Simple Planetary Drives

PLANETARY GEARING IS COMPOSED OF A TRAIN OF GEARS WHERE SOME OF THEM REVOLVE ON FIXED CENTERS WHILE OTHERS REVOLVE ON MOVING CENTERS. SUCH TRAINS MAYBE ARRANGED IN A GREAT VARIETY OF WAYS. THE GEARS THAT ROTATE ON FIXED CENTERS ARE CALLED SUN GEARS WHILE THOSE THAT ROTATE ON MOVING CENTERS ARE CALLED PLANET PINIONS. SOMETIMES TWO OR MORE PLANET PINIONS MESH WITH THE SAME SUN GEARS. IN SIMPLE PLANETARY DRIVES, THE SUM OF THE NUMBERS OF TEETH IN THE TWO SUN GEARS N ₁ AND N ₅ IN THE FIGURE MUST BE DIVISIBLE BY TWO IF TWO PLANET PINIONS ARE USED; WHEN THIS SUM N ₁ + N ₅ IS DIVISIBLE BY THREE, THEN THREE PLANET PINIONS EQUALLY SPACED MAY BE USED, ETC.

THE EQUATIONS FOR REDUCTION RATIOS, SPEEDS, LOADS, ETC, FOR SIMPLE PLANETARY DRIVES ARE GIVEN IN THE ACCOMPANYING CHART. THE LOAD-CARRYING ABILITY AND EFFICIENCY OF THESE DRIVES DEPEND UPON THE MAGNITUDE OF THE TOOTH LOADS AND THE VELOCITY OF THE TOOTH ENGAGEMENTS. THE PRODUCT OF THESE TWO VALUES GIVES THE POTENTIAL POWER. ON MANY PLANETARY DRIVES, THIS POTENTIAL POWER IS LESS THAN THE TRANSMITTED POWER.

POTENTIAL POWER FT. LBS.PER MIN.= W ₁V ₁ = W _SV _S

TRANSMITTED POWER FT LBS. PER MIN. = WV

NOTATION FOR CHART AND FIGURE

N ₁ = NUMBER OF TEETH IN INTERNAL SUN GEAR

N ₃ = NUMBER OF TEETH IN PLANET PINION

N _S = NUMBER OF TEETH IN HELICAL...