Drawing

DEPCOllc

3305 Airport Drive | Pittsburg, KS 66762

An Illustrated Look at Forces Acting on the Trebuchet Axle

A force that acts perpendicular to the center axis of the trebuchet axle will cause the axle to bend.

This is called deflection. The amount of deflection is proportional to the applied force and inversely

proportional to the cross sectional area of the axle. This simply means that if the axle is larger in

diameter, it will support greater loads and deflect less.

Deflection

Center

Axis

Axle Support

or Restraint

Fig A-9a

Tension Force

Acts to stretch or pull the axle material apart. A rod failing under tension will “Neck Down” when pulled apart.

Compression Force

Acts to push the axle material together. A rod failing under tension will bulge if the compressive forces act along the

center axis.

Fig A-9c

Fig A-9b

Fig A-9d

Tension and Compression

Occur simultaneously when the trebuchet axle is deformed. The material above the centerline is

under compression while the material below the centerline is under tension.

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