PowerPoint PresentationA simple quick return mechanism is shown in the figure. The forward to return...
131
Transcript of PowerPoint PresentationA simple quick return mechanism is shown in the figure. The forward to return...
Theory of Machine
Theory of Machine
Theory of Machine
.
1 HP= 2 LP
❖ Permanent contact
❖ Ex- TP, SP & Rolling pair
If DOF = 0, the assembly of links is a structure and no motion is possible.
If DOF < 0,then the assembly is a preloaded structure, no motion is possible, and in general stresses are present.
If DOF > 0, the assembly of links is a mechanism and will exhibit relative motion
Grubler’s Equation
Grubler’s Equation
❖ Grubler criterion does not include geometry, so it can give wrong prediction
❖ We must use inspection.
The Grashof’s law states that for a four-bar linkage system, the sum of the shortest and longest link of a planar quadrilateral linkage is less than or equal to the sum of the remaining two links, then the shortest link can rotate fully with respect to a neighboring link
S+L ≤ P+Q
S+L < P+Q
Shortest Fixed
S+L < P+Q
Adjacent to shortest fixed
S+L < P+Q
Shortest = coupler
S+L = P+Q
If all lengths are different(2,3,4,5)
Same as S+L < P+Q
S+L = P+Q
If lengths are same(2,2,5,7)
S+L = P+Q
If lengths are same(2,2,5,5)
Parallelogram linkage
Parallelogram linkage
S Fixed
l Fixed
Deltoid linkage
S Fixed
Deltoid linkage
S+L > P+Q
