The Natural Philosopher wrote:
Matty F wrote:
On Mar 13, 8:56 pm, Stuart Noble wrote:
Matty F wrote:
Apart from mending broken glasses and suchlike, you can make quite big
things using epoxy resin and a mould made from bits of old plastic
pipe:
http://i42.tinypic.com/mkdx0k.jpg
That's the old insulator on the right.
The epoxy turns up nicely on a lathe as long as you don't add silica
or anything that blunts metal tools.
That's mighty impressive. Which product did you use? I've done similar
things with polyester, but nothing as precise as that.

It's a very liquid epoxy resin with a hardener added in a 5:1 ratio.
The amounts have to be precise or it won't set. I coloured it with
blue and yellow pigment because I didn't have green.


Then it possibly isn't epoxy,.

Epoxy is not 'hardened' by a catalytic hardener,. It sets by direct
chemical reaction between two precisley mixed constituents. The mixture
ratio is crucial.

I tried a fast hardener but it got very hot and started smoking so I
had to dowse it in the sink.

That's very polyester like behaviour.


The next mould leaked like a sieve all
over the bench and I had to keep scraping the epoxy up and putting it
back in the top. The third one was successful. I patched the others up
and here they all a

http://i41.tinypic.com/ea1u1s.jpg

The old insulators have had a hard life. If you are very clever you'll
know what they are and why they are broken!

Beware of the propensity of resins like these to carbonise and track.

Structurally its a good material, but I have some reservations about
electrical properties.

Last job I did with epoxy it began thermal runaway, due to the size of
the thing. It does that if you put too much of it in one lump.
Solution was to submerge in cold water once it began to set. Fillers
reduce the tendency simply because there's then less epoxy in a given
volume of mix.


NT