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The German ECR (Electrical, Condenser ,Resistance) fuze was first manufactured by Rheinmetall in the 1930,s.it was designed by Hubert Ruhlemann .
Between 1931 and 1932 trials were carried out in Russia on the use of Mechanical and Electrical bomb fuzes (as Germany was forbidden to manufacture or produce weapons of war) 250 Mechanical and 250 electrical bomb fuzes were tested,it was found that electrical fuzes were far superior.
Photograph above shows a sectioned view of the German 50 Kg bomb,less fins..with a type (25)B fuze,
Description
The normal type of bomb fuze is 110 mm long by 50mm wide (measured from the head to the base) the fuze consists of , usually 2 charging pins on the top,below this the Shoulder,this may contains 3 fixing screws, it is this location , that the various markings are found,consisting of type of fuze ie EIAZ is an electrical impact type,next a ringed number this is very important (see types below) for example (17) is a long delay clockwork fuze,and is housed in a longer case approx 142mm long. Then there is the Triagramme or manufacturers 2 or 3 letter code ie RHS is Rheinmetall (Sommerda) plant,then the year followed by a batch number ie 2a = batch 2 sub batch A also there is the waffennapt stamp, an eagle with a number.56 is for the Rheinmetall.inspector.
Construction
Usually Aliminium,but can be steel,in two parts,the top part containing the pins is the SWITCH BLOCK (contains the trembler switches.)The bottom part contains the various Resistors and capicitors,that contain the electrical charge.At the very bottom of the case is a screw thread, its here that the gaine is attached see picture of a type (15) fuze below,
The (55) fuze and (89) airburst fuzes are constructed using tubular steel,instead of aliminum,and are in one piece,as against two.
How the ECR fuze works
The normal ECR fuze is one that is charged elecrtrically on leaving the aircraft, during the bombs fall,the electrical charge trickles through resistors , to a firing condenser.The impact of the bomb landing causes a sensitive vibrator switch to close the circuit and detonate the bomb through a firing bridge (similar to a match head) this creates a flash that detonates the sensitive penthrite wax contained in the attached gaine,which is the steel or bakelite container screwed into the base of the fuze (See picture below of gaine attached to a type (15) ECR fuze)
(15) with gaine attached
Sectioned (25)B
Notable dates in bomb disposal history
17 th October 1939 first German bombs dropped on Hoy Orkneys they were all 50Kg and were fuzed with a simple impact fuze type (15) which could be rendered safe using a crabtree , a device that shorted out the electrical charge contained in Capicitors inside the fuze
17 th November 1939 Germans start dropping parachute Magnetic mines
23 rd November 1939 Lt Cmdr Ouvery recovers first magnetic mine at Shoeburyness,and successfuly defuzes it.
1 st May 1940 Home security circular 88/40 confirms that war office is responsible for dealing with UXB,s
1 st May 1940 1 st UXB committee is held to discuss various ways and devices to tackle unexploded bombs .
May/June 1940 First 25 BD sections formed comprising of 1 x Lt ,1 x Sgt and 14 Other ranks.
June 1940 Steam Sterilizer developed to cut a hole in bomb casing and emulsify explosive
17 th August 1940 Lt Archer removes a type (50) anti disturbance fuze by hand this was needed for experiments.
17 th August Lt E.W.Reynolds defuzes bomb in Bristol with a type (17) fuze
27 th August 1940 Lt Archer recovers the first (38) Fuze
2 nd September 1940 Lt Archer removes a ticking type (17) fuze to find a new type Zus 40 Anti Withdrawl fuze underneath, this was succcessfully removed in tact.
12 th September 1940 The Steam Sterilizer was used for the first time by Captain Kennedy on a live 250 Kg bomb in Regents Street.
14 th September 1940 Lt Robert Davies defuzes bomb under St Pauls Cathedral.
16/17 th September 1940 Parachute delivered magnetic mines dropped on London 25 dropped , 17 failed to explode
23 rd September 1940 King George announces a new and high decoration for gallantry THE GEORGE CROSS
26 th October 1940 First acoustic mine recovered.
28 th October 1940 SD2,s Butterfly bombs dropped on Ipswich (this was the first time these bombs were dropped on the UK)
16 th November 1940 Fuze cap found on bomb in Shaftsbury Ave, couldnt determine which type of fuze was fitted, removed by Lt Neville Newitt.
18 th January 1943 New fuze type Y was recovered by Major Martin, this fuze was designed to kill the bomb disposal officer.
24 th January 1943 method found to defeat this Y Fuze was found by Maj John Hudson, the method used was to freeze the fuze with liquid Oxygen.
3 rd / 4 th March 1943 2 new types of fuze type numbers (67) time fuze and type (70) anti disturbance fuze found in Butterfly bombs dropped in Essex.the 67 was designed to explode 30 mins after hitting the ground.
13Th/ 14 th June 1943 1 st Large scale raid using SD2 Butterfly bombs were dropped on Grimsby
23 rd June 1944 UX flying bomb found in Sussex,fuzes had to be removed at all costs,radiography used by Major John Hudson and Dr Dawson .
2 nd July 1944 Fuzes removed successfully from V1 flying Bomb
11th March 1945 UX V2 Rocket Paglesham Essex
23 rd october 1945 Last of 48 meetings of the UXB Committeee held at shell Mex house on the Strand.
Types of Fuze
IMPACT FUZES
Aufschlagzuender Impact Fuze AZ
Electrical impact fuze is EI AZ
TIME DELAY
Zeitzuender Time delay Zt
LONG DELAY
Langzeitzuender long delay Fuze LZZ
German fuzes have their markings stamped around the shoulder the all important marking is the circled number ie (17) the number ending in 7 denotes that this is a delay fuze.a (0) ie (50) is an Anti disturbance fuze.
The interpretation of these are as follows
(0) Anti disturbance ie (50) (60) (70)B
(1) Mechanical/dual purpose fuze ie (41)
(2) used in Incendiary bombs ie (12)
(3) Mechanical fuzes ie (63) (73)
(4) Special fuzes ie (24) (34)
(5) Electrical Impact for general use ie (5) (15) (35) (55)
(6) Electrical Impact fuze for special use ie (26)
(7) Delay Fuzes ie (17) (67)
(8) Elecrical Impact fuzes with slight delay for use against Sea targets ie (28),(38)
(9) Aerial Burst fuzes ie (9) (59) (79)
From purely a collectors point of view the hardest fuzes to collect are the early Type A used in the Spanish Civil War and the Brass fuze no (5) which was later changed to a no (28)* as the delay was found to be too long ,this fuze is used on hardened targets( ie shipping)
There were 2 types of No (5) fuze one made in Brass and the other , Aliminium,the earliest one seen was dated 1936.
There are 3 versions of the Anti withrawl fuze type Zus 40 which could be fitted under any of the normal ECR fuzes,but more usually under the (17)
Type 1 (Rarest is in Ali)
Type 2 different design in Plastic,
Type 3 in Mazak
And the Clockwork Long delay fuze ie (17) (17)A (17)B all these are highly prized.
variations of (17)
The original long delay fuze type (17) had the clock screwed into the base externally,this was often covered with a black rubber sleeving to waterproof it.and had 2 plungers.see picture below with attached ZUS 40
Next came the (17)A this time the clock was fitted internally and had 1 plunger
The (17)A was manufactured early in 1940 having a steel lower sleeve and having only 1 plunger ,this is called the emergency pattern,when seen the steel appears to be rusty and pitted,this is normal SEE PICTURE Below
Another fuze worth looking out for is the Y fuze this is similar in length to the (17) fuzes ie 3 screws in the head, 2 plungers and instead of straight sides this fuze was flared out at the bottom with a wire collar,designed to stop the fuze from being removed,the markings are EIAZ (50)B Cpp Y 8d.this fuze contaned a seperate circuit below the normal one with 2 dry cell batteries,and 3 mercury switches.its sole purpose was to kill the bomb disposal officer.who attempted to extract the fuze.
50b Y Fuze
It is interesting to note that 1.6 Million type (15) fuze,s were manufactured between 1937 to 1940 .
The Type(25) which replaced the (15) fuze was produced in 9 variations and approx 2.2 million were made.this fuze it is stated arms in 3 seconds?
The Fuze type (57) Which was never dropped here in the UK contained a chemical delay,and a Anti Withdrawl device, the delay was up to 100 hours,there was no way to tell how long this fuze had before detonation.the (17) had a delay of 72 hours,but could run as long as 80 hours.
It was found that the (25) fuze was expensive to manufacture so the (55) fuze was produced instead,made from 1940 to 1942 a quantity of 840,000 were manufactured ,the case was made of one piece steel , it was found not to be very waterproof , and instances of this fuze being placed in the second fuze pocket of the bomb with its protective cap still in place,.were not uncommon.
The Zt Z (89) Fuze at its variants
The original Zt Z (89) fuze was only about 55 mm long as apposed to the more normal 110mm fuzes.and came in three types
The contents of this fuze is a clockwork mechanism , similar to the long delay (17) fuze it fact it was manufactured by the famous Jurgens clock factory.this clock ran for a maximum of 80 seconds , the delay being varied by pushing down the centre plate and turning it , using a special setting tool.the case construction was alimininum
The (89)B version had a delay from 1 to 80 seconds and was the normal full length fuze of 110 mm and was constructed of rolled steel, next came the (89) c version this had a minimum delay of 2 seconds and a maximum of 160 seconds .
Markings on the B and C charging plate reads NUR FUR HAND EINSTELLUNG which translates as ONLY FOR HAND SETTING.
If you have any questions , please do not hesitate to contact me
Steve Venus
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