Thermal Epoxy

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 (?).

Sure! A Dab is two Smidgeons (in the Northern Hemisphere, that is)

A Smidge is also used in the Southern Hemisphere, though the size of the smidge is often job dependent.

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.

John

"Royston Vasey" wrote in news:6fSdnUdhEryiqjnWnZ2dnUVZ snipped-for-privacy@westnet.com.au:

arctic silver or arctic alumina,which is cheaper,but not as thermally conductive.

DAGS.

Have you ever tried JB Weld. It's epoxy filled with iron (I think... it's filled with something.) It's strong and takes heat. I used some to patch up some cracks on the engine block of my tractor. Still working after 7+years.... (no water in the oil.) Great stuff, but it is magnetic.

George H.

You should just buy the stuff they wrap around water pipes to keep them from freezing. Also, you should apply "Rain-X" to the surface of the dish. That will allow the stuff to slide right off, once you free it up.

Except that the hi perf stuff you want ALWAYS has a minimum amount, even for the "sample size".

The stuff you want is silica filled Stycast, which is a hard epoxy room temp cure, OR you could use Silver filled epoxy that the chip bonder boys use. It is from EPOTEK, and is called H20E. It is, however, also electrically conductive

The stycast can be bought in a pint sized container. You want the thermal blue variety, but you also would want to fill it up with a filler that has good thermal properties.

The Epotek is VERY expensive. That same pint will likely be over $500. Silver ain't cheap, and fine grained Silver powder costs way more than raw Silver. Anyway, the stuff is by no means cheap.

The derivative term is "Smidgeon".

What was the original? What... Small Pidgeon?

Actually, it came from "smite" originally.

That depends entirely on the properties of the particular epoxy being used. Duh.

And neither are "epoxy". Both remain "wet", and neither have any adhesive properties..

Thank you for another brilliant insight.

John

"RST Engineering" kirjoitti viestissä: snipped-for-privacy@4ax.com...

There are also PTC heater foils like those from Conflux. Might be easier to attach. Mouser sells them.

Yessir, steel. What difference does that make?

RTFQ.

Means nothing to the question.

Lends nothing to the discussion.

Jim

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

Screw them to the back of the dish at the top.... Deform the dish a little so it is flat.

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)

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...

The only true thermal epoxy contains finely powdered metal as a suspensoid; two varieties: (electrically) conductive and non-conductive. All else is thermally speaking, crap.

And squints?

-- "Electricity is of two kinds, positive and negative. The difference is, I presume, that one comes a little more expensive, but is more durable; the other is a cheaper thing, but the moths get into it." (Stephen Leacock)

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