Thermal Epoxy
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From: David Eather on 20 Mar 2010 07:44 On 20/03/2010 6:57 PM, RST Engineering wrote: > On Fri, 19 Mar 2010 19:51:34 -0700, John Larkin > <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >> On Fri, 19 Mar 2010 18:47:25 -0700, RST Engineering >> <jweir43(a)gmail.com> wrote: >> >>> I need to bond a couple of 20 watt metal housing resistors to my >>> satellite dish to melt snow when it forms. I've found the perfect way >>> to do it on a relatively flat surface, but there are no attachment >>> fasteners. >>> >>> Is there a good, weatherproof thermal adhesive that will take a bit of >>> heat out in the weather 365/24/7 and transfer the heat from the metal >>> resistor housing to the dish ironmongery? That can be had for a >>> couple of ounces? Without some sort of huge minimum purchase? >>> >>> I mean, I need what, a couple of dabs? (Dabs, that's a technical >>> term, you'll get used to it.) >>> >>> Thanks, >>> >>> Jim >> >> You don't really need low theta, because you don't care much if the >> resistor body gets a few degrees warmer. Almost all the heat is going >> into the mongery anyhow. So use some strong epoxy. >> >> Or better yet, clamp it somehow and use some silicone grease, or >> almost any grease. Epoxy can fail in situations like this. Long >> stainless pipe clamps are good maybe. > > Ya know, a stainless worm clamp around each resistor with goose grease > between it and the dish arm isn't that bad of an idea. Thanks. > > Jim > Isn't goose grease used for it's heat insulating properties? - you wear it thick on your face if you go out in -40 (better to stick with the silicon stuff)
From: PeterD on 20 Mar 2010 09:09 On Fri, 19 Mar 2010 19:36:09 -0700, D Yuniskis <not.going.to.be(a)seen.com> wrote: >Hi Jim, > >RST Engineering wrote: >> I need to bond a couple of 20 watt metal housing resistors to my >> satellite dish to melt snow when it forms. I've found the perfect way >> to do it on a relatively flat surface, but there are no attachment >> fasteners. > >I assume the dish is metallic? Do you have any idea what sort >of metal it is made from? > >Is there some reason you can't *drill* a hole into the dish >for a pop rivet, or other "nearly flat" fastener (there are some >screw heads that resemble a *nail*)? > >Depending on size, you might want to use a greater number of >smaller (wattage) resistors to spread the heat across the >surface more uniformly (?). > >> Is there a good, weatherproof thermal adhesive that will take a bit of >> heat out in the weather 365/24/7 and transfer the heat from the metal >> resistor housing to the dish ironmongery? That can be had for a >> couple of ounces? Without some sort of huge minimum purchase? >> >> I mean, I need what, a couple of dabs? (Dabs, that's a technical >> term, you'll get used to it.) > >Sure! A Dab is two Smidgeons (in the Northern Hemisphere, that is) What one should do is get some rain gutter heat tape from the local hardware store, and use that instead of some resistors that will require mounting, wiring and a power supply. With heat tape, just attach to the back, maybe put an insulation blanket (fiberglass) and apply power. Use the cuttable heat tape and you can customize the length to allow a full circle around the perimiter of the dish (or two times around, or whatever). And, FYI, a dollop is two dabs, or four smidgeons. Oh, hell, a glob is two dollops...
From: Bill Sloman on 20 Mar 2010 12:20 On Mar 20, 2:47 am, RST Engineering <jwei...(a)gmail.com> wrote: > I need to bond a couple of 20 watt metal housing resistors to my > satellite dish to melt snow when it forms. I've found the perfect way > to do it on a relatively flat surface, but there are no attachment > fasteners. > > Is there a good, weatherproof thermal adhesive that will take a bit of > heat out in the weather 365/24/7 and transfer the heat from the metal > resistor housing to the dish ironmongery? That can be had for a > couple of ounces? Without some sort of huge minimum purchase? > > I mean, I need what, a couple of dabs? (Dabs, that's a technical > term, you'll get used to it.) Set epoxy resin has a "glass transition temperature" above which it isn't all that hard, and no use as an adhesive. For most epoxy resin, this is around 63C. There are high temperature epoxy resins for which the glass transisiton temperature - after setting - is around 120C. I had to look hard and long to find one back in 2002, and I can't remember any of the details. Even with 120C epoxy resin, you won't want to run your resistors anywhere near their maximum rated temperature. -- Bill Sloman, Nijmegen
From: WangoTango on 20 Mar 2010 13:10 In article <1dl8q516k88j8ld0e4fm7re36rjodjc1d7(a)4ax.com>, jjlarkin(a)highNOTlandTHIStechnologyPART.com says... > On Fri, 19 Mar 2010 21:37:14 -0700, Archimedes' Lever > <OneBigLever(a)InfiniteSeries.Org> wrote: > > >On Fri, 19 Mar 2010 19:51:34 -0700, John Larkin > ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > > > >>Epoxy can fail in situations like this. > > > > That depends entirely on the properties of the particular epoxy being > >used. Duh. > > > Thank you for another brilliant insight. > > John You didn't know his Super Hero personality it Captain Obvious?
From: Jim Yanik on 20 Mar 2010 13:25
PeterD <peter2(a)hipson.net> wrote in news:d3i9q5t5lr3ttkce4sg7226hpr05q9eqt8(a)4ax.com: > What one should do is get some rain gutter heat tape from the local > hardware store, and use that instead of some resistors that will > require mounting, wiring and a power supply. With heat tape, just > attach to the back, maybe put an insulation blanket (fiberglass) and > apply power. Use the cuttable heat tape and you can customize the > length to allow a full circle around the perimiter of the dish (or two > times around, or whatever). Plus you get the protection of circuit breakers and UL approval... OTOH,you just made a nice path for lightning to enter your home. ;-( > > And, FYI, a dollop is two dabs, or four smidgeons. Oh, hell, a glob is > two dollops... > -- Jim Yanik jyanik at localnet dot com |