Polytetrafluorethylene (plastic insulation history) [message #353508] |
Wed, 27 September 2017 00:38 |
hancock4
Messages: 6746 Registered: December 2011
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Our high tech world would not exist without durable electrical
insulation materials. They must not only prevent current from
leaking, but also be durable enough so that they don't tear or
break in normal handling or conditions. They also must protect
the conductor from physical damage. Bad insulation will cause
shocks, shorts, and fires.
Historically, rubber, textiles, and paper were used as insulation.
But then plastics came along and revolutionized insulation.
The Western Union Technical Review did a study of insulating
materials. While undoubtedly the materials have changed (I think
some of the plastics used originally are now known to be toxic),
some of the tests for both electrical properties (dielectric
strength, inductance resistance, power constant, and surface
resistivity are probably still applicable. Further, the physical
tests for abrasion resistance, cold, heat, solvents, flammability,
and tensile strength are probably still applicable.
http://massis.lcs.mit.edu/telecom-archives/archives/technica l/western-union-tech-review/07-3/p081.htm
I had an old fan that still worked, but the wire insulation was
so rotted everywhere that I had to discard it. Likewise with
some old radios and lamps.
As an aside, many of today's plastics were developed by companies
like DuPont and Rohm & Haas. Sadly, those companies have been
bought out. At present, DuPont is being dismembered.
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Re: Polytetrafluorethylene (plastic insulation history) [message #353547 is a reply to message #353508] |
Wed, 27 September 2017 15:12 |
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Originally posted by: andrew
In article <69b44ca7-a433-48c2-98aa-cf5d1b770ffc@googlegroups.com>,
hancock4@bbs.cpcn.com writes:
> Our high tech world would not exist without durable electrical
> insulation materials. They must not only prevent current from
> leaking, but also be durable enough so that they don't tear or
> break in normal handling or conditions. They also must protect
> the conductor from physical damage. Bad insulation will cause
> shocks, shorts, and fires.
>
> Historically, rubber, textiles, and paper were used as insulation.
Where paper was concerned the Post Office (forerunner to BT)
was always careful to emphasise the cables were air insulated,
paper spaced. The larger multi-core paper-spaced cables where
continuously pressurised with dry compressed air where they
left the telephone exchange, to keep moisure out of the cables.
Paper was also used in power cables, but again it was a spacer.
The insulation was usually wax, tar/pitch, or oil impregation.
> But then plastics came along and revolutionized insulation.
>
> The Western Union Technical Review did a study of insulating
> materials. While undoubtedly the materials have changed (I think
> some of the plastics used originally are now known to be toxic),
> some of the tests for both electrical properties (dielectric
> strength, inductance resistance, power constant, and surface
> resistivity are probably still applicable. Further, the physical
> tests for abrasion resistance, cold, heat, solvents, flammability,
> and tensile strength are probably still applicable.
>
> http://massis.lcs.mit.edu/telecom-archives/archives/technica l/western-union-tech-review/07-3/p081.htm
>
> I had an old fan that still worked, but the wire insulation was
> so rotted everywhere that I had to discard it. Likewise with
> some old radios and lamps.
>
> As an aside, many of today's plastics were developed by companies
> like DuPont and Rohm & Haas. Sadly, those companies have been
> bought out. At present, DuPont is being dismembered.
>
>
>
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
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Re: Polytetrafluorethylene (plastic insulation history) [message #353749 is a reply to message #353688] |
Mon, 02 October 2017 17:43 |
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Originally posted by: Chris
On 10/01/17 15:44, Gareth's Upstairs Computer wrote:
> <hancock4@bbs.cpcn.com> wrote in message
> news:69b44ca7-a433-48c2-98aa-cf5d1b770ffc@googlegroups.com...
>>
>> Historically, rubber, textiles, and paper were used as insulation.
>
>
> Pressspahn?
>
> Empire Cloth?
>
> (Both off the top of my head)
>
>
Empire cloth was widely use for transformer insulation, between
layers and in motors, though waxed card was also used. Remember a family
member rewinding a 1/4 HP AC motor by hand and using empire
cloth and wooden formers to shape the coils, around 1956. Worked
well and fitted to push style lawnmower, probably one of the
first electric mowers in the country at the time.
Mica sheet also used for some applications...
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Re: Polytetrafluorethylene (plastic insulation history) [message #353853 is a reply to message #353749] |
Thu, 05 October 2017 09:06 |
Jorgen Grahn
Messages: 606 Registered: March 2012
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Senior Member |
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On Mon, 2017-10-02, Chris wrote:
> On 10/01/17 15:44, Gareth's Upstairs Computer wrote:
>> <hancock4@bbs.cpcn.com> wrote in message
>> news:69b44ca7-a433-48c2-98aa-cf5d1b770ffc@googlegroups.com...
>>>
>>> Historically, rubber, textiles, and paper were used as insulation.
>>
>>
>> Pressspahn?
>>
>> Empire Cloth?
>>
>> (Both off the top of my head)
>
> Empire cloth was widely use for transformer insulation, between
> layers and in motors, though waxed card was also used. Remember a family
> member rewinding a 1/4 HP AC motor by hand and using empire
> cloth and wooden formers to shape the coils, around 1956.
Dad worked repairing motors, and they used shellac[0] a lot for
insulating the coils, well into the 1980s I think.
/Jorgen
[0] Or possibly some other resin they referred to as shellac out of habit.
--
// Jorgen Grahn <grahn@ Oo o. . .
\X/ snipabacken.se> O o .
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Re: Polytetrafluorethylene (plastic insulation history) [message #353876 is a reply to message #353853] |
Thu, 05 October 2017 20:40 |
hancock4
Messages: 6746 Registered: December 2011
Karma: 0
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Senior Member |
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On Thursday, October 5, 2017 at 9:06:14 AM UTC-4, Jorgen Grahn wrote:
> Dad worked repairing motors, and they used shellac[0] a lot for
> insulating the coils, well into the 1980s I think.
I'm not an engineer by any means. But I suspect a motor winding
needn't be concerned about induction or capacitance as would an
electronic device or a communications cable, so the insulation
wasn't as critical.
Depending on the specific application of the motor, I would wonder
if shellac would hold up if the motor got hot. Some motors, of
course, actually only work for limited time frames and then are
idle, so they don't as warm. I think that was a realization that
allowed cash register motors to be small--they only ran for a brief
period of time, then stopped. In contrast, a motor for an air
conditioner or appliance would run a lot longer.
I hate to say, but another issue might be expected useful life.
Maybe they only expected the motor to last 5-10 years.
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Re: Polytetrafluorethylene (plastic insulation history) [message #353909 is a reply to message #353876] |
Fri, 06 October 2017 13:53 |
Jorgen Grahn
Messages: 606 Registered: March 2012
Karma: 0
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Senior Member |
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On Fri, 2017-10-06, hancock4@bbs.cpcn.com wrote:
> On Thursday, October 5, 2017 at 9:06:14 AM UTC-4, Jorgen Grahn wrote:
>
>> Dad worked repairing motors, and they used shellac[0] a lot for
>> insulating the coils, well into the 1980s I think.
>
> I'm not an engineer by any means. But I suspect a motor winding
> needn't be concerned about induction or capacitance as would an
> electronic device or a communications cable, so the insulation
> wasn't as critical.
The person I responded to switched the topic slightly to AC motors.
> Depending on the specific application of the motor, I would wonder
> if shellac would hold up if the motor got hot. Some motors, of
> course, actually only work for limited time frames and then are
> idle, so they don't as warm. I think that was a realization that
> allowed cash register motors to be small--they only ran for a brief
> period of time, then stopped. In contrast, a motor for an air
> conditioner or appliance would run a lot longer.
As far as I recall, they mostly fixed motors for industrial and farm
use. So I think these tended to run long enough to get hot.
I suppose that's why the coils needed rewinding in the first place!
> I hate to say, but another issue might be expected useful life.
> Maybe they only expected the motor to last 5-10 years.
I don't know. Perhaps repair with that interval was a good tradeoff.
Also note that I wrote that I wasn't sure it was really shellac.
Anyway, I don't think it's done at all today, except maybe with
specialty motors. If it breaks, you buy a new one. Or a new of
whatever the motor was driving.
/Jorgen
--
// Jorgen Grahn <grahn@ Oo o. . .
\X/ snipabacken.se> O o .
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Re: Polytetrafluorethylene (plastic insulation history) [message #353951 is a reply to message #353909] |
Sat, 07 October 2017 06:20 |
Quadibloc
Messages: 4399 Registered: June 2012
Karma: 0
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Senior Member |
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On Friday, October 6, 2017 at 11:53:37 AM UTC-6, Jorgen Grahn wrote:
> Also note that I wrote that I wasn't sure it was really shellac.
This does remind me, though, that a lot of devices used copper wire that was
simply coated with something that usually was red in color.
Starting from this, I did some searching, and found that the term is "magnet
wire" or "enameled wire" for this kind of wire.
From that, I found that the actual insulating material is still usually a
kind of plastic, such as polyurethane or polyester, rather than shellac or
enamel paint.
https://en.wikipedia.org/wiki/Magnet_wire
John Savard
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Re: Polytetrafluorethylene (plastic insulation history) [message #353952 is a reply to message #353951] |
Sat, 07 October 2017 07:02 |
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Originally posted by: Gareth's Downstairs Computer
On 07/10/2017 11:20, Quadibloc wrote:
> On Friday, October 6, 2017 at 11:53:37 AM UTC-6, Jorgen Grahn wrote:
>
>> Also note that I wrote that I wasn't sure it was really shellac.
>
> This does remind me, though, that a lot of devices used copper wire that was
> simply coated with something that usually was red in color.
>
> Starting from this, I did some searching, and found that the term is "magnet
> wire" or "enameled wire" for this kind of wire.
>
> From that, I found that the actual insulating material is still usually a
> kind of plastic, such as polyurethane or polyester, rather than shellac or
> enamel paint.
>
> https://en.wikipedia.org/wiki/Magnet_wire
>
>
> John Savard
>
The advantage of Shellac being that it keeps your motors
beetling along for years :-)
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Re: Polytetrafluorethylene (plastic insulation history) [message #353964 is a reply to message #353951] |
Sat, 07 October 2017 13:42 |
Mike Spencer
Messages: 1004 Registered: January 2012
Karma: 0
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Senior Member |
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Quadibloc <jsavard@ecn.ab.ca> writes:
> On Friday, October 6, 2017 at 11:53:37 AM UTC-6, Jorgen Grahn wrote:
>
>> Also note that I wrote that I wasn't sure it was really shellac.
>
> This does remind me, though, that a lot of devices used copper wire that was
> simply coated with something that usually was red in color.
>
> Starting from this, I did some searching, and found that the term is "magnet
> wire" or "enameled wire" for this kind of wire.
>
> From that, I found that the actual insulating material is still usually a
> kind of plastic, such as polyurethane or polyester, rather than shellac or
> enamel paint.
>
> https://en.wikipedia.org/wiki/Magnet_wire
When I wanted to build a device to remagnetize magnetos from old
single-cylinder "make 'n break' engines, I went to my local electric
motor overhaul shop and described the wire I wanted. Who could have
known? You make electromagnets with "magnet wire"! Their machine
measured off the N feet I needed in almost no time. And when I later
wanted to rewind a spark coil for an engine whose magneto was
mechanically defunct, I knew just what to ask for.
The light brown insulating coating is definitely more plastic-y and
durable than the orange shellac coating I recall from taking apart
radios 60 years ago.
--
Mike Spencer Nova Scotia, Canada
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Re: Polytetrafluorethylene (plastic insulation history) [message #353966 is a reply to message #353952] |
Sat, 07 October 2017 13:59 |
Peter Flass
Messages: 8402 Registered: December 2011
Karma: 0
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Senior Member |
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Gareth's Downstairs Computer
<headstone255.but.not.these.five.words@yahoo.com> wrote:
> On 07/10/2017 11:20, Quadibloc wrote:
>> On Friday, October 6, 2017 at 11:53:37 AM UTC-6, Jorgen Grahn wrote:
>>
>>> Also note that I wrote that I wasn't sure it was really shellac.
>>
>> This does remind me, though, that a lot of devices used copper wire that was
>> simply coated with something that usually was red in color.
>>
>> Starting from this, I did some searching, and found that the term is "magnet
>> wire" or "enameled wire" for this kind of wire.
>>
>> From that, I found that the actual insulating material is still usually a
>> kind of plastic, such as polyurethane or polyester, rather than shellac or
>> enamel paint.
>>
>> https://en.wikipedia.org/wiki/Magnet_wire
>>
>>
>> John Savard
>>
>
> The advantage of Shellac being that it keeps your motors
> beetling along for years :-)
>
groan
--
Pete
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