THE ROYAL ARTILLERY INSTITUTION. 
45 
and 14 tons are really rather the expressions of blows than of pressures 
proper, and therefore that they are not strictly comparable; from which 
it follows that the balance between them of 9*703 tons may not be 
quite just. 
The greatest elevation permitted by the form of the carriage to the 
gun is 18°. When the gun is fired at this elevation, the effect of the 
force transmitted to the carriage (P = 43*74 tons) will be as follows :— 
P Y = P x sin 18° 
= 43*74 x *309 
= 13*515 tons, 
P x = P x cos 18° 
= 43*74 x *951 
= 41*596 tons. 
Also, P has a moment with respect to the point F = P x FI 
= 43*74 tons x 16"*6, which comes as a twist upon the bracket sides 
of the carriage, tending to bend them and tear them away from the 
second transom. This moment is opposite in direction to the moment, 
about the same point, of the weight of the carriage, with wheels and 
gun, acting at P, and = W x rF — 1*335 tons X 72"*05. When, there¬ 
fore, the first twist comes into play, it is opposed by the second, the 
resultant of both being a moment of 37*95 tons x 16"*6 that is acting 
in the same direction as P, and with the same arm. This resultant 
makes itself apparent on discharge by the “ jump” of the gun, which 
in effect increases the elevation of the latter beyond that shewn by the 
tangent scale, and consequently affects the range of the projectile. To 
reduce the jump to a minimum, it is evident that in the construction of 
a carriage the main point is to keep the axis of the trunnions at as 
small a height from the ground as possible. 
In addition to the small constant pressure upon the head of the 
elevating screw, from the centre of gravity of the gun being 0"*15 to 
the rear of the axis of the trunnions, there is a pressure upon it on 
discharge, due to the moment of the force P about the lower points of 
the trunnion-holes, upon which points the trunnions, having certain 
play in the holes, rested previous to the gun being fired. This moment 
equals 43*74 tons x 2", which, the screw being at a perpendicular 
distance of 28" from the bearing points, exerts a pressure upon it of 
3*124 tons, which is transmitted to and expended upon the trail. 
The statical breaking weight of the wooden bed first tried in the 
16-pr. gun-carriage, under the same conditions as before, was 8*966 tons, 
and of the axletree used with it 4*164 tons, giving a total breaking 
weight for the bed and axle of 13*13 tons. 
The gun and its charge not having been altered, the force P trans¬ 
mitted to this carriage was the same as to the latest pattern carriage— 
namely, 43*74 tons. 
From these data (R and P) the angle of elevation at which the gun 
