On the topic of BTH, I've had the pleasure of meeting Billy Bell who worked for BTH and was a mine of very fascinating stories of the delevopment of the Supas.... It seems the issue of heat is nothing new and was one of the problems that BTH faced.

I've used a number of different projectors, many of them now obsolete, BTH, Kalee 8-12-18-19-20-21, Simplex, Philips (Kinoton), Cinnemechanica, Westar etc etc. All of them were inovative in their own way.

I recall a problem with a vic 4, nice machine if you sealed the rear door. We used to scratch the middle of the frame every now and then. We checked the usual suspects, rollers and non-rewind, but found nothing wrong. It turned out to be the flat gate. Where the film entered the top of the gate the guide rollers had a tendancy to cup the film slightly, polyester prints especially as they were softer. As the apature plate was very close to the film surface it could touch and scratch. The solution was to force the film to enter the top guide rollers at a slight angle giving it more stability and thereby not allowing it to cup. A curved gate solves this problem perfectly. The curve does not have to be in the apature plate opening area, to be effective. Look at the Vic 8 as an example of this. The gate is not acutally curved as such but has a change of angle mid way enough to give the film extra stability as it passes the apature plate in a flat plane. How old is the Vic 8 design?

One of the problems with the BTH design was that the base side of the film was pressed aginst a fixed plane. Therefore focus could easily drift as the emulsion moved away from the fixed plane. Most, but not all, modern projectors press the film's emulsion against a fixed plane so the focus does not drift in the same way.

There's been the standard twin blade shutter, the contra rotating twin shutter, the drum shutter, the single blade double speed shutter of the Kalee 21 and of course the No shutter FP20 pulse lamp. All with their virtues and supporters. I wonder which of them will make a BIG come back in the next few years.

I remember the novel way the Kalee 8 framed the picture by moving the whole gate assembly up and down in relation to a fixed apature plate. The system was simple and I'm sure was very easy to manufacture. God how I miss some of these old machines and their character.

We don't know we're born now-a-days.....

Most projectors use the base edge as the reference edge. That is, the curved gate that uses tension bands (Century, Simplex, Norelco DP-70) have the base be the reference edge.

One thing straight gates do have over curve gates is that they have the emulsion on the reference edge so the focus wont drift from changes in stock thickness.

Steve

There were also side to side focusing issues, such that you could get the center of the film in focus, but not the sides, or vice versa. Not enough that customers noticed and complained, but definitely deserving of an F in my book. The only straight-gate projectors I have used that I was impressed with was the very early Christies. (Disclaimer, no I have not worked with a lot of straight gate machines.)

I have nevr had a problem with the traditional Simplex straight gate...now the circa '70s reversing straight gate was a nightmare! Never saw one that wouldnt' love to scratch your film! Just changed out another pair...located at the University of Penn....they now have modern Simplex curved gates...and oh what a difference! Even on their 50' screen the picture is NICE (complete with Strong Ultra-80 lamphouses).

Steve

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"As the heat goes up, their short comings show up too."

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That's probably why. The HVAC in this booth was under-spec'd from day one and UA wouldn't spend a dime fixing it properly. Couple that with the lack of real outside exhaust systems (they were vented above the ceiling tile with mini blower fans) and add to that the Strong lamphouses (which run hotter than an equivalent sized Christie or Cinemecannica lamphouse), and the machines were HOT!!! Most of those Strongs have been changed out with Christie machines and there is a noticeable improvement in not only light output, but also less heat.

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BTH SUPA did indeed have dreadful problems; well I think it was early versions that did. If I recall right the aperture was in front of the film, so more of the film was hit with heat from the lamp. There were mod kits for early ones, and later ones had the design altered somehow. I can't comment in more detail as I only ever saw one pair in the flesh, they were earlies, and to be quite honest, once was more than enough.
Likely as not, Bernard can tell us more of the SUPA, I'm really not old enough!

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Ken wrote,

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On the topic of BTH, I've had the pleasure of meeting Billy Bell who worked for BTH and was a mine of very fascinating stories of the development of the Supas.... It seems the issue of heat is nothing new and was one of the problems that BTH faced.

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The BTH Supa’s known as a couple of Elephants looking out of portholes. Pete’s summary is correct. Billy Bell used to service my Western Electric equipment at Cranleigh, so I also heard many fascinating stories like Ken. Large 2” hub spools, the take-up ran anti-clockwise! Billy told me that the best Supa he ever installed was over 50 years ago, trouble free to this day. It is in a glass case at the London Science Museum!

I did a days relief at the Classic, Brixton (now Ritzy) which had the Supa Mark 2s, they looked much better with round spoolboxes and seperate xenon lamphouses.

The last Elephant Supa’s I saw running over ten years ago, was in a twin cinema in Wadebridge, Cornwall. They were well maintained and quiet running. The Projected Picture Trust Museum at Bletchley Park has a BTH Supa on display.

I haven't seen SUPAs for very many years, except for the one at Bletchley Park. I remember the one on display at the Science Museum, but I don't think it is there now, I haven't seen it since the new Photography and Cinematography gallery was opened, years ago now.

In the box at the Phoenix there is a photograph of a young Peter next to one of these machines, at the Odeon Finchley, I think. Of course, the Odeon Leicester Square had three of them at one time, they were there at the same time as the Kalee Vista machines. The Telekinema at the Festival of Britain also had a pair, together with a television projector, which was replaced by a Bell and Howell 609 16mm machine after the Festival, when the Telekinema became the original National Film Theatre for a few years. The SUPAs would not have been ideal for the 3-D prrojection, with their 2000 foot capacity. Interestingly, the festival prints were all made on safety base, so I don't know iif they would have been allowed to use larger spools, or if the regulations at that time would have prohibited it, even though no nitrate was being used.

There were also two cinemas with BTH amplifiers giving very good sound considering.

All of these projectors were still earning their keep some 13 yaers ago and some possibly still are. It was always fun to visit a cinema and find these machines still in use. They were serviced by Westrex right up until they shut up shop.... god knows what they do for spares.

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Ken, was that the Playhouse, Peterhead? I was up there a couple of times in the last few years, it's now closed. Last time I was in there, one Westar and one FP20 were the kitin use. Another Westar lay in the foyer and various Kalees were slumbering in other areas of the building.

Thats the stuff I put in a long long time ago. The FP20 came from Grampian Television, no c/o shutter or lamphouse table or heat sheild. The westar(s) came from one of the companies Bingo halls, Regal Forfar if I recall correctly. The AEI lamphouse came out of the Victoria Dundee, now long gone, with a Westinghouse rectifier that I converted to diode. The Peerless conversion came from Morganite and was installed by Ernie Chinnery.... happy days

It was quite amazing that so many small town cinemas had survived so long, The Kings Brechin was all BTH, amplifier as well, and I was happy to be able to let him have a couple of mech's when the FP20 was installed.

But yes, the mighty Westar did rule for so many yaers due to the fact that you could lease the equipment rather than buy it outright. Mind you with the cold winters that far north you needed the valve amps to keep the box warm.

Do you rememeber Bob Brown, he was our Westrex engineer for many years in Peterhead.

Cheers, Thomas

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I assume that all Cinerama prints, and tracks were always safety, as this process always used large spools.

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And also because of the timings. Nitrate ceased to be manufactured in the US in February 1950, and the first Cinerama shows weren't until autumn 1952. Two and a half years would have been more than enough for residual stock supplies of nitrate to be used up, I would have thought.

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I couldn't remember the dates offhand, I thought it was later than that; if it was 1950 hen no prints would have been nitrate, at least not ones that ever went to theatres.

Do you know when triacetate stock first became generally available? Was there much of an overlap with Nitrate?

I know that Pathe was using diacetate safety stock for 28mm prints in 1912, and that similar stock was available in 35mm from about the same time, but was never very widely used.