Calculating Forces

Determine force information about all link lengths and link angles of the quick return mechanism.

Vectors & Angles

Calculating Forces

Calculating the dynamics of the mechanism requires more information than just calculating the kinematics. It requires the geometry and input angle and speed of the device as before. In addition, the masses, centers of gravity, and mass moments of inertia are needed. There can also be a resistance force placed on the output slider to simulate a load. This is typically applied on the slower stroke of the slider as that is when the work is done. Enter the following information:

Unit system
r_1,2,4,5,7 - Link lengths
m_2-6 - Link masses
rg_2,4,5 - Distances from tail of vectors to center of masses for links
ig_2,4,5 - Mass moments of inertia for all moving links (sliders considered point masses)
Angular units
Θ₂ - Angular position for the drive link
ω₂ - Angular velocity for the drive link (assumed constant)
δ_2,4,5 - Angles from link bodies to centers of mass
Turn load force on or off
fl - load force in X direction

To help describe some of the geometry (i.e. rg & δ) used in the analysis, here are free body diagrams for all the bodies in the mechanism showing the centers of mass.

Option 1 will output the numerical output for all the forces and the required torque at that instant. Option 2 gives you a choice of many output plots showing the force between links and input torque verses time. Ground is referred to as link 1. Option 3 displays the position of the entire mechanism .

Units:

Link Lengths (m or ft):
r₁: r₂: r₄: r₅: r₇:

Link Masses (Kg or slugs):
m₂: m₃: m₄: m₅: m₆:

Distance to Center of Mass (m or ft):
rg₂: rg₄: rg₅:

Mass Moment of Inertia of Links (Kg*m² or lb*ft*s²):
ig₂: ig₄: ig₅:

Angles:

Drive Link Position (° or rad): θ₂:

Drive Link Velocity (° or rad): ω₂: per second

Angles to Center of Mass (° or rad):
δ₂: δ₄: δ₅:

Load Force on Output Slider (N or lbs):
Add load force pushing against output slider.
Disable load force on output slider.
fl:
Note: This force acts on link 6 in the X direction. Negative values will act in the negative X direction.

Output Options:

Display forces and input torque.
Plot selected quantity against time.

Display mechanism position. Need to have Ch Mechanism Toolkit installed.

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