Motor cable - style question

[Lucien Nunes]

may we have some pictures please? I bet there is an interesting back-story to tell.

Westminster’s rare Fyvie Hall pipe organ is being restored to its former glory

www.westminster.ac.uk

It's a little 2/4 Compton, much smaller than the instruments we usually work on but one that punches above its weight. It's the 3rd organ in Regent Street that my colleague Peter and team look after.

Blowers are usually conservatively rated, infrequently used and left unmolested, so it is not unusual to find old plant still in service. Average church organ blowers typically range from 1/2-2hp and are quite often single-phase. At low wind pressures it doesn't take much motor-power to make a lot of sound, hence the ability for a team of human blowers to blow even cathedral organs in antiquity.

In the late 19th and 20th century with large instruments voiced on higher pressures, the larger blowers got very large indeed. With our focus on concert and entertainment instruments we tend to meet units in the 5-20hp range and occasionally multiple blowers. As an example of the very largest schemes, the Royal Albert Hall has seven blowers totalling 62hp. My favourite blower is on my favourite organ, the Southampton Guildhall Compton. It's really three blowers in one, on a shaft totalling 12 feet long, which makes very efficient use of its 17.5hp.

 

[timhoward]

I wondered if it was for an organ!
There are one or two organs where additions have necessitated additional blowers. The Harrison and Harrison at Westminster Abbey comes to mind, which had a 5th manual / Bombarde division added.
The extra blower has it's own extra switch, which occasionally leads the to the inevitable happening - an extra loud solo stop becomes completely missing when the poor organist thought he'd turned it on and hadn't.
The blower switches are not always conveniently sited to correct such mistakes, in the case above they can't be reached or even seen from the bench.
For the huge cost of the work to extend that organ I always wonder that at a minimum a small indicator lamp wasn't provided to provide some reassurance!

 

[timhoward]

For anyone interested in the more extreme end of organ blower installation, this video, naturally from USA is quite an interesting watch

(the video image is a generator not a blower!)

 

[Lucien Nunes]

The Boardwalk Midmer-Losh is indeed an extreme instrument and a good example of a multi-blower installation where each serves a particular division and pressure. There is another multi-blower scenario where for economy when full registrations are not in use, and to avoid wind heating when the demand is low (which affects tuning), different-sized blowers are provided feeding the same trunk in parallel. For example, Hull Minster has a 5hp and a 10hp blower that can be started independently. For choir practice etc the 5hp blower is adequate and allows any stops to be played, but both need to be running to use full registrations.

Stand-alone motor-generators for the action DC supply (as shown in this video) were rare and only found on the largest instruments. Historically, many organs with electric action used a generator driven from the blower motor, and a few remain in use. In fact the Fyvie hall organ was running on its 18V MetVick generator until a few weeks ago, when a regulated power supply replaced it, on account of the new multiplex transmission (to allow the console to be moved and plugged in via a data cable instead of a 300-core snake.) Historically it was difficult to rectify high currents at low voltages and a generator was a reliable and effective solution. From memory the Boardwalk M-G set puts out 150A at 12V.

As usual, Southampton is an excellent example in original working condition unaltered since 1937. Its generators (there are two, one main generator and a separate exciter) are belt-driven from the blower and deliver 100A @ 18.5V with inbuilt voltage-drop compensation for the main cables using over-compounding. The peak load can be much greater (200-300A) for which the generator ramps up by a few volts to overcome the drop. I have written about this before and will probably do so again.

Pics later, I am supposed to be working

 

[Lucien Nunes]

Dave and I popped down to Regent St. yesterday afternoon to first-fix this. We opted for 4c 1.5 SWA from the starter, an additional isolator next to the motor, and tri-rated in 20mm Adaptaflex SP to the motor. The FCU for the 18V DC PSU is run in 3c 2.5 SWA.

Strictly speaking we didn't finish the first fix as we were let down by a couple of rogue 25mm couplers with incomplete threads. Parking anywhere nearby is impossible, even stopping to drop off is a challenge, so we went on foot and didn't have all the spare bits that would normally be in the van. It seemed a waste of time on a Friday afternoon to walk down to Berners St. just for conduit couplers, so I'll take some on Monday.

With the larger installations and where blowers are hidden away many floors below, etc, I tend to spec custom star-delta or soft starters often with symmetry monitoring relays, electronic overloads and ELV controls. But here there is just one control point adjacent, the blower is small and in-the-room, therefore I went with an off-the-shelf DOL unit by ABB with 230V control, adding a DP contactor for the 230V PSU.