Linkage Mechanisms Flashcards
What is the difference between a structure and a mechanism?
A structure has fixed-length links and no motion, while a mechanism allows relative motion.
What are the two main types of joints in mechanisms?
Revolute (R) and Prismatic (P) joints.
What are some real-world examples of linkage mechanisms?
Windscreen wipers, car jacks, air compressors, steam engines, human joints, aircraft landing gear.
What is pure translation in motion?
All points of a body move in parallel paths without rotation.
What is pure rotation?
All points in the body rotate about a fixed axis.
What is complex motion?
A combination of rotation and translation.
How many degrees of freedom (DoF) does a rigid body have in 2D?
3 DoF: x, y, and θ.
What is Gruebler’s equation?
M = 3L - 2J - 3G, where M = DoF, L = links, J = joints, G = grounded links.
What is a binary link?
A link with two connection points or nodes.
What is a ternary link?
A link with three connection points.
What is a quaternary link?
A link with four connection points.
What is a crank-rocker mechanism?
A 4-bar mechanism where one link (crank) rotates fully while the other (rocker) oscillates.
What is a slider-crank mechanism?
A 4-bar mechanism converting rotary motion to linear motion.
What is the swept volume of a piston in a slider-crank?
Swept volume = A × 2R, where A is piston area and R is crank radius.
How do you find force on the piston in a slider-crank?
Fz = A × P, where P is the pressure.
What is the transmission angle in a linkage?
μ = π - θ - φ; ideal value is 90°, should be ≥ 40°.
What is the Grashof condition?
If S + L < P + Q, the linkage is Grashof and at least one link can fully rotate.
What are non-Grashof linkages?
S + L > P + Q; no link can make a full revolution.
What is graphical synthesis in linkage design?
A method using scale drawings, compass, and protractor to design motion profiles.
What is the main purpose of toggle mechanisms?
They lock into position and resist external forces until manually released.
What is a transmission angle used for?
Evaluates how effectively force is transmitted through a linkage.
What are common aircraft landing gear linkage types?
4-bar configurations using toggle mechanisms for reliable retraction/extension.
How is the degree of freedom for a crank-rocker mechanism calculated?
L=4, J=4 → M = 3(4) - 2(4) - 3(1) = 1.
What is the purpose of a coupler in a 4-bar mechanism?
To transmit motion between the crank and rocker.
What method is used to analyse forces in slider-crank systems?
Trigonometry, force components, and torque calculation.
What is the benefit of minimising R/L in slider-crank design?
Reduces friction and lateral forces.
What is the significance of the sine rule in linkage analysis?
Used to relate angles and lengths in link motion calculations.
What is the cosine rule used for in linkage design?
Calculating angles and lengths for range of motion and position analysis.
What is a practical application of the deltoid toggle linkage?
Controlling tailgate or landing gear motion.
How do you validate linkage designs like in an excavator?
Using models and animations to check range, forces, and motion profiles.
