Mechanical Technology 1
Tutorial Questions 5
1. A shaft running at 200 rpm is to drive a parallel shaft at 300 rpm. The pulley on the driving shaft is
60 cm diameter. Calculate the diameter of the pulley on the driven shaft:
(a) Neglecting belt thickness.
(b) Taking belt thickness into account, which is 5 mm thick.
(c) Assuming in the latter case a total slip of 4%.
2. The power is transmitted from a pulley 1 m diameter running at 200r.p.m. to a pulley 2.5 m diameter
by means of a belt. Find the speed lost by the driven pulley as a result of the creep, if the stress on
the tight and slack side of the belt is 1.44 N/mm2 0.49 N/mm2 respectively. The young’s modulus
for the material of the belt is 100 N/mm2.
[ Ans: 0.33 rpm]
3. A flat belt that is 6 mm thick transmits 45 KW from a 500 mm diameter pulley rotating at 1750
r/min. The coefficient of friction is 0.35. Assume that the contact angle on the driving pulley is 1600
and that the maximum stress in the belt should not exceed 2.25 MPa. Calculate the following;
a) A suitable width for the belt
b) The total driving pulley exerts a tensile force of 500 N and the pulley is mounted centrally
between the two bearings.
[ Ans: (a) 116.3 mm; (b) 2662.04 N]
4. An open belt drive connects two pulleys 120 cm and 50 cm diameters, on parallel shafts 4 m apart.
The maximum tension in the belt is 1855.3 N. The coefficient of friction is 0.3. The driver pulley
of diameter 120 cm runs at 200 r.p.m calculates:
(a) The power transmitted, and
(b) Torque on each of the two shafts.
[ Ans: 13. 73 kW; 273.4 Nm]
5. An open belt 100 mm wide connects two pulleys mounted on parallel shafts with their centres 2.4
m apart. The diameter of the larger pulley is 450 mm and that of the smaller pulley 300 mm. The
coefficient of friction between the belt and the pulley is 0.3 and the maximum stress in the belt is
limited to 14 N/mm width. If the larger pulley rotates at 120 rpm, find the maximum power that can
be transmitted. [Ans: 2.39kW]
6. The following information applies to a V-belt drive transmitting 30 kW: effective diameter of motor
pulley = 260 mm; speed of motor pulley = 1500 r/min; V-groove angle of pulley = 400; coefficient
of friction = 0.3; belt contact angle = 1550; mass of belt = 0.5 kg/per meter length; maximum
allowable tension per belt = 575 N. Calculate the number of V-belts needed for transmitting the 30
kW. [ Ans: 4 belts ]
7. Calculate the power that can be transmitted by a cross-belt drive, as well as the rotational speed in
r/min of the small pulley, when the large pulley is 350 mm in diameter and rotates at 700 r/min. The
diameter of the small pulley is 250 mm and the tension in the tight side of the belt is 650 N. The
contact angle of the belt on the pulleys is 1850 and the coefficient of friction is 0.3. [Ans: 5.167kW;
980r/min]
8. The single V-belt drive has to transmit 250 kW at 1500 r/min. The contact angle on the driving
pulley is 1650 and the included the v-groove angle is 400. If the coefficient of friction is 0.2, calculate
the following:
(a) Ratio of the belt tensions
(b) Effective tension in the belt.
(c) Tensile force on each of the two bearings. [Ans: (a) T1 = 5.385T2; (b) Te = 10kN; (c) 14.561kN]
9. Two shafts whose centres are 1 m apart are connected by a V-belt drive. The driving pulley is
supplied with 100kW and has an effective diameter of 300 mm. It runs at 1000 r.p.m. while the
driven pulley runs at 375 r.p.m. The angle of groove on the pulleys is 400. The permissible tension
in 400 mm2 cross-sectional area belt is 2.1 MPa. The density of the belt is 1100kg/m 3. The
coefficient of friction between the belt and pulley is 0.28. Estimate the number of belts required
10. A rope transmits 75 kW through a 1.5 m diameter, 450 groove pulley rotating at 200 r.p.m. The
coefficient of friction between the rope and the pulley grooves is 0.3 and the angle of lap is 1600.
Each rope has a mass of 0.6 kg/m and a safely a pull of 800 N. taking centrifugal tension into account
determine: (a) The number of ropes required for the drive (b) Initial rope tension. [ Ans 9; 510.2 N]
11. The reduction of speed from 360 r.p.m to 120 r.p.m is desired by the use of chain drive. The driving
sprocket has 10 teeth. Find the number of teeth on the driven sprocket. If the pitch radius of the
driven sprocket is 250 mm and the centre to centre distance between the two sprocket is 400 mm,
find pitch and length of the chain.
[Ans 30; 52.25 mm; 1.93 m]
12. An open belt drive connects two pulleys 1.2 m and 0.5 m diameter, on parallel shafts 3.6 m apart.
The belt has a mass of 0.9 kg/m length and the maximum tension in it not exceed 2 kN. The larger
pulley runs at 200 rev/min. Calculate the torque on each of the two shafts and the power transmitted.
Coefficient of friction is 0.3 and angle of lap on the smaller pulley is 168o (2.947 radians)
13. Find the power transmitted by a V-belt drive running at a speed of 1400 rpm over two pulleys with
diameters 240 mm and 600 mm on two parallel shafts 3m apart. The following data for V-belt are
as follows: Pulley groove angle = 45º; Coefficient of friction = 0.25; Mass of belt per meter length
= 0.472 kg/m; Allowable tensile stress 2.5 MPa; Cross-sectional area 400 mm2. Also, calculate the
speed (rpm) when maximum power is transmitted. [Ans. 12.940 kW; 26.575 m/s {2114. 771 rpm
or 845.909rpm}]
14. An elevator uses a certain number of ropes to transmit 60 kW of power through a 2 m diameter, 500 groove
pulley rotating at 250 rpm. The coefficient of friction between the rope and the pulley grooves is 0.3 and the
angle of lap is 1600. Each rope has a mass of 0.9 kg/m and an allowable tension of 1500 N, taking centrifugal
tension into account determine:(a) The number of ropes required for the drive (b) Initial rope tension.
15. Two pulleys on two shafts 1.2 m apart are connected by a flat belt. The driving pulley is 300 mm in diameter
and runs at 1500 rpm. The speed on the driven pulley is to be 900 rpm. The belt is 120 mm, 5 mm thick and
weighs 1000 kg /m3. The coefficient of friction between the belt and the pulley is 0.25. The allowable tension
of 1500 N, taking centrifugal tension into account, determine (a) Calculate the power that can be transmitted
between pulleys (b) shaft speed in rpm at when the power transmitted is maximum
16. The reduction of speed from 300rpm to 120rpm is desired by the use of chain drive. The driving
sprocket has 10 teeth. Find the number of teeth on the driven sprocket. If the pitch radius of the driven
sprocket is 250 mm and the centre to centre distance between the two sprockets is 400mm, find pitch and
length of the chain. [Ans. 30; 52.25mm; 1.93m]
17. Two shafts whose centres are 1.2 m apart are connected by a V-belt drive, the angle of groove on
the pulleys is 40°. The driving pulley has a diameter of 300 mm, runs at 500 rpm and is supplied
with 100 kW, while the driven pulley runs at 1000 rpm. The permissible stress on the belt is 2.01
MPa and has a 400 mm² cross-sectional area. The density of the belt is 1100 kg/m³. The coefficient
of friction between the belt and pulley is 0.3. Estimate the length of each belt and the number of
belts required.