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German ECR Fuzes
Picture shows the (15) and the longer(17) fuzes
Audio 1:
German 17 Ticking Clock
Audio 2:
German 17 Ticking
History of the German Fuze

The German ECR (Electrical, Condenser , Resistance) fuze was first manufactured by Rheinmetall in the 1930's, and was designed by Hubert Rhuleman

Description:
The normal type of bomb fuze is 110 mm long by 50 mm wide (measured from the head to the base) the fuze consists of usually 2 charging pins, although if the fuze has only one circuit, the (17) for example then only one is present, the other is a dummy.

Below this is the shoulder, this may contain 3 fixing screws, its this location that the various markings are found,consisting of type of fuze ie EIAZ is an electrical impact type. Next is a ringed number NB this is very important for example a ringed (17) is a long delay clockwork fuze, it's this type of fuze that is longer in length, the clockwork portion screws into the base and is 142 mm long. then there is the Triagramme or manufacturers mark which can be 2 or 3 letters ie RhS is Rheinmetall (Sommerda ) Plant.

On early fuzes the Germans marked which bomb the fuze was to be used for, marked C50 this was the 50kg the standard bomb used at the beginning of the war.

Then the batch code ie 2a is batch 2 sub batch a, this allowed any faulty batches to be easily found, finally there is the inspectors stamp (waffenampt ) Rheinmetalls inspector was number 56.
Construction:
Usually Aluminum, but could be steel, in two parts the top part containing the charging pins is known as the SWITCH BLOCK, which also houses the TREMBLER SWITCHES. The bottom section containing the resistors and capacitors, that contain the electrical charge, at the very bottom is a screw thread its here that the GAINE screws into.

The (55) fuze and the (89) fuze are constructed using tubular steel and are made in one piece instead of the usual two pieces.

How the ECR Fuze works:
The normal ECR fuze is one that is charged electrically ,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 vibratory 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 can be either steel or Bakelite,
Sectioned No (25) A fuze showing bitumen coating
Sectioned No (25) A fuze showing bitumen coating
Sectioned No (28) B
Sectioned No (28) B
Top view of sectioned (28) B
Top view of sectioned (28) B
Internal capacitor block from a (55) fuze
Internal capacitor block from a (55) fuze
Top view of above (55) Fuze
Top view of above (55) Fuze
Bottom view of (55) Fuze
Bottom view of (55) Fuze
Typical switch block this is from the (55) fuze
Typical switch block this is from the (55) fuze
View of Switch block from the other side showing the trembler switch
View of Switch block from the other side showing the trembler switch
Top view of (55) fuze switch block
Top view of (55) fuze switch block
Underside showing tags that solder onto the capacitors
Underside showing tags that solder onto the capacitors
Charging pins
Charging pins
Fuze fittings:
The early bombs were fitted into the fuze pocket using a slotted steel o ring and two screws, however it was often found that the screws would work loose and the fuze was likely to fall out !
Early slotted type of fitting
Early slotted type of fitting
The answer was to completely redesigned the fuze pocket , this idea was adopted throughout the war, and consists of two pieces
2 piece locking and locating ring fitted to a (25)B fuze
2 piece locking and locating ring fitted to a (25)B fuze
First the fuze was fitted, then a locating ring , and finally a threaded piece was screwed over the top, the fuze was then unable to shake loose
Left hand is the locating ring
Left hand is the locating ring
and the right hand the threaded locking ring
Bakelite disk found inside all fuzes
Bakelite disk found inside all fuzes
Screw dust cover from (9) fuze covering test pin
Screw dust cover from (9) fuze covering test pin
Felt washers and cup found on all fuzes
Felt washers and cup found on all fuzes
Felt washers as would be fitted
Felt washers as would be fitted
Charging pin assy showing cup, Washers and pin
Charging pin assy showing cup, Washers and pin
Delay element from a (55)fuze
Delay element from a (55)fuze
Tip of delay element as seen from the base of fuze
Tip of delay element as seen from the base of fuze
Bakelite distance piece fitted in (55) fuze
Bakelite distance piece fitted in (55) fuze
Screwed Bakelite plug from (55) fuze often found to be missing
Screwed Bakelite plug from (55) fuze often found to be missing
Plug shown from underside of fuze
Plug shown from underside of fuze
Rubber O ring found on fuzes to stop moisture
Rubber O ring found on fuzes to stop moisture
Bakelite dust caps hardly ever found on fuzes usually discarded
Bakelite dust caps hardly ever found on fuzes usually discarded
Side view of dust cap
Side view of dust cap
Charging pin covers the early ones
Charging pin covers the early ones
LH had the fuze type on them.
Steel Gaine screws into base of fuze
Steel Gaine screws into base of fuze
Bakelite gaine that is found on the (17)b long delay fuzes
Bakelite gaine that is found on the (17)b long delay fuzes
The two types of gaine Steel on the left Bakelite on the right
The two types of gaine Steel on the left Bakelite on the right
Bases of the 2 types of gaine
Bases of the 2 types of gaine
NOTE often Gaines were unmarked especially about 1941 onwards.
Notable dates of various fuzes when introduced:

Type Date Remarks
(5) 1936
(9) 1938 Test pin
(9) 1939 Screw cap
(15) 1937
(17) 1940
(17)A 1941
(25) 1939
(24)A 1941 Anti break up rupture fuze
(25)A 1940
(25)B 1941
(25)c 1942
(26) 1940 Oil bombs.
(28) 1937 Possibly this fuze was originally a Brass or Ali No5
(28)B 1940
(35) 1940
(38) 1940
(45) 1940
(45)A undated
(50) 1940
(50)B Y 1942 Specifically designed to kill the officer defuzing bomb
(55) 1940 ?
(55)A 1942 This was fitted with an external nose switch
(57) 1941 Never dropped over UK
(59) 1940
(59)A 1940
(59)B 1941
(79) 1942
(89) 1942
This list was compiled from various sources including specimens from my own collection. Its interesting to note that after a fuze was introduced often any variations or changes the date was omitted.
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