A week on the tools - including a nice little job with a puzzle for you

[Lucien Nunes]

Well it's not often that I get to do a solid week of electrical work these days. Most of my time is office/lab/workshop based, in the field it's mostly electronics. But last week I did Monday to Saturday, six days and two nights, about 100 hours of non-stop-sparking. The main job saw the core team of four of us back together that first worked as a unit doing theatre installations back in the 90s: Richard, Steve, Jason and myself. Anyway I digress, it's not this I wanted to talk about, it's the overnight job.

An old piece of kit on our round (we've got a lot of those) still working but in need of maintenance and in our sights for safety improvements. Not sure when it was installed, I think it's early 1930s but just possibly 20s as it is part of something that was installed in 1925. Peter and I had originally planned to overhaul this unit and upgrade its safety features while replacing the very ramshackle wiring to it that has been modified over the years. However, for various reasons, we decided it was better to decommission it and leave it in situ as a museum piece, and fit a new one alongside. This we tried to do last week but one component on the replacement was damaged in transit so we have to return there tonight to complete.

Let's begin with a pic of a little bit of the inside. I made a video of it before disconnection and this will be online in due course. If you are lucky you will also get to see the whole machine in operation, which is is fine working order. The pink bit is me, pointing out the accumulated wear from 85 years of use.

 

[SparkyChick]

Neat. I take it it's an electric action from the console to the wind chests, not a mechanical track rod. Would be great to see some pics of the wind chests, controllers and console if you've got some.

Love organs (keep it clean boys ), had the pleasure of working on a church organ or two in my time and they are just awesome.

 

[marconi]

My last stab - pondering on 'dolce meaning sweet' - is it a scented air system for which your images are the controller? Used in the days of London smogs perhaps? The compartment is loaded with scent the blower can be started and when it has all been used up the mechanism shuts down the blower.

 

[DPG]

Nice one SC. Not bad for a girl ;-)

 

[SparkyChick]

I'm looking for the 'Fisticuffs' rating @DPG

 

[DPG]

I know you've got a good sense of humour. I think I'm safe!

 

[Lucien Nunes]

Cinema organs are quite different to church organs; created to take the place of orchestras they have an enormous variety of sounds to offer and ingenious ways to enable one player to control them all at once. At the console of a good cinema instrument, an artist can express any human emotion from pure delight to utter despair, with any amount of presence from barely-there to overwhelming. He or she can tell complete stories without words, can be a full band, a soloist, an accompanist or an entertainer, in any style from jazz to classical to pop to epic movie soundtrack. But again, I digress.

Yes, the action (the bit between the console and pipes) on all cinema organs is electric and/or electropneumatic and on a large instrument fiendishly complex. This one is not huge but still has around 500 cores in the console main cable, all of which operate relays in the pipe chambers that sort out which pipes are to play - there's no direct mapping of keys-to-pipes because each pipe in a cinema organ serves multiple duties. As you've asked, I'll try to sort out some pics of the action, it does need a bit of explaining though as the relays and binary logic switching elements are unlike any you'll see in regular electrical work!

Here's the blower to look at while my video of the starter uploads...

 

[Gakure]

Transfer switch

 

[Lucien Nunes]

First video up, see the old starter operating here:

And here's a pic of the new starter with the old one behind. The box above the starter itself houses a supply monitoring relay that gives extra protection to the 85-year-old motor against e.g. singlephasing and regeneration when running very light, allied with the thermal overload relay in the starter. Also in there is a contactor for the 10V 30A DC power supply unit that feeds the electropneumatic action of the organ.

 

[Lucien Nunes]

I should have explained how the starter works. When the blower runs down at the end of a run the actuator rod falls. Its striker engages the slotted black contact operating pawl and pulls it down under the weight of the rod and piston, tensioning the two long springs. Once down, the tips of the pawl lock into the rectangular slot in the catch at the front, holding the three moving contacts (connected to one end of the windings) against the bottom row of fixed contacts which link them into star. To start, the 3-pole line contactor at the top engages and holds, and the blower runs up. When there is sufficient pressure the actuator rod rises and once the striker is clear of the pawl a ramp trips the catch off. The long springs pull it up, rocking the contact bar to open the star contacts and close the delta contacts (connected to the supply) in the top row. The speed of the transition is regulated by the dashpot cylinder to the left of the rod. The ramp holds the catch open and with it, the interlock contact. This disconnects the start button so that if the line contactor is released, it cannot re-operate until the blower has run down and the changeover mechanism has reset to star. I didn't show the stopping part of the cycle in the video as it takes nearly two minutes, due to the huge moment of inertia of the blower impellers.

 

[delano]

Well it's not often that I get to do a solid week of electrical work these days. Most of my time is office/lab/workshop based, in the field it's mostly electronics. But last week I did Monday to Saturday, six days and two nights, about 100 hours of non-stop-sparking. The main job saw the core team of four of us back together that first worked as a unit doing theatre installations back in the 90s: Richard, Steve, Jason and myself. Anyway I digress, it's not this I wanted to talk about, it's the overnight job.

An old piece of kit on our round (we've got a lot of those) still working but in need of maintenance and in our sights for safety improvements. Not sure when it was installed, I think it's early 1930s but just possibly 20s as it is part of something that was installed in 1925. Peter and I had originally planned to overhaul this unit and upgrade its safety features while replacing the very ramshackle wiring to it that has been modified over the years. However, for various reasons, we decided it was better to decommission it and leave it in situ as a museum piece, and fit a new one alongside. This we tried to do last week but one component on the replacement was damaged in transit so we have to return there tonight to complete.

Let's begin with a pic of a little bit of the inside. I made a video of it before disconnection and this will be online in due course. If you are lucky you will also get to see the whole machine in operation, which is is fine working order. The pink bit is me, pointing out the accumulated wear from 85 years of use.

View attachment 37047

It looks like on old isolator.

 

[Lucien Nunes]

Time to unveil the new starter in operation. In the starter itself to the very left we have the timer, which I set to make the transition a little later than the pneumatic one was set, so that the blower is very nearly at full speed and the current a few amps lower when it happens. Then there is the overload relay, in the delta loop so set at FLC/sqrt(3) or about 4.5A for a 7.7A FLC. Then the line contactor, with the start button mounted on top, the delta and star contactors with a dual N/C interlock contact mounted across them (there's a mechanical interlock hidden inside too) and the isolator. In the box above is the monitoring relay and the auxiliary supply contactor slaved off the line contactor. The two sets of three brown 2.5's at the bottom are the two ends of the windings.

When you press the start button, provided the monitoring relay and O/L are normal, you start the timer which outputs a feed to the star contactor coil. This operates and its aux contact extends the feed to the line contactor which also operates, holds via one aux contact and bypasses the star aux with another. This sequence, rather than making the line contactor hold directly, proves that the delta is out before anything can happen, as an operated delta would prevent the star operating both electrically and mechanically. When the time elapses the star coil is de-energised, releasing the interlock and allowing the delta to operate.

Music next...

 

[Lucien Nunes]

And here's the result, including a brief musical demo, which reveals the console and its location. Don't play this through a tinny phone speaker, try it on the computer with the real speakers on. It's only a mobile phone video but you need a bit of bass to get the proper effect.

One day I will make a video of how all the organ electrics work...

 

[freddo]

Nice write-up, I still prefer the old version though...

 

[Lucien Nunes]

NB for anyone who hasn't spotted there's a brief musical demo in the video above^^.

Me too Freddo, but there were issues that needed addressing such as disintegrating rubber parts, difficulty of integrating a retrofit thermal O/L (it originally had none) etc meant that the starter would have to be considerably reworked if it were to remain in use. We preferred to conserve it for posterity rather than tinker with it and still possibly not have an ideal solution. Organs are expensive enough to maintain and if, like this one, they are only heard occasionally, one does not want an avoidable technical hitch to render the whole thing unplayable at a critical moment.

OTOH, amongst the old starters still at work in our sightlines there's a similar unit by the same makers that we don't plan to replace any time soon. It's the version for wound-rotor motors that puts the stator DOL but cuts out the rotor resistance in a couple of steps with rising pressure. This is on the much larger blower feeding the 1936/7 Southampton Guildhall Compton, one of the largest instruments of its type in the UK with two 4-manual consoles controlling 50 ranks of pipes (the Wurlitzer in this thread has 8). The motor is 17.5hp, 24A line at 400V, with a 3-phase 212V 38A rotor.

 

[DPG]

Very nice. Didn't realise the motors were so big for these things.