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 Making a Type 3 Braybon AVR
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 Return to top of page · Post #: 1 · Written at 9:24:59 AM on 29 September 2023.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 1233

I know this is getting a bit out of vintage radio but while I am researching the subject I decided to make a replica of a 1940's Braybon AVR.
I guess I have to beg Brad's indulgence here to keep posting non radio topics!

I suppose a point is, surely there is somebody that posts on this site could do a similar thing with a valve 1940's radio?
I used to work for Braybon, surely there is someone who used to work for a similar size radio manufacturer who could do the same.
I have made a few valve radios from scratch, but I never worked in the trade so don't have that intimate connection.
This project may just prompt someone who worked in the trade to go for it.

I'll post up a part one that covers the background and developing a parts list.
Cheers, Fred.

Making a Vibrating Point Mechanical AVR - Part 1
Making a Vibrating Point Mechanical AVR - Part 2
Making a Vibrating Point Mechanical AVR - Part 3
Making a Vibrating Point Mechanical AVR - Part 4
Making a Vibrating Point Mechanical AVR - Part 5


 
 Return to top of page · Post #: 2 · Written at 7:12:19 PM on 29 September 2023.
Brad's avatar
 Administrator
 Location: Naremburn, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 7278

Indulgence is granted, Fred. Wink

I always look forward to the latest articles here.

The emergency generator, where I work, is a similar size, though the engine is a twin turbo V12, displacement of around 18 litres and putting out 1.5MW of power. It drinks 100 litres of diesel an hour under half load. Such a machine is too modern for this forum though.


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A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 3 · Written at 8:50:02 PM on 29 September 2023.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 1233

Thanks Brad!
Your mention of your "little" back up set remined me of the first time I ran one about the same size in a test room.
It was a Cummins TT similar size and the two of us left with it (other workers who did the assembly had fled!)
We were packing our pants.

A first run of anything is always a heart stopper, get the basics right!
So we fed it oil and water, double checked, rolled up the starter battery bank, bled the fuel system and bolted the silencers on.

One thing you always have on hand is a way to STOP an engine should the electronics / governor go mad and over speed.
(I have had a new engine overspeed on me and run away, another story for another time.)
For this big boy I had a plate ready to slam over the main intake on the air cleaner.
You shut off the air and they stop, trust me!

We went over the procedure about 10 times, then I keyed the starter and the thing ran up to speed like a big baby!
Quiet as mouse, (except for open intake and that shut up with the pre-cleaner put back on) and it nailed itself on 1500RPM.
I had a 500KVA load bank so put that on and the big boy just rocked a bit, the high DB mufflers let out a bit more whoosh and that was all.

We kept an eye on the gauges and the engine ECU, no alarms, no fuss, no bother.

The thing made less noise than some of our Lister Diesels 1/10 the size!
The loudest thing while it was running was the fan noise of the air being pulled through the radiator.

Fred.


 
 Return to top of page · Post #: 4 · Written at 9:34:43 PM on 29 September 2023.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6663

Back in the 70s, the organisation I worked for had 2 large standby diesel generators on the roof of the building. Gen 2 was backup for Gen 1.Both were tested weekly by connecting them to a huge dummy load also on the roof. I know they were tested because they shook the building when they ran.

Well, on the one occasion during my tenure when mains power went out, Murphy decided to appear. Gen 1 would not start automatically and so failed-over to Gen 2 which would not start either. Red faces in Engineering that day as we all filed out of the then dimly-lit building via the stair wells and headed for the pub.


 
 Return to top of page · Post #: 5 · Written at 7:16:40 AM on 30 September 2023.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 1233

Hi GTC, the archilles heel of all back up systems with diesel generators is the starter batteries.
If the batteries won't crank the engine you have NOTHING!

Starter Batteries were almost never maintained.
I did a service call at the Auburn hospital in Sydney back in the 1980's to investigate why the back up gen would not start.
It had been supplied and installed by others (who could/ would not attend!).
The hospital had called around to any firm that sold gensets for help.
Braybon would always help especially a hospital.
The root cause was the starter and control lead acid batteries were simply DRY.
The set had been installed for about 5 years.

I asked the usual questions, was the set regularly started and loaded, who maintained the batteries, checked the oil, water ect ect all I got from engineering was stupid looks. Unbelievable.
The most aggravating thing was a shelf beside the set had the original supplied top up distilled water in 5L cans just sitting there unused!

Yes, I filled the batteries to the plate tops, and we jumped my bosses car battery onto the starter battery and amazingly the engine cranked and the show started. The set was a big boy probably about 500KVA and boy was it noisy!
We handed the set over to engineering and suggested they go and buy a new set of batteries NOW and got out.

Fred.


 
 Return to top of page · Post #: 6 · Written at 7:54:56 AM on 30 September 2023.
Brad's avatar
 Administrator
 Location: Naremburn, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 7278

We have a fairly strict regime for generator testing - a 10 minute run once a week to prove it still works, then once every four weeks it undergoes a 4 hour test under half load, connected to a 500kVA dummy load (air cooled resistor bank). Written records are kept as 'evidence', as well as two big fuel purchases a year.

As an aside, emergency generators will fall into more common use down the track as our governments stupidly continue their attacks on baseload electrcitiy generation so there hasn't been amore important time to make sure they are in working order.

Hospitals, TV stations, some shopping centres, data centres, telephone exchanges, road tunnels, Parliaments, etc - they all need them.


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A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 7 · Written at 10:35:11 PM on 1 October 2023.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 5221

One place where I worked, got a Ship type Gen set which used an odd leg system to utilise a six throw crankshaft for 12 cylinders. From memory it was a Ruston ex power station. It was supercharged with two electric Napier blowers. It gobbled up around 19+ gallons an hour.

Flat batteries were not an issue as it had a300cuft air tank and that gave you 3 chances of getting it to run. It sat on over a100ton of concrete. It was tuned to perfection and was not much noisier than a diesel electric loco. The warning with it was that if let run badly, it would tear itself of its mount. Apparently there was 200 gallons of oil running around in the cylinder heads.


 
 Return to top of page · Post #: 8 · Written at 6:50:40 AM on 2 October 2023.
Brad's avatar
 Administrator
 Location: Naremburn, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 7278

Big diesels have big oil. Our one requires 180 litres when it gets its major service each year. It is a good thing that one of the lifts does go as far as the plant room. I'd hate to be the one carrying all that oil.


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A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 9 · Written at 6:38:00 PM on 2 October 2023.
DangerousDave's Gravatar
 Location: Toongabbie, VIC
 Member since 1 September 2020
 Member #: 2438
 Postcount: 129

500KVA air cooled resistor bank, wow! That’s some sort of hair dryer Brad. 500,000 Watts is a lot of heat to dissipate.

The emergency 3.5MVA aux generators at the old Hazelwood Power Station were all air start and ran at 750RPM. It was amazing just how easy it was for them to wind over and start. They were a gentle machine when running. You could stand beside them whist running and have a conversation.


 
 Return to top of page · Post #: 10 · Written at 10:52:52 PM on 8 October 2023.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 5221

You can get oil in various size containers, one tractor here takes 100 Litres to do everything. Bought a 20litre drum to have an oil changing session recently. Lawn tractor engine is well passed 1000 Hrs and you fill the oil & top up the petrol. However, if it blows up its shell shock.

All of the engines running Shell here are old.

I note that Radio Australia (defunct) used a chemical bath & similarly Alexanderson's Three phase motors running the LF transmitting alternators used chemical baths as the speed control resistors.

You can use salts to make resistors and use it to work out the power output. The power of AC compared to DC was actually done by heating water.


 
 Return to top of page · Post #: 11 · Written at 6:57:48 AM on 14 October 2023.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 1233

I have got the AVR project to a working stage where I could power it up and check that my coil winding turns and the type of steel used in the magnet was suitable for operation.
The coil turns that were used in production I have no absolute record of, just hints and scribble in the serial number registers.
Yes I used to wind them but in a winding shop it was just one little job in hundreds of jobs and the numbers eluded me after 50 years!
The steel used in the magnet was just plain "mild steel" I think.
I used the quotes there because there are many grades of steel.
My memory tells me we just used whatever flat bar and round that was in the steel rack but memory is not a good reference some times.
So I have used bits of common scrap for steel and brass and wound on the best guess for turns and the AVR buzzes away like they used to, from memory!
More work to do especially as I have to set up a test rig to simulate a generating set to put the AVR through its paces.
That will be fun.


Fred.


 
 Return to top of page · Post #: 12 · Written at 6:30:52 AM on 15 October 2023.
Brad's avatar
 Administrator
 Location: Naremburn, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 7278

Document uploaded.


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A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 13 · Written at 9:03:40 PM on 16 October 2023.
DangerousDave's Gravatar
 Location: Toongabbie, VIC
 Member since 1 September 2020
 Member #: 2438
 Postcount: 129

Very interesting Fred. I can easily see that this is your field of expertise. With these early alternator sets and their mechanical voltage control, how were they managed for parallel operation. Was there any automatic droop control systems and means of load sharing? \
Dave,


 
 Return to top of page · Post #: 14 · Written at 8:39:17 AM on 17 October 2023.
BringBackTheValve's Gravatar
 Location: Linton, VIC
 Member since 30 December 2016
 Member #: 2028
 Postcount: 465

Dave, not too far back in Special Projects you must find Fred's articles on magnetic amplifiers.

A must-read for anyone interested in power control using magnetic saturation techniques before the modern electronics era.


 
 Return to top of page · Post #: 15 · Written at 8:47:01 PM on 17 October 2023.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 1233

Hi Dave, good question about paralleling.
I have run both DC and AC generators in parallel.
The best machines to parallel were identical machines, the worst dissimilar types.

The saving grace in the olden days was both prime movers and generators were droopy types anyway.
Prime movers usually had a centrifugal governor to class A and with a linear droop say 2.5%.
The generator would be fitted with a rheostat motor AVR also with a droop inherent say 2 to 5%
Thus, they were like babies to parallel.

A simple parallel switchboard would have frequency meters, voltmeters, ammeters, if you were lucky Kw meters and three lamps or if you were really lucky a Synchroscope. Most times the prime mover speed and so load, had to be adjusted at the engine governor.
Assuming one set was online, the incoming set speed would be adjusted so it was slightly faster than the buss.
The sync lamps would be flashing or the scope going round and round.
You would trim the AVRs for identical voltage or a bit more on the incoming.
At the blackout point or zero on the scope, or just before, you pulled the knife switch/Breaker up and the incoming set would drop on line maybe pushing a bit of Kw or maybe motoring a bit.
Then by the ammeters or the Kwatt meters you would speed the incoming prime mover and force it to take load.
If you were really keen and the board was fitted with Power factor or Var meters you may skew the Pf of a set with the AVR volt control.
Most droopy sets then happily stayed in sync and load shared ok, because of the inherent droops.

Of course, once people got fussy about the exact voltage and frequency, we would fit Heisman, Woodward or similar electronic governors to the prime movers, fitted EC AVR's with drop kits or balance connections onto the alternators, fitted the auto sync and parallel relays and boxes to the switchboard and then just switched a set on, pushed the on button and stood back and watched the electronics do the whole show.
The Jesus boxes had trimmers to set the desired share or impot export values and you just set them up to the client's specs and smiled as the electronics did the work.

Very occasionally we snuck a set in the test room onto the mains and used the mains as a 100's Kw load in parallel. Shhhhh, Dont tell the council or commission! And yes the shop wattmeter's slowed down or went backwards! Very handy if all the load drums were being used else where and you just wanted to do a quick and dirty test. God knows what would happen if you did that now. Or maybe no one would notice a couple of 100 Kw back feeding compared to the crap that happens now with solar panels syncing in and driving the system mad.

Fred.


 
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