Planetary Gear Train (Epicyclic Gear Train)

Planetary Gear Train…

In this train, the blue gear has six times the diameter of the yellow gear

The size of the red gear is not important because it is just there to reverse the direction of rotation

In this gear system, the yellow gear (the sun) engages all three red gears (the planets) simultaneously

All three are attached to a plate (the planet carrier), and they engage the inside of the blue gear (the ring) instead of the outside.

Planetary Gear Train…

• Because there are three red gears instead of one, this gear train is extremely rugged.

• planetary gear sets is that they can produce different gear ratios depending on which gear you use as the input, which gear you use as the output, and which one you hold still.

Planetary Gear Train…

• They have higher gear ratios. • They are popular for automatic transmissions

in automobiles. • They are also used in bicycles for controlling

power of pedaling automatically or manually. • They are also used for power train between

internal combustion engine and an electric motor

TABULAR METHOD FOR FINDING THE VELOCITY RATIO

Ta= 30 teeth ; Tb = 40 teeth speed of arm = 80 rpm ACW .Determine the speed of gear B if (i) the gear A is fixed (ii) Gear A revolves at 240 rpm clockwise

Solution : (i) 7.1 rpm (ii) 28.6 rpm

i) 8.31 rpm CWii) 10.9 CCW

In an epicyclic gear train, as shown in Figure the number of teeth on wheels A, B and C are 48, 24 and 50 respectively. If the arm rotates at 400 r.p.m., clockwise,find 1. Speed of wheel C when A is fixed, and 2. Speed of wheel A when C is fixed.

Step No Motion Revolutions of elements

Arm Gear A Gear B Gear C

(i) 16RPM cw (ii) 16.67 ACW

Compound Epicyclic Gear Train—Sun and Planet Gear

In an epicyclic gear train, as shown in figure, the wheel C is keyed to the shaft B and wheel F is keyed to shaft A. The wheels D and E rotate together on a pin fixed to the arm G. The number of teeth on wheels C, D, E and F are 35, 65, 32 and 68 respectively. If the shaft A rotates at 60 r.p.m. and the shaft B rotates at 28 r.p.m. in the opposite direction, find the speed and direction of rotation of arm G.

Ans : (90 RPM IN THE SAME DIRECTION OF SHAFT A )

Two shafts A and B are co-axial. A gear C (50 teeth) is rigidly mounted on shaft A. A compound gear D-E gears with C and an internal gear G. D has 20 teeth and gears with C and E has 35 teeth and gears with an internal gear G. The gear G is fixed and is concentric with the shaft axis. The compound gear D-E is mounted on a pin which projects from an arm keyed to the shaft B. Sketch the arrangement and find the number of teeth on internal gear G assuming that all gears have the same module. If the shaft A rotates at 110 r.p.m., find the speed of shaft B

50rpm ACW

Solution Number of teeth :20 TEETH