![]() Not only are the failures typically in bending, but for long spans unacceptable (uncomfortable) deflections are usually the limiting factor. Although that does assume you have strong and rigid joints (what joint method are you using? - 8020 has several ways to make a joint and their strength and stiffness vary dramatically). If you do this math, what you will find is that the bending calcs you already did are really the only ones worth doing - structures like this typically fail in bending. While I do these calcs for a living, I did not do a single calc when I designed and built my 8020 structure (out of 10 series). ![]() 046 in^ profile), the length and the boundary conditions at each end of the column (probably clamped-clamped, but you could try the others and see how close you are to failure). For 8020 you will need to enter Young's modulus: 9,900,000 psi area moment of inertia (available on the 8020 website, but. Note that the answer is highly dependent on the end constraints (a single column not attached to anything will fail at a lower load vs one tied rigidly at the top another structure). If you want to do some calcs here is a buckling calculator. Are there any supports front to back? Assuming your dinette is the height of a chair (<18") and supported at the halfway point, there is very little chance you will have a buckling problem. In your diagram, it looks like each column is supported laterally halfway along their height - so that is great to prevent buckling. So the key is not to make long, slender members without any lateral support. Long, slender members in compression generally fail in buckling. The next issue you need to consider is buckling. In this example we compare the 1600lbs to 25000 and get 6.4% As you can see from this example, you can basically ignore this calc as there is no way you will exceed it with any sane design. The 8020 yield strength is 35000 psi, but it is generally accepted to reduce the allowable load on yield by 1.4, which give 25,000 psi as the allowable. For your example of 700 lbs and one 10 series 8020 column the math is: 700lbs /. For conservatism, you can assume one member carries the entire load. In your van, the amount of load each member carries will be more complicated. Bridges are sometimes built with a pin on one side and a roller on the other to achieve this "simply supported" constraint. If it is 2/3 of the way across the span it is 1/3 and 2/3 each. If it is directly over one column it takes 100%. If your structure is "simply supported" then it is just a function of how close the load is placed to that structure - if the load is exactly halfway between 2 columns, each column carries half the load. One is how much load each column takes or load sharing. However there are a couple of subtleties that need to be considered. I find this very odd as a method of online ordering, and this makes me very reluctant to use Mcmaster for online ordering.I think you are asking how to size a column to take vertical loads? In general compressive loads are easy to calculate - you take the load and divide by the cross sectional area and that is your stress. For this reason I do not include shipping costs for McMaster in this spreadsheet, as I would have to order every item to find out. Mcmaster-Carr shipping costs: McMaster does not calculate shipping costs prior to placing your order! Also, they do not tell you what the shipping costs are after you place your order! You find out what the shipping costs are after you get your bill. In general, smaller lengths of metal cost more per pound, and generally incur cutting costs.ħ. Be advised that price/pound of metal may vary significantly depending upon the specific size, alloy, and "amount" (by "amount" I mean whether the item is a standard length - which is typically cheaper on a per pound basis, or whether it is a "cut" length). In case you don't know what a "drop" is: this refers to a random length of metal left over after some other customer has purchased a cut-off piece of a standard length these are typically offered at a discount.Ħ. Further savings are possible by buying "drops," although of course the selection is more limited. ![]() "Local" suppliers represent vendors local to me, who provide bargains in the form of random lengths or "drops." These are included to show the value of using a supplier local to you if at all possible, if for no other reason than to avoid shipping costs. "Bundling" of several items in a single shipment may in some cases reduce overall shipping costs.ĥ. Note that shipping costs may be overstated in some cases, as these are calcultaed for single items. Seller 6061dude (Ebay) sells mostly aluminum, some brass, occaisonal tooling.Ĥ. Shipping costs to other locations may of course vary.ģ. Some vendors will occasionally offer free shipping coupon codes.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |