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.

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.

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.

Impressive piece of work!


--
Dave - The Medway Handyman
www.medwayhandyman.co.uk

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.

The epoxy doesn't stick to the plastic pipe that goes under a sink.
That's actually where the pipe I used came from!

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

"Matty F" wrote in message
...
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.

If you don't add some glass filler it doesn't last long if its subject to
vibration IME.
I am talking about stuff with a design life of 20+ years though.

On Mar 13, 10:01 pm, "dennis@home"
wrote:
"Matty F" wrote in message

...

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.

If you don't add some glass filler it doesn't last long if its subject to
vibration IME.
I am talking about stuff with a design life of 20+ years though.

Aargh now you tell me! It is subject to extreme vibration. And every
now and then a man in a 25 ton vehicle hits the insulator with a big
steel pole!

On 13 Mar, 03:15, Matty F wrote:

The epoxy turns up nicely on a lathe as long as you don't add silica
or anything that blunts metal tools.

Phenolic microballoons (from West System) are good as a filler if you
need to machine it afterwards.

In article ,
Matty F writes:

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.

The epoxy doesn't stick to the plastic pipe that goes under a sink.
That's actually where the pipe I used came from!

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

My father used to use epoxy for encasing electrical assemblies,
some of these very large. One of the key factors is working out
what setting time you need so the body of the epoxy can conduct
the heat away at a rate which is fast enough to not over-heat.
Epoxy isn't a good heat conductor anyway, and with the reaction
being exothermic, and with increasing temperature making it run
faster, it's very easy to have to run away, and wreck whatever
you're encapsulating and have the epoxy crack itself. I believe
some of the larger ones were designed to take weeks to set, in
order to stay cool and stable during the process.

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!

I was wondering.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Matty F wrote:

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

Well, from your other post, I would guess that it is part of the
overhead electrical supply system for a tram.

Chris
--
Chris J Dixon Nottingham UK


Have dancing shoes, will ceilidh.

On Mar 13, 11:06 pm, Chris J Dixon wrote:
Matty F wrote:
The old insulators have had a hard life. If you are very clever you'll
know what they are and why they are broken!

Well, from your other post, I would guess that it is part of the
overhead electrical supply system for a tram.

Yes it holds the wire up!

On Mar 13, 11:01 pm, Andy Dingley wrote:
On 13 Mar, 03:15, Matty F wrote:

The epoxy turns up nicely on a lathe as long as you don't add silica
or anything that blunts metal tools.

Phenolic microballoons (from West System) are good as a filler if you
need to machine it afterwards.

The epoxy seems to be very strong. The bolt inside has a flange so
that even if all the insulation broke off it the bolt cannot pull
through the support that is holding it up. In that case the circuit
breaker for the power supply would trip.
The old insulation is made from asbestos and maybe mica and some
horrible compound that breaks easily when I hit it with a hammer. The
epoxy does not break when I hit it with a hammer!

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.

On Mar 13, 11:02 pm, andrew@a20 (Andrew Gabriel) wrote:

My father used to use epoxy for encasing electrical assemblies,
some of these very large. One of the key factors is working out
what setting time you need so the body of the epoxy can conduct
the heat away at a rate which is fast enough to not over-heat.
Epoxy isn't a good heat conductor anyway, and with the reaction
being exothermic, and with increasing temperature making it run
faster, it's very easy to have to run away, and wreck whatever
you're encapsulating and have the epoxy crack itself. I believe
some of the larger ones were designed to take weeks to set, in
order to stay cool and stable during the process.

The largest castings I made set in a few hours, although they might
take a day to get really hard.
I made thousands of these 40 years ago using epoxy resin in silcone
rubber moulds.
I added a huge amount of silica flour to the mix. That made it much
cheaper and it was a better heat conductor and slowed the reaction
down. Red oxide was added to the hardener to show that it was mixed
well. It also looked more attractive than grey!
Here's a 33kV audio transformer and a couple of current transformers.
The Buddha is polyester resin.
http://i43.tinypic.com/osfh95.jpg

On Mar 14, 12:01 am, The Natural Philosopher wrote:
Matty F wrote:

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.

That's what I just said. It is epoxy.

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.

I made 33kV insulators using epoxy resin 40 years ago and they are
still fine.
I tested insulation to 80kV and epoxy was almost the best insulator
there is.

Here's a 33kV audio transformer and a couple of current transformers.
The Buddha is polyester resin.

33 kV!.. Whatever was that for electrostatic speakers or an AM
transmitter?...


http://i43.tinypic.com/osfh95.jpg

--
Tony Sayer

On Fri, 13 Mar 2009 11:01:05 +0000, The Natural Philosopher
wrote:

Matty F wrote:

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.

So why don't you consider '5:1' to be precisely mixed? There are at
least two major manufacturers of epoxy resin systems that specify a
5:1 ratio, West and SPS, there are also resin systems with 3:2, 5:2
and 1:1 ratios.

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.

Epoxy can also exotherm, when this happens, other than a lack of
styrene smell what you observe during such an occurrence is identical,
and the precautions taken to avoid exotherm are identical regardless
of whether you use polyester or epoxy resins. You could take any one
of dozens of resins of varying chemistry and by intentionally
introducing process errors during mixing or application and they would
all without exception exotherm with an ambient temperature of 15 deg
C, yet you could also mix and apply those same resins in a different
manner and they wouldn't exotherm when the ambient temperature was
raised to 25 deg C.

Also a 'fast hardener', when used as specified by the manufacturer is
no more prone to exotherm than a 'slow hardener'. All it requires is
attention to ambient temperature, mix volume, mix vessel geometry,
application vessel geometry, layup thickness, and curing temperature.

--

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

On Mar 14, 1:41 am, tony sayer wrote:
Here's a 33kV audio transformer and a couple of current transformers.

33 kV!.. Whatever was that for electrostatic speakers or an AM
transmitter?...

http://i43.tinypic.com/osfh95.jpg

The audio transformer was used for telephone wires that ran around the
country underneath 33kV powerlines using the same pylons. Every now
and then the 33kV wires would fall down on to the telephone line and
the telephone girls used to complain about their telephones exploding.
There were circuit breakers and fuses but those took too long to
operate. The transformer was required to withstand 33kV between
primary and secondary for up to a minute, as well as passing 30,000 Hz
plus 17 Hz ringing frquency.
This it did very well. I've always though there must be a use for such
a transformer these days. It could pass up to 100,000 Hz without too
much loss. It was rated at 100 watts. The production version had a
toroidal core of grain-oriented silicon steel. I am the only person
alive who knows why it works at such a high frequency, and the special
insulation that was successful after many prototypes failed. The
picture is of prototype 1, of 12.

In article
s.com, Matty F scribeth thus
On Mar 14, 1:41 am, tony sayer wrote:
Here's a 33kV audio transformer and a couple of current transformers.

33 kV!.. Whatever was that for electrostatic speakers or an AM
transmitter?...

http://i43.tinypic.com/osfh95.jpg

The audio transformer was used for telephone wires that ran around the
country underneath 33kV powerlines using the same pylons. Every now
and then the 33kV wires would fall down on to the telephone line and
the telephone girls used to complain about their telephones exploding.
There were circuit breakers and fuses but those took too long to
operate. The transformer was required to withstand 33kV between
primary and secondary for up to a minute, as well as passing 30,000 Hz
plus 17 Hz ringing frquency.

Right!.. This surely wasn't in the UK?. I know they sling wires on low
voltage 230/415 lines but can't say I've ever seen them on anything
higher volts...

This it did very well. I've always though there must be a use for such
a transformer these days. It could pass up to 100,000 Hz without too
much loss. It was rated at 100 watts. The production version had a
toroidal core of grain-oriented silicon steel. I am the only person
alive who knows why it works at such a high frequency, and the special
insulation that was successful after many prototypes failed. The
picture is of prototype 1, of 12.


--
Tony Sayer

Matty F submitted this idea :
I am the only person
alive who knows why it works at such a high frequency,

...and that would be something to do with the MOD or Civil Defence?

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

On Mar 14, 11:39 am, tony sayer wrote:
In article
s.com, Matty F scribeth thus



On Mar 14, 1:41 am, tony sayer wrote:
Here's a 33kV audio transformer and a couple of current transformers.

33 kV!.. Whatever was that for electrostatic speakers or an AM
transmitter?...

http://i43.tinypic.com/osfh95.jpg

The audio transformer was used for telephone wires that ran around the
country underneath 33kV powerlines using the same pylons. Every now
and then the 33kV wires would fall down on to the telephone line and
the telephone girls used to complain about their telephones exploding.
There were circuit breakers and fuses but those took too long to
operate. The transformer was required to withstand 33kV between
primary and secondary for up to a minute, as well as passing 30,000 Hz
plus 17 Hz ringing frquency.

Right!.. This surely wasn't in the UK?. I know they sling wires on low
voltage 230/415 lines but can't say I've ever seen them on anything
higher volts...

It was in New Zealand in about 1968. In those days there were
horrendous charges for nationwide toll calls, so the power company
(there was only one, the NZED) ran their own telephone lines.
Of course there were 110kV/220kV wires as well but the telephone lines
wouldn't go anywhere near those!
These days nationwide calls are negligible in cost, and they'd use
fibre anyway.

On Mar 14, 12:17 pm, Harry Bloomfield
wrote:
Matty F submitted this idea :

I am the only person
alive who knows why it works at such a high frequency,

..and that would be something to do with the MOD or Civil Defence?

No it's just a commercial secret which I discovered! However I should
probably give it away before too much longer. So what use is a high-
quality audio transformer these days?

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Matty F
saying something like:

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

If by 'very clever', you mean 'have seen them before and are not
psychic', then no.

On Mar 14, 8:34 pm, Grimly Curmudgeon
wrote:
We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Matty F
saying something like:

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

If by 'very clever', you mean 'have seen them before and are not
psychic', then no.

"Moderately clever" could include spotting that the answer has already
been correctly guessed and confirmed.

On Fri, 13 Mar 2009 22:39:33 +0000, tony sayer wrote:

Right!.. This surely wasn't in the UK?. I know they sling wires on low
voltage 230/415 lines but can't say I've ever seen them on anything
higher volts...

Predominantly on lv but there were isolated instances where they're on 11kv
lines. If they are attached to 11kv circuits, the steelwork at the top of
the pole is earthed. Never on 33kv - although there are a few dual circuit
lines where multicore protection circuits are slung as a catenary beneath
the power circuits.


--
The Wanderer

I'm retired. I was tired yesterday and I'm tired again today.

After serious thinking Matty F wrote :
On Mar 14, 12:17 pm, Harry Bloomfield
wrote:
Matty F submitted this idea :

I am the only person
alive who knows why it works at such a high frequency,

..and that would be something to do with the MOD or Civil Defence?

No it's just a commercial secret which I discovered! However I should
probably give it away before too much longer. So what use is a high-
quality audio transformer these days?

Multiplex?

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

In article ,
Matty F writes:
On Mar 14, 1:41 am, tony sayer wrote:
Here's a 33kV audio transformer and a couple of current transformers.

33 kV!.. Whatever was that for electrostatic speakers or an AM
transmitter?...

http://i43.tinypic.com/osfh95.jpg

The audio transformer was used for telephone wires that ran around the
country underneath 33kV powerlines using the same pylons. Every now
and then the 33kV wires would fall down on to the telephone line and
the telephone girls used to complain about their telephones exploding.

One of the regulars on uk.telecom ~20 years ago had an incident
where their phone cable snapped in bad weather someway down the
road, and the loose end blew onto 33kV conductors (not on the
same pole). Their phone and several other things blew up, but
they were unharmed. There was a Health and Safety investigation
of the incident.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On Fri, 13 Mar 2009 14:57:05 -0700 (PDT), Matty F
wrote:

It could pass up to 100,000 Hz without too
much loss. It was rated at 100 watts. The production version had a
toroidal core of grain-oriented silicon steel. I am the only person
alive who knows why it works at such a high frequency

Because it was used for simultaneous multiple calls with a carrier
group system.


--

In article
..com, Matty F scribeth thus
On Mar 14, 12:17 pm, Harry Bloomfield
wrote:
Matty F submitted this idea :

I am the only person
alive who knows why it works at such a high frequency,

..and that would be something to do with the MOD or Civil Defence?

No it's just a commercial secret which I discovered! However I should
probably give it away before too much longer. So what use is a high-
quality audio transformer these days?

Electrostatic speakers 'tho they don't need -that- many volts!..
--
Tony Sayer

On Mar 14, 11:53 pm, Mike wrote:
On Fri, 13 Mar 2009 14:57:05 -0700 (PDT), Matty F

wrote:
It could pass up to 100,000 Hz without too
much loss. It was rated at 100 watts. The production version had a
toroidal core of grain-oriented silicon steel. I am the only person
alive who knows why it works at such a high frequency

Because it was used for simultaneous multiple calls with a carrier
group system.

Actually it wasn't. But I was referring to the special core design
which allowed it to pass frequencies of up to 100,000 Hz. I'm no
expert on audio transformers but I'm told that they usually start
dropping off above 20,000 to 30,000 Hz.

On Mar 14, 11:58 pm, tony sayer wrote:
In article
.com, Matty F scribeth thus

So what use is a high-
quality audio transformer these days?

Electrostatic speakers 'tho they don't need -that- many volts!..

That's a thought. But surely a conventional audio transformer should
be able to do the job OK.

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Matty F
saying something like:

If by 'very clever', you mean 'have seen them before and are not
psychic', then no.

"Moderately clever" could include spotting that the answer has already
been correctly guessed and confirmed.

Sorry, it doesn't detract from the fatuousness of the question.

On Mar 13, 10:06 pm, Chris J Dixon wrote:
Matty F wrote:
The old insulators have had a hard life. If you are very clever you'll
know what they are and why they are broken!

Well, from your other post, I would guess that it is part of the
overhead electrical supply system for a tram.

Here's the arrangement for holding up the wire on a corner:
http://i43.tinypic.com/fvzbsz.jpg

The clamps on the left hold the wire. The insulator is held within the
brass casting. The brass cap on top screws down on the insulator,
keeping it rigid. An earthed steel cable is attached to the brass
casting at the same height as the wire so that it does not twist.
The wire is 600v DC potential.