Section XVII GUN GROUP

Fig 33. Pressure system disassembled, showing nomenclature and Chemical Warfare Service stock numbers for requisitioning spare parts.

(1)Release of pressure. Be sure all pressure has been released from the pressure system before disassembling or removing any part or assembly of the pressure system. To release pressure, operate fuel valve (Par 26) and hold open untilpressure is exhausted. As an added precaution, personnel should avoid facing the connections when disconnecting parts or assemblies.

(2)Removal procedure. After release of all pressure:

(a) Loosen the clamp from the valve flexible shaft.

(b) Using wrench, unscrew the large hex nut which holds the flexible shaft on the pressure-tank valve.

(d) Using wrench, unscrew the flared tube nut on the regulator tube adjacent to the pressure-tank valve.

(e) Open pressure-tank clamp (Fig 39) and swing clamp strap outward.

(f) Remove the pressure tank together with the pressure-tank valve and check valve.

(g) To remove valve handle, use the adjustable-end wrench to loosen and remove nut from threaded outer end of valve flexible shaft. Slide out the valve handle.

Fig 34. Lower portion of pressure system, assembled.

Fig 35. Check valve (cross section).

c.Installation. (Figs33and39) To install:

(1) Insert pressure tank (with pressure-tank valve and check valve mounted on the tank) through the pressure-tank clamp. Be sure to aline the regulator tube, elbow, and pressure-tank valve threads carefully so that they cannot be damaged when connecting.

(2) Close the pressure-tank clamp.

(3) Start the threaded connections by hand to be sure they are well alined. Do not force. Use wrench for final tightening, but do not apply great torque to the wrench.

(4) Insert the valve flexible shaft through small clamp into the pressure-tank valve. Using wrench, tighten the large hex nut located between shaft and valve.

(5) Tighten the clamp on the valve flexible shaft.

(6) Place pressure-valve handle on threaded end of the shaft. Place nut on threaded end and tighten with adjustable-end wrench.

d.Adjustment. If valve handle cannot be turned by hand:

(1) Remove flexible shaft and handle. Never apply a wrench to these parts.

(2) Turn end of pressure-valve stem with wrench to open valve.

(3) If stem will not turn, replace the tank and valve.

(4) If stem turns, work it back and forth with wrench.

(5) Reconnect flexible shaft and handle.

(6) If handle does not turn easily, repeat the process until handle turns, or replace tank and valve.

(7) Close valve before charging tank.

e.Maintenance.

(1) If either pressure tank, pressure-tank valve, or check valve are damaged or defective, all three must be replaced as a unit. No attempt may be made to repair any of these parts ortheir connections. If makeshift repairs or improvised parts are devised, serious accidents can result because of the extremely high pressures to which the equipment is subjected.

(2) Keep all threaded connections tightened. If a leak is suspected at any threaded connection, follow procedure in Paragraph53d.

a.Description and functioning. The regulator automatically reduces the variable pressure of air or nitrogen in the pressure tank to a constant operating pressure of approximately 350 pounds per square inch in the fuel tanks. The regulator is located at a protected position in the tank group of the M2-2 portable flame thrower, where it is not readily subject to tampering or damage from the outside. The regulator tube with fittings connects the pressure-tank valve and pressure regulator. (Fig 33) Its outlet is connected to the fuel tanks by the diffusion-pipe assembly. (Par 68a) Either of two interchangeable types of regulators is furnished: the spring type (Figs33,36, and37), and the dome type (Fig 38).

Fig 36. Rear of tank group, with carrier removed to show pressure regulator (spring-type) and connections.

b.Removal of pressure regulator. After release of all pressure:

(1) Remove carrier (Par 71b), if necessary.

(2) Using wrench, unscrew the flared tube nuts and other fittings.

(3) Lift out the pressure regulator.

c.Installation of pressure regulator. Line up pressure regulator, regulator tube, diffusion-pipe assembly, and fittings carefully so they will not be damaged when threads are tightened. Start threads with the hands. Apply only moderate wrench pressure to complete tightening. Replace carrier or carrier pack if either has been removed.

d.Adjustment of pressure regulator. The pressure regulator ordinarily requires no attention other than checking and tightening connections with the regulator tube and the diffusion-pipeassembly. If a defect in the regulator is indicated by falling off of the range of the weapon or by frequent breakage of the safety-head diaphragm (Par 56b), the following procedure should be carried out. (When using wrenches, do not apply excessive force.)

(1) Remove the filling plug (Par 69b) and ignition cylinder. (Par 30a)

(2) Fill the fuel tanks with 4 gallons of water (or fuel).

(3) Connect the 0-to 500-pound fuel-tank testing gage, found in the service kit, to the filling-plug hole. Tighten plug of gage with wrench.

(4) Charge the pressure tank to a pressure of 1,800 pounds per square inch. (Pars32and33)

(5) Open the pressure-tank valve.

(6) Read the pressure on the gage. If 350 to 390 pounds is indicated, omit steps (7) through (10).

(7)To increase the pressure of a spring-type regulator:

(a) Pry off the protective cap.

(b) Turn a set-screw wrench clockwise in the adjusting screw and read pressure on gage.

(8)To decrease the pressure of a spring-type regulator:

(a) Turn the set-screw wrench counterclockwise more than is considered sufficient to effect the desired reduction.

(b) Turn the pressure-tank valve off.

(d) Release the fuel valve.

(e) Open the pressure-tank valve and allow the system to reach a state of equilibrium, which occurs when the hissing sound ceases.

(f) Repeat the steps described above in (6) and (7).

(9)To increase the pressure of a dome-type regulator:

(a) Open needle valve No. 1 one full turn. (Fig 38)

(b) Open needle valve No. 2 one full turn. (There will be slight leakage around the needle-valve thread.)

(c) Open needle valve No. 3 very slowly, watching pressure gage closely. (As pressure builds up in fuel tanks there will be slight leakage through needle valve No. 1.)

(d) When the pressure gage indicates 350 pounds, close needle valve No. 3 tight.

(e) Close needle valve No. 2 tight.

(f) Close pressure-tank valve.

(g) When gage indicates zero, close needle valve No. 1 tight.

(10)To decrease the pressure of a dome-type regulator:

(a) Open needle valve No. 1 one full turn. (Fig 38)

(b) Open needle valve No. 3 very slightly, which will lower the pressure.

Fig 37. Pressure regulator, spring-type.

Fig 38. Pressure regulator, dome-type, showing needle valves and wrenches.

(d) Close pressure-tank valve.

(e) When gage indicates zero, close needle valve No. 1 tight.

(11) Open pressure-tank valve and press the fuel valve to observe the pressure with the weapon operating.

(12) After final adjustment:

(a) Close the pressure-tank valve.

(b) Open the fuel valve and release the pressure from the fuel tanks.

(d) Install filling plug.

(e) Tighten filling plug with wrench.

(f) If regulator is spring-type, replace its protective cap.

a.Description and functioning. (Figs4,5, and39) The fuel-tank assembly includes:

(1)Fuel tanks. Two alloy steel fuel tanks hold the fuel before it is propelled to the target. They have a combined capacity, including void, of 4-1/2 gallons. A void of approximately 1/2 gallon is left in tanks when filling to allow for expansion and to permit entry of the compressed nitrogen or air. To speed filling and cleaning of the tanks, two openings are provided on top of the fuel tanks. The openings are threaded to receive the filling-plug assembly and the safety-head plug assembly, which are interchangeable in the openings. Filling operations involve the use of auxiliary equipment and are described in Paragraphs34through40. The carrier and the pressure system are supported on the fuel tanks.

Fig 39. Fuel system of tank group and related parts disassembled, showing nomenclature and Chemical Warfare Service stock numbers for requisitioning spare parts.

(2)Tank connector. This open passageway between the fuel tanks makes them, in effect, a single container. The location of thetank connector and its large diameter permit easy flow of fuel and pressure between the two tanks.

(3)Hose connector. The hose connector is the outlet for fuel from the fuel tanks. It is located so that nearly all the fuel is propelled from the weapon if firing positions are correct. (Par 24) One end is welded to an opening in the tank connector. The other end is threaded into the tank coupling.

(4)Frame clamp. This small metal clamp, with bolt, nut, and washer, holds the hose connector to the carrier frame.

(5)Diffusion-pipe assembly. This T-shaped tubing carries compressed air or nitrogen from the pressure regulator to each of the fuel tanks. A flared tube connection and elbow connect the stem of the T to the pressure regulator. The horizontal tubes of the T extend into the fuel tanks and are welded to the fuel tank walls. Within the fuel tanks these tubes are perforated with holes which permit ready escape of the compressed nitrogen or air into the fuel tanks when the pressure-tank valve is open.

b.Removal and installation. The tank connector, hose connector, diffusion-pipe assembly, and the two fuel tanks are welded together and cannot be disassembled from each other. No attempt should be made to remove any of these parts or assemblies.

c.Maintenance. Other than cleaning (Pars51dand55e), repainting, and tightening of threaded joints, no repairs will be attempted by the first or second echelon on the fuel tanks, tank and hose connectors, or diffusion-pipe assembly. Emergency repairs may be made only by the third or fourth echelon. No attempt should be made to weld or patch any part of the fuel tanks.

a.Description and functioning.

(1)Filling-plug assembly. (Fig 39) This assembly fits into the 1-3/8-inch threaded opening at the top of either one of the fuel tanks. It permits filling and cleaning of the tanks, and seals the opening when the tank is not being filled or cleaned. The assembly includes the filling plug proper and a plug-retainer assembly. The latter is a metal rod which hangs from the plug on a metal chain. The rod and chain prevent accidental loss of the plug.

(2)Safety-head plug assembly. (Figs39and40) This assembly is screwed into the threaded opening on top of either fuel tank. It serves the same functions as the filling-plug assembly and moreover protects the firer and other personnel. It includes:

(a)Safety-head plug. This plug is similar to the filling plug except for the threaded hole which receives the safety head.

(b)Safety head. This metal head screws into the safety-head plug. It includes a soft metal diaphragm which bursts when the pressure in the fuel tanks exceeds 500 pounds per square inch.It prevents the building up of dangerous pressures in the fuel tanks.

Fig 40. Safety-head plug assembly (cross section).

Fig 41. Unscrewing safety head from safety-head plug, using wrench.

(c)Deflector tube. This short, curved piece of 1/8-inch pipe deflects fuel and pressure away from the firer if the safety head bursts. A lock nut holds the tube in position. (Par 12j)

(d)Plug-retainer assembly. This assembly consists of a metal rod and chain which hang from the plug and prevent accidental loss of the plug when filling or inspecting.

b.Removal of plugs.

(1) Before removing the filling plug, the safety-head plug, or an unbroken safety head, operate the fuel valve until any pressure which may have accumulated in the fuel tanks is eliminated. If the coupling plug is in the tank coupling, very slightly loosen the threads of either the filling plug or the safety-head plug, using the 1-3/4-inch wrench, to eliminate pressure in the fuel tanks. Keep face and eyes away from the threads.

(2) The plug-retainer assemblies should not be lifted completely out of the tanks unless required.

(3) If either the rod or the rod and chain breaks from one of the plugs and falls into the tank, upend the tank group to permit removal of the parts.

(4) To replace burst safety head, unscrew lock nut and deflector tube. (Fig 11) Using wrench (Fig 41), unscrew safety head. Never disassemble the safety head.

c.Installation of plugs. The filling plug, safety-head plug, and safety head are screwed in by hand and then tightened with wrenches. No substitution will be made for the safety head, which is manufactured to burst at the safe limit of pressure. The plug threads and seats should be cleaned with a cloth (Fig 29) before installing plugs. Screw in deflector tube, using hand pressure. The tube outlet should face to the rear and at a 45-degree angle to operator’s left shoulder. (Fig 18) Replace lock nut and tighten with wrench. (Use wrench on lock nut, not on deflector tube.)

d.Maintenance of plugs. Replace safety head if damaged or blown. Never repair safety head or use an improvised head.

a.Description and functioning. This quick-connecting coupling (Fig 42) connects and locks the fuel hose or the coupling plug to the tank group. The coupling cams, lock, and washer provide a secure and tight joint. The tank coupling makes possible rapid replacement of emptied tank groups with filled and charged tank groups in the field. No tools are needed for this operation.

Fig 42. Tank coupling and end of fuel-hose assembly.

b.Removal.

(1) To remove the tank coupling from the hose connector, apply a wrench and unscrew.

Fig 43. Closing cams of tank coupling to connect gun and tank group. This is done before locking. (See below.)

Fig 44. Closing lock of tank coupling to secure gun to tank group. This also provides a fuel-tight seal.

(2) To disconnect the tank coupling from the fuel hose or the coupling plug:

(a) Release pressure from fuel tanks by operating the fuelvalve or by opening very slightly the filling plug.

(b) Using hands, pivot the coupling lock back on the coupling body.

(d) Slide out the fuel hose or the tank coupling.

(e) If coupling washer is to be removed, pry out with a screw driver.

c.Installation of tank coupling. Proceed as follows:

(1) If coupling washer has been removed, replace.

(2) Insert coupling plug or hose nipple, tank end, in the coupling as far as it will reach. Close the two cams. (Fig 43)

Fig 45. Coupling plug in place in tank coupling. This arrangement is used when fuel tanks are brought back for filling with gun detached.

(3) Close the coupling lock (Fig 44), being sure to push it all the way, until it covers the ends of both cams. (Figure 45shows coupling lock correctly locked on coupling plug.)

(4) If the tank coupling has been removed from the hose connector, screw it on hand tight. Anti-seize compound should be applied lightly to the threads to assure a tight joint. Use wrench to tighten the coupling until it is in the position shown inFigure 34.

d.Maintenance of tank coupling. The coupling washer, made of synthetic rubber, should be inspected frequently. If it is damaged or swollen, remove it and replace. If the coupling leaks, inspect, and if necessary, remove and replace the washer.

a.Description and functioning. (Fig 46) The tank group is securely carried on the firer’s back and chest by the carrier, which includes the metal carrier frame, the canvas carrier pack, webbing straps, and cord, all of which are parts of the tank group.

(1)Carrier frame. This lightweight, tubular-metal frame is bolted to two pairs of brackets (upper and lower) on the fuel tanks. It is also bolted to the hose connector by the frame clamp, which helps support the connector. The frame is pierced by two parallel series of holes, through which the cord (lashing) of the carrier is laced.

(2)Carrier pack. This is a sheet of heavy canvas, reinforced on the tank side with strips of webbing. The smooth side of thecarrier pack rests against the firer’s back and cushions the back from contact with the metal tanks. A series of eyelets is located on each side of the pack.

(3)Seine cord (lashing). The carrier pack is fastened to the carrier frame by means of hard-braided cord which is laced through the eyelets in the pack and the holes in the frame. The cord that comes on the flame thrower stretches very little under load.

(4)Straps. The straps, made of wide cotton webbing, are adjustable to fit the wearer. (Fig 18) They are provided with snap release, hook-and-eye, and snap fasteners. The shoulder straps have quick-release fasteners for rapid removal, if necessary, of the tank group from the firer. The upper ends (steel loops) of the shoulder straps are secured by pins to the steel support which connects the two fuel tanks. Each of the pins is held in position by a split cotter pin, which is inserted through a hole in the pin and is then spread. The lower ends of the shoulder straps snap onto metal loops at the bottom of the carrier frame. The upper body straps are attached to metal loops on each side of the carrier frame. The lower body straps are fastened to one of the lower two pairs of eyelets of the carrier pack.

b.Removal of carrier.

(1) To remove carrier or carrier frame, use screw driver and adjustable-end wrench to take off frame clamp, bolt, nut, and lock washer. (Fig 34)Then remove two pairs of bolts, nuts, and lock washers which hold the carrier frame to bottom and top of the fuel tanks. Lift off the carrier.

(2) To remove body straps, unsnap ends and lift out of holes. To remove shoulder straps, unsnap lower ends and remove from holes. Pull out cotter pins, then pins, from upper ends of shoulder straps, and lift out straps.

(3) To remove carrier pack, unknot and unlace cord.

c.Installation of carrier.

(1) To install carrier frame (or a complete carrier) place frame in position adjacent to fuel tanks (Fig 46), insert bolts in holes, place lock washers and nuts on bolts, and tighten with screw driver and wrench. Replace frame clamp on fuel connector and frame. Insert bolt in holes, place lock washer and nut on bolt. Tighten with screw driver and wrench.

(2) If carrier pack has been removed, use cord to relash. Lace tight and use slip-proof knots. (Fig 46)

(3) To install straps, snap ends of body straps and lower ends of shoulder straps into positions shown inFigure 46. Place upper ends (steel loops) of shoulder straps in steel support between fuel tanks. Insert two pins through any two of the holes in the support and through the shoulder strap loops. Insert cotter pins in holes in pins and spread cotter pins to lock pins in place.

d.Adjustment of carrier. Carrier must be carefully adjusted to fit the individual firer so the load will not shift during sudden,rapid changes of firer’s position. Adjustments are as follows:

(1)Cord and carrier pack. Cord must be tight at all times. The cord furnished with the equipment has very little tendency to stretch. However, pull cord tight when lacing and use slip-proof knots at ends. Tighten cord periodically.

Fig 46. Carrier assembled on tank group.

(2)Straps. Adjust straps to fit each firer, moving slides on straps as necessary. Straps must fit snugly to prevent shifting of load and to keep tank group high on firer’s back. Lower body straps may be fastened in second pair from the bottom of carriereyelets to conform to firer’s physique. Pins, which hold top ends of shoulder straps to steel support between the fuel tanks, may be moved to any two of the three holes so as to provide the best balance in the load.

e.Maintenance of carrier. Keep carrier dry and clean. If flame thrower becomes wet or muddy, clean and dry carrier thoroughly. Store in a dry place. If rotted, mildewed, or damaged, replace affected parts. If cord frays or breaks, use special seine cord from service kit as replacement.

The gun group consists of the fuel-hose assembly and the gun. The gun includes the fuel valve, which controls the ejection of fuel, and the ignition head, which ignites the fuel.

a.Description and functioning. (Fig 47) Hose, fuel, flame thrower, M1, assembly, provides a flexible connection between the fuel tanks and the gun.

(1)Hose. Made of synthetic rubber and reinforced with a cover of metal wire and cotton braid, the hose resists the action of gasoline and oil, and withstands a pressure of approximately 1,000 pounds per square inch. Its inside diameter is 7/8 inch; its outside diameter is approximately 1-1/4 inches.

(2)Nipples. The hose nipple, tank end, connects the hose to the tank coupling on the tank group. The hose nipple, gun end, is a threaded connector between the other end of the hose and the fuel-valve body.

b.Removal of fuel-hose assembly. Remove the hose from the gun only when necessary for maintenance. The threads in the fuel-valve body will be damaged by frequent screwing and unscrewing of the hose because the body is a lightweight aluminum casting. Fuel hose is replaced as a unit and is not disassembled in the second echelon. To disconnect from tank group, see Paragraph70b.

c.Installation of fuel-hose assembly.

(1) To install in tank group, see Paragraph70c.

(2) To install in gun, apply anti-seize compound (from service kit) lightly to threads and screw hose in fuel-valve body by hand. Use wrench only enough to make a secure connection.

d.Maintenance of fuel-hose assembly. If the hose nipple, tank end, is badly nicked and does not provide a tight connectionwith a new coupling washer (Par 70):

(1) File the end surface, being careful to keep the surface at a right angle to the sides of the nipple.

(2) Couple hose nipple, tank end, to tank coupling. If coupling closes very easily, indicating washer is not being compressed, replace the washer and recouple. If coupling still closes too freely, the nipple has been filed too short, and the fuel-hose assembly should be replaced as a unit.

a.Description and functioning. (Fig 47) The valve grip is part of the fuel valve. It includes the controls and is held by the firer in his right hand to support the gun group. Parts of the valve grip are:

(1)Left and right valve grips. A pistol-type grip is formed by two aluminum housings designated as the left valve grip and the right valve grip. The two parts are held together by four screws and four lock washers.

(2)Grip support. This aluminum housing is mounted above the left and right valve grips and connected to them by two screws and lock washers.

(3)Valve lever. This control is made to fit the fingers and is mounted in front of and between the two parts of the valve grip. A pin at the top of the lever fits into holes in left and right valve grips and serves as a pivot, governing the movement of the lever. When the lever and the grip safety are compressed simultaneously by the operator, the valve is thereby opened and fuel is ejected from the gun.

(4)Grip safety. This control is grasped by the hand simultaneously with the valve lever. It is mounted back of and between left and right valve grips. A pin at the base of the safety fits into holes in the left and right valve grips and serves as a pivot in a manner similar to the pin on the valve lever. The fuel cannot be discharged unless both the valve lever and the grip safety are compressed simultaneously.

(5)Rocker arm. The rocker arm, a boat-shaped metal part, is mounted near its center on a pin. It is held in contact with the valve lever by means of a valve-grip spring and spring pin. At its top end, the rocker arm touches the yoke shaft of the valve-diaphragm assembly. When the valve lever and the grip safety are compressed, the rocker arm pushes the valve diaphragm assembly forward.

(6)Valve-grip spring. When the firer’s hand releases the valve grip, the valve-grip spring forces the valve lever, the grip safety, and the rocker arm back to their normal, nonoperating positions.

b.Removal of valve grip.

(1) Unscrew the four screws and lock washers that hold the grip support to the valve body. Remove the valve grip as a unit.

Fig 47. Fuel valve (disassembled) and fuel hose, showing nomenclature and Chemical Warfare Service stock numbers for requisitioning spare parts.

Fig 48. Location of parts in right valve grip before covering them with left valve grip.

Fig 49. Using screw driver to push long end of valve-grip spring into groove in grip safety.

(2) To disassemble valve grip, remove screws and lock washers from the grip. Lift off the left valve grip, exposing contents of grip. Lift out the following parts: valve-grip spring, rocker arm, grip safety, and valve lever.

c.Installing valve grip.

(1) Place grip safety, valve lever, and rocker arm in position in right valve grip. (Fig 48) Be sure the shorter end of rocker arm is at the top. Place grip spring over spring pin. Slip short end of grip spring in groove of rocker arm. Place long end of grip spring on outside of grip safety.

(2) Put left valve grip in place and insert the two lower lock washers and screws. Tighten the two screws enough to hold parts in place and still leave space for moving long end of spring into the groove in grip safety. Push spring into groove with a screw driver. (Fig 49)

(3) With spring in place, fully tighten the two screws with screw driver.

(4) Place grip support in position, and insert the two upper lock washers and screws. Tighten screws, using screw driver.

(5) Attach valve grip to valve body, using the four lock washers and inserting the four screws through the grip support. Make sure that the yoke shaft of the valve-diaphragm assembly is in front of rocker arm.

d.Maintenance of valve grip. No maintenance is required for the valve grip other than replacement of worn or damaged parts, tightening of screws, cleaning, and lubrication. (Par 49)

a.Description and functioning. (Fig 47) This assembly is part of the fuel valve. It includes the barrel, valve body, andoperating parts contained in the barrel and valve body. The assembly consists of:

(1)Valve body, an aluminum housing, located at the rear of the gun and mounted on the grip support by means of four screws and lock washers. The valve body has four large threaded openings. The lower opening leads into the valve grip. The side opening, which forms a Y with the main portion of the body, is connected to the fuel-hose assembly. The front opening is screwed on the barrel. The rear opening is closed by the spring retainer and plug.

(2)Valve-diaphragm assembly, which transmits and reverses the movement imparted to it by the rocker arm of the valve grip. (Par 74a) It also serves as a seal, keeping fuel from entering the valve grip. The valve-diaphragm assembly includes:

(a)Yoke shaft, on which the rocker arm bears at the lower end of the shaft.

(b)Yoke, a Y-shaped metal part which fits on the upper end of the yoke shaft and is held to it by a steel pin. The yoke transmits motion from the shaft to the yoke block, and is located within the valve body when the valve is assembled.

(c)Diaphragm, a synthetic-rubber diaphragm held in a steel sleeve, which fits snugly in the lower opening of the valve body. The yoke shaft passes through the diaphragm.

(3)Diaphragm support, washer, and cap, which hold the valve-diaphragm assembly in place in the valve body.

(4)Spring retainer, a brass, hollow bushing which screws into the rear opening of the valve body, and which is threaded internally to receive the plug. The retainer has a hexagonal head to take a 1-3/8-inch wrench. As its name implies, the retainer holds the valve spring in position.

(5)Plug, a brass part, resembling a cap screw, which fits into the spring retainer, closing off the rear end of the gun. It permits adjustment of the needle (seedbelow) without removing the valve spring and spring retainer.

(6)Valve spring, a coil spring located in the valve body between the spring retainer and the yoke block. The spring keeps the needle seated in the nozzle until compression of the grip safety and valve lever forces back the yoke block, spring, and needle.

(7)Yoke block, a steel piece, 1 inch long, which fits into the arms of the yoke Y. It is secured by an internal thread to the valve needle. Movement of the yoke in turn moves the yoke block and the valve needle.

(8)Lock nut, on the valve-needle thread at the rear of the yoke block, which locks the block on the needle.

(9)Valve-needle, a pointed rod, which extends through the inside of the barrel from the yoke block to the nozzle. The valve needle is seated in the nozzle except when firing. It controls theejection of fuel from the nozzle. Two sets of three fins each, known as needle guides, are mounted on the front and rear of the needle, respectively. These guides keep the needle centered in the barrel. The rear end of the valve needle is threaded to hold the yoke block and permit adjustment of the needle by means of the lock nut which screws on the threads. (Seedbelow.)

(10)Barrel(Figs47and54), which carries the fuel to the ignition head. It also supports or contains other components of the gun. The barrel assembly is replaced as a unit with the needle. It consists of a tube, made of thin metal, with a threaded fitting at the back end, and a nozzle brazed into the front end of the tube. The nozzle ejects the fuel from the barrel through the ignition head. The fuel emerges from two holes in the nozzle:

(a)Atomizer hole, a small opening which sprays a fine, readily ignited mist of fuel. This helps ignite the main stream of fuel.

(b)Main hole, which is tapered inside, and which conveys the main stream of fuel from the barrel. When the gun is not being fired, the valve needle is seated in the main hole of the nozzle. When the gun is being fired, the needle is withdrawn from the nozzle seat, permitting the fuel to be forced from the gun.

b.Removal of barrel and valve-body assembly. If gun group and tank group are connected, release any pressure in the fuel tanks by compressing the valve lever and the grip safety. Then disassemble as follows:

(1) Unscrew the fuel-hose assembly from the fuel-valve body only if this is necessary for maintenance.

(2) Remove spring retainer and plug from end of fuel-valve body and remove valve spring.

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