Yes the GL mat covers a huge area at Blantyre.  There is a pic somewhere of an even larger one in Orkney. I assume these large mats must have been early versions and that the later ones were much smaller. An acre of horizontal wire mesh would have been impossible at Larkfield for instance because of the contours of the land round about and I read that they could be upto an acre!

I still cannot find any info on the ramps as mentioned by Mr. Guy

I see you are having a bit of a Blitz on the AA Batteries Appollo. I have been trying to find out about the Glenacre site which appears to be a real mystery. No one seems to know of its existence!

The Glasgow and Clyde AA Batteries deserves a bit of a tidy.

There's more sites with confirmed names and location now, compared to when it was cobbled together, so it seems right to try and collate it there.

It's also filling in some of the blanks that some of the original entries had, and tying up loose ends on others.

There will always be inconsistencies, as the info is coming from different sources, but that can be appended to the table as a note or comment, and be chased later.

There should probably be a page for the various decoys, as there are a number of sites beginning to appear with info.

I'm still trying to adapt my thought processes to the best way to manage the info though. While the web is clearly the best way to disperse it, and maybe catch info from anyone that may offer it, I'm frustrated in the poor or awkward means available for managing the data. Web methods are (to me) atrocious, and I've written database systems that can control a small business, and automatically generate its accounts, invoicing and related documentation, so I must have at least some limited ability. I admit that I'm part of the problem, I think in stand-alone application terms rather than web developments, but that's not wholly down to me, as I'd happily use a web-based tool if I had it (and it didn't cost an arm and a leg).

That's why I use the wiki. It may not be optimal, but it lets things proceed without locking the contents into some weird structure, so the info can be collected and moved around as needed, and has the advantage of being searchable.

Interesting on Glenacre (I spotted your question ) It's last on the list, and I haven't looked at it at all, so maybe something will turn up.

Forgive the worn and fading memory, but does it tie in with the question I think you asked about a sighting point, and its visibility from Toward?

Well it would make sense of the statement from a local that he could see the Perch from the battery. The only problems being that the Perch would be to the right from Glenacre and to the left at Toward, the second being they are 3 miles appart and in different villages.

It is strange that the Curator knew nothing of the site as he seems to know everything about the history of the area.  I have joined the weekly off season working party at the museum which might bear fruit eventually.

Another local has emailed me to say he knows nothing of the site either which is strange as the given position is not at all remote.

I have put in a link to a picture of the Gleniffer Braes Starfish site and some I have found of AA Batteries. I hope this meets with everybody's approval.

Indeed, it's handy to stick that sort of thing in if it turns up.

I'm sure the RCAHMS database has changed at some point. I'm (almost) sure that months ago, if there were images, then they showed up on the report page, under the icon of the camera where it says images, I haven't seen anything there for ages, yet I know some of the reports I've been looking at have got images if you look them up separately. Or I've just got a good imagination

If you're new to the database, then it did (together with the mapping side) get fair bit of a shakeup and update a few months ago - it was terrible at one point, as there were days you could try and login in for some info and it would just not be there, but it seem to be more or less ok now. The only problem is if you look for report around 1 am, then the server seem to go offline for a few hours, and you have to remember what you were wanting until the next day.

I have been through all the AA Batteries and entered the photos.

On two of them I opted to put the info on the Discusssion page as I was not sure where to put it on the real page.

Have a look at the pic for Woodend (Hellensburgh) as it is particularly good and shows both the real and dummy batteries.

Sorry to hear that you vampires have trouble with servers at 1A.M. . I have no such problems as I am usually somewhere else at that time.

I guess we have moved on a bit since this thread was started in 2005!

I am still mulling over the reason for some decoys sites to have single roomed control bunkers and others 2 roomed ones. (Beware that John Guy in RCAHMS reports calls the single roomed ones as two room, presumably counting the corridor as a room.)

Having re-read the info on line and noted that the fire decoys were lit remotely by electricity it occurs to me that the power demands of such a site would greatly exceed that of a lighting decoy.  I assume some kind of element having to be heated to incandescence to light the fuel.  

Would lighting decoys not have required only a few hundred watts as nothing was well lit during the war and as I understand it they were largely pretending to be dull sources such as blackout failures at windows and doors.

All the 2 roomed ones so far viz. Drumnessie, Craigmaddie, Blairskaith and Auchenreoch could be described as quite remote in WWII terms.  The 2 single roomed ones viz. Foxbar and Whitelees moor seem somewhat less remote.  I wondered if they had a more handy source of mains power?   I cannot believe that the single roomed ones had their own generators as the room is quite small and generating equipment of that era was usually powered by a car engine.  Also there is no sign of any exhaust vent.

Think you're right; the standard set up for a'skylight' was a plywood box with a bulb in it, and just enough of an aperture to suggest a poorly blacked-out loft window. In a totally dark environment even the flare from a match would be seen at a great distance, so I think power requirements would have relatively low.
Feel free to correct me though; I've got a collection of ARP books I've been collecting for years, but I can't get into the book cupboard just now.

Don't confuse wartime propaganda with fact (remember, the wartime story of carrots being good for your eyes is one such story that has lasted even to today, and is still a favourite misquoted urban myth of the vegetarian foody brigade)- if lights were so visible, then why do lighthouses have such huge lens and mirror systems to get their beams visible at "great distances". Based on propaganda of the time, all they should need is a candle and the bottom of a glass bottle to get anywhere up to 5 miles and beyond.

If you imagine a QL dummy town or airfield set up with lamps of only 60 W, then using just 100 of those to make a reasonably decent pattern to fool a bomber into identifying the pattern as a town, city, airfield or dock would have needed a 6 kW generator driven by a 12 kW motor. As that would need them to run flat out, in reality they would be at least twice that size. That's over 30 bhp, and wartime engines were probably throwing out less than half what a modern engine can, so double that again in those days.

Double it again for the losses in the cable runs and their considerable lengths too (even though a decoy was only about 70% of the size of the place it was supposed to impersonate), and you soon need some decent motor generator sets of the time to run a proper decoy. Add another set of my fictitious 100 lamps, and you've just doubled the requirement again. The length of the cables would really preclude running at low voltage, eg 12 V car batteries, or even 24 V truck types, due to the increased losses in the cable.

I imagine electrically ignited QF fire deoys used very little power, as the electricity would surely have been used to trigger electrical detonators, and starts the fires using incendiary devices.

Unfortunately...

I've never come across any proper write-ups, so I'm guessing the above purely on engineering numbers, and throwing it in for discussion in relation to large-scale, organised decoys only, so as the_historian says...

Quoted Text

Feel free to corretc me thoug;

They also needed power to remotely operate devices apart from just igniting them there would be solenoids and motors as well as the uniselectors that selected them.

I'd no idea they had that level of control - told you I hadn't found much detail.

All I'd been aware of was some switchboard in the bunker to turn the electrical bits on and off, and valves an plumbing to control the flow - by gravity as far as I could see - of the fuel, oil, and water to the fire pools, but this was all based in the bunker, with no hint of remote control in the sense of having distant device that would control other things out in the field. I had imagined everything just running to/from the bunker from what I'd read.

Anything else

I will have a look in Fields of Deception later but sure that I have that they used a Strowger type system so they could dial up for a particular thing to be activated.

Another good book is Royal Air Force Beam Benders: 80 (Signals) Wing 1940-1945.  There is one good story, which I think is in that book, about a couple of the crew of one decoy site going into somewhere like Norwich which was their nearest big town.  They tended to be left to themselves and just had a supply lorry every week and wore overalls because it was a dirty job.  They were stopped by a RAF policeman and taken to the RAF police station (or whatever they are called).  The very smart officer demanded to know where they were from because they were improperly dressed.  They refused to tell him.  He asked them to just show the area on a map but they still refused.  They gave him an Air Ministry number to call where the officer was given a severe telling off and told to mind his own business.  They were sent on their way.

MB

I don't think gravity from the bunker to the decoy played any part at all as all the sites seem to have the bunker at a lower altitude than the site itself.

From what I have read the technique was to wait until the pathfinders had dropped their relatively small number of flares or incendiaries, extinguish these as quickly as possible meanwhile lighting the decoy fires.  Some of these had water cisterns above them and a device to discharge water into the burning oil from time to time to give an explosion of flame.   I assume these were operated remotely and not on a timer but I don't really know.

I understand that the Morris 10 car engine was often used to power the generating sets.  Probably less than 30 BHP.   I would imagine that dynamos rather than alternators would have been the order of the day and that the system ran on DC rather then involve the complications of correct phasing of AC supplies.   I do not know how they dealt with the heat from the engines but this might explain the 12" pipes on both sides of the bunkers.  A through draught might have been a good help.  

Lighthing decoys would not have required much power as on a clear dark night a small light shows up for miles.  Lighthouse are a poor analogy as their characteristic flash is required to be visible from distance under much less than perfect conditions.  Ships are also much slower to answer their helms, take the example of the Akka, and need searoom to manouvre safely.  Under clear conditions a lighthouse is clearly visible from the horizon.

I had another look through the pics of the vaious decoys.  The pipe stub found at Auchenreoch is duplicated at Drumnessie.  I wonder what it was for?   It cannot be chance.

Your message arrived while I was typing this.  You will have to explain Strowger.

STROWGER is the old clockwork telephone exchange system.

A uniselector stepped around each time it received a dialling pulse so with a simple telephone dial you could select 10 outputs.  Hang another uniselector on each of those lines and you can select 100 outputs with the same simple dial.

Normally powered from 50v in a telephone exchange but probably could run from other voltages.

There is a diagram in Beam Benders - 8hp engine and dynamo for electricity.  There were also dimmers so they could turn the lights down.

I was trying to remember where it was all controlled from - RAF Radlett.

MB

Lighthouse may be visible to the horizon under ideal conditions, but in the real world have ranges associated with their beams, and can be around 15 miles, but this of course varies with the light, how it is designed, and the weather and environmental conditions.

The analogy is good because it shows how far the light can be seen reliably when it is concentrated by whatever lenses and reflectors are used. These collect a fairly small light (15 -30 W so they can run from batteries in a power fail scenario and run for a decent time) and focus it to achieve that range. By comparison, the light from a bare bulb is distributed such that rather than illuminate a narrow cone of a few degrees width, its light (for the sake of argument) is distributed over a spherical area.

If you imagine how many of those lighthouse beam cone bases would fit onto the spherical surface at the same distance from the light, you can see that the light from a bare bulb, through an open skylight for example, is next to nothing compared to the lighthouse.

We could run numbers, but the much repeated warnings about the visibility for miles of a match, lit cigarette, crack in a blackout curtain etc were just propaganda, and well intended, as it was much safer to drill the public into showing NO lights at all, rather than trying to educate them about what level of light would be visible at what distance. Much easier to send the police and ARP wardens out with instructions to charge anyone showing a light - end of story, and no arguments.

The bomb aimers would need binoculars to see any such lights, and would also have had to be looking at a very, very narrow cone of illumination, which they would have had difficulty to spot from a less than stable platform. Add to that some cloud, and maybe some smoke, and the propaganda fiction become even more apparent.

Oh, incandescent lamps would, of course, have had no care as to whether they were fed DC or AC power, so dynamos would have been fine.

ok, had a look in Fields of Deception and came up with the following; the original sunken bunkers of 1940 had a t-shaped entrance and connecting passage, with a room on either end. These were built to AM drawing 339/40. These were prone to flooding and were replaced in early 1941 by the single room surface-built bunkers of AM drawing CTD557/41. These only needed one room because all they held was a telephone and the switchgear to illuminate the decoy.
The two-roomed surface bunkers are to AM drawing CTD151/41 and were built later in 1941. The power room held three generators, and there were external expansion tanks about 20 feet away.
On the subject of skylights, the book gives a schematic diagram of a real-life decoy near Derby; part of the layout includes 25w lamps and 60w ones.

I can't remember which one, but that ties in nicely, as The Fox has pics that show the three concrete generator bases together.

Hopefully it will ring a bell, and he can say which one so it can be referred to.

This reminds of a recent documentary which featured staff at airfield decoys, and their account of simulating taxiing aircraft on the field. They had to remember not to merely simulate the taxiing route of the aircraft on the field using a hand-held spotlight to replace the aircraft light, but also to make sure they shone the beam in the correct direction on the ground, and shook it to simulate the shaking the aircraft experienced as it rumbled across the runway.

They knew the Luftwaffe was not crewed by idiots, and steady or smoothly moving lights would immediately have been recognised as false targets.

I think my favourite deception was the trams, which required the operators to strike random arcs on wires along the decoy streets, to simulate their travel along the road and add to the effect of a populated place.

All the two roomed bunkers I have seen so far have the 3 engine beds.  One of these days I am going to have to clean up the floor of one of the single roomed version to see if there was an engine bed there.  I suspect not.

Reading the historian,s post above the concrete slabs and brick foundations I assumed were part of the fuel supply must have been for the expansion tanks for the engines.   This brings a further assumption that 2 of the usually 3 pipes in the wall carry the supply and return to/from these tanks.  What was the 3rd one for?  Only one such bunker has only 2 (I forget which one ).   This begs another question - where was the fuel supply?   Given that the engine were probably idle more than in use, was there a small tank in the room which was kept topped up with jerricans?

Looks like a bit of a page revision is already required.