Vintage Electrical Hazards BBC4

[dave walsh]

On at 9pm. New [or should that be old?] Hidden Killers:The Edwardian Home. The arrival of new fangled electrical devices without prior H+S testing. One headline is "Killed By A Telephone".

Dave W

[PaulR]

Very interesting programme. I had no idea that ammonia gas was very inflammable.

[dave walsh]

It was, wasn't it. I've got one of those little signs saying don't attempt to switch the electric light on with a match. Tudor Rees used to do repros and I bought one from his shop near Bristol circa 1980. The program is on again tonight at 10pm.
Dave

[Skywave]

Yes, a very watchable series - and so was the presenter!

Al. / Dec. 19, '13 //

[SteveCG]

Yes, a curious programme. I was surprised to be told that ammonia was inflammable (the old word meaning). so I refered to an Inorganic Chemistry text book I have and read that ammonia will not burn in air; however the book went on to say that an ammonia-air mixture will ignite if sparked.

Although the TV prog was concerned with the Edwardian times I had half expected to be told that early lights had an on-off switch next to the light bulb - just like a gas light. The idea of putting the switch beside a door came later. Or as my grandfather always called them, a 'tumbler' switch. Certainly switching DC mains required a good fast acting 'snap' mechanism. Also I thought the idea of fuses was in from the early times. I reckon I read that the early (late 1870s) Peterhouse college Cambridge installation gifted by Armstrong used fuses beside the lights. Later on, power generation in Cambridge from a power station beside the Cam and opposite Maudling college moved from 100 volts to 200 volts AC at a frequency of 80 c/s.

[Herald1360]

Originally Posted by SteveCG

Later on, power generation in Cambridge from a power station beside the Cam and opposite Maudling college moved from 100 volts to 200 volts AC at a frequency of 80 c/s.

Maudling?

Bit of a ho-hum sort of place is it?


Back OT....

The light switches at home in the fifties were hangovers from the DC era- they had an interesting mechanism which wasn't exactly a toggle type. There were two fixed springy contacts mounted on the ceramic base connected to the wires, the connection was made by a hinged metal lever with a spring at the hinge pin end which was forced between the fixed contacts by a roller on the switch lever running up a cam shape on the contact lever. So, slow forced make operation. On switch off, friction between the contact lever and the fixed contacts maintained the circuit as the roller moved away from the cam profile until the roller engaged with a hook at the far end of the profile. The contact lever was then pulled away from the fixed contacts with the spring ensuring that the final separation was quick. So, quick forced break operation. They still worked fine on AC even though many of the hinge end springs were broken by the time I was old enough to be investigating the system.

I thought it was quite a neat design, though clearly much more expensive to make than present day switches.

Wiring was at least insulated individual wires, though they did run in wooden battens with twin parallel grooves covered by a decorative lid moulding screwed on at about 18" intervals. Even under the floorboards!

[russell_w_b]

Originally Posted by SteveCG

The idea of putting the switch beside a door came later.

My dad's cousin's house in Dora Crescent, Workington, had gas lights worked by a 'switch' by the door. In reality, a simple tap, I suppose, with a pilot light on the luminaire. This would be in the 1930s.

This was a novel arrangement, and all the rellies used to visit just to play with it!

[Heatercathodeshort]

Originally Posted by SteveCG

The light switches at home in the fifties were hangovers from the DC era- they had an interesting mechanism which wasn't exactly a toggle type.

Sounds like the five I have controlling the workshop lights, on AC of course..John.

[Herald1360]

Mechanism looks similar, from what can be seen. Ours were posher, though, with a domed fluted sort of cover about twice as deep

[Heatercathodeshort]

Originally Posted by Herald1360

Ours were posher, though, with a domed fluted sort of cover about twice as deep

This one definitely looks a bit AC/DC and would be about right time wise for the programme [1904] It controls my 'museum' lights.. John.

[MrElectronicman]

I remember when I was a kid, the council houses near our house were being rewired with modern fittings and there tons of old switches and lamp sockets lying around waiting for someone to pick up and experiment with.

[Herald1360]

That's more like it. The forgettory suggests a top like that but on a shallower ceramic base- it was nearly 50 years ago

[emeritus]

My 1893 GEC catalogue has some house and warehouse wiring plans. Each switch has a fuse next to it, connected in the opposite wire from the switch. This was to allow individual circuits to be isolated for testing, by setting the switch to OFF and removing the corresponding fuse link.

[PaulR]

Originally Posted by russell_w_b

gas lights worked by a 'switch' by the door. In reality, a simple tap, I suppose, with a pilot light on the luminaire.

There were some pneumatic arrangements whereby a plunger in the "switch" activated a similar one at the fitting to turn on the gas. I have the gas fitting end of one of those somewhere.

Paul

What is the clearance/creepage of those switches to the (un earthed?) cap and toggle?

[Heatercathodeshort]

I have no idea about the leakage and guess it would have been difficult to measure it back in Edwardian times. I stand on wet grass when I turn on the 1904 switch, as it is positioned just inside the door and I don't feel any tingles. I made sure the connecting cables were well cut back so as not to come into contact with the brass cover..Care has to be taken and common sense. These switches were used for 50+ years and you don't see many gravestones engraved 'RIP Grandma. Killed by her lavatory light switch'.
People were different back then with more respect for everything and everybody, including electricity. Regards, John.

[OscarFoxtrot]

Originally Posted by merlinmaxwell

What is the clearance/creepage of those switches to the (un earthed?) cap and toggle?

Not always enough

[McMurdo]

One of the experts on the programme mentioned the lack of suitable insulating materials at the time, something we take for granted as available in this plastic world! The insulation in those old tumbler switches between the dolly and the tumbler is often paper or card soaked in shellac/some sort of varnish or even thick mica.
Can you whip the cover off yours John and take a pic?

[Herald1360]

Sounds like a possible reason to put the switch in the neutral line........

[Heatercathodeshort]

Oww OK. You won't be happy until I've zapped myself..and it's raining.
Not a lot of information I'm afraid. Space is limited and I can't get a direct face on shot. It is very positive with a nice 'clang' when operated. [It's not made by Clang] J.