Linkage Mechanisms

Question 1

A structure is a mechanism where all bars are of constant length

Answer 1

True

A structure is defined as a 3-bar mechanism where all bars are of constant length.

Question 2

Revolute and Prismatic are the two primary types of joints used in linkage mechanisms

Answer 2

True

Revolute (R) and Prismatic (P) joints are illustrated and discussed as fundamental joint types.

Question 3

A link in a linkage mechanism is defined as a rigid body with at least two nodes for attachment to other links

Answer 3

True

A link is defined as a rigid body that has at least two nodes (points for attachment to other links).

Question 4

According to Gruebler’s equation, the degree of freedom (DoF) of a linkage mechanism is calculated based on the number of links (L), the number of joints (J), and the number of grounded links (G)

Answer 4

True

Gruebler’s equation is given as M = 3(L - 1) - 2J or M = 3(L - G - 1) - 2J. The formula directly relates DoF to the number of links and joints.

Question 5

For a linkage mechanism to produce a definitive motion, it must have two or more degrees of freedom (DoF)

Answer 5

False

For a linkage mechanism to produce a definitive (predictable, controlled) motion with a single input, it typically needs one degree of freedom (DoF=1). Mechanisms with DoF > 1 require multiple inputs for deterministic motion.

Question 6

Grashof’s condition predicts the linkage behavior, specifically whether a link can make a full revolution, based solely on the lengths of the links

Answer 6

True

Grashof condition is stated to predict the linkage behaviour based only on link lengths (S, L, P, Q).

Question 7

If in a four-bar linkage the sum of the shortest and longest link lengths (S + L) is greater than the sum of the other two link lengths (P + Q), then at least one link is capable of making a full revolution

Answer 7

False

The condition for at least one link being capable of a full revolution (a Grashof linkage) is S + L < P + Q. If S + L > P + Q, it’s a non-Grashof linkage where no link can make a full revolution.

Question 8

The Human-Bicycle linkage mechanism, considering the legs, paddle crank, and frame, is an example of a structure

Answer 8

False

A structure is a linkage where all bars are of constant length. The human-bicycle system, involving motion and relative movement, functions as a mechanism, not a rigid structure.