ABSTRACT
Planetary gear trains (PGTs) with two compound and three external shafts can be converted into PGTs with two compound and four external shafts if both compound shafts become external. Two-carrier PGTs under consideration can be used as change-gears to realize two speed ratios. PGTs of the type in question are very convenient for reversible mechanisms with one speed in each direction. Different speed ratios in both directions are convenient for technology machines with slow-moving and a rapidly returning working body. Torque method allows for direct determination of load on the individual gears. If, from experience, the operating time of the gear under given load is known, it is possible to determine load spectrum of the individual gears and, consequently, their equivalent loads and, ultimately, their safety factors SF and SH. This possibility is a very significant advantage of the torque method.
