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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 26th Oct 2020, 4:00 pm   #21
frankmcvey
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Default Re: Small Insulated Tubes - Any Good Source?

Fibreglass tube? Not too expensive.

Cheers,

Frank
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Old 26th Oct 2020, 5:50 pm   #22
merlinmaxwell
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Default Re: Small Insulated Tubes - Any Good Source?

How about a making a mould and casting the new resistor in plaster of paris? That way all the little fiddly bits on the ends could be replicated for how ever many you want.
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Old 26th Oct 2020, 5:58 pm   #23
ms660
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Default Re: Small Insulated Tubes - Any Good Source?

Das Pronto?

Lawrence.
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Old 26th Oct 2020, 8:21 pm   #24
MotorBikeLes
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Default Re: Small Insulated Tubes - Any Good Source?

Not a pottery "enthusiast", but once a ceramic technologist, so maybe I can add a bit.
You can not easily make a clay based ceramic ON a glass tube, plaster former or whatever, as it will simply crack as it shrinks on drying.
You could of course make a two part plaster of Paris mould, and cast your tubes (just like high class bone china cups).
However, if you have any machinery, you could make a "stupid" pug, or extrusion machine. A proper "pug" has an auger like a hand mincer, with a reduced orifice but which has a central plug, so tubes can be continuously extruded.
The so called "Stupid" is where you have a cylinder with a screw piston pushing the clay out through the nozzle. I can only do small batches, then needs retracting, opening, refilling and repeating.
Portland cement? Yes. Better still, "Ciment Fondue", or whatever is the current trade name. That is an aluminous cement, not a siliceous cement like Portland. It will withstand VERY high temperatures.
Glass tubing? We used to get Pyrex glass tubing in various sizes. We used thick wall, 3/4" for rollers on various of our glaze spraying machines. Joe Muggins used to be the one who cut (broke) it to length for the fitters to use.
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Old 26th Oct 2020, 10:14 pm   #25
Silicon
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Default Re: Small Insulated Tubes - Any Good Source?

Apparently Milliput epoxy putty is heat resistant and non conductive when set.

Ideally we need a material with good thermal conductivity if we intend to bury a resistor inside it.
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Old 27th Oct 2020, 6:47 am   #26
jamesinnewcastl
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Default Re: Small Insulated Tubes - Any Good Source?

Hi All

Thanks for all the replies! I thought I might not get any! All good ideas, many the wrong size sadly. Andy, B&Q have 3 and 5mm tubing (quaintly called Eliza Tinsley) Kevin and Kens styrene tubing look great. Ed, the melting point is 240 degrees C apparently, but I guess it might soften before that. Of course the candle-in-a-box scenario is always a warning to those who dismiss heat out of hand!

Lathe - yes! But as soon as I started looking I couldn't stop at 'small model making lathe'.....

Attached are pics of the first attempt at moulding a resistor, I found it tricky to do and the amount of fettling was too much and the body had all sorts of holes in - admittedly I only had one go! But as Silicon points out it it might have been the candle-in-a-box! Also pics of the result using carbon fibre tubes that some idiot had tried.

I'll put up the final result when I get to it, but thanks to all again!

James
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Last edited by jamesinnewcastl; 27th Oct 2020 at 7:05 am.
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Old 27th Oct 2020, 8:36 am   #27
Syrinx1
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Default Re: Small Insulated Tubes - Any Good Source?

What about polymer clay or 2 part epoxy clay?
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Old 27th Oct 2020, 2:51 pm   #28
G6Tanuki
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Default Re: Small Insulated Tubes - Any Good Source?

Larger branches of B&Q used to sell white GRP tube that was about 7mm diameter; I used a length of it [painted black] to replicate the old 1930s Ebonite 'Aerial lead-in' windowframe-mounted tubes with a brass threaded rod down the middle.

The hole would - from memory - be about OK to take a modern 1-Watt carbon-film resistor.
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