This document discusses torques in epicyclic gear trains. It states that there are three relevant torques: (1) the input torque on the driving member T1, (2) the output torque on the driven member T2, and (3) the holding torque on the fixed member T3. It then provides an equation showing that the net torque applied to the gear train must be zero: T1 + T2 + T3 = 0. The document also derives equations to calculate T2 and T3 based on T1 and the angular speeds of the various members. It notes that if the input and output shafts rotate in the same direction, the input and output torques will be in opposite directions, while

1. Sanjivani Rural Education Society’s
Sanjivani College of Engineering, Kopargaon-423603
( An Autonomous Institute Affiliated to Savitribai Phule Pune University, Pune)
NAAC ‘A’ Grade Accredited, ISO 9001:2015 Certified
Subject :- Theory of Machines II
T.E. Mechanical (302043)
Unit 3
3.4 Torques in Epicyclic Gear Trains
By
Prof. K. N. Wakchaure(Asst Professor)
Department of Mechanical Engineering
Sanjivani College of Engineering
(An Autonomous Institute)
Kopargaon, Maharashtra
Email: wakchaurekiranmech@Sanjivani.org.in Mobile:- +91-7588025393

2. Torques in Epicyclic Gear Trains
1
Gear B
2
3
1. Input torque on the driving member (T1),
2. Output torque or resisting or load torque on the driven member (T2),
3. Holding or braking or fixing torque on the fixed member (T3).
The net torque applied to the gear train must be zero.
T1 + T2 + T3 = 0
F1.r1 + F2.r2 + F3.r3 = 0
𝑭 𝟏, 𝑭 𝟐 and 𝑭 𝟑 are the corresponding externally applied forces at radii r1, r2 and
r3.
𝝎 𝟏, 𝝎 𝟐 and 𝝎 𝟑are the angular speeds of the driving, driven and fixed members
respectively

3. Torques in Epicyclic Gear Trains
the friction be neglected, then the net kinetic energy dissipated by the gear
train must be zero, i.e.
But, for a fixed member, ω3 = 0
T1. 𝝎1 + T2. 𝝎2 = 0
T2 =
− T1. 𝝎1
𝝎2
F1.r1 + F2.r2 + F3.r3 = 0
T1. 𝝎1 + T2. 𝝎2 + T3. 𝝎3 = 0
As T1 + T2 + T3 = 0
T3 = - (T1 +
− T1. 𝝎1
𝝎2
)
T3 = T1(
𝝎1
𝝎2
-1)
• When input shaft (or driving shaft) and output shaft (or
driven shaft) rotate in the same direction, then the
input and output torques will be in opposite directions.
• Similarly, when the input and output shafts rotate in
opposite directions, then the input and output torques
will be in the same direction.

4. Torques in Epicyclic Gear Trains
T2 =
− T1. 𝝎1
𝝎2
As T1 + T2 + T3 = 0
T3 = T1(
𝝎1
𝝎2
-1)
Input Power =T1. 𝛚1
• When input shaft (or driving shaft) and output shaft (or
driven shaft) rotate in the same direction, then the
input and output torques will be in opposite directions.
• Similarly, when the input and output shafts rotate in
opposite directions, then the input and output torques
will be in the same direction.
1. Input torque on the driving member (T1),
2. Output torque or resisting or load torque on the driven member (T2),
3. Holding or braking or fixing torque on the fixed member (T3).

5. •Thank You…