The gearing of a machine tool is shown in fig 133 the

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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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