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Model Forum / General / Railroads / July 2005Mechanical analysis of part made in eMachineShop
This wide ranging news-group list has had apparently on-topic posts regarding eMachineShop. Feel free to trim. ---- I have produced a mechanical part description using the software from http://www.emachineshop.com and placed it online at http://aubrey.vima.austin.tx.us/rotor.pdf and http://aubrey.vima.austin.tx.us/rotor.ems http://aubrey.vima.austin.tx.us/rotor.dxf (does not re-import correctly) I wonder if there is any way to calculate whether this will deform under its own weight, or other interesting properties, using available software. The construction material will be dense, and likely candidates are gold or tungsten. Platinum is (way) out of the budget, and I didn't price iridium. Osmium is generally regarded as dangerous. http://www.webelements.com/webelements/elements/text/Pd/phys.html I don't know if the .DXF file problem is on export or import. If someone imports it with another package and they get the results that are like the .pdf file it may be worth mentioning. > This wide ranging news-group list has had apparently on-topic posts > regarding eMachineShop. Feel free to trim. [quoted text clipped - 14 lines] > > http://www.webelements.com/webelements/elements/text/Pd/phys.html Any good mechanically-oriented finite-element analysis (FEA) program will calculate deformity due to gravity. You have to identify the constraints, and you may have to add library terms on your own -- density and Young's Modulus -- for those unusual materials, but the program will take over from there. I'm not judging this particular part, because I can't quite see what's going on in the middle of the cross-span from the *.pdf. However, if it's a real-world part, FEA will cope with it. The FEA modules that are integrated with CAD programs are generally the easiest to use. I use a cheap one (CADRE, from CADRE Analytic) and that would do the job, with some messiness in inputting the mass locations. I believe that the integrated ones will do that for you automatically. -- Ed Huntress > This wide ranging news-group list has had apparently on-topic posts > regarding eMachineShop. Feel free to trim. [quoted text clipped - 18 lines] > someone imports it with another package and they get the results that > are like the .pdf file it may be worth mentioning. I tried to load it into my 3D version of TurboCAD and it was a top down 2D I'm not a real 3d user so that may be an issue.... line with of 0in... I think you went from a 3D to a 2D output file type. Martin  SignatureMartin Eastburn @ home at Lion's Lair with our computer lionslair at consolidated dot net NRA LOH, NRA Life NRA Second Amendment Task Force Charter Founder > This wide ranging news-group list has had apparently on-topic posts > regarding eMachineShop. Feel free to trim. [quoted text clipped - 18 lines] > someone imports it with another package and they get the results that > are like the .pdf file it may be worth mentioning. Probably an export problem. The innermost circle is on a Z coordinate of 39370 units. What are the units? Scaling the .dxf, the largest dimension appears to be about 0.76 units. Since it's called "rotor", I assume it spins. Are you concerned about it failing due to centrifugal force? It'd be a pretty nasty part to make from tungsten. Ned Simmons >>This wide ranging news-group list has had apparently on-topic posts >>regarding eMachineShop. Feel free to trim. [quoted text clipped - 15 lines] > > Ned Simmons The export command produces a note that 3D info is lost, but on import most of the 3D info is consistent with the original. I downloaded "Bentleyview" and when I imported the .dxf, I only saw about 3 outlines in 3 planes, much less info than I started with, not enough for a new viewer to know what the object is. I updated the pdf file so it shows standard drafting views instead of a single wire frame. The views have errors in them, but they are enough to visualize the part. This is my first part with eMachineShop, and I drew it upside down --- the pendulums hang down. The two pendulums will fit on either side of a 0.500" cylinder, so the whole thing could be milled from a piece of metal about the size of three nickels stacked on each other. The longest dimension is 0.762" It is actually a miniature "Cavendish balance." The top piece is an optical sensor for position. The hole beneath the center is for support. I want to minimize the mass in the cross beam, but don't want it to fail during handling and assembly. In the meanwhile I looked up iridium. It is only about 1/4 the price of gold, and depending on the reference, it may or may not be denser than osmium. If it is something I can machine it is the best choice. I am thinking of hydraulically pressing it into an injection mold. I've done this with tin and bismuth, but copper is a little beyond my equipment. I think gold should work. (I also looked at Rhodium prices while there. It's pretty expensive at about $1,600 / troy ounce) >In the meanwhile I looked up iridium. It is only about 1/4 the price of >gold, and depending on the reference, it may or may not be denser than >osmium. If it is something I can machine it is the best choice... It's notoriously hard and brittle, which is why it's seldom used except in alloys with other metals. Apparently it can be worked when white-hot. >I am thinking of hydraulically pressing it into an injection mold. Uh, iridium's melting point is about 2450degC. What were you thinking of making the mold out of? Signature"Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | henry@spsystems.net >>In the meanwhile I looked up iridium. It is only about 1/4 the price of >>gold, and depending on the reference, it may or may not be denser than >>osmium. If it is something I can machine it is the best choice... > > It's notoriously hard and brittle, which is why it's seldom used except > in alloys with other metals. Apparently it can be worked when white-hot. [reads] [pauses] Iridium is cheaper than gold? I'm surprised. ... On poking around, that's some wacky pricing. ~$400 around 2000, dropping off steadily thtough 2002, and spending 2003 at an average of under $100. Now still pretty low, but rising. Any idea why? I guess it'd also be tricky to deal with - it's not something most organisations will have any experience of procuring or machining. Signature-Andrew Gray andrew.gray@dunelm.org.uk > [reads] [pauses] > [quoted text clipped - 5 lines] > I guess it'd also be tricky to deal with - it's not something most > organisations will have any experience of procuring or machining. [pauses more] Is it time to buy? >> Iridium is cheaper than gold? I'm surprised. ... On poking around, >> that's some wacky pricing. ~$400 around 2000, dropping off steadily [quoted text clipped - 3 lines] > [pauses more] > Is it time to buy? I don't know, but next time my mother is wondering what to do with her share dividends I'll suggest she look into rare-metal futures ;-) I can't comment on the validity of the data, or indeed how the hell one goes about actually buying iridium, but you might be interested to look at http://www.engelhard.com/eibprices/DPCharts.aspx?MetalName=Iridium - set it to a five-year graph, and look at that drop. Weirdness, not that I pretend to understand these things. Interesting to play around with, mind you. Signature-Andrew Gray andrew.gray@dunelm.org.uk >>> Iridium is cheaper than gold? I'm surprised. ... On poking around, >>> that's some wacky pricing. ~$400 around 2000, dropping off steadily [quoted text clipped - 13 lines] >I pretend to understand these things. Interesting to play around with, >mind you. It's produced as a byproduct of refining nickel. Perhaps someone is .... or it could be that one of it's major uses went into decline. SignatureCliff >>> Iridium is cheaper than gold? I'm surprised. ... On poking around, >>> that's some wacky pricing. ~$400 around 2000, dropping off steadily [quoted text clipped - 6 lines] >I don't know, but next time my mother is wondering what to do with her >share dividends I'll suggest she look into rare-metal futures ;-) The Hunt Brothers still around? <G> >I can't comment on the validity of the data, or indeed how the hell one >goes about actually buying iridium, but you might be interested to look >at http://www.engelhard.com/eibprices/DPCharts.aspx?MetalName=Iridium - >set it to a five-year graph, and look at that drop. Weirdness, not that >I pretend to understand these things. Interesting to play around with, >mind you. Gunner "Veterans, and anyone sensible, take cover when there's incoming. A cloud of testosterone makes a piss poor flack shield." <Offbreed> >>>>Iridium is cheaper than gold? I'm surprised. ... On poking around, >>>>that's some wacky pricing. ~$400 around 2000, dropping off steadily [quoted text clipped - 22 lines] > A cloud of testosterone makes a piss poor flack shield." > <Offbreed> They played with silver. Last heard one was still around. Low profile now. Martin SignatureMartin Eastburn @ home at Lion's Lair with our computer lionslair at consolidated dot net NRA LOH, NRA Life NRA Second Amendment Task Force Charter Founder > I can't comment on the validity of the data, or indeed how the hell one > goes about actually buying iridium, but you might be interested to look > at http://www.engelhard.com/eibprices/DPCharts.aspx?MetalName=Iridium - > set it to a five-year graph, and look at that drop. Weirdness, not that > I pretend to understand these things. It's just that not that many people wanted handheld satellite phones. Oh, wait... Paul >> I can't comment on the validity of the data, or indeed how the hell one >> goes about actually buying iridium, but you might be interested to look [quoted text clipped - 3 lines] > >It's just that not that many people wanted handheld satellite phones. It was sad. That's why I bought their stock, mostly. Oops ... SignatureCliff >>In the meanwhile I looked up iridium. It is only about 1/4 the price of >>gold, and depending on the reference, it may or may not be denser than [quoted text clipped - 7 lines] > Uh, iridium's melting point is about 2450degC. What were you thinking > of making the mold out of? I have pressed tin and bismuth at room temperature in an IR salt pellet press -- 13 mm piston, about 12,000 lbs force. Almost every college chemistry department has both the press, and bismuth. Bismuth flows like water, creeps up the side of the piston, flows into paper thin crevices despite the fact that it is brittle to normal handling. I assume the relevant metric is the rigidity modulus (shear modulus) but would welcome comment from someone who actually knows. Rigidity modulus agrees with your comment that Ir is notoriously difficult. Tungsten is also, IIRC, very difficult. At the other end, gold is known to be malleable, and I have my own experience with tin and bismuth. I found some numbers for a few elements. There is a really big break between W and Pt. You can see from the numbers why I went and priced platinum. Even though price is going to exclude it for this project, it might be the material of choice for some other project. Rather than asking if Pt can be extruded or pressed, it might make more sense to ask what value of rigidity modulus indicates that something is too difficult. Element Density Rigidity Youngs Os 22.61 222 n.a. Ir 22.65 210 528 W 19.30 161 411 Pt 21.25 61 168 Ti 4.57 44 116 Au 19.30 27 78 Sn 7.13 18 50 Bi 9.78 12 32 >Bismuth flows >like water, creeps up the side of the piston, flows into paper thin >crevices despite the fact that it is brittle to normal handling. It's electrical resistance also changes with externally applied magnetic fields IIRC. SignatureCliff |
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