barrel and bolt were derived by noting the difference between the heights of the ordinates of the travel and velocity curves. The velocity ratio curve was
obtained by dividing the bolt velocity by the barrel velocity.
Having the data shown in figs. 2-27 and 2-28, the shape of the accelerating lever can be plotted by the conventional methods employed for cam layout. In designing the lever, it should be noted that the lever ratio which exists at any instant must be equal to the velocity ratio shown for that, instant in fig. 2 28. Also, to minimize wear on the contact surfaces, these surfaces should be designed as far as possible to have a rolling action, and sliding contact at the surfaces should be held to a minimum. Since the details of the layout process will depend largely on the space requirements of a particular design and because it is not the intent in this publication to describe conventional machine design procedures, no attempt will be made here to explain the layout of the lever. The general shape and action of a lever for one particular design is shown in fig. 2-15. However, it should be realized that the shape of the lever for a different gun may differ considerably from that shown in fig. 2-15, depending on the arrangement of the mechanism and the desired motion characteristics.
Before the analysis of the accelerating action is concluded, it is interesting to note the magnitude of the forces which act on the barrel and bolt during acceleration. Fig. 2 28 shows that the maximum deceleration of the barrel mass is equal to 5600 feet per second per second (at 0.009 second). Since the barrel weighs 45 pounds, the force required to produce this deceleration is:
Although this force is large, it is not excessive.
The maximum acceleration of the bolt occurs at 0.00705 second and is equal to 8000 feet per second per second. Since the bolt weighs 5 pounds, the force required to producc this acceleration is:
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