243,004. Biquard, R. Nov. 12, 1924, [Convention date]. Testing' balance of rotary apparatus.-Comprises a method of determining in magnitude and direction both static and dynamic lack of balance, by rotating the body in its usual bearings which rest on two bearings which are adapted to be displaced in a horizontal direction perpendicular to the mean direction of the axis and returned by an elastic arrangement, and in measuring by means of one and the same pivotal arrangement, on the one hand, the static unbalance by the amplitude of oscillation of the centre of gravity of the body, and on the other hand, the dynamic unbalance by the angular amplitude of oscillation of the axis of rotation of the body about its mean direction. Supports 2, 3 fixed to slides on a bed 1 and adapted to move parallel to the axis Z, Z' terminate at their upper parts in sliding tracks provided with grooves or balls upon which two bearings 4, 5 move perpendicularly to the axis Z, Z<1>. These bearings receive the bearings 6, 7 of the rotary body 8. The bearings 4, 5 are connected together by a horizontal bar 9, rods 10, 11 fixed to the bearing, and a fitting 12, 13 formed of two sleeves at right angles through which slide the bar 9 and rod 10 or 11. The bar 9 is rigidly connected by a sleeve 14 to the upper end of an elastic blade 15 fixed at the lower end to the frame 1. The sleeve 14 carries in the vertical axis of the blade 15 a vertical concave mirror 16 which reflects the image of a point source of light 18 on to a screen 17. A mass 19 adjustable along the bar 9 serves to bring the centre of gravity of the system formed by the bearings 4, 5 and parts 9, 10, 11, 12, 13 into the planer of the spring 15. The body 8 is rotated, and the horizontal components of the oscillations due to out of balance masses are transmitted to the bar 9. The component perpendicular to the axis Z, Z' .and corresponding to static unbalance produces a vertical displacement of the image, while the angular oscillation about the mean axis produces a horizontal displacement of the image. The resultant is a straight line or closed curve according to the relative positions of the central planes in which act the unbalanced, forces. Experiments on a given body at a given speed with definite, act of balance masses enable tables to be constructed from which the connection between the amplitudes of the oscillations and the magnitude of the out of balance masses may be calculated. As shown in Fig. 3 a rod 21 attached to the sleeve 14 so that its axis coincides with the axis of the blade 15 is connected to a horizontal rod 22 perpendicular to the axis Z, Z<1> by means of a part 23 formed of two sleeves at right angles and a pin 24. The rod 22 is guided in a fixed sleeve 25 and bears on a strip carrying at one end a concave mirror 28 and fixed at the other end to the frame. In Fig. 4 a similar mirror 34 is carried by a strip 32 fixed to a part 29 fixed to the sleeve 14 and forming a bearing 30 for a rod 31 parallel to the shaft 9 and bearing at the ends against the mirror and the fixture 27 respectively. Light from the same point source 18, Fig. 5, is reflected from a mirror 36 on to the mirrors 34, 28 and thence to the screen. The end of the shaft carries a disc 39 which is insulated on its periphery except for a narrow band parallel with the axis of the body. Upon this bears a metal brush 41 carried by a crown 42. The circuit of a magnet 38 is completed through the brush 41, the conducting band and the machine. For each turn of the body 8, the magnet is excited and the plate 37 is attracted turning the mirror 36 about a horizontal axis perpendicular to the axis of the body 8. This causes a slight bending of the luminous lines forming the images from the mirrors 28, 34. By rotating the crown 42 the brush is displaced until the bend in the line from the mirror 28 is at the end of the line. The circuit is thus closed at the moment when the centre of gravity of the body is at its maximum amplitude of horizontal displacement. The body is then rotated at the same speed in the opposite direction and a second position for the brush 41 found. The latter is adjusted midway between the two positions and the body 8 placed in an azimuth such that the circuit of the magnet is closed. The plane of the force due to stater unbalance is then horizontal. The same method used with the mirror 34 determines the central plane for the defect in dynamic balance.