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3\" Rocket 12 lb No 1 Mk 1 HE Warhead


Ordnance approved
Has anyone got any information of the British 3 inch 12 lb HE No 1 Mk 1 warhead? It was probably in service 1945-1960ish and was fitted with a No 931 Base Fuze. The fuze worked on an induction coil principle from a contact switch on the tip of the warhead. I have a pretty poor picture of the fuze but no information on the warhead. Can anyone help?
Re:3" Rocket 12 lb No 1 Mk 1 HE Warhead

Strange, according my information (OP 1665)
the Shell No.1 Mk1 had a No. 700 or 731.
Data shell: length 14 Inches, diameter 3,25 Inch
Total weight: 17,74 Lbs filled with 4,28 Lbs TNT.

The shell No.1 Mk1 is threaded externally at the base.
The forward part of the shell is threaded internally
to receive an adapter for the fuze.

Maybe there's a big HOLE in my information and
you are describing another (not known to me) warhead.
Re:3" Rocket 12 lb No 1 Mk 1 HE Warhead

the only things i can find for the 12lb warhead say it was a practice warhead,and looking up the 931 fuze on the list of fuzes i have(others exist) it says the 931 was for the 3.7\" HE/AT rocket warhead and was introduced into service in 1956
Re:3" Rocket 12 lb No 1 Mk 1 HE Warhead

Not sure if this is what you are looking for, Tony.
see attached pics..

No.700 listed for 3 Inch UP Rocket
And the two Warheads (named shells in the doc)
Re:3" Rocket 12 lb No 1 Mk 1 HE Warhead

PS i have send the datasheets to eodda
by private mail in order to get familiar
with this material.

Let's hope he has more and better documentation
on this very interesting subject!

PS the pics are only extracts from the datasheets.
Thanks to everyone for replying.

The information I have comes from the RAF technical publication on rockets - Air Publication 2802A and the chapter on the fuze is dated May '59. It therefore post-dates OP1665 by 13 years. Unfortunately I don't have the corresponding chapter from the publication on the warhead, but the fuze is definitely an air-to-ground type. I don't think that it was in service for very long. I did my Armourer's training in 1959 and I certainly don't remember it. There were only three 3 inch fuzes in service by then - the No 878/938 and the No 893.

To Tony - the colour illustration you posted is (I think) from the Defence Standard on ammunition markings, or from the RN Book of Reference on aircraft ordnance. The top left 3 inch warhead is fitted with a No 865 or 878/938 Fuze and the top right warhead has no fuze.

I'm going to (try to) attach a picture (in Word) - which is all I have - apart from a description of how the fuze works which, put simply, is...

The Fuze is an electrically initiated base type used in a hollow charge HE warhead.

The Fuze body contains an induction coil, a condenser, an off-set biased detonator holder controlled by a clutter escapement and holding an electrically initiated detonator, and a magazine. The induction coil generates the firing current when a soft iron slug is pushed through its electrical field. The slug is connected to an arming rod, which itself is connected to a diaphragm in base of the Fuze. The diaphragm is exposed to the output of a Thermal Initiator closing the end of the Fuze. The arming rod also holds a number of locking balls in place. These balls act on a stud retaining the detonator holder at 145 off-set from the magazine stemming. The charge generated by the induction oil is stored in the condenser which is electrically connected to the detonator. The condenser is also connected to a contact switch on the tip of the rocket head by means of leads passing along the exterior surface of the warhead.

The magazine contains a CE stemming and booster pellets.

The Thermal Initiator, which although it is a separate component is actually part of the warhead, consists of a steel cup containing Gunpowder and LDNR compound. The side of the cup nearest the rocket motor is closed by a thin metal septum; the output side of the cup nearest to the Fuze is closed off by cardboard and thin metal discs.

As the rocket accelerates away from the aircraft the heat from the burning rocket motor ignites the filling in the Thermal Initiator. The gases produced reverse the diaphragm pushing on the arming rod, thus in turn pushing the iron slug through the field of the induction coil. This generates an electrical charge which is stored in the condenser. Further movement of the iron slug by the arming rod breaks the electrical circuit from the induction coil to the condenser.

Movement of the arming rod displaces the locking balls releasing the stud retaining the detonator holder. The bias on the detonator holder causes the holder to rotate under the effect of the forward motion of the rocket. This rotation is controlled by the clutter escapement to ensure that the Fuze is not fully armed until the rocket has travelled approximately 400 feet / 122 m from the aircraft.

When the tip of the warhead strikes the target a contact switch on the warhead closes completing the electrical circuit and allowing the condenser to discharge through the detonator. The stand-off displacement between the contact switch and the Fuze allows the hollow charge warhead to function correctly.

My questions are: (i) does anyone have any information on the 12 lb HE No.1 Mk. 1 air to ground warhead, and (ii) does anyone have better illustration of the fuze?

Thanks for any help and a Happy Christmas and New year to all.

eodda [file name=No931_Fuze.doc size=85504]http://www.bocn.co.uk/images/fbfiles/files/No931_Fuze.doc[/file]