Strange Bofors Bombs

[Dreamk]

I found this photo some time ago in a German book of the early thirties dealing with aircraft armament. I was rather puzzled by the shape of these bombs, this "collar step", moreover as they were different from what I always considered as being the first bombs produced by Bofors, the 1931 series adopted by the Swedish Airforce and sold quite successfully, the world over, from Argentina to China. It's also what is found in the sources I could access on Bofors bombs production.
While looking lastly for information on the development of Czech bombs I happened to find this patent for a bomb rack devised in 1929 by Tolfvan - that seem to be the natural complement of the above mentioned bombs, and the explanation for this "collar step".
This is interesting by two aspects:
1) This is the indication that Bofors began developing and producing bombs quite earlier than previously thought.
2) This also indicates that Tolvan went in the "bombs' business already by 1929 (it was previously a shipbuilding company) and this bomb rack may well have been the occasion of developing an interaction with Bofors that culminated when, from 1932 onwards, Tolfvan became the exclusive bombs producers for Bofors - till 1937, the "separation" coming as a result of the Swedish reform of the armament industry in late 1936 and the creation of SAAB.
The end-1920s mysterious series:
:
The 1931 "Typ Utter" series:

Czech Patent for Tolfvan rack 1929 (patent deposed in 1929, published in 1931)


Can someone share more info on these bombs ?

 

[John T]

I was rather puzzled by the shape of these bombs, this "collar step", moreover as they were different from what I always considered as being the first bombs produced by Bofors, the 1931 series adopted by the Swedish Airforce and sold quite successfully, the world over, from Argentina to China. It's also what is found in the sources I could access on Bofors bombs production.
While looking lastly for information on the development of Czech bombs I happened to find this patent for a bomb rack devised in 1929 by Tolfvan - that seem to be the natural complement of the above mentioned bombs, and the explanation for this "collar step".
This is interesting by two aspects:
1) This is the indication that Bofors began developing and producing bombs quite earlier than previously thought.

2) This also indicates that Tolvan went in the "bombs' business already by 1929 (it was previously a shipbuilding company) and this bomb rack may well have been the occasion of developing an interaction with Bofors that culminated when, from 1932 onwards, Tolfvan became the exclusive bombs producers for Bofors - till 1937, the "separation" coming as a result of the Swedish reform of the armament industry in late 1936 and the creation of SAAB.


Can someone share more info on these bombs ?

1. What was the expected date, and I think Bofors had a quite a lot of experimenting before finalizing on a design.

Venezuela ordered bombs from Tolfan/Bofors in 1930, that's the first time I heard of exports from Bofors.

A book with interesting background should be Lennart Anderssons "AB Flygindustri i Limhamn", regarding the aircrafts sold to South America with arms.
Link:
http://z-bok.se/catalog.8.html

2.
I Think the cause and effect might been less clearly connected to the creation of SAAB.
I'd have it to the 1936 Defence plan, starting the Swedish rearmament and providing stable funding for production in Sweden.


Cheers
/John

 

[Dreamk]

Hi John!
The 1936 Defense plan was the cause of the "rupture" between Bofors and Tolfvan. SAAB took over the bomb designa nd productions, and the new autochtonous produced Swedish bombs were quite different from the original Bofors designs.
Junkers indeed associated its sales worldwide with Bofors - fro instance China imported Bofors bombs for its Ju K47 dive bomber, and Argentina also imported Bofors bombs in 1930-31 for operational testing, when they looked to develop dive-bombing.
The year 1930-31 was a turning point for military aviation in South America, with a huge drop of the traditional French equipment predominance. Bofors tried to fill this gap but very soon had concede the field to the Italian (Venezuela, Uruguay, Peru) and above all the US producers (Federal Laboratories Inc and the AAC) - by 1940s most aviation armament in South America was US made, with at least two of these countries (Argentina and Brazil) beginning from 1936 their own license production of the US M30 series of bombs.
Do you happen to know whether other countries, beyond China, Venezuela and Argentina, bought Bofors bombs in the thirties?

 

[John T]

I feel it is too much to talk about "rupture" between Bofors and Tolfvan, they continued to cooperate.
I would say they expanded the production base with plants on both sides of the Baltic.

What makes you think SAAB had anything to do with design of bombs?

Countries I seen:
Columbia
Great Britain tested 2 000 - 2 kg Incendiary bombs
Norway
Finland
Sweden

Cheers
/John

 

[Dreamk]

Hi John

It took me some time to understand the exact nature of the relationships between Bofors and Saab and why the original "Bofors" bombs became "SAAB bombs". the picture that emerges is the following:
By 1935 it had become evident that a major strengthening of Sweden's defense was vital. More industrial resources were needed and firm long-term procurement planning was necessary.

In 1936 the Swedish Parliament approved a new decision regarding the defense forces covering the fiscal years 1936-43.
The Parliament confirmed its earlier opinion that production should be undertaken by private industry while the military workshops should concentrate on maintenance and repair. The Swedish industry should have the capability to develop its own designs. The Swedish authorities took here a strategic decision to concentrate the defense productions in a consortium of local companies with development and production taking place in Sweden only.

In March 1936 Bofors had acquired Nohab Flygmotorfabriker, an acquisition that enabled Bofors to concentrate virtually all aircraft and related manufacture (aircraft, engines,weapons) at Trollhattan, while Bofors declared a willingness to invest in workshops, aerodynamic and engine laboratories and an aerodrome.
Discussions were initiated between ASJA and Bofors on forming a single company for the manufacture and design of aircraft.

SAAB company was then in the process of being established by the Bofors group at the direct request of the Government. SAAB (Svenska Aeroplan Aktiebolaget AB) was incorporated at Trollhattan on 2 April, 1937. The share capital was set at 4 million Swedish Crowns of which 1.5 million belonged to Bofors-Nohab and 2.5 million to AB Ars which was part of the Electrolux group.After protracted negotiations a joint development and management company AB Forenade Flygverkstader (AFF) was formed in Stockholm, in March 1937 by AB Svenska Jarnvagsverkstaderna (ASJ) and Saab.

Concerning aircraft bombs this process had direct repercussions. It appears that Bofors bombs were, till this 1937 reorganization ....exclusively produced for Bofors by a Finnish subsidiary company called...Tolfvan OY. Tolfvan had been oprginaly a shipyard company that entered in partnership with Bofors in 1929, dedicating from then its activities to bomb production. After 1937, SAAB took over the design and production of bombs. A key person in the relationship between Bofors and Tolfvan was a very successful engineer named Ernst Wilhelm Otto UTTER. A German by birth but from a family involved in Finland affairs for some generations, he fought in 1918 in the Finnish independence war, then attended the Finland's Officer school in Viborg and served as an officer in the Finnish White Guard. He became involved in weapons development, and more specifically bombs and fuses. He retired as a Major in 1932 to become the Bofors representative at Tolfvan, and in 1937 passing to Tolfvan as "technical adviser". His death in 1938 remains somewhat a mystery (he was only 38 years old by then) - I have identified a number of his patents (that went into production by the Bofors/Tolfvan complex).

From 1937 onwards the design of Swedish bombs ("SAAB") was drastically different from the previous Bofors design, while the Finnish bombs developped by Tolfvan evolved around this same original Bofors design.
The SAAB designed bombs were developped around the Bofors centrifugal fuze (a Bofors patent of the late 1930s) known as centralrör M/37, M/40 and M/41, which was unique in being a side-pocket centrifugal fuze. Its use is at the origin of the special characteristic look of the Swedish bombs after 1937, with a strong ring conneting the tip of the fins to insure that the spinning, needed to activate the fuze, would indeed take place accurately, by maintaining the correct original orientation of the fins on the longitudinal axis of the bomb. The fin deformation problem had been the cause that led most countries to abandon the spinning stabilization in aerial bombs design - with very few exceptions. Another characteristic of SAAB bombs was teh use of a liquid explosive, the Nitrolit.

 

[John T]

One thing that puzzles me.
What source claims that m/37 bombs where named SAAB bombs?
I never heard that designation.
Nor anything that SAAB took over design or production, what source do you have?


2. When Sweden bought the Ju 86 the bomb bay where equiped with ESAC/VIII - and thus could not use the previous Finnish/Swedish standard.
(from Lennart Anderssons Book on B3)

Kind Regards
/John

 

[Dreamk]

John Hi!
You are right, the plans drawings of the 12 kg sprängbomb m/37 and the 50kg minbomb M/37 still present the mention Bofors. However the 250 kg M/40 and 500 kg 500kg minbomb M/41 were produced by Aktiebolaget Svenska Järnvägsverkstäderna i Linköping (AJS) which was a sub part of Saab. The year 1937 was a turning point. I have not found that the appellation "SAAB bombs" was used - the designation was simply stating the type of the bomb with its weighjt and serial year - for instance 50 kg Lysbomb m/43, etc...

A lot of worthy information on the development an SAAB can be found in the book authored by Hans Andersson and published in 1989 by the Smithsonian Institution Press "SAAB aircraft since 1937". On the early development of Bofors bombs, there are two very good (but sadly too short) articles in the "Forepoken" magazine of the Swedish airforce (no 2 and 9). However sources and documenation on Swedish bombs are really scarce, and there is quite room for research on this topic.

I must say that I missed this detail in the book on the B3, thanks for recording it - it's quite interesting as if we take into account that the Ju86 could not accomodate, in its pre-ww2 versions, electric fuzes, the acquisition of these planes by Sweden seems to have had quite an influence on the design of the Swedish bombs.

Best Regards

 

[John T]

Hi Dreamk
What I have seen the Bombs (up to m/1940 at least) all where designed by Bofors but production was farmed out on a number of companies,
ASEA Västerås, Eskilstuna Stålpressning, Hedemora verkstäder et al.

And understands the use of Nitrolit was an expediency, produced by NitroNobel and leaving Bofors TNT production for more demanding use.

(small nitpickin - m/year means approved for servcice use in the Army or Airforce while capital M means approved by the Navy)
Cheers
/John T

 

[Dreamk]

Hi John
Thanks for the info.
I have just found photos of bombs used by Bolivia in 1931-32, sold by Finland to this country according to the reports of the Leagues of Nations dealing with weapons sales and delivery to countries involved in the Chaco war - an undirect confirmation that Tolfvan served as a production and export centers for Bofors bombs, as these are obviously the classical 50 and 100kg Bofors 1931 Type "Utter" (what would become the Swedish M/32 series). They are curiously designated as 30 and 80kg.
I am presently far from my computer and therefore I'll be able to upload the photo only in a week time, by next week-end;
Best Regards