Section XVII GUN GROUP
72. GENERAL
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.
73. FUEL-HOSE ASSEMBLY.
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 Paragraph [70 b].
c. Installation of fuel-hose assembly.
(1) To install in tank group, see Paragraph [70 c].
(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 connection with 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.
74. VALVE GRIP.
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])
75. BARREL AND VALVE-BODY ASSEMBLY.
a. Description and functioning. ([Fig 47]) This assembly is part of the fuel valve. It includes the barrel, valve body, and operating 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 74 a]) 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 (see [d] below) 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 the ejection 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. (See [d] below.)
(10) Barrel (Figs [47] and [54]), 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.
Fig 50. Valve needle, yoke block, and lock nut ready for installation in fuel-valve body.
(3) Unscrew diaphragm cap and pull out washer, support, and valve-diaphragm assembly. To prevent loss of valve-needle adjustment ([Fig 54]), do not disturb position of yoke block by turning the needle.
Fig 51. Placing diaphragm assembly in position in fuel-valve body.
Fig 52. Installing parts in fuel-valve body.
(4) Slide the valve needle out of barrel; the yoke block and the lock nut may then be unscrewed from the valve needle, but adjustment (see [d] below) will be necessary when reinstalling.
c. Installation of barrel and valve-body assembly.
(1) To install valve needle, screw the yoke block and lock nut on the needle ([Fig 50]). Insert needle in valve body and barrel.
(2) Insert valve-diaphragm assembly into valve body ([Fig 51]), making sure that the yoke slips into the flat notches of yoke block.
Fig 53. Installing spring retainer in fuel-valve body.
(3) Slip the diaphragm support, washer, and cap over the yoke shaft. ([Fig 52]) Screw on the diaphragm cap by hand. Do not use a wrench. Install valve grip. ([Par 74 c])
(4) Place valve spring over end of needle and install spring retainer. ([Fig 53]) Apply wrench very lightly to tighten spring retainer.
(5) Adjust needle (see d below), and screw plug into the spring retainer.
(6) If hose has been removed, apply anti-seize compound lightly to the threads. Screw hose into fuel-valve body. Wrench should be applied very lightly to tighten.
d. Adjustment of valve needle. Needle is adjusted after installation of parts in barrel and valve assembly. Use care when resetting needle, as smooth operation of the weapon depends on accurate adjustment.
(1) Remove ignition shield ([Par 18]) and plug from gun.
(2) Use the valve-adjusting wrench ([Fig 8]) to hold the lock nut and apply a cabinet (narrow-bladed) screw driver ([Fig 8]) in the end of the needle. Turn needle until it makes a snug fit in the nozzle opening.
(3) Compress the valve lever and grip safety. The needle should draw back into the nozzle with the tip of the needle at the smallest diameter opening in the nozzle. ([Fig 54])
(4) When the needle has been correctly adjusted, as in (3) above, tighten the lock nut with the valve-adjusting wrench, keeping the needle from turning with the screw driver. This will lock the adjustment. Screw plug into the spring retainer.
(5) Replace ignition shield. ([Par 18])
e. Maintenance of barrel and valve body.
Fig 54. Valve-needle adjustment. Solid lines show needle in correct open position with point at smallest diameter of nozzle. Broken lines show needle in closed position.
(1) Damaged parts. Replace worn or damaged parts. If the diaphragm shows evidence of tears or separation, or if leaks occur at the diaphragm, replace the valve-diaphragm assembly.
(2) Valve spring. If valve spring has lost resiliency, grasp it by the ends and stretch slightly, or replace.
(3) Nozzle leaks. If valve leaks at nozzle, and cleaning ([Par 55 d]) does not remedy the leak, adjust needle (see [d] above). If leak persists, either replace barrel and needle, or lap seat. To lap, place lapping compound on seat (in nozzle) and on needle point. Turn needle in seat until parts make a tight connection when seated. Remove lapping compound, reassemble, adjust needle, and test fire.
(4) Atomizer hole. If atomizer hole is clogged, clean with fine wire. ([Par 52 i])
76. IGNITION HEAD.
a. Description and functioning. ([Fig 55]) The ignition head ignites the fuel when the flame thrower is fired. It is mounted on the fore part of the barrel. It consists of:
(1) Ignition-head body, which includes half of the front grip. Three set screws serve to tighten the ignition-head body to the barrel. The ignition-head body is made of aluminum.
(2) Trigger and trigger bearing, held between the ignition-head body and the coverplate by the trigger screw.
(3) Trigger rod, one end of which is held in the trigger bearing, the other extending through the ignition-head body. Pulling the trigger shoves the trigger rod forward, causing it to push a match in the ignition cylinder. The match ignites an incendiary charge in the ignition cylinder.
(4) Trigger spring, which hooks over a projection of the trigger and is held at its lower end by a screw, which is held in the ignition-head body. This spring pulls the trigger rod back from the firing position after the firer releases the trigger.
(5) Latch, located in the ignition-head body, in front of and above the trigger guard. The latch, set on a pin, engages the notch of the ignition shield, locking it in place. A latch spring holds latch in position.
(6) Coverplate, an aluminum casting which constitutes the left section of the front grip and covers the working parts seated in the ignition head body. The coverplate and body are held together by four screws and four lock washers.
(7) Spring case, which turns the ignition cylinder when the trigger is pulled.
(a) Four projections on the inner spring case are bent over the outer spring case to hold the two parts together.
(b) The inner-case pin ([Fig 56]) engages a stop on the inside of the ignition cylinder. The five projecting metal matches on the inside of the ignition cylinder are each in turn stopped by the lug on the forward-facing surface of the ignition-head body.
Fig 55. Ignition head disassembled, showing nomenclature and Chemical Warfare Service stock numbers for requisitioning spare parts.
When the trigger is pulled, the trigger rod pushes a match forward, causing an incendiary charge in the ignition cylinder to ignite. The spring in the case rotates the ignition cylinder until another match is stopped by the lug.
Fig 56. Parts of ignition head and ignition cylinder.
(c) The outer-case pin (on the outside surface of the outer spring case) fits into the notch in the ignition shield and holds the spring case as the shield is screwed into position. This action winds the spring in the case.
(d) A snap ring holds the spring case on the ignition-head body.
(8) Ignition shield, a cylindrical, thin-metal tube with a conical front end. The shield guides the flame and protects the firer. Eight holes around the base of the cone provide an air intake for burning the fuel. The base of the shield is threaded, and it screws onto the ignition-head body. A notch ([Fig 56]) in the base of the shield receives the latch and the outer-case pin of the spring case.
b. Removal of ignition head. To remove the ignition head, proceed as follows:
(1) Remove shield by lifting latch and unscrewing shield counterclockwise. ([Fig 14]) Keep hands and face away from front of barrel.
(2) If ignition cylinder has not been removed, remove it or allow it to fall off barrel.
(3) Pry off snap ring which holds spring case in position, using screw driver. ([Fig 57]) Be careful not to damage or break the ignition-head body by applying too much leverage.
(4) Remove the four screws and lock washers which hold ignition-head body and coverplate together. Lift off coverplate.
(5) Trigger, trigger spring, trigger rod, latch, and latch spring may be removed.
(6) Using a hex wrench, loosen set screws ([Fig 58]) and withdraw barrel from ignition head.
c. Installation of ignition head. To install ignition head, proceed as follows:
(1) Insert barrel in ignition-head body, pushing it as far forward as the shoulder on the barrel permits.
(2) Aline front grip and valve grip.
(3) Using hex wrench, tighten set screws on barrel enough to hold but not so tight that barrel is dented.
(4) Place latch, latch spring, trigger and bearing, trigger rod, and trigger spring in position.
(5) Put coverplate on ignition-head body and replace the four lock washers and screws.
(6) Slip spring case over barrel, and lock by forcing snap ring into the groove.
(7) When weapon is to be used on a mission, fit ignition cylinder and ignition shield in place on nozzle end of barrel as described in Paragraph [18].
d. Maintenance of ignition head.
(1) Servicing. The ignition head should be cleaned and lubricated each time it is disassembled. ([Par 49])
(2) Spring-case assembly. If outer case rotates and inner case does not, and no spring action occurs, spring is broken and spring case should be replaced as a unit. Do not disassemble or repair this part.
(3) Trigger rod and lug. When trigger is pulled all the way, end of trigger rod should extend 1/16 inch beyond lug on forward-facing surface of ignition-head body. If end of trigger rod is worn, replace rod. Lug on the ignition-head body should be approximately 7/32 inch high. If lug is worn or broken, replace ignition head body.
Fig 57. Prying snap ring from ignition head to remove spring case.
Fig 58. Loosening set screws with wrench so ignition head may be lifted off barrel.