Design Notes

A Poor Load Path – Inducing Bending

The configuration in Figure 5.5(b) represents a poor design choice. Here, a single vertical web is placed beneath the bearing. When the load is applied downward, it acts directly on the central region of the bearing block, but the support exists primarily only at the sides through the channel flanges.

Bending introduces:

• Higher and localized stresses
• Reduced structural efficiency
• Increased material thickness requirements

This leads to heavier and less economical components without real structural benefit.

The load is not traveling in a straight, supportive path. Instead, the structure is “forced to bend” itself to transfer that force, which is undesirable.

A Smarter Load Path – Compression Only

The improved configuration is shown in Figure 5.5(c). Instead of relying on a single vertical rib, two inclined ribs are used, directing the load diagonally outward toward the supporting channel flanges. These inclined ribs align themselves with the natural flow of the applied load.

As a result:

• The ribs work primarily in pure compression.
• Bending stresses are minimized.
• Smooth load transition from bearing to supports.
• Stronger and lighter design.

Rather than fighting bending, we redesign the geometry to eliminate it.

Rethinking Traditional Designs

This way of thinking often challenges long-standing design habits. A classic example is the bell-crank lever where redesigning for direct load paths can reduce material usage by up to 50% while maintaining the same performance.

The traditional bell-crank design typically requires a relatively thick cross-section to prevent excessive bending under load. While this approach is familiar and widely accepted, it is not necessarily the most efficient solution. An alternative design, which may initially appear unconventional or even incorrect, can significantly reduce bending by redirecting forces more effectively through the structure.

By minimizing bending stresses rather than simply resisting them with added material, this alternative configuration can achieve the same function using up to 50% less material. This example highlights the value of questioning conventional designs and focusing on load paths and structural behavior, rather than relying solely on familiar forms.