Coughtrie light

[G6Tanuki]

Good to hear you've got a solution.

I have fond memories of a Coutrie-type fitting over the doors of the machine-barn at a local farm; it had two horizontally-mounted, parallel-connected Edison Screw bottles, at least 150W each [with a bucket-sized glass bowl for waterproofing]. Which was great because one of them would fail but the other would go on working so we didn't need to get the cherry-picker out immediately.

We always replaced both bulbs when faced with one that had failed. Cheaper that way.

[McMurdo]

I've just dug out a 1950's electrical catalogue and the Coughtrie fittings say they're all equipped with a 'BS31 3/4 ET thread', the old conduit entry, just slightly smaller than a 20mm metric tube.

[matthewhouse]

I love these lights they always seem to come up like new when restored, and I always save any I take down. I wish they still made the FS10 I think it looks a lot smarter than the SW10. I did 3 FS10s for my father when I rewired his house a few years back, one of which was originally on his house from new.

I often re-tap the entry hole in the bracket to M20 to fit modern conduit and glands. I have several more corner and wall versions waiting for restoration, I just need time to do them...

[pmmunro]

Thankfully dobson165's problem seems to be solved - his lamp has a BS31 thread. However, I was convinced that Emeritus was onto something with his suggestion that it might be a PG13 thread and I now have solid evidence!

This is from Coughtree Catalogue 1987 #1 and I hope it may be of use to someone in the future. This catalogue does not list the SW6 which was the subject of the recent enquiry but does list types SW10, SY6 and SY10. Both the SY6 & SY10, but not the SW10 (top entry) state under "Entry" that '13.5 pg thread available to order'. This also applies to several other lamps with die-cast bodies.

As there seems to be quite a lot of interest in these often long-lived luminaires, would anyone be interested in a scan of this catalogue? I can't promise it will be soon and I may newed a reminder or two.

PMM

[Graham G3ZVT]

As we have just had the garden tided up including re-laying the lawn, so I treated the Coughtrie WP10 to a new bulb and cleaned and acrylic bowl.

One thing though, the two bolts securing the bowl seem to be captive, but they aren't really. Fortunately I found the errant fastener in the sink.

[Techman]

Picked this one up this morning at a local car boot sale for a couple of quid.

[Wellington]

Is this a Coughtrie lamp, or merely in the Coughtrie style? I suspect it isn't a Coughtrie because it lacks fins.

It's well-made, though. I've just had to replace the bulb and, despite fearing the worst corrosion-wise, the two brass thumbscrews undid with no trouble. The seal/gasket around the glass has hardened and cracked though, and needs replacing. A replacement seal offered by Coughtrie looks right, but I'll have to contact them to confirm the diameter (~5").

Also, the glass on my lamp is pretty long. I fitted one of those big 200W Philips bulbs (that I saw in charity shop for only a quid), and even that seems rather dwarfed in there. Would this lamp have taken a larger, more industrial bulb?

[bobbyball]

Don't think that one is a "Coughtrie", it doesn't seem like any of their designs, but I could be wrong of course. The Coughtrie ones usually or at least sometimes have a model number stamped somewhere on them and their back catalogues can be found online.

There were a number of other makers, some far less well known, producing similar designs to the Coughtrie ones - "Revo" is one that springs to mind. In those days, things were made to last!

The "long" glass will be to accommodate the older 150 (or even 200) Watt tungsten lamps which were significantly bigger than the regular 60-100 Watt types.

[Wellington]

Originally Posted by bobbyball

The "long" glass will be to accommodate the older 150 (or even 200) Watt tungsten lamps which were significantly bigger than the regular 60-100 Watt types.

The bulb in the photo is one of those big 200W ones!

[bobbyball]

Here is a 300 watt lamp which would undoubtedly be bigger

[emeritus]

I think that 200W was the highest wattage GLS lamp available with BC bayonet base.

[broadgage]

Originally Posted by emeritus

I think that 200W was the highest wattage GLS lamp available with BC bayonet base.

I bet that someone, somewhere made a BC lamp of more than 200 watts for some special purpose, including I think photoflood lamps, and carbon radiator lamps.
200 watts was the upper limit of generally available GLS lamps, some manufacturers stopped at 150 watts.

[Graham G3ZVT]

Originally Posted by bobbyball

Here is a 300 watt lamp which would undoubtedly be bigger

It certainly is, and also has a GES (B40) base.
I had one years ago complete with an unused ceramic holder.

[dobson156]

Originally Posted by pmmunro

As there seems to be quite a lot of interest in these often long-lived luminaires, would anyone be interested in a scan of this catalogue?
PMM

Sorry, I've been away. I'll try and take a photo of the 1 of the 3 lamps I've restored now that one is hanging.

I would be interested in a scan for that catalogue for sure!

[dobson156]

I also have another question, the newer lamps all seem to use an M5 partially threaded (retaining) cheese head bolt to hokd the reflector/retaining ring onto the main body.

The older ones however use something altogether different. It measure in at just over 5mm (5.19) wide at the threads, and has a TPI of approx 28.

I am struggling to tell if this would be 7/32 BSF or (in keeping with other parts of the lamp) 1BA which has a TPI of 28.22.

The bolts which retain the ceramic bulb holder to the main body were also BA so that leads me to think it might be a BA.

[Wellington]

Originally Posted by broadgage

I bet that someone, somewhere made a BC lamp of more than 200 watts for some special purpose, including I think photoflood lamps, and carbon radiator lamps.
200 watts was the upper limit of generally available GLS lamps, some manufacturers stopped at 150 watts.

My light has a ceramic BC socket fitted. I suppose it could've started life with something different. My father put it up, and I don't know where he got it from. That gap at the bottom of the glass just looks kind of wrong, somehow.

[Nickthedentist]

I saw a load of 200W NOS lamps in a charity shop in Witney today if anyone needs one!

[Techman]

There's absolutely no ventilation in those fittings. You'll cook it with a 200 watt bulb, plus you'll cook the gasket, the wiring and it may even explode! I've got a 40 watt candle shaped white opaque type in mine. I've killed a few of those low energy CFL type lamps in mine over the years with the lack of air flow within the fitting, the electronics couldn't cope with the heat in the confined and unventilated space. I'm wondering how a modern LED lamp/bulb would cope?

[emeritus]

Probably very poorly. At the heritage railway where I volunteer, a footpath alongside the engine shed is lit using eight bulkhead luminaires (not Coultrie ones), controlled by a photocell so they are on all night at night. The GLS-replacement LED bulbs with an alleged 30,000 hours life, that had been fitted during the past 4 years, have been consistently failing after about 18 months on average. On checking manufacturers' data sheets last year, courtesy of CPC's web site, it transpired that they are only stated to be suitable for indoor use in well-ventilated fittings. Some explicitly state that use in sealed luminaires will result in a shorter life. Certainly a couple of the failures I dismantled, showed signs of severe overheating, some with charred printed circuit boards and electrolytics that had got so hot that the plastic sleeving carrying the type and rating, had completely disintegrated due to heat.

However, I see that Toolstation do now list LED bulbs, with built-in light sensors, that are specifically stated to be suitable for use in sealed outdoor fittings.

As far as the railway is concerned, we were given a box of fairly low wattage CFL lamps, and I fitted some last autumn to see how they last. The slow warm-up period is not an issue as they stay on continuously . I have been using a 20W CFL on my Coultrie at home with no problems, although it only gets intermittent use. The light distribution of a CFL bulb is actually better for my Coultrie with its clear glass globe (and bulkhead luminaires) than general purpose LED GLS replacements. This is because a stick CFL bulb emits most of its light sideways, and the fact that less light is emitted at the end of the stick element, helps produce a more even level of illumination. Most general purpose GLS LEDs seeem designed to emit most of their light away from the base, less light sideways, and little towards the base.

[Wellington]

Originally Posted by Techman

There's absolutely no ventilation in those fittings. You'll cook it with a 200 watt bulb, plus you'll cook the gasket, the wiring and it may even explode!

That's a good point.

So my fitting is presumably designed for incandescent bulbs (rather than something more exotic like gas-discharge) and because it's unventilated (to prevent moisture/insect/dust etc. ingress), it's going to get hot (hence the use of a ceramic socket).

I wonder then, what 'wattage' of incandescent bulb was originally specified? Techman uses a 40W in his, but as an outside light, I'd expect something a bit brighter than that. Maybe I'm expecting too much – i.e. modern levels of brightness from old technology.