Some text for two unusual lamps of their kind.
I found these lamps in the lamp catalog of the British company A.E.I. from 1956.


Source: A.E.I. Lamp Catalogue, August 1956

I am particularly interested in the MBF/U 400 lamp with its unusual shape.
Does anyone know the reasons why this cylindrical shape was chosen and not an isothermal shape, like RADIUM did in Germany for example?


Source: A.E.I. Lamp Catalogue, August 1956

I also find it remarkable that the lamps MAF/V 400W and MBF/U 400W were still offered in parallel in the range.
I would have guessed that the obsolete MAF/V 400W lamp would have been taken out of production immediately when the new MBF/U 400W lamp was produced.

The second lamp that interests me is the MBT/U 200W.

Who has seen these lamps before? As always: additions are welcome


Regards

Olav

The cylindrical MBF lamps were made in both 250W and 400W ratings in Britain, starting in 1955.  The reason was because they use a quartz arc tube and were rated for vertical burning either cap-up or cap-down.  There was no point to use the isothermal cap-up shaped bulbs of the MAF 400W because that would have been ineffective when used cap down.  So they opted for symmetrical cylindrical bulbs of 89mm and 115mm diameter.  The original goal was to make the bulb as small as possible so as to maximise optical control from reflector luminaires.  Later it was found that the phosphors degraded rather quickly and that the light output ratio from high-bay luminaires could be increased by opting for an ellipsoidal shaped bulb.  That had been introduced by the British lampmakers sometime between 1959 and 1963, although Philips was already producing that shape in Holland at least as early as 1955.

The MBF cyldindrical 400W was first listed in the 1955 AEI catalogue and in that year the MAF 400W was delisted.  However, the MAF 400W was back in 1956.  Probably the cost is the reason : the MBF type was more than double the price of the MAF.  Quartz used to be an extremely expensive material at that time.  Even in 1959 MAF was still being listed and although the MBF had been reduced considerably in cost by then, it was still 50% more expensive.  You can also see that the 250/400W MA lamps were produced even later, before being replaced by MB Tubular types.  Again due to the initially huge cost differences.  Quartz was only affordable for the lower wattage lamps that used less quartz.

The MBT 200W lamp was the first British self-ballasted quartz lamp.  Over time it was gradually replaced by the more standard 160W European rating.  I do have one of those, it was one of the first lamps uploaded to my site in 1998 and the page is very basic and requires updating!  See http://lamptech.co.uk/Spec%20Sheets/D%20MB%20Mazda%20MBT200.htm

I think i found a photo of the 400 watt MBF/U inside an old GEC luminarie:


https://www.worthpoint.com/worthopedia/large-vintage-gec-street-lamp-454199717

This is 100% this lamp MBF/U 400W. 
At least a photo of it, very good research by you. I suspect that the base is unfortunately loose on this example. 
Nevertheless, the photo is worth seeing.

if a picture of such a lamp is what your looking for then here you go!



sadly not mine! but belonging to another british collector who has a prolific collection of all sorts of very rare and awesome lamps, bulbs and tubes!


they are indeed very peculiar lamps, not sure If I have ever see any others besides the 2 shown here in this thread

(I remember when the streetlight mentioned above showed up, there was quite the flurry of interest of course! but I dont know who ended up with it sadly)

The photo is a very good addition. Thank you for your research.
So I have to scan another page from the OSRAM GEC catalog from that time of production.

An addition from the OSRAM GEC catalogue, September 1956 edition:


Source: OSRAM GEC catalogue, September 1956, page 36



Source: OSRAM GEC catalogue, September 1956, page 37

What phosphors did the cylindrical MBF/U lamps use?

Im guessing /C judging by the timeframe.

Here you can read a lot of information on James' website about phosphors:

Phosphors for Mercury Lamps

Yesterday I received a heavily used example of this 400W cylindrical MBF/U lamp in a trade.
It gets very hot and is quite greened out but at least it works.
Since originally discovering that this shape was made I have been keen to find an example as the only other lamp with this shape was a Russian MV lamp of high power.