Fine wire tensile strengths?
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From: Spehro Pefhany on 5 Aug 2010 11:04 On Thu, 05 Aug 2010 05:16:21 -0700, "JosephKK"<quiettechblue(a)yahoo.com> wrote: >On Fri, 30 Jul 2010 22:49:58 -0400, Spehro Pefhany ><speffSNIP(a)interlogDOTyou.knowwhat> wrote: > >>On Fri, 30 Jul 2010 19:01:37 -0700 (PDT), the renowned "Ken S. Tucker" >><dynamics(a)vianet.on.ca> wrote: >> >>>I've been asked to 'light-up' aircraft models, such as, >>> >>>http://www.flickr.com/photos/35156618(a)N03/4754110575/ >>> >>>It is suspended from a rope. >>>I need to use very fine 120V wire (like magnetic wire), >>>the model uses 8# test monofilament right now and weighs >>>1/2 # , but a strong wind requires that 8# test. >>>Is there a table that gives wire gauge & tensile strength? >>>The current will likely be a max of 1/2 amp. >>>Ken >> >>You can pick the material and look up the yield strength. >> >>In Imperial units, maybe steel wire (like music wire) you could use >>300,000 PSI, say. >> >>So for something that would break at 20lbs you would need >>7E-5 in^2, which is about 0.01" diameter, if I did the sums correctly. >> >>You should calculate and test the strength and self-heating effect >>before using it, of course. >> >> >>Best regards, >>Spehro Pefhany > >OK. diameter for wire gauges found here: > >http://www.interfacebus.com/Copper_Wire_AWG_SIze.html > >Yeild strength for several alloys can be found here: > >http://www.copper.org/resources/properties/144_8/144_8.html > > >Using 60,000 psi for yeild strength we want 30,000 or 40,000 psi for >test strength. Thus to get 8 lb test we need 8/30,000 ~= 266 E-6 >square inches. Solved for diameter D=sqrt(A/(2*pi)) for >A=sqrt(266/6.28) about 6.5 mils. Thus from the table, 2 #39 enameled >magnet wire lightly twisted ought to provide the mechanical strength >needed and a complete circuit and handle 18 mA without trouble. AFAIUI, usually "x pound test" mono line has an actual typical breaking point 20-100+% higher than x, so more safety margin might be required.
From: Nunya on 5 Aug 2010 11:11 On Aug 5, 5:51 am, "JosephKK"<quiettechb...(a)yahoo.com> wrote: > On Mon, 2 Aug 2010 09:47:30 -0700 (PDT), "Ken S. Tucker" > > > > <dynam...(a)vianet.on.ca> wrote: > >On Aug 2, 2:13 am, Uwe Hercksen <herck...(a)mew.uni-erlangen.de> wrote: > >> Ken S. Tucker schrieb: > > >> > I need to use very fine 120V wire (like magnetic wire), > >> > the model uses 8# test monofilament right now and weighs > >> > 1/2 # , but a strong wind requires that 8# test. > >> > Is there a table that gives wire gauge & tensile strength? > >> > The current will likely be a max of 1/2 amp. > > >> Hello, > >> you might need a combination of steel wire for tensile strength and > >> copper wire for low resistance to the electric current. To keep the > >> weight low, replace copper with aluminium. > >> Bye > > >Hi > >We did an experiment yesterday, we connected a AWG 36 wire > >in series with a 100W bulb, dimmer and Current meter. > >(The AWG 36 wire was carefully wrapped around a couple of > >3/16" bolts and carefully snugged with nuts, a poor man's fuse). > > >As we turned up the dimmer we expected the wire to fuse but it > >didn't, it took the full current supplying a 100W bulb, I kid you not, > >that's about 0.9 amps! > >We got the wire from unwrapping a reed switch and checked the > >gauge twice by tensile strength. > >I invite anyone else to try the experiment. > >Regards > >Ken > > Alas, the temperature rise on the wire is far more than i care for. I > get over 200 C. That could be enough to cause problems with plastics. Copper also becomes a bit more 'elastic' as temps go up. Batteries and LEDs and use the wire to operate a trickle charger for the batteries. Take the wires off between photo sessions. That way, you can go back to high tensile strength, fine gauge piano wire, which has been specifically crafted to endure tensile force. Paint it neutral gray, if needed.
From: JosephKK on 6 Aug 2010 00:14
On Thu, 05 Aug 2010 11:04:14 -0400, Spehro Pefhany <speffSNIP(a)interlogDOTyou.knowwhat> wrote: >On Thu, 05 Aug 2010 05:16:21 -0700, >"JosephKK"<quiettechblue(a)yahoo.com> wrote: > >>On Fri, 30 Jul 2010 22:49:58 -0400, Spehro Pefhany >><speffSNIP(a)interlogDOTyou.knowwhat> wrote: >> >>>On Fri, 30 Jul 2010 19:01:37 -0700 (PDT), the renowned "Ken S. Tucker" >>><dynamics(a)vianet.on.ca> wrote: >>> >>>>I've been asked to 'light-up' aircraft models, such as, >>>> >>>>http://www.flickr.com/photos/35156618(a)N03/4754110575/ >>>> >>>>It is suspended from a rope. >>>>I need to use very fine 120V wire (like magnetic wire), >>>>the model uses 8# test monofilament right now and weighs >>>>1/2 # , but a strong wind requires that 8# test. >>>>Is there a table that gives wire gauge & tensile strength? >>>>The current will likely be a max of 1/2 amp. >>>>Ken >>> >>>You can pick the material and look up the yield strength. >>> >>>In Imperial units, maybe steel wire (like music wire) you could use >>>300,000 PSI, say. >>> >>>So for something that would break at 20lbs you would need >>>7E-5 in^2, which is about 0.01" diameter, if I did the sums correctly. >>> >>>You should calculate and test the strength and self-heating effect >>>before using it, of course. >>> >>> >>>Best regards, >>>Spehro Pefhany >> >>OK. diameter for wire gauges found here: >> >>http://www.interfacebus.com/Copper_Wire_AWG_SIze.html >> >>Yeild strength for several alloys can be found here: >> >>http://www.copper.org/resources/properties/144_8/144_8.html >> >> >>Using 60,000 psi for yeild strength we want 30,000 or 40,000 psi for >>test strength. Thus to get 8 lb test we need 8/30,000 ~= 266 E-6 >>square inches. Solved for diameter D=sqrt(A/(2*pi)) for >>A=sqrt(266/6.28) about 6.5 mils. Thus from the table, 2 #39 enameled >>magnet wire lightly twisted ought to provide the mechanical strength >>needed and a complete circuit and handle 18 mA without trouble. > >AFAIUI, usually "x pound test" mono line has an actual typical >breaking point 20-100+% higher than x, so more safety margin might be >required. Gosh, i am at 50% of _yeild_ strength already. Do you really think i need more margin? |