ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades Edison Screw type Lamp-holders

I found a picture (and the website it came from) of the London Underground bulb I mentioned:



And here is the website: http://electriclights.tripod.com/bulbs/londontrain.htm

According to the site, the bulb operates at 100 volts.

[This message has been edited by SvenNYC (edited 12-02-2002).]

I'm not sure about the pin spacing on this special bulb, but the ones we were talking about above have the three pins spaced 120 degrees apart around the base. A normal BC bulb has its two pins opposite each other, so just filing one pin down wouldn't work.

I wonder how long this base has been used by London Transport?

Anyone else (probably from the U.K.!) remember seeing an old Arthur Askey movie where he's sleeping in the Underground station (as many did during WWII) and then opens up a signal lens at the end of the platform to run his electric shaver?



[This message has been edited by pauluk (edited 12-02-2002).]

Paul,
I have actually seen that film, through some cruel twist of fate, I think that it was part of last years Christmas-New years fare on TV over here.
Not expecting anything better this year either.
Interesting comments on the 3-pin BC lamp though, it sounds to me to be like a lamp manufacturers attempt to future-proof thier
investment.
They must have been in cahoots, with a lamp base manufacturer, as mongrel fittings like this don't do any of us any good, in years after the fittings and lamps have died out.

I've got a few suggestions for Edison lampholders.

1.) They should be made out a heat resistant plastic, so that it is safe to use 100W bulbs.

2.) Bulbs should not be allowed to exceed 100W. With 1.) this would much reduce the risk of fire in lampholders. Higher wattage bulbs should have a special incompatible holder.

3.) The lampholder should be designed so that the wires have a higher degree of protection from the heat generated by the bulb. E.g. increased distance between bottom of bulb and terminals.

4.) The lampholder should be designed in such a way that the bulbs only becomes energized when it is almost fully screwed in.
This to prevent people from touching the base of the bulb when it's live.

Is this Christmas wish list realistic?

OT sorta...
Sven — the London Underground lamp has very interesting filament construction. If they just could bring out four terminals in the base, it could be a truly “universal/international” version, usable in 100- or 200-volt service—sort of...as series/parallel connected? :-)

C-H:

re. heat resistant plastic lampholders. I'm more of an old fashioned guy. I would prefer porcelain. It doesn't deteriorate at all with high heat.

However if you're going to use plastic....the best plastic for a lampholder is thermo-set phenolic (Bakelite) which is that brown plastic that was so ubiquitous 50+ years ago.

It's still widely used here in the USA and also in Asia for wiring devices. I wouldnt recommend melamine (white) and certainly NOT urea.

Both of these deteriorate and discolor under high heat. Bakelite does not.

---
Bjarney:

Apparently the reason for the double filament is that if one of the filaments burns out, the second one takes over. That way the bulb lasts twice as long and you don't have the problem of a disabled signal light in a tunnel holding up train service. The second filament holds up until the tunnel maintenance crews make their normal inspection rounds I guess.

And also crews don't have to go down into those tunnels to replace bulbs that often, which from what I've seen here in New York, is no piece of cake (what with the rats, water, 600-volts of electricty, crack-heads and heroin addicts and that ever present soot and dust that gets in your lungs and made my silver ring go BLACK when I walked into one of them).

You'd actually need only three terminals do to this. A lot of miniature vacuum tubes (e.g. 12AX7/ECC83 etc.) had such an arrangement for their filaments, enabling them to be wired for 6.3 or 12.6-volt operation.

Concerning plastic lampholders: I've seen many abused ones which crackled, discolored and stank like old fish. Personally, I only buy metal ones, but I've to deal with the cheapest imagineable plastic ones because I'm in charge of changing bulbs in our appartment building, and the new basement lights that replaced the 1914 porcelaine ones are hardware store type IP 44 and fall apart upon touching them (just had the pleasure of dealing with two of them today, one fell apart completely). One of the porcelaine ones was broken and dangerous, but the other one would probably have lasted forever (but it was a pity to have the beautiful thing with it's white glass shade hanging in the basement, just imagine someone with a ladder passing by and *smash*..., so when we rewired I took them down and salvaged them)
Quality IP 44 fixtures here have a porcelaine socket inside a plastic and glass enclosure, not just a tiny backstabbed plastic monster. At least they supplied silicone tubing to protect the wires from heat.

Ranger:

You're lucky you didn't get shocked when the socket fell apart on you.

Does your dad own the building?

If so, tell him to stop being such a Scrooge and go out and buy lamps with porcelain sockets instead of the cheap-crap!!! hehehehe

P.S.: Bakelite (when overheated) smells like carbolic acid. It will break down under VERY high heat, but it will not melt. It disintegrates instead.

If you're using 100-watt bulbs and above in a base-up fashion, I would go for porcelain sockets. They're designed for that sort of use, I think.

As for metal lamp-holders, I hate them. The paper sleeve always dries and crumbles because of the heat from the bulbs. I don't know if the European-market metal ES-27 holders have cardboard sleeves to insulate the mechanism from the metal shell, but the American-market ones do. And you see lots of old table lamps with crumbled paper insulators (requires one to replace the lampholder). I always replace them with Bakelite-shell lampholders.

By the way, can you take pictures of the old porcelain fixtures you took out?

[This message has been edited by SvenNYC (edited 12-24-2002).]

So noted, Paul. Too used to ac magnetics, I guess.

--Bjarn