Chapter VIII

SPECIFICATIONS FOR THE MANUFACTURE AND INSPECTION OF THE COMBINATION FUSE FOR RUSSIAN 3-INCH SHRAPNEL SHELLS

The following specifications contain all the essential information relating to the Russian aluminum 22-second combination or double-acting fuse for shrapnel shells used in 3-inch quick-firing field and mountain guns, as given in the official specifications. This chapter, therefore, contains a complete description of every part used in the fuse, together with complete details relating to the manufacture, inspection, and tests.

=Component Parts of Fuse.=--The fuse consists of over thirty separate parts, the names of each of which are specified in the table below, together with their weights.

FUSE PART Weight in Ounces,
Avoirdupois
Stem (with cloth) 3.7166

Chamber bushing with needle for percussion detonator
cap (without powder) 0.1971

Bushing with needle for time detonator cap 0.0331

Plug (brass) in the flange of the stem 0.0150

Upper time ring (complete with powder; for filling in
both upper and lower time ring 0.24075 ounce avoirdupois
of powder (fuse) are required; for 1000
fuses, the following quantities of fuse powder are
required: for pressing into the time rings, approximately
16.25 pounds avoirdupois; for powder pellets
in the vents of the lower time ring, approximately
3.912 ounces avoirdupois) with powder and parchment 1.1586

Lower time ring (see note in parenthesis on upper time
ring) with powder, asbestos, pins, and tin disk 1.1496

Nut 3.6278

Two set-screws for nut 0.0361

Tightening ring (split) 0.5492

Time detonator (assembled) 0.2632

_Time detonator parts_:
Pellet 0.1429
Rod 0.1023
Spiral brass spring 0.0030
Cap 0.0150

Safety bushing for the time detonator (the bushing for
the time detonator for mountain guns weighs 0.0677
ounce avoirdupois) 0.1128

Percussion detonator (assembled) 0.4514

_Percussion detonator parts_:
Pellet 0.3671
Brass bushing 0.0451
Lead disk (washer on flange) 0.0226
Cap 0.0166

_Safety arrangement for percussion detonator_:
Brass safety stirrup with brass control spring 0.0481

Steel spiral spring 0.1655

Lock bushing for the safety stirrup for percussion
detonator 0.5597

Base plug with counter safety lug and brass disk 0.5718

Lead disk 0.1520

Powder for the chamber bushing and transmitting duct
of stem 0.0572

Mean weight of complete and ready-for-firing fuse for
3-inch field gun 2.8628

Mean weight of complete and ready-for-firing fuse for
3-inch mountain gun 2.8177

The weights of the additional parts not included in
above list are:

Tin protecting cover with tape 1.0533

Copper wire for removing the cover 0.1053

Shell grease for lubricating grooves of stem 0.0196

=Design and Construction of Stem.=--The stem is to be cast of aluminum (or an alloy of aluminum and copper) and pressed. The top of the stem is to be turned on the outside into three cylindrical shoulders, the upper one being threaded for receiving the nut; on the surface of the two upper shoulders, parallel to the axis of the stem, three guiding grooves are milled. The base of the stem top serves as a turning axis for the lower time ring. The interior of the top of the stem is to be bored out to form three cylindrical chambers, the lower of which is threaded to receive the brass bushing with the conical steel needle; the latter is lacquered and inserted into the bushing from the bottom, its head being riveted. To prevent the unscrewing of the bushing, the latter is nipped in two places. A vent is drilled through the wall at the top of the stem.

The upper face of the flange of the stem has a rim on its circumference, and on a radius located in a vertical plane with the vent of the stem top, a transmitting duct is drilled, reaching from the lateral surface of the flange to the powder chamber of the fuse; the upper face of the flange communicates with this duct through an ignition hole pasted onto the top with a muslin disk. The transmitting duct (covered with a neutral varnish) is filled, in the assembled fuse, with grain powder (for 100 fuses, about 3.84 pounds avoirdupois of unpolished rifle powder is required) and closed with a brass plug. On the lateral surface of the flange two annular grooves are milled out, the lower of which has four recesses for staking in the tin cover.

On the lower face of the flange (two marks shall be placed on this face, one giving the last two digits of the year of manufacture of the fuses, and the other the number of the control consignment of the same year), at the ends of a diameter, two slanting cuts are milled for the wrench which screws the fuse into the shrapnel. On the same lateral surface a conical mark is cut, colored red, for the setting of the graduations of the fuse; on the top face of the flange a cloth washer is pasted, with a hole punched in it over the ignition hole. The cloth is pasted with a special thick varnish which is also used for pasting the twilled tape to the cover. The varnish consists of white resin, shellac and turpentine soluble in alcohol. Through the lateral surface of the flange a hole is drilled, leading to the lower face of the flange and intended for fastening the copper wire for tearing off the cover.

The _tail of the stem_ is shaped with a smooth cone on the top and a threaded cylinder at the bottom; the interior of the tail is to be bored out to form three cylindrical chambers, the upper and lower of which are threaded to receive the chamber and the base plugs, and the smooth, middle one, is intended for the percussion arrangement.

=The Chamber Bushing.=--The chamber bushing (brass) has four holes in its bottom for transmitting the flame into the interior of the shrapnel shell, and one central hole into which the varnished steel needle is screwed from the top. The lower face of the bottom of the bushing is recessed for locating the compressed brass counter spring of the percussion safety stirrup. The inside surface of the bushing is covered with neutral varnish, and, before filling it with powder, a muslin and wax paper disk are deposited at the bottom. The powder in the bushing is compressed slightly, to prevent its scattering in handling, before screwing the bushings in their places. The screwed-in bushing is nipped in two places and its wall is drilled through the transmitting duct, before charging the latter, for exposing the powder in the bushing.

=The Time Rings.=--Both time rings are cast from an aluminum-copper alloy (copper from 2¹⁄₂ to 3 per cent) and stamped in a die; on the under side of each ring a groove with an intervening bridge and semicircular arch is formed by first stamping it in a die and then milling it. The grooves are coated on the inside with Ossovetski’s neutral varnish, and fuse powder pressed into them. The portions filled with powder are then turned off and a thin, parchment washer pasted on their under surface with a neutral varnish. The parchment of each time ring is punctured over the transmitting hole, to hasten the transmission of the flame in grape-shot firing.

The _upper time ring_ is turned on the inside to form two cones connected by a circular section; the lower cone also terminates into a circular section having three protruding lugs fitting into the three slots of the stem top, thus allowing the time ring to slide vertically only along the axis of the fuse. On the upper side of the time ring an annular groove is to be turned for the reception of a soaked leather washer. From the lower cone of the time ring an oblique hole is to be bored, near one end of the bridge (left end in looking at the lower end of the time ring) communicating with the transmitting hole drilled through the composition groove. Through this oblique hole the composition is ignited from the time detonator cap of the fuse, assisted by the powder preparation pasted by means of alcohol varnish on the side wall of the hole next to the bridge. From the circular section connecting both cones of the time ring to the under side of the same, four gas escape holes are provided, facilitating the escape of the gases from the burning lower time composition.

The _lower time ring_ is turned on the inside, providing a slight cylindrical shoulder fitting on the base of the stem top and turning freely around same. At one end of the intervening bridge (opposite the one in the upper ring) a transmitting hole is drilled through the bottom of the composition groove of the time ring, transmitting the flame from the upper to the lower composition. To insure the ignition of the composition, a powder pellet with a central hole is inserted into the transmitting hole. From this transmitting hole, a gas escape hole, located on a radius of the time ring is provided, which at its base has a bursting charge of powder (varnished) pressed into it, plugged up with asbestos, and covered with a foil ring pasted with varnish. This hole facilitates the escape of gases from the burning composition of the lower time ring. The asbestos plug prevents the possibility of a premature ignition of the lower composition from the upper one, and the powder charge is intended for an immediate clearing of the plugging at the gas escape hole soon after the ignition of the lower composition through the transmitting hole. The lateral surface of the lower time ring is provided with:

1. Four pairs of pins inserted into corresponding holes for the setting of the fuse by hand.

2. Two holes for a wrench, if same should be required for setting the fuses.

3. Graduation from 10 to 130.

4. Separate graduation marked with the digit “5.”

5. One notch marked in red and one notch marked in black with letters as directed by the contracting government.

The upper side of the lower time ring is covered with a cloth washer having an opening opposite the transmitting hole.

=The Brass Nut.=--From the outside, the nut presents a rounded surface terminating into an umbrella. Inside the nut a thread is cut for screwing onto the top of the stem; the threaded hole opens into an oval cylindrical cavity communicating with the outside atmosphere by means of four openings in the neck of the umbrella. The edges of these four openings are milled out on a side opposite to the direction of the rotation of the shell to facilitate the escape of gases. At the bottom of the nut an arch-like annular recess is milled out for the accumulation of gases from the burning compositions of the time rings, whence they escape into the above-mentioned oval cylindrical cavity through four inclined channels, and then out of the fuse through the openings in the neck of the umbrella. The nut is provided with two brass screws for securing it in place, after being screwed home on the top of the stem.

=Upper Percussion Arrangement.=--The upper percussion arrangement consists of a brass time pellet and safety ferrule; the time detonating cap is inserted into the pellet and is held in place by means of a brass rod and brass spiral spring wound on the head of the latter. The safety ferrule is a hollow cylinder with a side slot, resting on the shoulder between the upper and lower chambers of the stem top. In its outside appearance the time pellet represents a cylinder of two different diameters connected with a conical slope; with the latter, the pellet resting on the conical enlargement of the ferrule. The lower cylindrical part of the pellet slides into the inside of the ferrule, and the upper, together with the projecting part of the rod, is located above the top of the stem in the cavity of the nut leaning with its steel spring against the arch of the cavity. The rod is kept firmly in place, being staked in on the circumference of the joint in two places.

On the top of the stem, embracing the middle smooth cylindrical portion, the brass conical tightening ring is put on, fitting into the conical seat of the upper time ring. The ring is provided with a pin, which is guided in its movements by one of the three grooves in the top of the stem, opposite the vent. In order not to cover up the vent in the stem top, a longitudinal slot is cut in the ring opposite the former; the eight other grooves on the outside of the ring facilitate the tightening of the ring.

=Lower Percussion Arrangement.=--The lower percussion arrangement is located in the tail of the stem between the chamber and the base bushing and consists of a percussion pellet, lock bushing, brass safety stirrup with counter spring, steel spiral spring, and lead washer. The brass percussion pellet, turned all over, is provided with: 1. Bottom shoulder resting on lead washer in base plug; the top of this shoulder is turned off and the strips of the counter safety catch hold onto it. 2. Cylindrical shoulder with lower turn of steel spiral spring embracing same and guiding the compression of the spring when the lock bushing is settling down. 3. Lead washer with rectangular opening, coated with varnish, and placed on the upper face of the shoulder. 4. Parallel faces along which are placed the leaves of the safety stirrup. On the upper part of the two opposite faces of the percussion pellet transverse cuts are milled out into which special tongues of the leaves of the safety stirrup fit. The safety stirrup with the counter spring soldered to it has four leaves, two of which (opposite ones) are bent in the middle outwardly and two of which are straight, with only a slight outward bend at their ends; the latter leaves have tongues for fitting into the cuts of the pellets, as shown in Fig. 4, Chapter I.

The lock bushing is a hollow brass cylinder, the outer upper portion of which is rounded off and made wider than the lower one; the interior is bored out cylindrically and then widened into a cone, which catches the straight leaves of the safety stirrup when the lock bushing is settling down, thus preventing the latter from moving upwards. The steel spiral spring in conjunction with the bent leaves of the stirrup hold the lock bushing over the percussion pellet. The percussion cap is kept in place by means of a brass bushing which is staked in from below in two places.

=Base Plug.=--The base plug, which is made of brass, has an annular groove formed at the bottom near the wall, which serves for fastening the counter safety lugs made of two strips of copper. At one end, the lugs are inserted in the groove (at the opposite ends of a diameter), and at this place the metal is jammed; with their other ends the lugs catch onto the shoulder of the bottom flange of the percussion pellet, inserted in the base plug together with the lead washer. The base plug has a flat bottom with a central opening covered with a brass disk; in order not to leave any space between this disk and its seat, the former is covered with varnish from below; two other holes at the bottom of the bushing, not drilled through, serve for the insertion of a wrench.

=Testing Fuses and Their Component Parts.=--These tests are carried out as follows:

1. The brass safety stirrups and bushings (time and percussion) are divided into lots of 500 each. Five per cent of each lot shall be tested for bending in a hydraulic testing press. The resisting force of the percussion safety stirrups must be within the limits of 58.68 to 85.77 pounds avoirdupois, that of the brass counter springs between 2.71 to 3.16 pounds avoirdupois, and that of the time safety bushing between 72.23 to 99.31 pounds avoirdupois. (For fuses for mountain artillery, from 40.63 to 54.17 pounds avoirdupois.) All the time safety bushings shall also be subjected on the same press to a compression test of 72.23 pounds (for fuses for mountain guns, 45.14 pounds avoirdupois), and only those which have stood this test are finally considered suitable for the assembly of the fuses.

2. The steel spiral springs shall have no more than 2³⁄₄ turns, and the upper and lower one must lie in a horizontal plane and approach the nearest turn. In compressing the springs to 0.33 inch, the springs must withstand a pressure of from 20.76 to 47.08 pounds avoirdupois, and after removing the compressive load must resume the dimensions within the given limits.

3. One-quarter per cent of the completely assembled percussion arrangement must be tested for determining the correctness of the locking of the lock bushing with the safety stirrup, with the former in its settling down position.

4. The counter safety lugs with the base plugs are made up into lots of 500 each; 5 per cent of each lot, with the inserted percussion arrangement held in place by bending the lugs on the shoulder of the lower flange, are tested under load for unbending the catches of the counter safety lugs. At a load of from 3.61 to 5.42 pounds avoirdupois, the lugs must release the pellet. The percussion and time safety bushings and stirrups should be numbered with the number of the lot, in the order of their manufacture.

5. In order to secure easy turning of the lower time ring by hand, in setting the fuse, the pressure on the nut in screwing it home should be determined by readings of an automatic control wrench and should be between 6.32 and 8.12 pounds avoirdupois.

6. For testing the degree of uniformity of the fuses, they are divided into lots of not more than 500 each. The testing for the full burning time of the fuse is to take place on a special apparatus and shall be determined by a stop-watch; the mean arithmetical difference from the mean time of burning shall be determined from six tested fuses and shall not exceed 0.13 second. If a greater difference is obtained, nine more fuses shall be burned and the mean difference determined from fifteen separate readings. If the result is more than 0.13 second, ten more fuses shall be burned and the mean difference determined from all the twenty-five fuses. If a lot does not fulfill the required test, all the time rings shall be rejected and the powder in same burned out.

7. In order to determine whether all the component parts of a fuse are properly assembled and kept firmly in place without moving, each fuse is shaken by hand and weighed; if the smallest weight of a fuse is not less than 12.862 ounces avoirdupois (for a mountain fuse, not less than 12.81 ounces avoirdupois) and no displacement of any of its component parts ascertained, the fuse is set on “grape-shot” and provided with a protective tin cover; otherwise the fuse shall be taken apart to determine whether all the parts are inserted in the fuse.

8. The percussion and time detonator caps shall be tested for their sensitiveness to ignition by being thrown from a height of two feet for the former, and 1.5 feet for the latter, on the same apparatus as caps for other fuses. For testing the percussion caps, the lower percussion arrangement is set, _i.e._, the lock bushing is set until locked with the percussion pellet by means of the leaves of the safety stirrup, and then carefully thrust onto the needle of the tail of the stem.

For testing the time detonator caps, the time pellet is first inserted into the safety bushing; this is done in order to increase the weight of the pellet, as its own weight is too small and would necessitate a considerable lifting of the rod of the testing apparatus. In order to conveniently insert the time pellet within the safety bushing, the chamber in the top of the stem (the middle one) is bored out, and the percussion pellet is carefully thrust onto the needle. In testing the percussion detonator caps, the tail of the stem is screwed into the end sleeve of the rod of the testing apparatus, and in testing the time detonator caps the top of the stem is treated in the same manner; in the latter test, the time rings are first put on the flange of the stem.

For testing the caps delivered to the works manufacturing the fuses in hermetically sealed boxes (1500 percussion and 2500 time detonator caps in each lot), ¹⁄₂ per cent of the percussion caps and 1 per cent of the time caps are selected for this purpose. The caps are regarded as satisfactory if, in testing the percussion caps, there will not be more than 1 per cent of cases missing fire or failing to knock out the brass disk from the base plug; in testing the time caps the number of cases of non-ignition of the time rings shall not exceed ¹⁄₂ per cent. The ignited percussion caps must burn the muslin and paper disks placed at the bottom of the chamber bushing and ignite its powder.

9. Out of a control consignment of 25,000 fuses, 25 shall be selected for shaking tests on a testing machine during 1¹⁄₂ hour (10 fuses will be shaken in a horizontal position and 15 in a vertical), in order to determine the serviceability of the fuses under the most unfavorable conditions which can be encountered in transporting the shells.

=Equipment of Fuses with Protective Covers.=--The tin cap covering the fuse is pressed into both grooves on the lateral surface of the flange of the stem; opposite the holes in the lower groove the cover is staked in; for waterproofing the fuse, the grooves should be filled with grease (consisting of 58¹⁄₂ parts of beeswax, 29¹⁄₂ parts of naphtha grease, and 12 parts of white resin). To conveniently throw off the cover, a copper wire, stranded of four separate thin wires to preserve its flexibility, is inserted in the upper groove before putting on the cover. One end of the wire is slipped through the opening in the flange and fastened at the bottom; the wire then runs around almost the whole circumference of the groove, is bent in a right angle in the direction of the markings on the flange to the top of the cover, where it is knotted and kept in place by a protruding button pressed out of the cover. A piece of twilled tape is fastened to the wire, which tape, in turn, is pasted to the body of the cover.

=Boxing of Fuses.=--Each fuse with cover, after being examined and the varnish of the tape being found perfectly dry, is carefully wrapped in wrapping paper; 15 fuses are placed in a zinc box padded at the bottom with perfectly dry felt, and the spaces between the fuses filled in with felt or cloth cuttings. The fuses are covered with felt padding and the cover is soldered to the box. A paper ticket, pasted on the top of the box, should contain the following information: The number of the box in the order of manufacture of the fuses in the current year, the year of their manufacture, the name of the fuses and the quantity per box, the number of the control consignment and of the daily output, the time of pressing in the composition, and the time of the ignition test. The dimensions of the box are: length, 12.15 to 12.20 inches, width, 7.25 to 7.30 inches, and height, 3.11 to 3.16 inches. Four zinc boxes are put into a wooden box.

The following information should be given on the tag pasted on the lower side of the wooden box cover: The number of the box in the order of their manufacture in the current year, the year of the manufacture of the fuses, the kind of fuses, and the quantity in the box. On the top of the box a stenciled inscription should be made giving the number of the box, the quantity and kind of fuses, and the year of their manufacture. On the side of the box the number of the control consignment and the year of manufacture should be marked. On boxes containing fuses with alloy time rings, the number of the box and the year of manufacture on the cover of the box, as well as the number of the lot and the year of manufacture on the side of the box, should be colored red. The weight of one zinc box containing fifteen fuses should be approximately 16.7 pounds avoirdupois, and the weight of one wooden box containing four zinc boxes be approximately 90.3 pounds avoirdupois.

=Instructions for Conducting Firing Tests.=--The following instructions for conducting firing tests are given in the official specifications:

1. For firing tests, fifty-five fuses should be tested out of a lot of 25,000 fuses or less.

2. The fuses are to be subjected to the following firing tests, using cast-iron experimental shells: Field fuses will be fired from a 3-inch quick-firing field gun at a muzzle velocity of 1930 feet per second and mean pressure of not more than 2400 atmospheres (35,500 pounds per square inch), and a maximum pressure of not more than 2550 atmospheres (37,500 pounds per square inch). Fuses from a 3-inch quick-firing mountain gun, model 1904, are fired at a muzzle velocity of 950 feet per second and a mean pressure of about 1250 atmospheres (18,400 pounds per square inch), or from a 3-inch quick-firing gun, model 1909, at a muzzle velocity of 1250 feet per second and mean pressure of approximately 1700 atmospheres (25,000 pounds per square inch).

(a) 25 fuses should be tested by firing for percussion action at a distance of about 4900 feet.

(b) 25 fuses should be tested for firing for time action by setting the fuse at 52 (mountain guns at 66), or at any other graduation depending on the atmospheric conditions of the day, in order to obtain a mean bursting distance of 7000 feet, whereby the mean height of the bursting should amount to approximately 0.012 of the distance.

(c) 5 fuses should be tested for “grape shot” action without removing the protecting cover.

(d) Mountain fuses are also tested with 25 shots for time action from a counter-storming gun at a distance of 3500 feet and a mean pressure of approximately 1100 atmospheres (16,200 pounds per square inch).

3. A lot of fuses is considered satisfactory if:

(a) In firing for percussion action not more than 2 failures shall take place, whereby the bursting on ricocheting at the second or further falls is considered as a failure.

(b) In firing with the fuse set at 52 or at any other graduation, depending on the atmospheric conditions of the day, in order to obtain a mean exploding distance of 7000 feet, not more than one failure shall result, and the probable deflection determined from not less than 20 shots will not exceed 84 feet. In case no failures should occur, it is permissible in figuring the probable deflection not to take into consideration one of the shots deflected not more than 420 feet from the mean point of explosion on the smaller side, or one deflected on the larger side.

(c) In firing “grape shot,” the mean point of explosion shall not be farther than 42 feet, and any individual explosion not farther than 140 feet.

(d) In firing for time and percussion action not a single premature explosion shall take place.

4. A lot which did not satisfy these conditions is accepted for a second test, if at the first test the following conditions prevailed:

(a) Not more than 3 failures were obtained in firing for percussion action.

(b) In firing for time action not more than two failures took place, and the probable deflection did not exceed 98 feet.

(c) In testing for “grape shot” action not more than one failure took place, the mean point of bursting being not farther than 56 feet and any individual explosion not more than 175 feet.

(d) In firing for time and percussion action not a single premature explosion took place.

5. A lot which failed in the first test, but which satisfied the requirements of Paragraph 4 shall be tested over again, according to Paragraph 3, on that point only in which the lot failed in testing.

6. In order to be accepted for service, a lot must, at the second test, give such results that the percentage of failures on time and percussion action obtained at the first and second firing shall not exceed in its entirety the percentage which was determined in Paragraph 3 for corresponding tests. The probable deflections and mean distances of explosion obtained at the second test for time action, and in testing for “grape shot” action must satisfy respectively the requirements as laid down in Paragraph 3.

7. A lot which did not satisfy both tests will not be subjected to any more tests, and any further action will depend upon the military authorities.

=Action of Fuses at Firing.=--In setting the fuses it is necessary to bear in mind that each of the 130 graduations of the fuse corresponds to approximately 140 feet (in fuses for mountain artillery of the Russian 1904 model to 104 feet) in the change of the firing distance, the same as the graduations on the sight of the gun. In firing, the time pellet passes through the safety bushing, expanding the latter, and falling with the cap on the needle. The detonator cap ignites the composition of the copper time ring through the vent in stem top and the hole in upper time ring.

When the fuse is set on “percussion”, the transmitting opening of the lower time ring and the ignition of the flange of the stem are located opposite the intervening bridges, and the burning of the upper time composition is not transmitted into the chamber of the fuse. In such a case the shrapnel continues its movement until striking an obstacle. At this instant the lower percussion arrangement, releasing itself from the grip of the lugs of the counter safety catch and compressing the counter safety spring, approaches the needle, which punctures the detonating cap; the flame from the latter together with the flame from the powder of the chamber bushing are transmitted to the bursting charge in the shrapnel shell. When the fuse is set for “grape shot,” the transmitting openings in the time rings and the ignition openings in the flange of the stem are brought so close to one another that the bursting of the shrapnel must take place on the average not farther than 42 feet in front of the muzzle of the gun.

=Russian Combination Time and Percussion Fuse--Vickers Type.=--Since the outbreak of the present war, various fuses have been used on Russian shrapnel shells. One of the principal of these fuses is the Vickers type of combination time and percussion fuse shown assembled in Fig. 1, and in detail in Figs. 2, 3, 4, and 5. While the original Russian fuse shown in Fig. 4, Chapter I, and described in the preceding pages, has, up to the present war, been the only fuse used in this shell, it has largely been replaced by other fuses, because of the difficulties experienced in manufacturing it. The Vickers type of fuse is somewhat easier to manufacture and, therefore, has been used to some extent on Russian shrapnel shells. Another fuse that is now being adapted to the Russian shrapnel shell is the American combination time and percussion fuse, Fig. 3, Chapter I, which is also of the same type as the British fuse described in Chapter XI. The chief difference in design between the standard Russian and the Vickers type of combination time and percussion fuse is in the percussion and concussion arrangements. It will be noticed in Figs. 1 to 5, inclusive, that the details of the Vickers fuse are much simpler to manufacture. There is also an absence of the numerous springs in the original Russian fuse.