Mechanisms Flashcards
Equation to degrees of freedom of a 4 bar linkage
Gruebler’s equation: N = 3 x (No. of mechanism links -1) - (2 x No. of 1 degree of freedom joints) - (No. of 2 degrees of freedom joints)
Nb: 1 degree freedom joints = pin or slider joints
2 degree of freedom = cam and gear joints
4-bar linkages that at least one link can rotate through a full revolution
Crank rocker
Drag link or Double crank
Double-rocker
Grashof Condition
4-bar linkages where no links can rotate a full revolution
Double rocker
Grashof Limit
Toggles and positions
What is the grashof condition of 4 bar linakges?
Sum of the longest and shortest links is less than or equal to the other two links:
Longest + Shortest =< Linkage 2 + Linkage 3
Purpose of shortest link in crank-rocker
Shortest link is crank
Purpose of shortest link in the double-crank
shortest link is grounded
What link in the double rocker is the ground?
link opposite the shortest link
What are the toggle positions and what do they mean?
when two or more adjacent links are colinear, thus one of the joints is presented from fully driving the mechanish
Label the highlighted parts and the type of follower
vector loop analysis
FIND A QUESTION TO ANSWER FOR VECTOR VELOCITY ANALYSIS
Label stages of cam operation
Disadvantages of cam-follower system (three)
- susceptible to vibrations
- may experience wear over long-term use
- lubrication usually needed
What section(s) of cam operation reflect the Critical Extreme Positions? (Dwell, Rise, Fall)
The Dwell Sections
What are requirements of a cam design? continuous functions/finite where/SVAJ diagrams
Must be continuous in displacement, velocity and acceration functions
Must be finite across the entire interval
what are appropriate functions for cam design?
Simple harmonic motion, polynomial (5th order or higher)
