Mechanism Balancing: Total and Partial Methods Explained
Mechanism Balancing: Total and Partial Methods
Mechanism balancing aims to eliminate or mitigate the effects of inertia forces. Achieving a complete balance isn’t always feasible or desirable due to economic factors. Therefore, we can distinguish between two approaches:
- Total Balance: Completely cancels forces and moments of inertia acting on the frame.
- Partial Balance: Reduces, but doesn’t eliminate, the effects of inertia on the frame.
Total Balance Methods
There are three methods to achieve total balance:
- Add bodies to each member, modifying its center of gravity and moment of inertia, to nullify the resulting force and moment of inertia on the frame.
- Redesign the mechanism to strategically distribute moving members, compensating for each other’s inertia forces and resulting in a zero net force and moment on the frame.
- Incorporate additional members to the mechanism so that all inertia forces (including those of the added members) result in a zero net force and moment on the frame.
The first method balances an existing mechanism by modifying individual members without altering its kinematic design. The second and third methods balance the mechanism by modifying its original design. The third method is applicable to any mechanism, while the second may not always be applicable or may compromise the mechanism’s intended function.
Partial Balance Approaches
There are two approaches to achieve partial balance:
- Use low-density materials (e.g., aluminum, plastic) to reduce the inertial forces of the members.
- Optimize the kinematic design of the mechanism to minimize accelerations of high-mass members, thereby reducing inertia forces.