Dr. D. Y.
Patil Unitech Society’s
Dr. D. Y. Patil Institute of Technology
Pimpri, Pune 411 018.
Department of Automation and Robotics
Design of Robot Elements
Question Paper Pattern:
Q. No. Unit No. Total Marks
1 Unit 3 Problem on shaft and theory on shaft 18
OR
2 Unit 3 Problem on belt and theory on belt 18
3 Unit 4 Theory 17
OR
4 Unit 4 Theory 17
5 Unit 5 Problem on gear box 18
OR
6 Unit 5 Problem on gear box and theory on gear box 18
7 Unit 6 Problem on rolling contact bearing and theory on 17
rolling contact bearing
OR
8 Unit 6 Problem on sliding contact bearing and theory on 17
sliding contact bearing
Unit 3
Q.1 The layout of a shaft carrying two pulleys 1 and 2, and supported on two bearings A and B is
shown in Figure. The shaft transmits 7.5 kW power at 360 rpm from the pulley 1 to the pulley 2.
The diameters of pulleys 1 and 2 are 250 mm and 500 mm, respectively. The masses of pulleys 1
and 2 are 10 kg and 30 kg, respectively. The belt tensions act vertically downward and the ratio of
belt tensions on the tight side to slack side for each pulley is 2.5:1. The shaft is made of plain
carbon steel 40C8 (Syt = 380 N/mm2) and the factor of safety is 3. Estimate suitable diameter of
shaft. If the permissible angle of twist is 0.5° per metre length, calculate the shaft diameter on the
basis of torsional rigidity. Assume G = 79300 N/mm2.
Q.2 A transmission shaft supporting a spur gears B and the pulley D is shown in Figure. The shaft
is mounted on two bearings A and C. The diameter of the pulley and the pitch circle diameter of
the gear are 450 mm and 300 mm respectively. The pulley transmits 20 kW power at 500 rpm to
the gear. P1 and P2 are belt tensions in the tight and loose sides, while Pt and Pr are tangential and
radial components of gear tooth force. Assume, P1 = 3P2 and Pr = Pt tan (20°) The gear and pulley
are keyed to the shaft. The material of the shaft is steel 50C4 (Sut = 700 and Syt = 460 N/mm2 ).
The factors kb and kt of the ASME code are 1.5 each. Determine the shaft diameter using the
ASME code.
Q.3 Assume the data of the transmission shaft given in Q. 2. For this shaft, the permissible angle
of twist is 3° per metre length. The modulus of rigidity for the shaft material is 79300 N/mm2.
Calculate: (i) the permissible angle of twist; and (ii) the shaft diameter on the basis of torsional
rigidity.
Q.4 The layout of a transmission shaft carrying two pulleys B and C and supported on bearings A
and D is shown in Figure. Power is supplied to the shaft by means of a vertical belt on the pulley
B, which is then transmitted to the pulley C carrying a horizontal belt. The maximum tension in
the belt on the pulley B is 2.5 kN. The angle of wrap for both the pulleys is 180° and the coefficient
2
of friction is 0.24. The shaft is made of plain carbon steel 30C8 (Syt = 400 N/mm ) and the factor
of safety is 3. Determine the shaft diameter on strength basis.
Q.5 The layout of an intermediate shaft of a gear box supporting two spur gears B and C is shown
in Figure. The shaft is mounted on two bearings A and D. The pitch circle diameters of gears B
and C are 900 and 600 mm respectively. The material of the shaft is steel FeE 580 (S ut = 770 and
Syt = 580 N/mm2 ). The factors kb and kt of ASME code are 1.5 and 2.0 respectively. Determine
the shaft diameter using the ASME code. Assume that the gears are connected to the shaft by
means of keys.
Q.6 Derive equations for shaft design using maximum principal stress theory and maximum shear
stress theory.
Q.7 Explain significance of equivalent bending moment and equivalent twisting moment.
Q.8 Explain design of shaft design using ASME code.
Q.9 Derive equations for center distance, length of belt for open belt drive.
Q.10 Derive equations for center distance, length of belt for crossed belt drive.
Q.11 Derive equations of flat belt for analysis of tensions in the belt.
Q.12 Derive equations of V-belt for analysis of tensions in the belt.
Q.13 Derive the expression for the condition for maximum power in the belt drive.
Q.14 The layout of a leather belt drive transmitting 15 kW of power is shown in Figure. The centre
distance between the pulleys is twice the diameter of the bigger pulley. The belt should operate at
2
a velocity of 20 m/s approximately and the stresses in the belt should not exceed 2.25 N/mm . The
density of leather is 0.95 g/cc and the coefficient of friction is 0.35. The thickness of the belt is 5
mm. Calculate: (i) the diameter of pulleys; (ii) the length and width of the belt; and (iii) the belt
tensions.
Q.15 The following data is given for a V-belt drive connecting a 20 kW motor to a compressor.
The centre distance between pulleys is 1 m and the dimensions of the cross-section of the belt are
given in Figure. The density of the composite belt is 0.97 g/cc and the allowable tension per belt
is 850 N. How many belts are required for this application?
Q.16 The following data is given for an open-type V-belt drive: diameter of driving pulley = 150
mm, diameter of driven pulley = 300 mm centre distance = 1 m groove angle = 40° mass of belt =
0.25 kg/m maximum permissible tension = 750 N coefficient of friction = 0.2 Plot a graph of
maximum tension and power transmitted against the belt velocity. Calculate the maximum power
transmitted by the belt and the corresponding belt velocity. Neglect power losses.
Q. 16 Explain with design equations basic procedure for selection of flat belt.
Unit 4
Q.1 Explain in details considerations for gripper selection and design.
Q.2 Write basic design process of gripper.
Q.3 Write a note on using tools as end effectors.
Q. 4 What do you mean by integrated end effector attachment. Explain with neat labelled diagram.
Q.5 Write a note on remote compliance center design with neat labelled diagram.
Q.6 What do you mean by payload in the design of robots. Explain payload force analysis with
neat diagram and mathematical equations.
Q.7 Explain in detail with examples and diagrams elements required for the physical support of
the end effector.
Unit 5
Q.1 A 3 x 3 Gear box is transmitting a power of 10 KW. Choose the best ray diagram based on
minimum summation of shaft diameters made of same material with permissible shear stress of 36
N/mm2. Use GP ratio of 1.26 and Lowest speed N1 = 100 RPM
Q.2 Design a nine-speed gear box having 𝑁𝑚𝑖𝑛 = 100 rpm and 𝑁𝑚𝑎𝑥= 630 rpm. Assume motor
speed 1400 rpm. The design should include structural diagram, ray diagram, speed chart, gearing
diagram and number of teeth of the gear.
Q.3 Design a machine tool gear box for following Specification: Z = 12 Speed, Minimum speed
Nmin= 40 rpm, Progression ratio Φ = 1.41
Q.4 How to determine a variable speed range in the gear box.
Q.5 Why geometric progression is selected in machine tool drives ?
Q.6 What are guidelines for selecting proper geometric progression ratio?
Q.7 Write a note on Structural Diagrams and write steps in selecting best possible version
Q.8 Explain with suitable example open structural and cross structural diagrams.
Q.9 What do you mean by Ray Diagram? Explain procedure of plotting ray diagrams.
Q.10 Write a note on general recommendation for developing the gearing diagram.
Unit 6
Q.17 Derive Stribeck’s equation for rolling contact bearing.
Q.18 Explain in details equivalent bearing load in rolling contact bearing.
Q.19 Explain load life relationship in rolling contact bearing.
Q.20 In a particular application, the radial load acting on a ball bearing is 5 kN and the expected
life for 90% of the bearings is 8000 h. Calculate the dynamic load carrying capacity of the bearing,
when the shaft rotates at 1450 rpm.
Q.21 A taper roller bearing has a dynamic load capacity of 26 kN. The desired life for 90% of the
bearings is 8000 h and the speed is 300 rpm. Calculate the equivalent radial load that the bearing
can carry
Q.22 A single-row deep groove ball bearing is subjected to a pure radial force of 3 kN from a shaft
that rotates at 600 rpm. The expected life L10h of the bearing is 30 000 h. The minimum acceptable
diameter of the shaft is 40 mm. Select a suitable ball bearing for this application.
Q.23 A single-row deep groove ball bearing is subjected to a radial force of 8 kN and a thrust force
of 3 kN. The shaft rotates at 1200 rpm. The expected life L10h of the bearing is 20 000 h. The
minimum acceptable diameter of the shaft is 75 mm. Select a suitable ball bearing for this
application.
Q.24 A transmission shaft rotating at 720 rpm and transmitting power from the pulley P to the spur
gear G is shown in Figure. The belt tensions and the gear tooth forces are as follows: P 1 = 498 N
P2 = 166 N Pt = 497 N Pr = 181 N The weight of the pulley is 100 N. The diameter of the shaft at
bearings B1 and B2 is 10 mm and 20 mm respectively. The load factor is 2.5 and the expected life
for 90% of the bearings is 8000 h. Select single row deep groove ball bearings at B1 and B2.
Q.25 A single-row deep groove ball bearing No. 6002 is subjected to an axial thrust of 1000 N and
a radial load of 2200 N. Find the expected life that 50% of the bearings will complete under this
condition.
Q.26 Explain design procedure for rolling contact bearing against cyclic loads and speeds.
Q.27 A ball bearing is operating on a work cycle consisting of three parts—a radial load of 3000
N at 1440 rpm for one quarter cycle, a radial load of 5000 N at 720 rpm for one half cycle, and
radial load of 2500 N at 1440 rpm for the remaining cycle. The expected life of the bearing is 10
000 h. Calculate the dynamic load carrying capacity of the bearing.
Q.28 A single-row deep groove ball bearing is subjected to a 30 second work cycle that consists
of the following two parts: The static and dynamic load capacities of the ball bearing are 50 and
68 kN respectively. Calculate the expected life of the bearing in hours.
Q.29 Derive Petroff’s Equation for sliding contact bearing.
Q.30 Derive Reynold’s Equation for sliding contact bearing.
Q.31 Write a note on selection parameters in sliding contact bearing design.
Q.32 The following data is given for a 360° hydrodynamic bearing: radial load = 3.2 kN journal
speed = 1490 rpm journal diameter = 50 mm bearing length = 50 mm radial clearance = 0.05 mm
viscosity of lubricant = 25 cP Assuming that the total heat generated in the bearing is carried by
the total oil flow in the bearing, calculate (i) coefficient of friction; (ii) power lost in friction; (iii)
minimum oil film thickness; (iv) flow requirement in 1itres/min; and (v) temperature rise.
Q.33 The following data is given for a full hydrodynamic bearing used for electric motor: radial
load = 1200 N journal speed = 1440 rpm journal diameter = 50 mm static load on the bearing =
350 N The values of surface roughness (cla) of the journal and the bearing are 2 and 1 micron
respectively. The minimum oil film thickness should be five times the sum of surface roughness
of the journal and the bearings. Determine (i) length of the bearing; (ii) radial clearance; (iii)
minimum oil film thickness; (iv) viscosity of lubricant; and (v) flow of lubricant. Select a suitable
oil for this application assuming the operating temperature as 65°C.
Q.34 Design a full hydrodynamic journal bearing with the following specification for machine tool
application: journal diameter = 75 mm, radial load = 10 kN, journal speed = 1440 rpm, minimum
oil film thickness = 22.5 microns, inlet temperature = 40°C, bearing material = babbitt. Determine
the length of the bearing and select a suitable oil for this application.
Q.35 The following data is given for a 360° hydrodynamic bearing:
length to diameter ratio = 1
journal speed = 1350 rpm
journal diameter = 100 mm
diametral clearance = 100 mm
external load = 9 kN
The value of minimum film thickness variable is 0.3. Find the viscosity of oil that need be used.
Q.36 The following data is given for a 360° hydrodynamic bearing:
radial load = 10 kN
journal speed = 1440 rpm
unit bearing pressure = 1000 kPa
clearance ratio (r/c) = 800
viscosity of lubricant = 30 mPa s
Assuming that the total heat generated in the bearing is carried by the total oil flow in the bearing,
calculate:
(i) dimensions of bearing;
(ii) coefficient of friction;
(iii) power lost in friction;
(iv) total flow of oil;
(v) side leakage; and
(vi) temperature rise
