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Thread: Pom-1s

  1. #11
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    Quote Originally Posted by frogman View Post
    This is a diagram for tilt ball switch of POM-1S. A is plastic container, B is a metallic ring with metallic tilt ball inside and C are two metallic rings. Regardless of what position the mine lands, B is going to make a contact with C. This 'make and break' contact action doesn't matter during the arming delay period. But, after the expiration of arming delay, any movement of mine causes the contact between B and C to break momentarilly and the sensing electronics detect the current interruption and send a signal to a transistor or SCR which open the patch for discharging of firing capacitor to detonator. I'd really like to see sensing electronic diagram for POM-1S or BLU-42B, but there is no publication that I can find. One curious collector could easily trace the components and produce a diagram though, if he is inclined.
    I have manual for BKF-POM-1S. Made for Air Forces.

  2. #12
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    Quote Originally Posted by Ivashkin View Post
    I have manual for BKF-POM-1S. Made for Air Forces.
    Does that include electronic diagrams? They are very hard to come by. I am looking for electronic diagrams of POM-1, МВЭ-92, and МВЭ-72. I think the only way is to draw them manually from the deactivated items. I have made one for type 72b AP mine. It's not really hard as they contain few components.

  3. #13
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    Frogman-sorry about delay. The "fleeting Contact" anti-disturbance ball switches used in the POM-1S and BLU-42/B work in a slightly different way to your surmise. They are designed, after the weapon comes to rest, to have the ball come to rest in a depression in the track, where it does not close the circuit. Only upon movement is the ball dislodged from the stable position, and then makes contact, before rolling into the next depression. However, contact has been made. Thus there is no need for a transistor. U S patent 3372253 has a good exposition of one design, which looks very like the BLU-42/B. Earlier fleeting contact switches were sometimes of the mercury type, where a small amount of mercury, in passing through a narrow constriction, bridged contacts at the point. However, the mercury could not remain at this point, as the constriction had tapered lead-ins and outs. A Vickers patent in the twenties just used a pendulum, accepting that the device might sometimes explode on ground contact!

  4. #14
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    A point about the device that has puzzled me is the "Pyrotechnic Lock", combined with a safety wire. This Pyro lock has an advantage over the use of spin to arm, as a fast moving plane would cause it to arm more rapidly, whereas the pyr lock is purely time. A flash tube from the dispenser lights the pyrotechnic pellet before the ejection charge functions, so that it is still burning after the safety pin is extracted. The munition is prevented from activation while it might be jostled by other subs. When the blowing part of the pyro pellet is reached, the metallic sleeve containing the pellet is ejected (I think the end of same may be split and expanded, to ensure it grips the bore strongly in which it is housed.) If the safety pin should be in position, the blowing charge cannot eject the sleeve, so the pressure exits via the ignition hole, and the device remains inactive.

    If a stored container should be in a dump fire, being made of plastic, the pyro pellet is probably likely to be ignited before the ejection charge ignites, as this is well insulated in two metallic castings? Thus, the pyro may have burnt out, igniting the blowing charge before the safety wire is ejected, so no arming again takes place. Has anybody any other thoughts-no mention of the exact functioning of this lock is available! I am not too convinced by this argument! Perhaps, but unlikely, that safety for a Dump Fire could be relaxed, due to the small size of the explosions!
    I am pretty sure that this weapon uses an electrochemical timer, as did the U S BLU 42A (On the Drawings, there is a canister which is not identified) I think that the trip-line spools are mounted in the base of the cups housing the trip-line ejectors, but the US version appears to mount the spool in the ejected cap.
    Who disagrees?
    Martin.

  5. #15
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    Latest update-please disregard musings previously sent! I have now learnt that the device differed from its US progenitor in not only not using centrifugal force to arm same (A pyrotechnic lock being used. which probably led to a more compact fuze assembly), but the weights attached to the trip-lines were released during its descent to ground. This meant that centrifugal force helped to extend the lines, so ensuring full deployment, whereas the BLU42B, extending after impact, might well find some of the weights directed into the ground! The Russian design uses serrated discs on the weights, which would dig in on ground impact, so stopping rapidly the whirling motion, and helping to ensure the line remained taut.

    The fact that the X-shaped retainers detached themselves from the support rods on the POM could be to ensure that the air drag on the supports might otherwise have prevented full ejection of the retainers-the US sub would not have this to contend with, as it was stationary at release. Also, the Russians appear to have placed the line spool in the bottom of the well mounted in the body. This would avoid line being tangled by the slipstream during the descent. It made sense for the US version to mount the spool on the weight, so adding its mass to that of the weight itself.

    Probably America, in view of its use in Vietnam, wanted to avoid the triplines becoming caught in jungle canopy, so voted for ground launch.

    The POM-1s, I think, used a hydraulic, silicone fluid timer, with all its innaccuracy with varying ambient temperature, as the more accurate US electrica E-C timer would have been more costly, and also would drain the battery, life of which was a major problem for the POM-1s. Also, the Russians used a fleeting contact disturbance sensor, as opposed to the BLU-42 having an intemittent contact sensor, reguiring attendent electronic circuitry, and a small continuous current drain. It would be a more sensitive switch, though! (Birdman-I was incorrect when I stated that the BLU-42B used a fleeting contact switch-my apoologies! The circuit diagram of the US munition would be the one that would be of interest to you. The drawing of the switch for the POM-1s is incorrect, a ball with a projecting rim not being used, but a misinterpretation of a drawing)

    I hope that no-one disagrees on any of these points. If agreed, I will then reference the positions of the actual internal switches, tieing in with the circuit diagram that EOD supplied.

    Martin Cummins.

 

 
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