From the balance between tbe generated heat io a gear box and the dissipated beat from the gear case surface the mean
value for the expected lubricant temperature can be evaluated. The maximum oil temperature in a splash lubricated
enclosed gear drive limits the transmittable power. High oil temperatures influence wear, scuffing, micropitting and
piting load capacity of the gears as well as the gear oils’ service life.
Experimental investigations of no-load and load dependent gear losses in cylindrical and bevel gears as a function of
lubricant type and viscosity, load, speed and temperature are reported. The mean value for the coefficient of friction ina
gear mesh is evaluated and compared to measurements in twin disk machines. A rating method for gear mesh power loss
is derived.
Iavestigations, using model and actual gear boxes, show the influence of radiation, free and forced convection as well as
conduction to the foundation on the heat dissipation from the gearcase surface. The influence ofdesign, size, airvelocity,
surface finish of the housing, etc, is reported.
The results of such investigations together with accepted rating methods for bearing and seal power loss are introduced
into a calculation method for the evaluation of the oil temperature in tbe sump of a gear box. In sample calculations the
possibilities as well as the limits of this thermal rating method is shown.

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