Progressive and Rotary Motion
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Lewis Masquerier. "Progressive and Rotary Motion." Transactions of the American Institute of the City of New York, for the Years 1860-61. Albany: C. Van Benthuysen, 1861. 576-578.
AMERICAN INSTITUTE, POLYTECHNIC ASSOCIATION,
February 14, 1861.
Prof. Mason in the chair.
Mr. Lewis Masquerier read a paper on " Progressive and Rotary Motion."
Can a rotatory motion have a leverage upon the progressive motion of a bullet or planet, so as to deflect it from a rectilinear into a curvilinear direction ?
The aberration of balls fired from a smooth bore ordnance, is said to have suggested the cutting of the spiral grooves in them, by which they invariably receive a rotatory motion, around an axis pointing one of its poles to the mark, and strike with more certainty. If the rotatory motion can have such a deflecting of straight lines. Whenever the axis of rotation of the ball is horizontal and at right angles to its progressive course, it will strike under the mark, if the rotation in its front is in a downward direction; but if upward it will strike above the mark. If the rotation is around a vertical axis from left to right, it will strike to the left of the mark, and if from right to left, it will strike on the right side of the mark. • I believe, it is laid down, that if a ball or globe could be placed without the influence of any resisting or attracting medium, that its centrifugal force would be equal on all its sides. But, if it has a projectile motion in addition, this force may vary on different sides. When it revolves around a horizontal axis at right angles to the direction of the progressive motion, and downwards, the matter of the ball in front, is carried down more or less, in its rear, upward, underneath, in a contrary direction, and on top in the same direction, more or less to its progressive course.
Now, it would seem, that as the momentum of the rotatory motion in one half of the bullet or planet, is, more or less, in the direction of the progressive motion, and the contrary way in the other half, might it not have a leverage and cause a deflection from a right line direction ? As two forces from different directions will propel a ball in their averaged direction, why will not the projectile and rotatory forces unite in an averaged direction ? The tendency of a balance wheel to revolve after the impulse is withdrawn, and of a globe hung by moveable gudgeons upon the periphery of a large wheel, to revolve in the same direction with the progressive course, seems to be some evidence that the rotatory force has a leverage upon the projectile force.
May not then the aberrations given to projectiles fired from smooth bore pieces be owing more to their globular shape, by which they get a rotary motion, and that by using long cylindrical ones, pointed and hollowed out at the other end may not sharp shooting be attained with the progressive motion only. But if a rotatory motion around an axis pointing to the mark, is absolutely necessary, may not a spirally shaped chamber, behind the ball, give such motion, and thus avoid the great expense of rifling.
Though some of the conditions in which the planets exist, may be different from that of our projectiles, yet I do not see but that the effect of the rotatory motion upon the projectile may be the same, and thus cause the circularity of their orbits. Now have we not a little clearer perception, how a rotatory force can deflect a planet into a curvilinear orbit than an attractive force can ? But both forces may act together and assist each other. But may not this same rotatory force throw out the waters of the ocean, on the conjunction and opposition sides of the earth, and be a cause also of the tides, which, being impeded by the continents, may be the cause again of their happening at every position of the sun and moon.
Mr. Dibben said that there was no such leverage in rotary motion. The rotary motion of globular balls is caused simply by the eccentricity of the center of gravity.
The President inquired whether a cannon ball was ever made without this eccentricity.
Mr. Dibben said that Mr. Hotchkiss had a method of centering his ball to accomplish that result. It is easy to determine upon which side of a round ball is its center of gravity, by immersing it in mercury.
Mr. Parkhurst said that, according to the law illustrated last week, there is a tendency in the lengthened ball for rifled cannon to take the shortest axis of rotation, and showed by experiment that a model of these balls would thus change its axis of rotation, even in opposition to the force of gravitation. In practice, however, this tendency may be overcome if the rotary motion is not too rapid, by placing the center of gravity forward of the center of the mass, or by the feathering of the rear of the ball from the action of the expanding gases upon the leaden belt, so that the atmospheric resistance shall counterbance the lateral centrifugal force, the progressive momentum will tend very much to retard the change of axis.
- Lewis Masquerier, "Progressive and Rotary Motion," in American Institute of the City of New York, Transactions of the American Institute of the City of New York, for the Years 1860-61 (Albany, NY: C. Van Benthuysen, 1861).