(^712) „„„„„ A Textbook of Engineering Mechanics
Speed of wheel B when wheel A makes 300 r.p.m.
Since the wheel A makes 300 r.p.m. anticlockwise, therefore
NA= – 300 r.p.m.
Substituting this value of NA in equation (i),
–150
–300–150
NB ––– 36 4
45 5
A
B
T
T

∴ NB=
4
450 × + 150 = 510 r.p.m.
5
⎛⎞
⎜⎟⎝⎠^ Ans.
34.16.COMPOUND EPICYCLIC GEAR TRAIN (SUN AND PLANET WHEEL)
A compound epicyclic gear train consists of three toothed
wheels known as the sun wheel (S), planet wheel (P) and annular
wheel A as shown in Fig. 34.13. The axes of sun wheel and planet
wheel are connected by an arm C by pin connections. The planet
wheel meshes with the sun wheel as well as the annular wheel.
It may be noted, that the planet wheel (P) rotates about its
own axis and at the same time it is carried round the sun wheel (S)
by the arm C. A little consideration will show, that when the sun
wheel (S) is fixed the annular wheel (A) provides the drive. But
when the annular wheel (A) is fixed the sun wheel (S) provides
the drive. In both the cases, the arm C acts as a follower.
Let TA= No. of teeth on the annular wheel A,
NA= Speed of the annular wheel A,
TS, NS= Corresponding values for the sun
wheel (S) and
TP, NP= Corresponding values for the planet wheel (P).
Now the velocity ratio of a compound epicyclic gear train may be obtained by preparing a
table of motions as usual.
Example 34.7. An epicyclic gear consists of three wheels A, B and C as shown in Fig.
34.14. The wheel A has 72 internal teeth, C has 32 external teeth. The wheel B gears with both the
wheels A and C and is carried on an arm D, which rotates about the centre of wheel A at 18 r.p.m.
Fig. 34.14.
Determine the speed of the wheels B and C, when the wheel A is fixed.
Solution. Given: No. of teeth on wheel A (TA) = 72; No. of teeth on wheel C (TC) = 32 and
speed of arm D (ND) = 18 r.p.m.
Fig. 34.13. Compound epicyclic
gear train.