ICING

MARK 6 PISTOL AND BOOSTER EXTENDER MECHANISM

11. To avoid freezing of the internal operating parts, an anti-freeze mixture of 2/3 gly-cerine and 1/3 alcohol is recommended for use in both the booster and pistol ends. Both of these constituents possess anti-freeze properties. Furthermore the increase in vis-cosity of the glycerine at low temperatures is such that it aids in the retention of the mixture within the booster extender in the absence of a sealing substance, and at the same time does not become stiff enough to interfere with proper operation. At low tem-peratures, in the range of 0° F. to 20° F., and without any retaining grease or putty, the leakage of antifreeze around the booster spindle has been found to be negligible for a period in excess of 24 hours.

12. In case of the unavailability of the mixture mentioned in paragraph 11, other non-corrosive antifreeze combinations may be used but these have certain limitations. For example, a 70% glycerine-30% water mixture possesses a good anti-freeue qualities but will have a higher freezing point than the glycerine-alcohol combination with the same amount of sea water dilution. Alcohol, if used separately, runs out of the booster exten-der quite readily, and it is advisable, therefore, to use a sealing substance applied around the safety fork and booster spindle. Kerosene is not too satisfactory since it not only runs out too readily without a retainer but also reduces appreciably the effectiveness of practical sealing substances such as putty or plastilene.

13. Possible methods of introducing anti-freeze mixtures into the booster extender and pistol are suggested as follows provide the pistol and booster extender are removed from the depth charge or the depth charge turned up on the appropriate end:

(a) For the booster extender, the safety fork should be removed and anti-freeze should be poured into the clearance between the booster spindle and the spindle bushing by means of a funnel, trough, or oil can. If difficulty is encountered using this method, an alternate method is suggested in which a screw driver or other suitable rod may be used on the booster spindle end, with the safety fork removed to force the end into a position about 1/16 inch inside the outer surface of the spindle bushing. The anti-freeze may then be poured by means of a funnel into the spindle bushing opening and will filter by the spindle end into the booster bellows chamber. Caution must be taken not to push the spindle end farther down the spindle bushing opening than 1/16 inch. If such a precau-tion is not observed, the locking balls will slip out of position in the locking slide and pre-vent the spindle's return to the normal unarmed position without use of a special tool.

(b) For the pistol, alternate methods may be employed. An oil can may be used to squirt the antifreeze into the 1/8 inch inlet valve holes or through the orifice in the valve seat head. A service pistol cover, with the knob removed, may be successively screwed on each pistol and used as a funnel, the anti-freeze being poured into the cover hole.

14. Tests have indicated that serious sticking of the booster extender mechanism at low temperatures is mainly due to the effect of frost or ice around the locking balls of the booster release mechanism rather than to the results of water freezing in the bellows. Jamming is also known to occur at low temperatures in seemingly dry boosters because of the condensation and freezing of water vapor from the air within the extender. It is evident therefore that an antifreeze solution is necessary even in the event that a wa-terproof seal is used. It is recommended that 2 or 3 ounces of anti-freeze be poured into the booster spindle opening. This should be sufficient to furnish an initial coating of all the working parts and provide a reservior for subsequent coatings and for dilution of any water that may enter.

15. Laboratory tests indicate that putty may be used as a sealing substance for the booster end. Putty sticks to the metal radialy and breaks off cleanly on removal of the safety fork. Plastilene also possesses sealing properties comparable to putty but is not as easy to apply. If difficulty is experienced in causing the sealing substance to cling to the metal, a retainer of adhesive tape ("Scotch" tape, for example is recommended). The use of a seal such as putty when the viscous glycerine-alcohol mixture is employed in the booster, while possibly not necessary at etremely low temperatures, is advisable as an added assurance against seepage of water into, or anti-freeze out of the booster ex-tender. With the less viscous liquids mentioned in paragraph 12, it is considered essential that a sealing that a sealing substance be used to avoid the necessity for frequently re-plenishing the anti-freeze.

16. The use of wax or grease, including gun slushing compounds and ice machine grease, as a seal is not recommended because of the tendency to prevent water inflow under depth-charge operating conditions. Furthermore, these substances should especially not be used inside either pistol or booster extender because of their tendency to cause slug-gish action.

17. It is suggested that the safey forks on the depth charges in position on the racks be rotated so that the knobbed end of the fork is up. This procedure avoids the funnel ef-fect that the prong end of the fork, in upward position, offers to the spray.

Recent laboratory tests have shown that the dry pistol, unlike the booster extender will not fail to operate due to the formation of frost. Also, the locking ball mechanism which would be expected to cause jamming on freezing is located in a position to which water is not readily admitted. However, water is frequently known to enter the pistol around the inlet valve cover and quite conceivable may freeze in the inlet valve. It is therefore considered desirable to flush the pistol end with anti-freeze through the inlet valve or through the orifice in the valve seat head. It must be emphasized that this flushing pin release mechanism. It is possible that the flooding of this unit will cause a dashpot effect that will retard the firing pin motion. Proper coating of parts with polar type rust preven-tive compound is considered sufficient protection of this mechanism against any possible freezing or corrosion.

18. It is understood that inlet valve covers are frequently broken in handling and that occasionally they leak. Naturally, these should be replaced at once if broken. Although the design of these covers has been strengthened, regular inspections of covers for leakage should not be relaxed.

20. Both in connection with difficulties from icing and difficulties from corrosion it is con-sidered desirable, after a ship return to port, generally to replace firing mechanisms im-mediately with spares and to clean and recondition the old ones so that they can be tur-ned in to the pool of spares for this purpose. To facilitie that plicy a more liberal supply of spares is being obtained. Replacement on shipboard of firing mechanisms which seem probably in doubtful condition after rough or icy weather seems also desirable.

21. The use of anti-freeze within the depth charge operating mechanisms does not as-sure by itself proper functioning of the depth charge. Ice on the exterior of the ends of the depth charge is likely to cause malfunctioning of both booster and pistol. The safety fork on the booster end generally will not wipe off if completely iced over, and it is pos-sible that the knobbed cover on the pistol end will not break off cleanly. To date, ice re-moval has been accomplished by means of steam and hot water flushing. Tests have proved the latter to be the more successful method and steps are being taken to supply all ships concerned with the necessary equipment.

22. Tests by the fleet under actual operating conditions have indicated the uncertainty of safety fork removal by the wiping plate even when the booster end has seemingly been deiced by steam hose. The requirement that the safety fork should be removed au-tomatically by the wiping plate may be relaxed with the discretion of the Commanding Officer of each ship, with due regard for the added danger connected with the sinking of the ship or the accidental loss of a depth charge overboard.

23. Depth charges should, of course, not be expended without good reason. However, in order to determine the effectiveness of these instructions it would seem justified, and it is recommended when circumstances make it desirable that destroyers before returning to port occasionally drop one or two depth charges under freezing conditions to test the efficiency of these measures.