Picture shows the (15) and the longer(17) fuzes
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
The normal type of bomb fuze as shown above 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 50 Kg 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.
Picture shows the various types of construction from the left is the early (15) next is the (25) series and last the (55)
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
Sectioned No (25) A fuze showing bitumen coating
Sectioned No (28) B
Top view of sectioned (28) B
Internal capacitor block from a (55) fuze
Top view of above (55) Fuze
Bottom view of (55) Fuze
Typical switch block this is from the (55) fuze
View of Switch block from the other side showing the trembler switch
Top view of (55) fuze switch block
Underside showing tags that solder onto the capacitors
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
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
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
LH is the locating ring The right hand the threaded locking ring
Component parts of fuzes
Bakelite disk found inside all fuzes
Screw dust cover from (9) fuze covering test pin
Felt washers and cup found on all fuzes
Felt washers as would be fitted
Charging pin assy showing cup, Washers and pin
Delay element from a (55)fuze
Tip of delay element as seen from the base of fuze
Bakelite distance piece fitted in (55) fuze
Screwed Bakelite plug from (55) fuze often found to be missing !
Plug shown from underside of fuze
Rubber O ring found on fuzes to stop moisture
Bakelite dust caps hardly ever found on fuzes usually discarded !
Side view of dust cap
charging pin covers the early ones LH had the fuze type on them.
Steel Gaine screws into base of fuze
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
Bases of the 2 types of gaine NOTE often Gaines were unmarked especially about 1941 onwards.
TO LISTEN TO A RECORDING OF A GERMAN 17 FUZE CLICK ICON BELOW
Notable dates of various fuzes when introduced
Type Date Remarks
(9) 1938 Test pin
(9) 1939 Screw cap
(24)A 1941 Anti break up rupture fuze
(26) 1940 Oil bombs.
(28) 1937 Possibly this fuze was originally a Brass or Ali No5
(55)B Y 1942 Specifically designed to kill the officer defusing bomb
(55) 1940 ?
(55)A 1942 This was fitted with an external nose switch
(57) 1941 Never dropped over UK
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 ?