gravel grizzly project

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Designing a gravel grizzly to sift gravel.What would be the weight to cause a 8 foot long tube of 2.0 square tubing with 0.25 thick wall welded on to a steel frame on its angle; welded so the tip of a corner is pointed up, another down and the other right and left, not welded on a flat side on its corner.How much weight would it take to bend the tube?What about if I place a brace half way under the 8 foot tube length so its 4 feet long?Want to build a gravel grizzly for sifting gravel with the steel tubing sloped downward on an inclined deck with several tubes along side each other, say 2 inch gap between the tubes.It will be fed with a wheel loader dropping gravel and rock on to the steel tubing deck. Large rock would be say 18 inch square so it would weigh 600 pounds the rock. total weight of loader bucket load would weigh 5,000 pounds, rock and gravel.Screen deck would be 10 feet wide. Bucket is 8 feet wide.Steel tubing spaced evenly across the 10 feet wide deck.Question is how much weight would it take from a rock to bend the 2.0 inch tubing welded on the deck at and angle.If the rock hit an individual tube and if the rock hit two tubes or if it hit three tubes, how much weight would cause the tubes to bend?This question is beyond my data base, hopefully some one reading this may know the answer.
Reply:It seems like the 2" is gonna be too light for what you want to do.  Maybe 2 7/8" heavy wall oilfield tubing (best used stuff you can buy, or even better, new).Big problem you will face is, that there is a BIG difference between say, one rock weighing 600#, just laying on the tubing versus dropping the rock from a loader.  The momentum of a 600# rock(s) hitting your grid is pretty high!!  If you're just dumping coarse gravelley material that's one thing, but big rock is another.
Reply:I don't think the tubing is the way to go. The large rocks will bend it very easy. If the price was right on the tube and you already have it, go ahead, but I think you'll be disappointed real quick. 1"x 6" flatbar on edge will be stronger. If it's spaced so the bottoms are 1/2" further apart than the tops it won't have such a tendency to get rocks stuck between the bars. It will also help to have the flat bar loosely bolted top and bottom so they have a little wiggle room. If possible build it so the angle can be adjusted to find the sweet spot so all the 2"- falls thru yet the oversize slides off easily.   I worked 32 yrs in the aggregate industry so I guess I can say this is the voice of experience speaking.                                  MikeOl' Stonebreaker  "Experience is the name everyone gives to their mistakes"Hobart G-213 portableMiller 175 migMiller thunderbolt ac/dc stick Victor O/A setupMakita chop saw
Reply:I don't think tubing would be right for this project myself. I know it wouldn't even come close to holding up at the local quarry.   Here's what I did for a local quarry.http://weldingweb.com/vbb/showthread.php?t=125511  I used 1" A514 steel plate to make the bars. What was on the old one was 1" rod welded to the top of 1/2" x 3 strap. It didn't hold up well as you can see.Millermatic 252XMT 304'sDynasty 280DXHypertherm PowerMax 1250Miller Trailblazer 302 EFIOptima PulserXR feeder and XR Edge gun and more athttp://members.dslextreme.com/users/waynecook/index.htm
Reply:OK, pictures helped a lot.  Tubing if not supported probably would be weaker than the bars "irishfixit" and "mla2ofus" suggested and showed.  Just tossed an idea out there to see if someone had a better solution and you guys did.  I based my tubing idea on a gravel sifting screen a guy up the road from me made, and he didn't work in an aggregate plant. I can see from the pics that the bar stock would hold up better.
Reply:Tubing will also tend to let the bigger rocks get wedged in between them because of the taper to the narrowest point. That is why you want squared off leading edges as soon as the material is introduced.
Reply:Originally Posted by AKmudTubing will also tend to let the bigger rocks get wedged in between them because of the taper to the narrowest point. That is why you want squared off leading edges as soon as the material is introduced.