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Unformatted text preview: The motor shaft is connected to gear A and rotates
at 975 r.p.m . The gear wheels B, C, D and E are fixed to parallel
shafts rotating together. The final gear F is fixed on the output
shaft. What is the speed of gear F ? The number of teeth on
each gear are as given below : Fig. 13.3 Gear A B C D E F No. of teeth 20 50 25 75 26 65 Solution. G iven : N A = 9 75 r.p.m. ;
T A = 20 ; T B = 50 ; T C = 25 ; T D = 75 ; T E = 26 ;
T F = 65
From Fig. 13.3, we see that gears A , C
and E are drivers while the gears B , D and F are
driven or followers. Let the gear A rotates in
clockwise direction. Since the gears B and C are
mounted on the same shaft, therefore it is a
compound gear and the direction or rotation of
both these gears is same (i.e. anticlockwise).
Similarly, the gears D and E are mounted on the
same shaft, therefore it is also a compound gear
and the direction of rotation of both these gears
is same (i.e. clockwise). The gear F will rotate in
anticlockwise direction.
Let Battery Car: Even though it is run by batteries,
the power transmission, gears, clutches,
brakes, etc. remain mechanical in nature.
Note : This picture is given as additional information
and is not a direct example of the current chapter. N F = Speed of gear F, i.e. last driven or follower. We know that Speed of the first driver Product of no. of teeth on drivens
=
Speed of the last driven
Product of no. of teeth on drivers Chapter 13 : Gear Trains l 433 50 × 75 × 65
N A TB × TD × TF
=
=
= 18.75
20 × 25 × 26
N F TA × TC × TE or
∴ NF = NA
975
=
= 52 r. p. m. Ans.
18.75 18.75 13.5. Design of Spur Gears
Sometimes, the spur gears (i.e. driver and driven) are to be designed for the given velocity
ratio and distance between the centres of their shafts.
Let x = Distance between the centres of two shafts,
N 1 = Speed of the driver,
T 1 = Number of teeth on the driver,
d1 = Pitch circle diameter of the driver,
N 2 , T 2 and d2 = Corresponding values for the driven or follower, and
pc = Circular pitch.
We know that the distance between the centres of two shafts,
x=...
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 Fall '08
 CELGHORN

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