When the nut is drawn down, the lower fibers of the beam are stretched, simultaneously causing a stretching of the wires of the working strain gauges. Therefore, the total ohmic resistance, which is proportional to the relative strain, changes. A change in the ohmic resistance unbalances the bridge. The voltage unbalance is balanced by a compensating instrument which has a scale graduated in relative units. Balance of the bridge is achieved by listening to an audio signal through headphones. Disappearance of the audio signal indicates that the bridge is balanced and that it Is time to take a reading on the scale of the compensator. The conversion factor from a scale division to the corresponding force is established by calibrating the dynamometer. A calibration curve is constructed from the calibration data. The curve expresses the linear dependence between the applied load and the reading of the compensator scale. The technical characteristics of the dynamometer follow: range of force measurement- from 100 kg to 8 tons[ value of a scale division - 50 kg; error of the reading from the full value of the load being measured 1.0 to 1.5%. During operation it was established that the beam dynamometer functions stably and is convenient to use.

T O R S I O N ARM D Y N A M O M E T E R W I T H O P T I C A L A R R A N G E M E N T

V. I. M e l a m e d

Electromagnetic, electrostatic, piezoelectric, and other dynamometers or wire strain gauges glued to the surface of compliant elements are used for measuring forces d~ing the cutting of thin shavings. However, all these arrangements are structurally "~ v,vtlull "~. . . . . %,h, complicated. Spring and hydraulic dynamometers are less complicated, but their measuring arrangements register only relatively large displacements of the springy elements of these instruments, This shortcoming rules out the possibility of using mechanical and hydraulic dynamometers of the usual construction for measuring cutting forces while taking light cuts. Therefore, a torsion arm dynamometer with an optical arrangement, mounted on a lathe, is used in the cutting laboratory ChIMESKh for measuring the horizontal component of the cutting force while planing thin chips. A diagram of the arrangement is shown on the figure. The workpieee 1 Is planed by a wedgecutter 2, fastened to the holder 8 by two screws. The holder with the wedge is inserted in the socket of a torque arm dynamometer of the ENIMS construction, and is clamped in it by set screws. The displacement of the arm 4 is * Metric tons. 45

transmitted to the indicator 5, on whose pointer is fastened a mirror 6. The rotation of the mirror is registered on the scale 8 by the deviation of a ray emanating from the light source 7, Adjustment of the depth of cut is accomplished by a slide whose displacement is registered on a dial, with the value of a division being 0.02 ram. The advancing motion of the workpieee during cutting is accomplished by the carriage. Because of the deflection of the cutting wedge while cutting, the depth of cut set on the dial of the vertical slide does not correspond to the actual depth of cut. An additional indicator is set up on the machine for measuring the actual depth of cut. The dynamometer is mounted on a special bracket at a distance of 2 m from the light source and 3 m from the scale. A scale of length 400 cm, placed on the wall, makes it possible to read the cutting force to 125 g. The dynamometer was tested while planing light cuts of annealed copper, On the basis of the tests car-, ried out, one can assume that the dynamometer described can be used for measuring the cutting forces while taking light cuts.

S E R V O M O T O R LEVEL METER A N D FLOW D E N S I M E T E R B. Z . V o t l o k h i n

Figure 1 shows the construction of a level meter for loose or other free-flowing material, an electronic relay circuit (upper right), and a channel for registering the readings of the level meter (lower right). The level meter consists of a reversing electric motor 8, type RD-47, connected through a compliant coupling 6 to a drum 10 which, together with the 7r -shaped support 4, is fastened to a strip 7. One end of the strip is hinged, and the other end is freely suspended on the spring 3. A cable with a float 12 at its end is wound on the drum I0. A downward displacement of the strip 7 opens the contacts 2 (terminals 6, 7), and an upward displacement closes them. An electronic relay (Fig. 1, upper right), connected to the tube 6P3, controls the rightward and leftward rotation of the electric motor 8 by closing the contacts 2,3 or 1,2 of the electromechanical relay R. type MKU-48, A network C~(R~ + Rs) with a definite time constant is connected into the grid circuit of the tube. Normally, with the capacitor C 2 discharged, current flows through the tube, causing an attraction of the armature of the relay R and closing of the contacts 2,3. Measurement of the level of loose material, liquids with different specific weight, etc., is accomplished in the following manner. Due to the weight of the float, the strip 7 drops down, and since the terminals 6,7 of the pair of contacts 2 are open, capacitor C~ is disconnected. The relay R closes the contacts 2,8 causing a rightward rotation of the motor and drum, and lowering of the float. After the float attains the level being measured, it touches the surface of the medium being measured. Due to the tension of the spring 3, the strip moves upward and closes the contacts 6,7. The voltage rectified by the selenium rectifier B5 (VS-I8-26) charges the capacitor C 2 such that the control grid of the tube T I goes negative. The tube T 1 cuts off, and stops the anode currentl this leads to a release of the armature of the relay R and a closing of the contacts 1,2 connecting the reverse of motor 8, causing a leftward rotation of the drum, and a lifting of the float. After a certain time interval, the capacitor G~ is discharged through the resistances (Rz + Ra), and the relay R operates, closing the contacts 2,3. The drum 10 contains a r~ghtward rotation,during which the float begins to drop. There occurs a periodic oscillatory process of probing the Interface of the two media, which is the level being measured. The necessary amplitude of oscillation of the float is adjusted by changing the vatue of the resistance R~. The tension of the spring 3 is adjusted relative to the weight of the float. Transmission of the readings and automatic registration of the change of

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