Lesson 45. – TESTING THE CLINOMETER
A INSTRUCTORS NOTESAim
1. To teach officers and NCOs how to ascertain if the clinometer is in adjustment.
Class and instructors
2. Squads under squad instructors. This lesson should only be taught to officers and NCOs.
Periods
3. This period will not normally take a full 45 minutes to teach.
Stores
4. Gun, tripod and clinometer.
B CONDUCT OF LESSONApproach
5. State the aim of the lesson (see para 1).
Testing the clinometer
6. Explain and demonstrate that the clinometer is set at zero. It is then placed on the gun with the arrow pointing to the front of the gun and the bubble leveled with the hand wheel. The clinometer is now reversed and the position of the bubble noted. If it is central the clinometer is in adjustment. This should, however, be confirmed by repeating the process with the clinometer set at 10 degrees elevation and 10 degrees depression. State that if the bubble is displaced in either test, it indicates that there is an error.
7. Demonstrate that if there is an error, the clinometer is left on the gun and the micrometer head is rotated until the bubble is central and the scale reading noted. This reading should now be halved and set on the scale, eg, if the scale had read 20 minutes elevation, it should be set at 10 minutes elevation. The clinometer should now be placed back on the gun and retested as before. If the bubble is still not central, it should again be brought central by means of the micrometer head and then the reading should be halved as before and the clinometer tested again until a reading is obtained at which the bubble is central with the clinometer facing in both directions. This reading is the amount by which the clinometer is out of adjustment.
8. Ephasize that any adjustment must be carried out by an armourer.
9. Practise the squad.
Conclusion
10. Questions to and from the squad.
11. Sum up main points.
Lesson 46. – TESTING AND ADJUSTING THE DIAL SIGHT
A INSTRUCTORS NOTESAim
1. To teach the officer or NCO how to test, and if allowed, to adjust the dial sight.
Class and instructors
2. Squads under squad instructors. This lesson should only be taught to officers and NCOs.
Period
3. One 45-minute period.
Stores
4. Gun, tripod, dial sight, clinometer, spare parts case and blackboard.
B CONDUCT OF LESSONApproach
5. State the aim of the lesson (see para 1 above). Dial sights should be tested periodically for both elevation and direction. Whenever a new dial sight or gun is received, the dial sight should be tested.
Testing for elevation
6. State that a clinometer Vickers is required. This must first be tested for accuracy (see Lesson 45).
7. Demonstrate that the clinometer scale is set at zero, or, if out of adjustment, at the error discovered when tested. The dial sight is placed on the gun and clamped up; its drums and dials set at zero. The rear cover is then opened and the clinometer placed on the breech casing with the arrow pointing to the front of the gun. The gun is then elevated or depressed by the handwheel until the clinometer bubble is central. If the dial sight bubble is then level, the dial sight is in adjustment for the gun used. If it is not central, it should be brought so by the angle of sight drum. The dial sight i thus out of adjustment by plus or minus the amount shown on the angle of sight drum.
8. State that any error must be corrected by an armourer. Practise the squad in the drill of testing for elevation.
9. Tell the squad that if it is not possible to have the dial sight adjusted before firing, a label should be attached to it showing the amount of error. The amount of error now becomes the zero mark for this dial sight, eg, if the amount of error was plus 30 minutes the dial sight would only be at ‘zero’ when the bubble was central and plus 30 minutes on the angle of sight drum. Corrections would now be put on as normal from this new ‘zero’ mark.
10. Question the squad on off-setting errors in a dial sight which is out of adjustment.
Testing for direction
11. State that the lensatic sight should be zeroed for line on the thirty yards range at the same time as the lateral adjustment of the foresight is carried out.
12. Using a blackboard, explain that a thick line is drawn parallel to and 3.4 inches to the left of the thin line on which the shots would fall. If, when the MPI of the group fired falls on the thin line, the tip of the lensatic sight coincides with the thick line, the lensatic sight is in adjustment.
13. Tell the squad that as an alternative test without firing, the gun can be laid on a distant target with the tangent sight. Then if the lensatic sight also coincides with the target, it is in adjustment.
14. Demonstrate how to adjust the lensatic sight for direction. The screws below and to the side of the ramps are loosened. The appropriate screw is then tightened until the line of sight is 3.4 inches to the left of the barrel. The screw is then locked in position by tightening the opposite screw.
15. Question the squad on the method of testing and adjusting for direction. Opportunity can be taken to practise when firing on the 30-yards range.
Conclusion
16. Questions to and from the squad.
17. Sum up main points. Stress that a dial sight is only tested and adjusted when attached to its own guns.
Lesson 47. – TESTING THE DIRECTOR
A INSTRUCTORS NOTESAim
1. To teach officers and NCOs to test the director for accuracy in measuring an angle of sight.
Class and instructors
2. Squads under squad instructors. This lesson should only be taught to officers and NCOs.
Periods
3. One 45-minute period.
Stores
4. Gun, tripod, dial sight, chalk and as many directors as are available.
Ground
5. The ground selected for the lesson should have two upright walls or posts about 200 yards apart and on level ground.
B CONDUCT OF LESSONApproach
6. State the aim of the lesson (see para 1). There are two methods of ascertaining if the director is in adjustment for measuring angles of sight – one which can be used in barracks or billets and one which can be used under active service conditions.
Method 1
7. Tell the squad that this method entails laying out a horizontal plane. A position must be chosen where there are two walls or upright posts about 200 yards apart and on fairly level ground. In the diagram below, the post A and the wall B have been chosen.
8. Demonstrate that the director is erected near the wall B and laid on post A. With both bubbles lever, a mark with chalk is made in the wall B level with the object glass. Instruct an assistant to make a mark on the post A where the zero line of the angle of sight cuts it. Now move the director to the post A and erect it so that the object glass is level with the mark made by the assistant. With both bubbles level lay it on the wall B and get an assistant to mark on the wall where the zero line cuts it. unless the director being used is in adjustment, there will now be two chalk marks on the wall B. Make a third mark halfway between the first two. The line from the mark on the post A to the centre mark on the wall B will be a horizontal plane.
9. Tell the squad that any director can now be tested against this horizontal plane by placing it on one end of the horizontal plane and measuring the angle of sight to the other. The angle of sight measured is the amount of error in that director.
10. Practise the squad in setting up a horizontal plane and testing directors and question the squad in making allowance for the errors when measuring angles of sight.
Method B
11. State that, on active service, directors can be checked for angle of sight using a dial sight that is known to be in adjustment.
12. Demonstrate that the angle of sight to any distant object is measured with the dial sight. The director is then set up with the object glass level with the dial sight and the angle of sight to the object measured. If the reading is the same as the reading on the angle of sight drum, the director is in adjustment. If not, the amount of error should be noted.
13. Practise the squad.
Adjustment
14. Tell the squad that all adjustments must be carried out by an armourer.
Conclusion
15. Questions from the squad.
16. Sum up main points.
| <– Chapter 8 | Manual Index | Chapter 10 –> |
