and not a standard fractional size (hence my other note about custom grinding a spade bit) and the wall thickness is around .035" - quite a bit thinner.
I built a test fixture and applied my body weight to the bar to see if it bent. I found I could bend it with considerable weight on the end but very difficult to bend with well over half my body weight on the middle of the bar (simulating a distributed load). The bar bent right at the fulcrum (where it entered the hole in the wood (edge drilled in 2x4). Taking my mechanical engineer friends suggestion, I cut a 4" piece of poplar 5/8" dowel (nominally .625" OD) and hammered it into the .61 ID of the EMT conduit. This strengthened the bending point sufficiently I was not able to bend it at all with more than half my body weight on the center of the bar. I think this will suffice. The cost of the dowel raised the price to about $0.41 but that's still a lot better than $2 or $3 per bar.

I'm going to have to buy a $3 3/4" spade bit and custom grind it so I won't have as loose a fit of the bar in the 2x4 edge.
I was also going to use a 5° slant to my bars but the wood gives a bit so I'm going to make it somewhere around 8-10°. This will keep the goods on the "shelves" including dowel stock and pipe goods with little or no danger of rolling off.

I'm not sure if the metal of the EMT conduit will mar or react with the wood any... if it does I may cut some PVC pipe and slip it over the conduit. Anyone know about this?

[billwmeyer]

Loring, I did this about 3 years ago on a wall mounted lumber rack. I measured the metal conduit that I used and it measured 7/8" diameter. I used a spade bit, and set the angle a little more than Big Tim did. It has been overloaded, and I haven't had a bit of a problem. I don't remember what I paid for the conduit, but I bought it at home depot, and bing rather monetarily challenged all of the time, I'm sure it was pretty cheap.
Good luck.

Bill

[Uncle Cracker]

If you are worried about the strength of the conduit, you could always slip a piece of rebar down inside it.

[Brian G]

Hi Loring,

For my lumber rack, http://www.bt3central.com/showthread.php?t=2782 I used 3/4" EMT conduit. As I described in the linked thread, I used a 15/16" spade bit. The hole was a little loose, so I made up the difference by wrapping some aluminum tape around the conduit and pounding it in.

I used pipe insulation as a "cushion" over the conduit.

After nearly four years, I don't notice any sag and have had no collapses.

[jonmulzer]

What about using epoxy or some other adhesive to lock them in place and make up the difference in diameter?

[jking]

You could fill the inside of the conduit with concrete to add strength. You'd have to pack it in the make sure there are no voids.

[crokett]

Loring,

I used black pipe when I did mine. Plenty strong enough but it does cost a little more.

[big tim]

FWIW, Loring, a couple of observations about my lumbercart since it's been in use now for a couple of weeks:
If I were to do it again I would make the sheetgoods storage area even larger even though I made it 2" wider than the plans called for.
I still might remove some of the lower tube brakets on the backside of the cart to store 1/2 or narrower sheets. I found out that I have more than ample storage for solid lumber but could use more sheetgoods storage.
In retrospect I wouldn't worry about angling the brackets, the stuff hasn't moved. After all you're not towing the cart behind your car, you're just moving it around your shop. More important, I think, is making sure that the tubes are properly aligned, so that the load is evenly distributed on all the tubes.
I considered EMT, but couldn't come up with an idea for a properly sized drill bit, what you are suggesting makes sense. I wanted something I could put in the router though, to make sure I would 'drill' at a constant angle to the surface.
FWIW.

Tim

[LCHIEN]

...
I considered EMT, but couldn't come up with an idea for a properly sized drill bit, what you are suggesting makes sense. I wanted something I could put in the router though, to make sure I would 'drill' at a constant angle to the surface.
FWIW.

Tim

that's why my drill press has a top that tilts at an adjustable angle!
Altho I'm thinking it's easier just to put an inclined plane on top of the table and clamp the board to the fence for the work of resetting the settings.

Having a close tolerance drill bit for the rods/tubes helps in that with a loose bit, the weight all bears on the holes bottom front edge and the back top of the bar. It will flatten these out and change the geometry somewhat. With a close fitting tube and hole the forces are distributed all along the length of the hole with less deformations of the parts.

[big tim]

Good point, Loring. using your drill press.
I couldn't use my drill press but had to 'drill' the holes in the partially finished lumbercart because of the plywood panels, unless I was prepared to drill right through the 2x4's and then later drill from the backside of the 2x4's to drill through the plywood panels. Didn't want to do it that way though because I wanted a bottom to the holes.

Tim