inertia of the reducer it is expedient to increase the width of the gear and decrease its diameter. In the designing of small inertia reducers one should decrease the distance between their centers, increase the width of the teeth, and for small gears, the number of teeth should be minimized. One must also use very durable materials and use them as efficiently as possible (the teeth of the gears of these reducers are usually rated for the tensile strength of the material with a durability of 1.0- 1.10). To implement these recommendations one should, in addition to reducing the inertia, also decrease the size and mass of the drive. Due to the large launch momenta of the direct current engines in the drives, as a rule, protective couplings are used. The following types of couplings are used: 1) bearing couplings, which scatter the momentum on the input shaft of the drive to ±35-40% of the nominal value; 2) friction couplings with a ball regulator (in the docking mechanism drive) with a scatter of up to ±10-15%; 3) magnetic hysteresis couplings with a scatter of ±5-10%. To stop the rod of the docking mechanism and the locks of the docking frame in the retracted position, uncontrolled cam-type irreversible rotation couplings are used. As a rule, the casings of the drives are manufactured of aluminum alloys or magnesium alloys, in the latter case with the use of anti-corrosive shielding (oxide coating and paint and varnish coating). The casings are frequently closed (without complete hermetization) which prevents contamination of the drives with foreign objects, thus increasing the lifetime and time in a vacuum. It is expedient in drives with differentials to completely duplicate all potentially "dangerous"elements for redundancy. This includes electrical engines, rapidly rotating parts of the reducers, brakes, and protective couplings, etc. Great care should be taken in designing elements whose failure would lead to the breakdown of the drive as a whole, for example, shafts which are directly kinematically connected before and after the differential. 3.5.2. Electrical Engines of the Drives and Their Control The drives of electromechanical docking devices use direct current collector
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