In the mechanism shown in Figure (II.5), the crank AB is 75 mm long an...
Solution:
Given Data:
- Crank AB length, rAB = 75 mm
- Angular velocity of crank AB, ωAB = 8 rad/s
- Distance between crank pivot B and piston C, L(BC) = 300 mm
- Distance between crank pivot B and point D, L(BD) = L(CD) = L(DE)
Velocity of Piston C:
- Let ω be the angular velocity of the link CD.
- The instantaneous center of rotation of link CD is at point G, where the perpendiculars to links CD and BC intersect.
- The velocity of piston C is given by vC = vG + GC x ω, where GC is the perpendicular distance from point G to piston C.
- From the geometry of the mechanism, we have GC = BD - DC = L(BD) - L(BC) = L.
- The velocity of point G is zero since it is the instantaneous center of rotation.
- Therefore, vC = L x ω = L x (ωAB / 2) = 150 mm/s.
Acceleration of Piston C:
- The acceleration of piston C is given by aC = aG + α x GC + ω^2 x GC, where α is the angular acceleration of link CD and aG is the acceleration of point G.
- The acceleration of point G is given by aG = GC x α, where GC is the perpendicular distance from point G to piston C.
- From the geometry of the mechanism, we have GC = BD - DC = L(BD) - L(BC) = L.
- The angular acceleration of link CD is α = dω / dt = -ω^2 / L.
- Therefore, aG = GC x α = -ω^2 x L = -1200 mm/s^2.
- The acceleration of piston C is given by aC = aG + α x GC + ω^2 x GC = -ω^2 x L + α x L + ω^2 x L = α x L = (-ω^2 / L) x L = -ω^2 = -64 mm/s^2.
Velocity of Piston E:
- Let θ be the angle between links BD and DE.
- The instantaneous center of rotation of link DE is at point H, where the perpendiculars to links DE and BD intersect.
- The velocity of piston E is given by vE = vH + HE x ω, where HE is the perpendicular distance from point H to piston E.
- From the geometry of the mechanism, we have HE = DE x sin(θ) = L x sin(θ).
- The velocity of point H is zero since it is the instantaneous center of rotation.
- Therefore, vE = L x sin(θ) x ω = L x sin(θ) x (ωAB / 2).
Acceleration of Piston E:
- The acceleration of piston E is given by aE = aH + α x HE + ω^2 x HE, where α is the angular acceleration of link DE and aH is the acceleration of point H.
- The acceleration of point H is given by aH = HE x α, where HE is the perpendicular distance from point H to piston E.
- The angular acceleration of link DE is α = d^2θ / dt^2 = -ω^
To make sure you are not studying endlessly, EduRev has designed Mechanical Engineering study material, with Structured Courses, Videos, & Test Series. Plus get personalized analysis, doubt solving and improvement plans to achieve a great score in Mechanical Engineering.