KPOM Yugoslav magnetic influence anti tank mine

[pzgr40]

Cutaway model of a Yugoslav KPOM magnetic influence anti-tank mine. The mine is air dispensed and delivered by the R262 artillery rocket of the Orkan MLRS which has a payload of 24 KPOM mines, and the M77 rocket of the OGANJ MLRS which has a payload of four KPOM mines.

The mine is build up of a sheet steel outer casing (1), in which the explosive charge (2)and the magnetic infulence fuze housing (3) are placed. To the top of the outer casing the four retarding and orientation fins are placed. These pop out as soon as the mine has left the carrier housing of the rocket. In the base, a lead grid (4), packed in a sheet aluminium housing is placed. In my opinion it is meant to absorb the shock of impact on hard soil by deforming the lead. The mine in the casing is build up of a Self forming fragment (SFF) in top (5) http://en.wikipedia.org/wiki/Explosively_formed_penetrator , which functions according to the miznay-shardin effect. The 0,4 kg explosive charge (2) is packed in an aluminium container which is screwed into the green PVC fuze housing (3).

The greenPVC fuze housing contains the electronics (6) which are cast in transparent resign, the brass mechanical reduction gear box (7) housing the electric firing cap, the battery (8 ) and the metal detection spool (9 ).

As no descriptions of the mine are available in pamphlets, either on the internet, containing any detailed info, I have to make an educated guess as to some parts of the functioning of the mine.

Upon impact with the ground, an inertia switch is activated most probably in the mechanical reduction gear-, allowing the spring loaded mechanical reduction gear box to run down, rotating the last gearwheel which houses the electric firing cap under the detonator (10,red). It also releases a circuit breaker pin which allows the electric circuit to be closed (present, not visable in picture) , powering up the electric circuits. These form the arming delays after impact. When the detection spool (9) detects a large amount of metal passing over, it will activate the electric firing cap which will activate the detonator (red), igniting the main charge (2). This will form the concave steel disc (5) in top of the charge into a hypervelocity steel slug, that will penetrate the belly of a tank or an armoured vehicle. The required distance needed to form the slug is formed by the distance from the top of the mine to the belly of the tank.

-I do not know if there is a discrimination mechanism in the mine which can tell the difference between a tank, an armoured vehicle, a truck or a normal car. The relatively large amount of electronics makes me think it could possibly discriminate between a car and a tank.

-It is also unknown to me if the mine deactivates itself after a certain amount of hours by self destruct or if it is shut down and deactivated by the battery running out.

-Looking at the size of the battery and electronics, I guess at least 5 to 7 days of functioning can be expected, but thats a wild guess.

If anyone has more info about this mine, do not hesitate and let me know. Id be more than interested to learn more details.

Regards,DJH.

A Big thank you to Joop Dijkman from the MTM-DAWN (Munitie Technologisch Museum - Demining Academy Wanroy Netherlands) for allowing me to picture the loose parts of his mine (pict 04 and 05)

 

[weberoed]

again - great work and write up

 

[pzgr40]

Thanks Weberoed, you're welcome.

I hope to get some drawings and official descriptions too

On the Wikipedia link I found the following tekst:

"As a rule of thumb, an EFP can perforate a thickness of armour steel equal to half the diameter of its charge for a copper or iron liner,"

As the working cone diameter with this steel disc is 85mm, the penetration should be around 42,5mm. However, one should note this is with optimum stand off conditions.

 

[al'saad]

This is not KB-2, and KB-2 and KPOM-1 are not same munitions. KB-2 is a bomblet similar to KB-1 but has steel body which is internally prefragmented unlike KB-1 which is prefragmented by 3mm dia steel balls in plastic wrapping.

I think that I am among few who had opportunity to dispose few of KPOMs, but on the test ground as this type of ordnance has never been adopted in Yugoslav army inventory. Following the instructions I have received by and engineer who worked on it's development prior to disposal, the mine has electronic self destruct device that will set off the mine 24hrs upon arming. Due to malfunction of self destruct mechanism on the mines we had to dispose all precautions had to be taken.

Initially KPOM-1 mine was developed for use in M87 262mm MLRS, but due to its diameter it was planned to be used also on M77 128mm MLRS.

In M87 warhead mines are placed in 8 containers. each container holds 3 mines-24 in total. containers are chute retarded after they are released from the warhead. after 2,5 seconds after chute is deployed those containers open and packed mines are dispensed and in free fall stabilized by their four wings.

 

[Tarbelin51]

Kptm

Hello

I am not really of agreement for name KPOM-1.
One finds same name for KPOM- PFM-1 and1S.
KPOM being the container of thesubmunition.
At the time documentation found infactory VOGOSKA (1998) mentioned KPTM.
Here are some photographs of the mine and the KPOM with its ammunition.
As well as a cutaway of the rockets 262mm.

 

[pzgr40]

@ al'Saad and Tarbelin; Thank you very much for the added info and the pictures!

@ al'Saad; I got the info from a manual, that supposedly is wrong. I had forgotten that I have described the KB-2 before , and you are right,it is the modified KB-1. So we can scrap the KB-2 text.

@ Tarbelin, thank you for your input; we will now have to find out which name is fully correct; KPOM-1 , either KPTM

@ moderator; can you please (temporary) edit the title and the first alinea to:

"KPOM Yugoslav magnetic influence anti tank mine
Cutaway model of a Yugoslav KPOM magnetic influence anti-tank mine. The mine is air dispensed and delivered by the R262 artillery rocket of the Orkan MLRS which has a payload of 24 KPOM mines, and the M77 rocket of the OGANJ MLRS which has a payload of four KPOM mines."

Until we get the final correct name; either KPOM or KPTM.
I am really interested to know which name is correct. Is there a manual available on this mine?

Regards, DJH

 

[al'saad]

KPOM-kasetna protiv oklopna mina (cluster anti-armour mine)
KPTM-kasetna protiv tenkovska mina (cluster anti-tank mine)

on the container on tarbelin's image stands: 4 kom KPOM which means 4 pcs of KPOM- standard writing on any packing of ammo in Yugoslavia, so it is not container's name KPOM but of its contents.

 

[stecol]

Was this landmine known also with the nickname "Ababeel" ?

Regards
stecol

 

[blu97]

Yes it is also known as ababeel.

 

[al'saad]

Ababeel was a code name in Yugoslav military industry regarding program of production of KPOM-1
Code name for 262mm rocket system was Col.

For M84 main battle tank (yugo version of T72) code name was Capella.

KPOM-1 was never adopted in the service and never used in combat due to beginning of the war in Yugoslavia.

 

[pzgr40]

@ al'saad; Thank you very much for the added info.
So the mine has never been used in active service.

Regards, DJH

 

[Sprockets]

Thanks, pzgr40, for the cut-away. Could the string threaded through a hole in the base of each fin be wound around a pulley forming part of the gearbox, (Round drum, next to battery in image no. 4?) The fins expanding would then wind up the gearbox spring, until possibly deformation of the lead grid on ground impact would then sever the cord, or the end runs off the drum. The mine would then be armed as the gearbox mainspring re-exerted itself, now moving the disc carrying the electric firing cap via a ratchet and pawl. Perhaps there is an escapement to slow movement of the firing cap, though if severance of the cord by ground impact was used, there might not need to be a delaying mechanism. This would enable the submunition to be proof against handling shocks, as there would be no inertia release. The fins seem to have an unusual number of torsion springs-Not only a double torsion but what looks like two additional single torsion springs, suggesting that they had a problem with the string fully tensioning the gearbox! Shoot me down!

By the way, I have sent some P.M's, which I imagine you have too high a workload at present to look at, so disregard the questions, but were you aware of the Danish situation?

Martin.

 

[pzgr40]

Hi Sprockets , I have restudied the mine and I came to the following conclusion; the wires in the wings are not attached to the escapement delay gearbox in any way.
This gearbox uses a pre tensioned clockwork spring. I suppose the wires through the wings are used for reloading purposes; a battery has a certain span of life in which it is reliable. After some years in stock, the batteries will have to be replaced to keep a near 100% function reliability. For that reason the wire is inserted to keep the wings fixated inward, as once they pop out, they fall into a lock. My mine had a flat duracel battery placed.

I took apart the cutaway model to study the backside of the clock , and came to the following conclusion:
A black plastic gearwheel on the far end of the geartrain is fixated by a springloaded pin through a hole in the gearwheel disc, that is kept in downward position by a powderpellet. The electricly ignited firing cap is also placed in this gearwheel, out of line with the detonator. In the electronics disc there must be an impact sensor, a contact switch that closes when the mine hits the ground near vertical ( that's what these four big retardation flaps are ALSO meant for). The closing of this inertia contact means two things happen, the battery is activated, and the gearwheel fixation pellet is ignited. The springloaded pin retracts, allowing the geartrain to start to slowly rotate the electrically ignited firing cap in line with the detonator. By using slider contacts, the same wires (grey wires just above the white 6 in picture '04 fuze housing' in the initial posting) that ignite the powder pellet is now used to acitvate the electrically ignited firing cap if a tank drives over the mine and a signal is passed from the metal detection ring.

In gereral, most air delivered AP & AT mines have one thing in common; Between starting up the electronics and being live, there is most often a few minutes time lapse. This allows the mine to settle, and also to avoid mines to explode when mines of subsequent dropped bombs, rockets or shells bump into the mines which have allready landed. this is mostly between 1 to 5 minutes. This time is used to switch to a new electric circuit: 'battery, electric firing cap, metal detection sensor switch'. A secondary, parallel circuit is the: 'battery, electric firing cap, self destruct timer', which expires after 24 hours.

There are four moments of inertia working upon the mine: during launch, during ejection backward from the carrier projectile, the other way around as the wings pop open, and upon impact. Of all four, the impact is by far the strongest and most abrupt. I expect an inertia closing switch with a strong spring will be cast in with the electronics.

Regards, DJH

 

[Sprockets]

Hello, pzgr40,

Thanks for putting me right-I had a feeling that wires running through the "wings" could easily jam, and it was rather a stupid idea! I suppose that the flaps are wired shut while still in the missile, and are removed after the battery is replaced and the mine has been reinstalled? What I had never appreciated is that batteries could be replaced. The bottom skeleton plate, joined to the lead cushioning grid, appears to have eyes at the outside to anchor the temporary wire, but I cannot see how it could be removed to change the battery. Perhaps the milled edge, silver coloured knob shown in picture 4 of the fuze housing , adjoing the R.H.S of the battery, and the top of the mechanical timer, is used to release the bottom plate? I had assumed that the munition was disposed of after the battery expired! You live and learn!(You probably are having a laugh!)

The one worry I would have is that there seems to be no provision for ensuring the safety of the carrying rocket, prior to launch, should it be dropped heavily during transportation, when the munitions could become armed.(No safety pin or switch) Could the wires through the flaps and through the four holes in lugs around the base perhaps somehow short out the firing cap (Are they plastic coated), so also protecting against EMI? Only when the very strong springs open the flaps, would the shorting wire be cut? just a thought, or perhaps Yugoslav weapon designers were not so worried about safety?

Thanks again,

Martin.

 

[Sprockets]

Hello, again,

A)-The search coil would ideally have its axis vertical when on the ground. The large flaps would stop the munition falling completly on to its side upon ground impact, and then the heavy lead base would ensure that it uprighted itself. Also, having its weight concentrated at the base would make it stable against wind blowing it on to its side, and perhaps reduce oscillation during descent.

B)- The waffle-pattern base might serve to reduce oscillation in descent, since horizontal movement would be damped by turbulent air flow? Possibly, more likely, the idea was to overcome ground suction on wet clay if the container landed on a corner. The open grid would reduce the area in contact with the ground, and allow air to reach the corner, so assisting the weight in uprighting the search coil.

C)-Tarbelin50, in his interesting photographs, shows in picture 4 a view of the base. Though an aperture can be seen a screw with a white plastic washer. If the wire through the holes in the flaps was plastic coated, made into a loop, and twisted into a strand, before being fed though the flaps and base holes, perhaps it's end loop was held under the washer. The other two ends of the loop might end in a connector to the electronic package, so acting as a shorting link.(The photos look as if it is twisted, with possibly a plastic sleeve, so that the loop would break at a weakened area within the sleeve, preventing shorting afterwards) Perhaps a single wire was used, and this is the final anchoring terminal, with the plastic washer helping to hold the wire, as it is tightened after closing the flaps?

D)- Could the battery be removed somehow through a space in the base grid?

Regards,

Martin.

 

[pzgr40]

Hi Martin,

A - you are right. , ideally the mine stands up straight. This also enshures maximum penetration by the EFP. The popped out wings also anshure the mine will not be able to roll over after landing, as the width /height ratio is over 3:1
I think the lead base only protects upon landing on soft soil, not on concrete or tar roads. Most air /missile/shell delivered mines have that noted in their user instructions... "will shatter upon impact with concrete or tarmac"
The weight is quite evenly distributed through the mine; the heavy EFP disc in top with the explosive charge ibelow it against the brass delay gear and cast in electronics in the base.

B - I Think the wafle pattern is made that way to allow a certain amount of deformation untill rest. Try to imagine it being a full lead plate, real deformation would not be possible. It must be noted that I can still remember it was very soft lead, therefore it is most probably packed in a thin aluminium housing.

C - There are two screws :
-Red arrow: this is a positioning screw. The white ring is a rubber gasket ring, preventing moisture from reaching the electronics and the mechanical reduction gear. In the electronics cast piece, a small blind 5 mm deep hole is drilled in the casting where this screw fits in. It has no other use. It is the hole soutwest of the 6 in picture 4 of 7 in my initial posting.
-Green Arrow: The screwed mechanical arming wheel is in fact a hollow bolt with a flange. Inside the bolt is a spring loaded piston that can move upward. It pushed upon a springloaded tapered pin in the end of the brass geartrain housing. This tapered pin sticks in a hole in the oscilating escapement wheel. As this oscilating movement is only one mm, pushing the cone down will place a smaller diameter part of the cone in the hole, releasing the oscilating escapement wheel to move half a mm left, half a mm right. When the mine is taken out of the carrier projectile for maintenance, the wheel is turned loose, allowing the cone to move upward, the bigger part of the cone fitting the hole, fixating the oscilating escapement wheel.
As the arming wheel is completely turned downward (mine armed), the piston is pushed inward, and a 3mm dia pin sticks out of the top of the flange appr. 3mm, making the mine recognizable as armed.

-It has absolutely nothing to do with the wire through the wings that is just placed to prevent the wings to pop out in locked position. It's the hell of a job to get them out of lock again. When placed back in the carrier projectile the wire will shurely be removed.

D - No, not possible. One has to remove the four screws in the upper rim, than remove the ring housing the four flaps (therefore they are tied together when removed from the carrier). Than one takes the black mine housing in hand and turn it upside down. The inner works now fall out. There is a slot in the side of the aluminium housing, that allows the battery to be shaken out and replaced. Build up is the other way around.

Regards, DJH

 

[Sprockets]

Hello, DHM,

I just cannot win! Each time you provide the evidence to show how off track I am! I have now spotted that the waffle-type bottom plate, incorporating the lead shock-absorber, is held by screws passing thugh the four upturned lugs, so my idea that these were for passing a shorting wire through couldn't possibly work. The fact that screws are used to hold the base in position, rather than the cushion being mounted internally, suggests the it may have been a design modification, after unacceptable damage to the electronic package-Perhaps heavy impacts were still compromising the long-term reliability of the self-destruction timer, possibly because of moisture penetration though cracks in the potting resin, which led to the project being abandoned?

So there is an escapment (Clutter) immobiliser! What a relief that there is an external safety, but the designers seem to have overlooked the possibility of eliminating any danger from stray EMI by a simple modification to this safety, where impact with the ground would operate a release device, which would be detented to stay released, and indicate externally the armed condition. Perhaps the problem of an initial angular impact led to it being dropped? Would such a munition be allowed in the Netherlands?!

It is surprising that this safety wasn't applied, when such care was taken in providing for battery replacement!

Thanks, again, DHM, for taking the time out to answer my quibbles in so much detail!

Best regards,

Martin.