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Post by mgk1951 on Dec 12, 2009 8:39:17 GMT 8
Hi
While searching for information on a particular Anti-Aircraft Gun, I came across a passage in a Catalogue of Ordnance Items which read: "The Audio Reception System, M1, was developed as a result of a request from the Commanding Officer of Fort Mills, Corregidor, P.I., for some method of determining the difference between bomb or shell bursts and an approaching hostile vessel when mines in a defense field were armed. As designed, the system will distinguish between mines being armed by the explosion of depth bombs, aerial bombs, and shells, by wave action, and the approach of a vessel.
The distinctive sounds of an approaching vessel are audible at a distance of from 500 to 3,500 yards, depending on hydrographic conditions. The audible sounds are picked up and translated to a visual signal as the vessel comes closer to the hydrophones. Experienced operators can often identify the nature of a vessel as it passes over the line by the character of its signature and sound output".
The Army Controlled Mine Fields of Manila Bay used a system of anchored mines that sent a signal to the land based Mine Casemate control panel when one of the mines was bumped by a vessel. The decision would then be made whether to set of that particular mine.
Exploding bombs or artillery shells were found to interfere with the mines and a signal would be sent to the control panel. Without visual confirmation and particularly at night, there would be no way of knowing what had caused the mine to react and send the signal
The Audio Reception System M1 would have allowed shore operators to determine if a vessel was in the vicinity of the mine field, prior to any mines reacting. A sudden reaction without hydrophone contact could/would indicate a mine's reaction to something other than a vessel.
The Catalogue is dated 1944; I am guessing the request from Corregidor was during the siege.
Regards
mgk
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Post by mgk1951 on Dec 20, 2009 16:03:43 GMT 8
Hi By 1941, the southern and some of the northern Army Controlled mine fields, protecting Manila Bay, had been replaced by Navy contact mines. Until that time, a fairly large infrastructure was required to control, plant, retrieve, maintain and test mines of the Army Controlled mine fields. Some of that infrastructure is still visible on Corregidor today. Let's look at the typical infrastructure of the 1920's and 30s and then look to see what remains of Corregidor's, through a series of postings starting with some basic detail. "Submarine mines - Responsibility for controlled mines. The Coast Artillery Corps is charged with the responsibility for the design, supply and tactical operation of all submarine mine equipment to be used in coast defense"."Controlled mine fields are planted to effect the destruction or damage of hostile vessels attempting to enter such portions of the harbor entrances as lead to channels used by frienfly shipping. The fields are normally limited to distances of 10,000 yards from shore and to water not over 300 feet deep.""A mine field consists of from two to four parallel lines of mines. Individual mines are composed of groups, each of which contains nineteen buoyant mines or thirteen ground mines. This arrangement insures the probability of a vessel passing over at least one mine and probably several other mines. Mines within a group are separated by 100 foot intervals in the case of buoyant mines and by 150 foot intervals in the case of ground mines"."Controllable electric mines are arranged so as to give a signal to the operator when they are struck. They may be set to fire automatically when struck or tampered with, or may be fired at the will of the operator. In the latter case the firing may be delayed, in which case the operator fires the mine some a short interval after the signal indicates that it has been struct: or by observation, in which case he fires it after the position-finding system shows that the vessel has come within the mine's destructive radius.""The Elements of a mine system are: 1. The mining casemate, consisting typically of four rooms: (1) The operating room, containing the power panel and the operation boards; (2) the engine room, containing the engine and the generator; (3) the battery room, containing the storage battery; and (4) the sleeping room for the personnel. 2. The multiple cables, 7 and 19 conductor, leading from the casemate out to the distribution boxes, one of which is in the center and the rear of each group of mines. 3. The single-conductor cables, radiating to the front from the distribution boxes, one leading to each mine. 4. The mines in groups of 19 or less. 5. The mine planters and other boats with the necessary equipment for planting and maintaining the planted mines. 6. The range finding system, the same as or similar to that used for the guns, enabling accurate plotting of the positions of the individual mines, and consequently permitting vessel tracking and observation firing. 7. Searchlights, for illuminating the mine fields at night. 8. Rapid fire guns, for the protection of the mine field. Other shore structures and installations consist of a mine storehouse; a loading room; a cable tank; trackage or roads to connect the various structures, a mine commander's station; base stations; a plotting room, and cable terminal huts. There are also wharves, mine yawls and Distribution Box boats. Image from an Ordnance Catalogue of 1944 illustrating the Mine Planting Flotilla. The Mine Planter is of a later type than Corregidor's USAMP Harrison. Next post - the mines and mine planting. Regards mgk
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Post by okla on Dec 21, 2009 0:02:05 GMT 8
Hey mkg..... Good stuff. You seem to be a fountain of technical information. Always enjoy your posts. Very informative.
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Post by The Phantom on Dec 21, 2009 1:38:57 GMT 8
Very interesting indeed!
There is a Mine Casement building by the road, to the east of, and behind Malinta Point, across from Enlisted Man's Beach.
There is also a Mine Casement location in Jame"s Ravine, both noted on the 1932 map and on my copy of the 1936 map.
There is evidence that many cables ran into these locations. None remain of course.
Rooms per se, no longer exist in either location. Both locations took it hard in the fighting, probably in the retaking in 1945.
The location in James is embedded in the hillside near the beach, and has caved in to a degree.
The location by Enlisted Man's Beach is a free standing building today, built into the hillside, somewhat sheltered from Bataan, but may have been totally covered with earth at one time?
Are there more Casements on Corregidor?
Did James control the mines between Corregidor and Cavite?
While the Enlisted Man's Beach/ Malinta Point location those between Corregidor and Bataan?
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Post by fots2 on Dec 21, 2009 8:48:35 GMT 8
Phantom, have a look on your maps at the big structure just up the hill (south) from Battery James.
It is a very strongly constructed building labeled as being East and West Mine Group Command Post.
My understanding is that all mines off of Corregidor were controlled from here. Perhaps someone can confirm or shoot that idea down.
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Post by mgk1951 on Dec 21, 2009 18:00:13 GMT 8
Hi All
I'll complete the series of posts over the next few weeks and cap it off with a mapmaster map showing the original locations of Corregidor's buildings and structures related to the Submarine Mines of Manila Bay.
In the meantime, has anyone some good profile shots of the USAMP Harrison to post here?
Regards
mgk
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Post by fots2 on Dec 21, 2009 20:55:14 GMT 8
Hi mgk1951, You probably already have this but I’ll post it anyway.
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Post by The Phantom on Dec 23, 2009 8:12:49 GMT 8
Fots, is it the building labeled M/W M/E straight south from Battery James on the 1932 on line map? Have not been there I don't believe, at least not with Mine control as an incentive to be there.
Want to visit that spot and see what sight lines they had from there. Or are those inside going entirely by mechanical means to detect possible mine field breaches?
They are sitting in a bad spot with no defense against bombers or shelling from Cavite or Bataan.
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Post by fots2 on Dec 23, 2009 8:38:54 GMT 8
Yes that is the building. Lets go have a look.
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Post by mgk1951 on Jan 10, 2010 12:09:49 GMT 8
Mines and Mine Planting
By 1930, "Three types of mine cases are in service; Spherical, plain sphero-cylindrical and corrugated sphero-cylindrical. They are made of open-hearth steel of great toughness and elasticity, and are galvanized". "Those of early manufacture were subjected to a pressure of between 100 and 120 pounds per square inch, while those of later manufacture were tested to 400 pounds per square inch".
Spherical mine cases were produced in two sizes, 32 or 40 inches in diameter. Plane sphero-cylindrical mine cases were produced by adding a cylinder between two hemispheres. These were again sized 32 and 40 inches in diameter. Corrugated mine cases were 32 inches in diameter.
The smallest of the mine cases held 100 pounds of TNT (trinitrotoluene), which is "a fine crystalline yellow powder manufactured by nitrating toluene. It was relatively insensitive to friction or ordinary shock, insoluble in water, very stable in storage and very powerful when detonated". Larger mines contained 200 pounds of TNT.
There were a number of types of mine anchors ranging from 1,000 and 2,000 pound cast iron to 2,300 and 3,000 pound automatic anchors. Automatic anchors contained a reel of anchor rope, which included a pawl operated lock controlled by a planting rope and weight. During planting, the weight and planting rope allow the reel to unwind until the weight contacted the ocean floor. The anchor rope then locked and the anchor settled to the ocean floor with the mine at the correct depth.
Buoys were and aid to marking out a mine field and helped space planted mines. They were removed after planting.
[Mines were planted in groups of 19 in water not over 300 feet deep and within 10,000 yards of the shore. Mines within the group are separated by 100 foot intervals. Each group of mines was connected to a distribution Box. The distribution boxes was designed to securely hold the ends cabling to each mine in the group and the 19 connector shore cable. Later, the Distribution Box also contained the water proof single connector Selector Box, which provided a means of electrically selecting, testing or firing any mine in that group.
There were also ground mines available for planting at depths up to 35 feet. They rested of the ocean floor and contained between 200 and 300 pounds of explosives.
There were a number of different types of mine plugs. Their function was similar. The mine plug was controlled by a direct electrical current. The mine could be set to react to a being interfered with or being hit by a vessel. The reaction completed a circuit to the Mine Casemate which showed as a light on the Operating Board.
A decision could then be made to explode that mine then or after a delay. Delayed firing could be advantages if the vessel was large and the mine might be pulled under a more vulnerable part of the vessel.
If required, any or a number of mines could be set to explode on contact. The same circuit closer that signaled a contact with the mine could also be set to explode the mine on contact.
The mines could also be fired from observation. Course and speed of enemy vessels were observed and plotted on a plotting board and the decision could be made to explode one or a number of mines. However, the mine was to operate, there were a number of safety devices incorporate to avoid explosions when friendly vessel contacted a mine.
The mine plug screwed into the bottom on the mine case and contained the circuitry that set of the mine under controlled or contact firing. The plug contained the circuit closer, which operated on direct electrical current.
To fire, alternation current was applied to the mine plug circuitry at the transformer in the plug. The alternating current then induced a current in a coil connected to two fuzes. The mine would then explode. This was one of the safety devices. To fire a mine alternating current had to be applied to the Operating Board in the Mine Casemate.
The second safety device was the Mine Switch in the Mine Casemate. It had to be closed for a mine to fire.
The photograph posted by Fots2 shows USAMP Gen. George F. E. Harrison (in some publications the Harrison was mentioned as the Col. George F. E. Harrison) alongside the North Mine Wharf at Corregidor. Comparing that photograph with the one of the USAMP c1916, with mine and mine anchor on davits, it is possible to see the same davits on the USAMP Harrison.
Regards
mgk1951
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