Swiss BZ37 bomb fuze

[Dreamk]

Swiss Brandt Bomb Zunder 37 (BZ 37) - used for the new, cylindrical, Swiss bombs of 6.5kg, 12kg and 50kg entering in service in the 1930s and in use till after ww2
Impact fuze that could also be equipped with a delay sleeve for delay times between 2.0 and 4.4 s
The BZ 37 bomb fuze activated at impact speeds above 160 km/h on hard ground, and above 320 km/h on swamps and water if the impact angle was greater than 20°

- a drawing (Zeichnung) M18948 dated December 1940



The only difference I can see with the drawing is that the percussion pin is emphsized but may be someone with a more expert eye can find more on this drawing M19411 dated June 1941

 

[Fusse2004]

A page from Peter Jaeggi's bookSwiss Fuze.

 

[Dreamk]

It's interesting that Jaeggi does not mention the delay sleeve for delay times between 2.0 and 4.4 s, but only the 0.5s delai. May be this was not a current parctice or only an experimental one.
In fact, as it appears through browing the documents of this archive, the Swiss spent a lot of time in trying to develop extended delays for the 12kg splitter bomb - the only reason I can see for it is the need for a fuze suited to low level attacks so as not to endanger the aircraft releasing the bombs.
This led them to develop the delay fuzes VBZ 4301 with targeted delays of 5-7 seconds and the VBZ 4303 with delays of 4.4 - 5.6 seconds (both fuzes were intended for the 12kg splitter bomb and 50kg sprengbomb)
This is indeed the rationale mentioned for the fuzing of the 3kg splitterbomb:
".....To meet the requirements, we therefore see only one option: equipping the small fragmentation bomb with a drop fuse (fallzunder), similar to that used for standard bombs dropped at low altitude. This would result in the small fragmentation bombs also detonating with a delay of 5-7 seconds."