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DESIGN AND FABRICATION OF
ROCKER BOGIE MECHANISM
BY
DINESH CM (211414114087)
GIRIDHARAN TS (211414114100)
HANIROOTH C (211...
ABSTRACT:
2
• The need to develop a highly stable suspension system
capable of operating in multi terrain surfaces while k...
INTRODUCTION:
3
• The Rocker bogie system is the suspension arrangement
used in Mars rovers introduced for Mars Pathfinder...
PRINCIPLE:
4
•The front wheels are forced against the obstacle by the rear wheels. The
rotation of the front wheel then li...
5
ADVANTAGES:
6
• This mechanism allows climbing obstacles twice the size of
wheel diameter
• Does not employ springs and st...
WORKING OF ROCKER BOGIE MECHANISM:
7
COURTESY: MARS CURIOSITY ROVER
ON ROCKER BOGIE SUSPENSION
8
Curiosity Rover:
Curiosity is a car-sized robotic rover explor...
9
APPLICATIONS
•RBM was employed in Viking 1 & Viking 2 space landers of NASA in 1996.
•In 1997, The Mars Pathfinder (MPF)...
COMPONENTS REQUIRED:
COMPONENT NAME QUANTITY
SHAFT 1
LINK 4
WHEEL 6
BEARING 2
MOTOR 6
BEARING BUSH 4
10
PROCESS INVOLVED:
11
• Design of bogie
• Cutting of links
• Welding of links and bushes
• Drilling
• Facing and turning of...
VELOCITY 80mm/s VELOCITY 100mm/s VELOCITY 120mm/s
SPEED(N) DIA(D) SPEED(N) DIA (D) SPEED(N) DIA (D)
rpm mm rpm mm rpm mm
1...
CALCULATION OF TILT ANGLE & WHEEL BASE:
Θ=tan-1
(y/x)
Θ=tan-1
(120/400)=16.69⁰
Tilt angle:
Wheel base:
To deduce the wheel...
CALCULATION OF LENGTH OF LINKS:
Length of link AC: Length of link DB:
BC2
=AB2
+AC2
BE2
=DB2
+ED2
4002
=2(AB2
) 202
=2(DB2...
HEIGHT AND TRACK WIDTH CALCULATION
 HEIGHT CALCULATION
Height2
= AC2
– EC2
(2802
– 2002
)1/2
= 195.95mm
Net Height = heig...
GROSS WEIGHT CALCULATION
 MASS = VOLUME X DENSITY
DENSITY OF MILD STEEL = 0.00785 g/mm3
1)Weight of rocker arms = 2[(320*...
DIMENSIONS AND MATERIAL SPECIFICATIONS
17
DESCRIPTION DIMENSIONS
Wheel Thickness 20mm
Wheel Diameter 70mm
Height 230mm
Whe...
PART MODEL WITH DIMENSIONS
BEARING BUSHBEARING BUSH
PIN LENGTH PIN DIAMETERPIN LENGTH PIN DIAMETER 18
PART MODEL WITH DIMENSIONS CONTD.
19
ROCKER BOGIEROCKER BOGIE
SHAFT
PART MODEL
20
BEARING ROCKER PINBEARING ROCKER PIN
BOGIE BUSHBOGIE BUSH
SHAFTSHAFT
POWER DISTRIBUTION CIRCUIT
21
• The power from the battery is equally distributed to all the six
motors through the power ...
POWER DISTRIBUTION
CIRCUIT
22
• Most common SPDT slide switch is used
• A Single Pole Double Throw(SPDT) individually cont...
COST ESTIMATION
23
MATERIAL/COMPONENT NOs COST/UNIT COST
MS Frame 2 Rs.25 Rs.50
MS Shaft 1 Rs.30 Rs.30
Ball bearing 4 Rs.3...
COST ESTIMATION
24
PROCESS COST
Frame cutting Rs.50
Bush machining Rs.250
Welding Rs.100
Lathe operation Rs.100
Drilling R...
FAILURES
25
Initially the rocker and bogie link are
made from 1mm thickness stainless
Steel sheets; Which resulted in fail...
FAILURES
26
During the assembly of shaft and the bearing an 8mmDuring the assembly of shaft and the bearing an 8mm
MS rod ...
CONCLUSION:
27
• The various components of the rocker bogie is assembled and the
total weight of the frames and shaft is c...
FUTURE SCOPE
28
• With the development in technology the rover can be used for
reconnaissance purposes with the cameras in...
REFERENCES
29
• "NASA Patent Abstracts Bibliography, Section 1. Abstracts”
June 1990: 19. ARTICULATED SUSPENSION SYSTEM
• ...
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Rocker bogie mechanism

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Suspension system which can handle the harsh environment of Mars.

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Rocker bogie mechanism

  1. 1. DESIGN AND FABRICATION OF ROCKER BOGIE MECHANISM BY DINESH CM (211414114087) GIRIDHARAN TS (211414114100) HANIROOTH C (211414114115) HARISH T (211414114123) Under the guidance ofUnder the guidance of Department of Mechanical engineering Panimalar Engineering College, Chennai-123 BATCH NUMBER: 76
  2. 2. ABSTRACT: 2 • The need to develop a highly stable suspension system capable of operating in multi terrain surfaces while keeping all the wheels in contact with the ground. • To design a mechanism that can traverse terrains where the left and right rockers individually climb different obstacles. • To sustain a tilt of over 50deg without tipping over the sideways.
  3. 3. INTRODUCTION: 3 • The Rocker bogie system is the suspension arrangement used in Mars rovers introduced for Mars Pathfinder and also used on Mars Exploration Rover(MER) and Mars Science Laboratory(MSL) missions • This bogie can resist mechanical failures caused by the harsh environment on MARS • The primary mechanical feature of the Rocker Bogie design is it’s drive train simplicity, which is accomplished by two rocker arms
  4. 4. PRINCIPLE: 4 •The front wheels are forced against the obstacle by the rear wheels. The rotation of the front wheel then lifts the front of the vehicle up and over the obstacle. • The middle wheel is the pressed against the obstacle by the rear wheel and pulled against the obstacle by the front, until it is lifted up and over. •Finally, the rear wheel is pulled over the obstacle by the front two wheels. During each wheel’s traversal of the obstacle, forward progress of the vehicle is slowed or completely halted. • These rovers move slowly and climb over the obstacles by having wheels lift each piece of the suspension over the obstacle one portion at a time.
  5. 5. 5
  6. 6. ADVANTAGES: 6 • This mechanism allows climbing obstacles twice the size of wheel diameter • Does not employ springs and stub axles • Equal distribution of load on all wheels • Independent movement of rocker on either sides of the bogie • The front and back wheels have individual drives for climbing, enabling the rover to traverse obstacle without slip • The design is simple and reliable
  7. 7. WORKING OF ROCKER BOGIE MECHANISM: 7
  8. 8. COURTESY: MARS CURIOSITY ROVER ON ROCKER BOGIE SUSPENSION 8 Curiosity Rover: Curiosity is a car-sized robotic rover exploring Mars as part of NASA's Mars Science Laboratory(MSL) mission. Launch date: November 26, 2011 Rocket: Atlas V Manufacturer: NASA Operator: NASA Mission Type :- Mars Exploration Rover Launch Mass:- 900 Kg Max Speed:- 50mm/s Average Speed :- 10mm/s
  9. 9. 9 APPLICATIONS •RBM was employed in Viking 1 & Viking 2 space landers of NASA in 1996. •In 1997, The Mars Pathfinder (MPF) lander delivered the Sojourner Rover to the surface successfully which was mounted on this bogie system. •Two other Mars rovers namely Spirit and Opportunity launched by NASA in early 2004 was also built on RBM. •Most Recently in 2011, RBM was used in NASA’s Mars Science Laboratory (MSL) with a rover named Curiosity rover.  
  10. 10. COMPONENTS REQUIRED: COMPONENT NAME QUANTITY SHAFT 1 LINK 4 WHEEL 6 BEARING 2 MOTOR 6 BEARING BUSH 4 10
  11. 11. PROCESS INVOLVED: 11 • Design of bogie • Cutting of links • Welding of links and bushes • Drilling • Facing and turning of shaft • Assembly of wheels, motor, bearing, shaft, pin. • Soldering in power distribution circuit • Testing of Rig
  12. 12. VELOCITY 80mm/s VELOCITY 100mm/s VELOCITY 120mm/s SPEED(N) DIA(D) SPEED(N) DIA (D) SPEED(N) DIA (D) rpm mm rpm mm rpm mm 10 152.77 10 190.96 10 229.15 20 76.38 20 95.48 20 114.58 30 50.92 30 63.65 30 76.38 40 38.19 40 47.74 40 57.29 50 30.55 50 38.19 50 45.83 60 25.46 60 31.83 60 38.19 70 21.82 70 27.28 70 32.74 80 19.10 80 23.87 80 28.64 We have chosen 30rpm motor. From the above table for 100mm/s ; the wheel diameter is 63.6mm(70mm approx) Velocity, V =(πDN)/60 12
  13. 13. CALCULATION OF TILT ANGLE & WHEEL BASE: Θ=tan-1 (y/x) Θ=tan-1 (120/400)=16.69⁰ Tilt angle: Wheel base: To deduce the wheel base, Wheel base=Total length - (radius of front wheel + radius of rear wheel) b=400-(35+35) b=330mm 13
  14. 14. CALCULATION OF LENGTH OF LINKS: Length of link AC: Length of link DB: BC2 =AB2 +AC2 BE2 =DB2 +ED2 4002 =2(AB2 ) 202 =2(DB2 ) AB=AC=282mm DB=DE=141mm 14
  15. 15. HEIGHT AND TRACK WIDTH CALCULATION  HEIGHT CALCULATION Height2 = AC2 – EC2 (2802 – 2002 )1/2 = 195.95mm Net Height = height + radius = 195.95 + 35 = 230.95mm. TRACK WIDTH CALCULATION SSF = Tw/(2h) 0.5= Tw/ (2*230.95) Tw= 230.95mm 15
  16. 16. GROSS WEIGHT CALCULATION  MASS = VOLUME X DENSITY DENSITY OF MILD STEEL = 0.00785 g/mm3 1)Weight of rocker arms = 2[(320*25*3*0.00785) + (200*25*3*0.00785)] = 612.3gm 2)Weight of bogies = 2[2*(180*25*3*0.00785)] = 423.9gm 3)Weight of shaft = [(π/4)*9*9*230*0.00785) = 114.8gm 4)Weight of pin = 2*[2((π/4)*8*8*7*0.00785) + ((π/4)*9*9*7*0.00785)] = 18.02gm 5)Weight of bearings = 4*10 = 40gm 6)Weight of bush = 4*28.7 = 114.8gm  Total weight = 612.3+423.9+114.8+18.02+40+114.8 =1323.82gm 16 GROSS WEIGHT OF THE MECHANISM IS 1.323Kg
  17. 17. DIMENSIONS AND MATERIAL SPECIFICATIONS 17 DESCRIPTION DIMENSIONS Wheel Thickness 20mm Wheel Diameter 70mm Height 230mm Wheel Base 340mm Track Width 231mm Bogie length 141mm Rocker length 282mm, 141mm Bearing ID 8mm OD 22mm Bearing bush ID 22mm OD 26mm Shaft diameter 9mm Shaft length 230mm, 18mm COMPONENTS MATERIALS Frames Mild steel Shaft Mild steel Bearings Hardened carbon steel Bearing housing(bush) Stainless steel EN8 COMPONENTS DIMENSION Shaft 9mm dia., 400mm length Frames 1250*25*3mm Bush 26mm dia., 100mm length
  18. 18. PART MODEL WITH DIMENSIONS BEARING BUSHBEARING BUSH PIN LENGTH PIN DIAMETERPIN LENGTH PIN DIAMETER 18
  19. 19. PART MODEL WITH DIMENSIONS CONTD. 19 ROCKER BOGIEROCKER BOGIE SHAFT
  20. 20. PART MODEL 20 BEARING ROCKER PINBEARING ROCKER PIN BOGIE BUSHBOGIE BUSH SHAFTSHAFT
  21. 21. POWER DISTRIBUTION CIRCUIT 21 • The power from the battery is equally distributed to all the six motors through the power distribution circuit • Negative terminals make 1 solder joint; positive terminals from 3 motors from both side make 2 solder joints with 3 SPDT switches • The direction of the motor rotation is reversed by changing the input poles from the battery • Drawback of this circuit is the heating of the connecting wires due to the failure in calculating the resistance of the wires for 12V.
  22. 22. POWER DISTRIBUTION CIRCUIT 22 • Most common SPDT slide switch is used • A Single Pole Double Throw(SPDT) individually controls a single circuit as for single throw and has two positions(ON/OFF) as for double throw • SPDT switch has 3 terminals one common pin and two support pins; in general practice, one of the support pin is left unconnected (contd.)
  23. 23. COST ESTIMATION 23 MATERIAL/COMPONENT NOs COST/UNIT COST MS Frame 2 Rs.25 Rs.50 MS Shaft 1 Rs.30 Rs.30 Ball bearing 4 Rs.300 Rs.1200 MS Bush rod 1 Rs.30 Rs.30 DC Motor 6 Rs.300 Rs.1800 12V Battery 1 Rs.800 Rs.800 Wheels 6 Rs.35 Rs.210 PCB 1 Rs.40 Rs.40 Wire plug 6 Rs.15 Rs.90 Connecting wires 5m Rs.40 Rs.40 SPDT switch 3 Rs.5 Rs.15 Battery cap 2 Rs.2 Rs.4
  24. 24. COST ESTIMATION 24 PROCESS COST Frame cutting Rs.50 Bush machining Rs.250 Welding Rs.100 Lathe operation Rs.100 Drilling Rs.50 Labor cost:Labor cost: TOTAL COST ESTIMATION IS Rs.4859 (contd.)
  25. 25. FAILURES 25 Initially the rocker and bogie link are made from 1mm thickness stainless Steel sheets; Which resulted in failure due to bending of the links which was the effect of drilling operation and excessive load condition. A bearing was lost due to the uneven and irregular fitting of the Shaft and bush. The bearing was Broke to disassemble the bearing bush and the shaft
  26. 26. FAILURES 26 During the assembly of shaft and the bearing an 8mmDuring the assembly of shaft and the bearing an 8mm MS rod was found to be a loose fit with a 8mm ID bearing.MS rod was found to be a loose fit with a 8mm ID bearing. This was a failure due to error in measuring the diameterThis was a failure due to error in measuring the diameter of the rod during purchase. Due to presence of chip at theof the rod during purchase. Due to presence of chip at the tip of the rod; it was wrongly measured as 8mm;tip of the rod; it was wrongly measured as 8mm; but was actually 7.5mm.but was actually 7.5mm. (contd.)
  27. 27. CONCLUSION: 27 • The various components of the rocker bogie is assembled and the total weight of the frames and shaft is calculated to be 1.3Kg. • In reference to the specification of the DC motor, the allowable net reaction on the motor is 1.5Kg. Hence the design is safe. • This is a wide field of study which is very less explored. So this gave us the motivation for the development of this rocker bogie suspension system in a cost effective manner. • In future rocker bogie mechanism can be used in defense related operations and also in wheelchairs for climbing stairs.
  28. 28. FUTURE SCOPE 28 • With the development in technology the rover can be used for reconnaissance purposes with the cameras installed on the rover and minimizing the size of rover • By the development of a bigger model it can be used for transporting humans and material through a rough terrain or obstacles containing regions like stairs • It can also be used for geological mapping of unknown terrains as it can even provide live video feed and images of the terrains being explored
  29. 29. REFERENCES 29 • "NASA Patent Abstracts Bibliography, Section 1. Abstracts” June 1990: 19. ARTICULATED SUSPENSION SYSTEM • IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE) e-ISSN:2278-1684, p-ISSN:2320-334X, Vol. 12, Issue 3 Ver. III (May-June 2015) , PP64-67 • Synge J L and B A Griffiths : Principles of Mechanics, Section 6.3, McGraw-Hill Kogakusha Ltd,3rd Edition, 1970.
  30. 30. Thank you

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