Forces Acting on Worm Gears

Introduction:

The radial or separating force tends to force the worm and worm gear out of mesh. This force also bends the worm in the vertical plane.

Forces Acting on Worm Gears

• When the worm gearing is transmitting power, the forces acting on the worm are similar to those on a power screw.

• Fig shows the forces acting on the worm. It may be noted that the forces on a worm gear are equal in magnitude to that of worm, but opposite in direction to those shown in Fig.

The various forces acting on the worm may be determined as follows :

1. Tangential force on the worm

= Axial force or thrust on the worm gear

The tangential force (WT) on the worm produces a twisting moment of magnitude (WT × DW / 2) and bends the worm in the horizontal plane.

2. Axial force or thrust on the worm,

W_A = W_T / tan λ = Tangential force on the worm gear

The axial force on the worm tends to move the worm axially, induces an axial load on the bearings and bends the worm in a vertical plane with a bending moment of magnitude (WA × DW / 2).

3. Radial or separating force on the worm,

WR = WA . tan φ = Radial or separating force on the worm gear

The radial or separating force tends to force the worm and worm gear out of mesh. This force also bends the worm in the vertical plane.