Mk II ‘Beethoven’ Exploder Condenser Unit

Last week we looked at the Shrike Exploder unit, used to set off explosive charges. Tonight we have another demolitions exploder unit to look at, however this design is much earlier and dates to the late 1950s:imageThis exploder is much larger and heavier than the Shrike and is frequently known as the ‘Beethoven’ exploder. It was manufactured by a company called Arbra and was used by both the military and for civilian explosive work such as in a quarry or coal mine. This example is a British Army version, as evidenced by a plate marked ‘MOD’ at one end. Similar to field telephones of the era, the exploder works by having the operator crank a handle very quickly to turn a dynamo that creates electricity. This is stored in a capacitor and released all at once when the firing button is depressed. Unlike a field telephone however, the charge an exploder makes is far higher, approaching 650V, making it potentially lethal so one should never put fingers on the terminals and discharge the electricity! This safety warning is included on the instructions printed on the side of the exploder:imageA webbing carry handle is fitted to the top of the exploder to make it easy to handle:imageThe firing button is on the rear of the device, note also the M.O.D. ownership plate:imageA small spring loaded gate is fitted to allow the charging handle to be fitted:imageWhen the handle is removed, any remaining charge in the exploder is transferred to a special capacitor that slowly releases it safely. There are three handles provided with this exploder:imageThe explosive charge is wired up to two large terminals at the front of the exploder, each having a large Bakelite screw button to secure the ends of the wire:imageNote also there is a ‘WA’ code moulded into the Bakelite on the front:imageThis is a military stores code and this seems to have been a standard marking, even on civilian examples.

To test the exploder is working correctly a special testing device is provided:imageThis fits over the terminals like so:imageA piece of fuse wire or a bulb can then be fitted here to test the strength of the charge produced by the exploder. The fusion tester is carried in the leather carrying case and a special plate advises the user only to test the exploder with the correct tester unit:imageThe leather case is a large leather box that protects the exploder and gives the user a carrying handle to better carry the instrument (it weighs about 14lb!):imageThis has the exploder’s designation embossed in the lid:imageThe lid opens up and the exploder fits snuggly inside, with the terminals and charging handle slot free so they can be operated without removing the case:imageThis cutaway diagram illustrates the internal parts of the exploder:26471171122_5a1cdf8918_oThis is a very interesting piece of demolitions kit, if extremely heavy. My thanks go to Sean Featherstone for helping me add both this and the Shrike to my collection. By the way, the units are called ‘Beethovens’ apparently because the sound of the explosions they made down a mine sounded like the opening bars of Beethoven’s 5th Symphony and the company decided this would make a good trade name…

One comment

  1. MOD on these labels is short for Modification. Although they are often seen on military equipment they are also used commercially. Each number struck off with a stamp represents a specific modification applied.

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