401-01-01 describe the 81mm mortar e

8/8/2019 401-01-01 Describe the 81mm Mortar e

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INFANTRY SCHOOL

BASIC MORTAR COURSE

MASTER LESSON PLAN

PREPARED BY: WO DOYLEDATE: MAY 00

REVISED BY:

DATE:

1. PO/EO NUMBER : 401.01.01

2. PERFORMANCE OBJECTIVE STATEMENT : Fires the 81mm mortar ground mounted.

3. ENABLING OBJECTIVE STATEMENT : Description and Maintenance.

4. MAIN TEACHING POINTS : Describe the 81mm mortar:

a. the component parts;

b. their functions; and

c. ancillary equipment.

5. REFERENCES DOCUMENT :

a. 385-017/PT-001 81mm Mortar the Weapon, Chapter 2, lesson 1

6. TIME REQUIRED : 2 X 40 min periods.

7. LOCATION : Classroom.

8. METHOD : Theory and Practical.

9. EVALUATION : Practical.

ADMINISTRATION

10. STORES .

a. four mortars complete; and

b. chalkboard.

11. TRAINING AIDS :

a. blackboard; and

b. PPT projector and PPT presentation.

12. DRESS : Combats.

13. INSTRUCTOR PREPARATIONS :

a. check TP & references;

b. revise the lesson plan;

c. master the subject;

d. obtain training aids and necessary equipment; and

e. prepare classroom.

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CONDUCT OF THE LESSON

14. INTRODUCTION :

a. Review: Nil

b What: You will learn is the description and maintenance of the 81mm mortar

c. Why: So you will understand the parts of the mortar and how to properly care for it.

d. Where: On this course, in your unit and in combat.

15. STAGE I COMPONENT PARTS AND THEIR FUNCTIONS

a. Introduction. In order to properly maintain and operate the 81mm mortar it is necessary to have adetailed knowledge of the component parts of the weapon and their functions

b. The Baseplate CDN MK 1. The baseplate is circular in shape and is made of forged aluminum. In

the center of the upper surface, it has a rebound socket which provides a seat for the breech plug of

the barrel. The baseplate is strengthened by four braces which are spiked to prevent slippage of thebaseplate when the mortar is fired. It has four grooves on the upper surface and four triangular

shaped openings which can be used as an aid in aligning the baseplate. The baseplate weighs 11.3

kg and has two purposes:

(1) it provides a platform for the mortar; and

(2) it transmits the shock of recoil to the ground on firing.

c. Barrel ML 81 mm L16A1/A2. The barrel is a smooth bore steel tube of forged monoblock con-

struction weighing 12.2 kg. It consists of the following five main parts:

(1) Muzzle Cover. The muzzle cover is a rubberized canvas bag which fits over the outside

of the muzzle preventing water, snow and other foreign material from entering the barrelwhen the mortar is not being fired;

(2) Blast Attenuation Device (B.A.D.). The B.A.D. is a device designed to provide a

reduction of blast and overpressure. It consists of the following components; cone, three

(3) collets, RING and Locking Nut;

(3) Barrel. The muzzle has a collar and internally has a short taper which provides a lead-in

for rounds during loading. Below the collar are two unpainted surfaces which provide

seating for the sight testing attachment. The lower half of the barrel is finned to assist in

cooling. On the plain portion of the barrel are two shoulders, one approximately 18 cmfrom the muzzle, the other just above the finning. These shoulders define the area within

which the barrel clamp must be positioned. At the breech end it is reduced in diameter,

and screw-threaded internally, for the breech plug. At the extreme lower end of thebarrel are two flats, which are provided for the large wrench, to remove or replace the

breech plug;

(4) Breech Plug. The breech plug is ball shaped. Forward of the ball, the plug is screw-threaded for assembly into the lower end of the barrel, which is fitted with a copper

sealing washer for proper seating, and is tapered to permit the use of 3 inch mortar

rounds. The ball has two flat surfaces which are provided for the small wrench to remove

or replace the breech plug, and to lock the barrel into the rebound socket of the baseplate.

A hole drilled at an incline to the axis of the plug tapers at the front end and is threaded at

the rear to house the firing pin; and

(5) Firing Pin. The firing pin is threaded for assembly into the breech plug. At the front it is

tapered to a radius point. Just back of the screw-thread is a collar. Around thecircumference of the collar are a number of semi-circular slots on which the peg of the

firing pin wrench locks during assembly or removal of the firing pin.

d. Bipod. The bipod provides a front support for the barrel and carries the gears necessary to lay the

mortar. The bipod assembly consists of three major components with a total weight of 11.8 kg.

These are:

e. Traversing Assembly. The traversing assembly consists of the following:

(1) Barrel Clamp. This secures the barrel to the bipod and consists of an upper and lower

clamp. Attached to the upper clamp is a curved handle, a spring-loaded locking rod and

ball. The lower clamp is shaped to cradle the barrel, and is bored on each side to house

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the buffer cylinders. On its right side it is recessed to house the ball end of the locking

rod. Above the recess is a safety latch which, when closed, locks the rod into the recess.

On the left side of the upper clamp is a safety lock. This ensures both upper and lower

clamps lock together,

(2) Buffer Carrier. This is shaped on the top to fit under the barrel and on each side it is

bored to hold the buffer cylinders. It is bored transversely and attached to the outer tubeof the traversing mechanism. On the left side is a sight bracket which has a dovetailed

recess that provides a mounting for the sightunit, and

(3) Traversing Mechanism. This is of the telescopic type, consisting of an internal screw

operating within a nut and tube. On the right is a traversing hand wheel and crank which

moves the assembly and traverses the mortar 100 mils left and right of center, one

complete turn of handwheel and crank equal 10 mils;

(4) Cross-levelling Assembly. The cross-levelling assembly consists of the yoke, the cross-

levelling arm, and the cross-levelling mechanism. The yoke is bored at each end for

attachment to the traversing screw assembly and is bored at its center for an axis pin to

which one end of the cross-levelling arm is attached. The other end of the cross-levelling

arm is attached to the elevating screw. The axis pin is fitted with a lubricator. A boss on

the left side of the yoke is screw threaded internally, for the ball socket of the cross-

levelling mechanism. The cross-levelling mechanism is positioned vertically betweentwo lugs on the cross-levelling arm, and can be elevated or depressed by means of the

cross-levelling handwheel and crank; and

(5) Leg Assembly. The leg assembly consists of two tubular metal legs terminating in spiked

feet. The upper end of the plain leg has a serrated facing which locks to the serrated

facing on the lug of the elevation leg. On the other side is a recess into which the

handwheel is fitted to hold the leg in other positions. A retaining strap attached to theplain leg is used to secure the barrel to the bipod. The elevating leg houses the elevating

mechanism which consists of the elevating screw, the elevating handwheel and crank.

The elevating mechanism will provide for angles of elevation from 800 mils to 1511

mils, subject to suitable positioning of the bipod. On the inside of the elevating housing,

adjacent to the plain leg, is a spring loaded locating catch. When depressed it releases thecatch from the recess of the plain leg.

16. CONFIRMATION OF STAGE I .

a. Question from class; and

b. Question to class.

17. STAGE II ANCILLARY EQUIPMENT

a. Introduction. Ancillary equipment supplied with the mortar is important to its operation. Thenames and uses are:

b. the sightunit C2A1 is provided to lay the mortar by indirect means;

(1) the boresight M45 is provided to test and adjust the sightunit C2A1;

(2) three aiming posts that are used to obtain and check direction;

(3) the baseplate flags are used to indicate the locations of baseplates on the ground prior to

coming into action;

(4) a cleaning staff is used to clean the bore of the barrel;

(5) the periscope extension is provided to overcome a barrel obstruction when the field of

view of the sightunit C2A1 is obscured by the barrel; and

(6) the accessory spare parts chest contains the following items:

(a) three aiming posts,

(b) three trilux lights (one orange, two green),

(c) oil can (gun type),

(d) firing pins,

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(e) muzzle cover,

(f) cleaning rod,

(g) cleaning brush,

(h) wrench firing pin #382,

(i) wrench breech mechanism #383,

(j) wrench breech mechanism #384,

(k) tools releasing baseplate MK 1,

(l) periscope extension C2A1 sightunit,

(m) pliers,

(n) arc marking flags (Red/Green),

(o) baseplate flags,

(p) strap wrench (B.A.D.),

(q) high density plastic hammer,

(r) tool box,

(s) boresight M45, and

(t) small brush;

c. Tool, Removing Jammed Round, 81 mm Mortar is a device designed to remove rounds that arestuck in the barrel and cannot be removed by the conventional misfire drills.

18. CONFIRMATION OF STAGE II .

a. Question from class; and

b. Question to class.

19. FINAL CONFIRMATION :

a. Question from class on lesson; and

b. Final confirmation.

20. CONCLUSION .

a. To properly maintain and operate the 81mm mortar it is essential to have a detailed knowledge of

the component parts and their functions; and

b. Your next lesson will be...

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401-01-01 describe the 81mm mortar e

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