IOT POLY ENGINEERING 4-09 MECHANICAL TECHNOLOGY REVIEW OF MECHANISMS FOR QUIZ ON TUESDAY 26 MAY 2009 TUE 5/26 - QUIZ ON MECHANISMS, BEGIN TEST REVIEW WED 5/27 - REVIEW LESSON FOR FINAL TEST THU 5/28 - FINAL TEST (VECTORS, TRIGONOMETRY, ELECTRICITY, MECHANISMS) FRI 5/29 - EXTRA CREDIT WORK

IOT POLY ENGINEERING 4-09 A 4-bar linkage mechanism has a crank that rotates at a constant angular speed. The crank is connected to the coupler which is connected to the follower. The frame does not move. crank coupler follower frame KINEMATICS is the branch of physics that studies the motion of a body or a system of bodies without consideration given to its mass or the forces acting on it.

IOT POLY ENGINEERING 4-09 A Grashof linkage is a planar four-bar linkage with S + L < P + Q where S = length of the shortest link L = length of longest link P and Q are the lengths of the two remaining links. 1. Crank-Rocker : a Grashof linkage where the shortest link is the input link (crank). 2. Double-Rocker: a Grashof linkage where the shortest link is the floating link (coupler). 3. Rocker-Crank : a Grashof linkage where the shortest link is the output link (follower). 4. Crank-Crank : a Grashof linkage where the shortest link is the ground link (frame).

IOT POLY ENGINEERING Crank-Rocker : a Grashof linkage where the shortest link is the input link (crank).

IOT POLY ENGINEERING Double-Rocker: a Grashof linkage where the shortest link is the floating link (coupler).

IOT POLY ENGINEERING Crank-Crank : a Grashof linkage where the shortest link is the ground link (frame).

IOT POLY ENGINEERING 4-09 frame crank coupler follower Door Closer Mechanism Folding Table frame crank coupler follower TWO COMMON EXAMPLES OF A 4-BAR MECHANISM

IOT POLY ENGINEERING 4-09 A pantograph is a mechanism that is used to create a drawing that is larger or smaller than an original drawing. The pantograph simulation below creates a drawing that is larger than the original drawing.

IOT POLY ENGINEERING 4-09 A parallel bar mechanism is a mechanism that retains parallelism in its members.

IOT POLY ENGINEERING 4-09 Two more examples of the parallel bar mechanism are shown below. On the left is a ‘scissors lift’ which is used in the construction industry. On the right is a ‘scissors jack’ which is used when changing an automobile tire.

IOT POLY ENGINEERING 4-09 A straight line mechanism is a mechanism that is used to create straight lines. The examples below are Peaucellier mechanisms.

IOT POLY ENGINEERING 4-09 Two more examples of a straight line mechanism are shown below. These are the Tchebicheff mechanism.

IOT POLY ENGINEERING 4-09 Another example of a straight line mechanism is shown below. This is the Watt mechanism, invented by James Watt of steam engine fame. If you look closely, you will see that the path deviates from a straight line at the top and the bottom of motion.

IOT POLY ENGINEERING 4-09 There is no end to the ingenuity of engineers who invent various mechanisms for desired outcomes. This is a CAM-FOLLOWER. The cam is red. As the cam rotates, it causes the flat follower to rise and fall. Thus, rotational motion has been converted to linear motion.

IOT POLY ENGINEERING 4-09 This is a SCOTCH YOKE. As the yellow knob rotates, it causes the light gray yoke to move side to side. Thus, rotational motion has been converted to linear motion.

IOT POLY ENGINEERING 4-09 This is a GENEVA MECHANISM. As the small black knob rotates at a constant rate, it causes the dark gray mechanism to rotate one-sixth of a turn and stop, rotate one-sixth of a turn and stop, etc. The Geneva mechanism on the right side causes one-fourth of a turn movements. Rotational motion has been converted to sporadic rotational motion.

IOT POLY ENGINEERING 4-09 This is a PISTON & CRANK. As the crankshaft on the right rotates at a constant rate, it causes the light blue connecting rod to push and pull on the piston (two-tone gray). Thus, rotational motion has been converted to reciprocating motion.

IOT POLY ENGINEERING 4-09 TUE 5/26 - QUIZ ON MECHANISMS, BEGIN TEST REVIEW WED 5/27 - REVIEW LESSON FOR FINAL TEST THU 5/28 - FINAL TEST (VECTORS, TRIGONOMETRY, ELECTRICITY, MECHANISMS) FRI 5/29 - EXTRA CREDIT WORK REMINDER