Pencil detonator

from Wikipedia, the free encyclopedia
Pencil detonator from the attack on July 20, 1944, exhibit in the Military History Museum of the Bundeswehr in Dresden

A pencil detonator ( English pencil detonator or time pencil , literally, time pencil ') is a chemical-mechanical time fuse . The time delay between activation and ignition is based on the decomposition of a tensioned wire by a chemical substance which attacks the material of the wire and slowly decomposes it. The pencil fuse was developed in Germany during the First World War and significantly improved in Great Britain. There and in the United States, pencil fuses were produced on a large scale during World War II . The official British name was Switch No. 10 , in the United States of America the detonator was called M1 delay fuze or M1 delay firing device . Because they were used in several assassinations on Adolf Hitler , these detonators are also known beyond military circles.

history

Pencil detonator in a box

The principle was developed in Germany between 1915 and 1916 and improved in Poland. Colin Gubbins brought the Polish detonators with him in 1939 as a member of the British military mission during the German invasion of Poland . The detonator was perfected by Station IX of the British Special Operations Executive . Around twelve million units were manufactured during the war, many of them by the United States , whose armed forces used the slightly modified detonator under the name M1 delay fuze or M1 delay firing device .

The Royal Air Force parachuted the detonators in large numbers for resistance groups over areas occupied by Germany. As a result, some detonators came into the hands of the Wehrmacht and were used by conspirators in Wehrmacht circles for assassinations on Hitler.

After World War II, detonators remained part of the equipment until they were replaced by more reliable electronic models.

construction

Internal structure and functionality of the detonator

The detonator is reminiscent of a thick pencil, which is where the name comes from. The total length is 127 millimeters, the diameter 8 millimeters with a mass of 18.5 grams. It consists of an initial ignition head made of sheet steel, a spring sleeve made of brass or aluminum and a copper cap. The material of the spring sleeve depended on the manufacturer: brass was used in American production, aluminum was usually used in English production.

In the initial detonator there is a primer with an initial explosive charge. The end ends in a perforated steel plate to hold the detonator . The time fuse is designed for a specific detonator, the Detonator No. 8, which was later used by detonator No. 27 was replaced. The US version has an adapter instead of the perforated sheet steel to be able to hold other detonators.

The spring sleeve contains a helical spring held under tension by a metal wire , at the end of which a firing pin is attached. Various metals such as copper or steel are used as the material for the retaining wire, depending on the design . A steel wire was used in the types improved in World War II.

With the pencil igniter with steel wire there is a glass ampoule with copper (II) chloride under the cap made of brass or aluminum , which is stored on both sides with a cotton ball against impact, and the holding wire led past the ampoule. The end of the tube is sealed by a slotted screw to which the retaining wire is attached.

function

The pencil detonator is a chemical detonator, which in the optimized version from the Second World War is given the lead time from the decomposition of the steel wire, chemically this is iron , through copper (II) chloride . The steel wire has the same thickness for all lead times. The lead time is chosen by the different concentration of copper (II) chloride in aqueous solution during the production of the detonator: Due to a high concentration of copper (II) chloride in the glass ampoule, there is a short lead time, with a stronger dilution with water there is a longer lead time. In contrast to the exact thickness of the wire, which can vary due to notches and material defects, the concentration of the copper (II) chloride can be precisely dosed.

It is relatively easy to use: The glass ampoule is destroyed by crushing the cap with a pair of pliers or stepping on it with a boot heel, as stated in the original instructions. The cap does not have to be compressed completely. It is sufficient if the glass ampoule bursts. The igniter is then shaken and the copper (II) chloride is distributed in the cotton ball and chemically attacks the steel wire.

The inspection hole in the front area is then used to check whether the spring is still under tension. If, for example, if the cap is crushed and the glass ampoule breaks, the retaining wire is also damaged and torn, this can be seen through the inspection hole. In this case the igniter must be discarded as defective. When the retaining spring is still tightened, the detonator cap is attached to the initial detonator head and the detonator is pushed into the explosive mass. Only now is the security strip pulled off the primer to arm the detonator .

The copper (II) chloride breaks down the steel retaining wire over time. When it finally breaks, the coil spring drives the firing pin onto the primer , whereupon this detonates the detonator. Depending on the concentration of the copper (II) chloride solution, the lead times varied from 10 minutes to 24 hours. The security strips were therefore marked in different colors (black: 10 minutes, red: 30 minutes, white: 2 hours, green: 5½ hours, yellow: 12 hours, blue: 24 hours). The times were based on a temperature of 15 ° C. The tolerance is said to have been ± 3 minutes for 10-minute detonators and ± 1 hour for 12-hour detonators. In fact, the discrepancies could be much larger. Because of the temperature dependence and the limited reliability of the chemical detonators, the instruction was given to use two detonators.

Advantages and disadvantages

The detonator is silent, small, light, insensitive to shocks, inexpensive and easy to assemble.

Due to the compact design, however, it can happen that the firing pin jams in the spring sleeve. The ignition point cannot be determined precisely, as with a clock, because the delay time is strongly dependent on the temperature. Once triggered, the chemical process of decomposition of the retaining wire cannot be stopped. To prevent ignition, an object can be inserted into the inspection hole. Just like the original security strip, this item prevents the firing pin from hitting the primer - after which the detonator can be separated from the explosive.

Known missions

Operation Chariot, March 28, 1942

The dry dock at Saint-Nazaire was destroyed in the British Operation Chariot . For this purpose, a discarded destroyer prepared with explosives was rammed into the gate of the dock and detonated with a pencil detonator.

Attempted assassination attempt on Hitler, March 13, 1943

In the plane in which Hitler flew back from a front inspection near Smolensk on March 13, 1943, a 30-minute pencil fuse was plugged into the neck of an explosive charge disguised as a cognac bottle. The bomb didn't explode; the detonator worked correctly, but the detonator could not detonate the explosives. Either it was defective or the temperature in the plane was so low that the chemical reaction did not take place quickly enough.

Attempted assassination attempt on Hitler, March 21, 1943

At the opening of an exhibition of Soviet looted weapons in Berlin, Rudolf-Christoph Freiherr von Gersdorff wanted to blow himself up with Hitler, Göring, Himmler, Keitel and Dönitz. Because no instant detonator could be found, Gersdorff used a 10-minute pencil detonator. Hitler left the exhibition after a few minutes; Gersdorff was able to prevent the ignition just in time by separating the pencil detonators from the explosives.

Assassination attempt on Hitler, July 20, 1944

Claus Schenk Graf von Stauffenberg carried out the assassination attempt on July 20, 1944, on Hitler during a meeting at the Fuehrer's headquarters. Since his remaining hand was missing two fingers, he used a pair of pliers made for him to crush the fuse cap of the pencil fuse. Two detonators were used with a lead time of 10 minutes. The detonator detonated the charge, but it only slightly injured Hitler.

literature

  • Vladimir Dolinek: Illustrated lexicon of weapons in the 1st and 2nd World War . Munich 2000, ISBN 3-89555-223-2 .

Web links

Commons : Pencil Detonator  - collection of images, videos and audio files

Individual evidence

  1. ↑ Mark Seaman: Special Operations Executive: A New Instrument of War . Routledge-Verlag , 2013, ISBN 1-134-17524-8 , pp. 24 .
  2. ↑ a b M. RD Foot : SOE: An outline history of the special operations executive 1940-46 . Random House , 2011, ISBN 1-4481-0401-7 , pp. 94-95 .
  3. ↑ David Lampe: The Last Ditch: Britain's Secret Resistance and the Nazi Invasion Plan . MBI Publishing Company, 2007, ISBN 1-85367-730-2 , pp. 75 .
  4. ^ George C. Chalou: The Secret War: The Office of Strategic Services in World War II . DIANE Publishing, 1995, ISBN 0-7881-2598-2 , pp. 298 .
  5. ^ Gordon Rottman: World War II Allied Sabotage Devices and Booby Traps . Osprey Publishing, 2013, ISBN 1-4728-0162-8 , pp. 84 ( limited preview in Google Book search).
  6. ↑ United States. Dept. of the Army (Ed.): Army Ammunition Data Sheets for Demolition Materials . 1989, p. 2–33 ( limited preview in Google Book search).
  7. ↑ a b c David Lampe: The Last Ditch: Britain's Secret Resistance and the Nazi Invasion Plan . MBI Publishing Company, 2007, ISBN 1-85367-730-2 , pp. 76 .
  8. ↑ M147 Time Delay Firing Device. Retrieved September 16, 2013 .
  9. ↑ a b c d SWITCH No. 10. Retrieved July 20, 2014 .
  10. ↑ Stephen Bull: Descriptive Catalog of Special Devices and Supplies . MBI Publishing Company, 2009, ISBN 978-0-7603-3751-6 ( limited preview in Google Book Search).
  11. ↑ Detonator No. 27. Retrieved September 15, 2013 .
  12. ^ Gordon Rottman: World War II Allied Sabotage Devices and Booby Traps . Osprey Publishing Publishing, 2013, ISBN 1-4728-0162-8 , pp. 85 ( limited preview in Google Book search).
  13. ^ Michael Asher: The Regiment: The Real Story of the SAS , Verlag Penguin UK, 2008, ISBN 0141889438 , page 86 [1]
  14. ↑ Terry Crowdy: SOE Agent: Churchill's Secret Warriors , Verlag Osprey Publishing, 2008, ISBN 1846032768 , page 27 [2]
  15. ^ Michael C. Thomsett: The German Opposition to Hitler: The Resistance, the Underground, and Assassination Plots, 1938-1945 . McFarland Verlag, 1997, ISBN 0-7864-0372-1 , pp. 177-178 .
  16. ↑ Guido Knopp , Alexander Berkel: You wanted to kill Hitler . C. Bertelsmann Verlag , 2004, ISBN 3-570-00664-6 , pp. 130 .
  17. ↑ Der Spiegel 28/1984