M Bombs

[Antoon]

In a document of Bomber Command is mentioned that Hampden Bombers on 25/26 July dropped "M Bombs" in the Dordmund-Ems canal.

In another documents they named them special bombs.

I think this were the 35 lb. W(water) bombs, (by aircraft dropped river mines).

Someone another idea?

 

[Dreamk]

Antoon, in another record of the Bomber Command concerning Hampdens operations I found these mentions:

"1x1500lb M Mine parachute mine"
"the Hampden being able to carry two 1,500lb parachute sea mine ..."

Considering the period and the weight, these would be the Mk1 Air dropped Sea Mine - though the official designation was Mine "A" MkI

Concerning the Water Fluvial Mines, The bombs are disegnated in the records as "W" bombs.
I found the following:
826 Sqn FAA (Fairey Albacore), on detachment to Bircham Newton are mentioned dropping "W" bombs in a raid on the Nieuwe Waterweg on June 24, and on June 25 in river Maas and in the channels between the Maas and the Scheldt. Between June 25 and July 2, 1940 they dropped a total of 240 W Bombs in the river Meuse and in channels between the Meuse and the Scheldt.
In the night 6-7 July 1940 Costal Command 53rd Squadron Blenheims dropped 48 Water Bombs in the North Sea, and in the night of 25-26 July 1940 dropped a mix of Water Bombs and 250 lb. GP bombs on the shipyard at Spaarndam.


I hope this will help

 

[Antoon]

Dreamk,

Thank you very much.

Thanks to your reply I found the following information: The 'M' bomb was a specially adapted naval mine which was slowed by a drogue parachute and was fitted with a delayed-action fuse (using soluble aspirin). [FONT=&amp]
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See:
https://www.bomberhistory.co.uk/canal_raids/muenster1940
https://www.bomberhistory.co.uk/canal_raids/calendar
https://www.youtube.com/watch?v=uWzYdViAyZ8

The question is, what were the modifications on this A Mk 1 Mine?

Was the magnetic triggering unit removed? And as far as I understand the fuze was adapted special for this raids because it had 10 minutes delay.


Greetings - Antoon

 

[Dreamk]

The A Mark I was an Influence mine, originally designed to fit the same dropping gear as the 18 inch (45 cm) Mark XI torpedo. Weight was about 1,500 lbs. (680 kg) with a 750 lbs. (340 kg) charge. The diameter was 0.45m and the body of the mine itself was 2.825m long.
It was the basis of quite a number of drastic modifications, to fit the intended operational requirements:
1) It first used a magnetic only triggering
2) later versions incorporated acoustic and acoustic-magnetic triggering.
3) a version with magnetic-pressure triggering was also developed but was not used in service.
4) The mine could be equipped with a parachute instead of the usual metallic tubular stabilizer extension. The length of the unit with a chute was 3m. The length with a stabilizer was. 4.7m.



A Mine A Mk I air-dropped parachute version being loaded aboard Hampden bomber:

 

[Antoon]

Found also some information in the book BOMBS GONE from Wing Commander John A. McBean & Major Arthur Hogben.

Both sizes of mine were occasionally converted for use as parachute land-mines, code-names 'Magnum and Tim' respectively. This was achieved by increasing the explosive content by some 46 per cent, fitting a bomb firing system and a domed nose. For example, the explosive in the 'Magnum', the 1,500 lb. A Mk I-IV, was increased to 1,100 lb. giving the mine an overall weight of 1,850 lb.

 

[Snufkin]

Worth checking the entries in "Aircraft-launched Mines" on the NavWeaps website:

http://www.navweaps.com/Weapons/WAMBR_Mines.php

 

[Antoon]

Has someone a drawing of this 1850 lb. heavy 'Magnum' parachute mine and his firing system with 10 minutes delay? So not pictures from the normal 1500 lb. A Mk I-IV Mines.

 

[Dreamk]

Bomber Command Executive Codeword: "GARDENING"
Target Type: Docks, Ports, Seaways
Up to 6 x 1,850 lb parachute mines with magnetic and/or acoustic actuation. (3-3 in Lancaster Bomb bay)

In the Operational records of the 419 Sqn RCAF equipped with Lancaster I, we find the bomb load defined for such operations as:
6x1850lb Mines MkVI

The MkVI Mine was an Influence mine. Its production started in 1944. It was intended to replace A Marks I-IV.
It used an acoustic-magnetic trigger. For a total weight of 817kg Its explosive charge was either 1,000 lbs. (454 kg) of amatol or 1,100 lbs. (499 kg) of Minol.
It could also be laid without parachute by MTBs or dropped from low altitude.
In 1949, some 5,707 were still in storage.

From Deminest by Henry Belot:

and from a German source:


If some one could scan and upload the original complete version of the Mine Disposal handbook Part III British Underwater Ordnance, the Chapter I deals with Influence Mines, the Chapter II with Contact Mines.
Till now I have been unable to find a digital copy of these chapters.

 

[Antoon]

As asked before.

No pictures of the normal influence mine(s) but about the 'M Bomb' what is a modified A Mine Mk I-IV with a domed nose and a bomb firing system. We speaking about the 'M bombs' used in 1940 and only dropped by Hampden from 5 Group!

 

[Dreamk]

Antoon there is some confusion here:
1) The M bomb was a 1500lb Mine A MkI and variants and indeed the Hampden was able to drop it
The MAGNUM was a 1850lb Mine A Mk VI and it was dropped by the "Heavies" such as the Lancaster.

2) The "domed nose" of the M bomb was not a convex semi circular dome but an added piece (called by the Germans "Holzkasten") that made the nose of this mine cylindrical instead of the original truncated cylinder shape - the part in red on these drawings - see also the photograph of such a mine without this "dome":

 

[Antoon]

I found some information in the German Navy handbook from 1942: M.Dv. Nr. 454 Bergen und Entschärfen deutcher und fremden Sperrwafen.

The “M Bomb” was a modified A Mk I influence mine that could be used as a "land bomb" and as "water bomb". The induction coil was removed and as land bomb the switch close the electric circuit directly on impact.


As water bomb you could have a delay only as long as the salt needed to dissolve and after that the electric circuit was closed. Or you could have the mechanical clock delay till 45 days.

Enclosed the text and drawings from the German manual and the same drawings from the switches in colour from the book from Peter Voss.

 

[Antoon]

Also this document says that the A Mk I-IV may be used as an instantaneous or delayed-action firing bomb.
Fitted as a bomb the charge is increased to about 1100 lb. and the total weight is about 1850 lb.