**Helical Wheel** .When the worm screw goes one full turn, just one tooth of the helical wheel rotates, that is, to make the helical wheel one full turn, the worm screw has to turn the number of times the teeth have the helical wheel.

## Types of helical wheel pitches

- The normal pitch Pn of a worm wheel

It is the distance measured perpendicularly between the axes of the consecutive teeth . They are made by modules, as for ordinary teeth. The tilt of the teeth is made of 150 for the wheels of parallel axles , and of 450 for those of the perpendicular axles. The teeth of the two wheels have the same angle of inclination, but in one propeller wheel it is from left to right, and in the other from right to left; in the second case the propellers are both in the same direction.

- The circular step Pc also called front step ===

It is the measured distance , as in the previous case, but parallel to the two sides of the wheel .

- The propeller pitch Pe

Is the distance measured, as for screws, on the generatrix of the cylinder , which in this case has the same diameter D that the pitch circle of the same wheel. Both the circular pitch and the helix pitch are calculated using trigonometric lines .

- Formulas to calculate the dimensions of the steps

Pc = Pn / cos∞ = D x π / N Pn = Pc x cos ∞ = π x M Mc = D: N, M = Mc x cos ∞ N = D: Mc, D = N x Mc = (N x PC ) / π D ‘= D + 2M = Mc x (N +2 cos ∞) Pc = D x π x tga

Mc indicates the modulus of the circular wheel arch

## Helical wheel types

- Helical wheels with V-shaped teeth

The angle at the vertex is 110 degrees.

- Helical wheels that mesh with worm gear (fig. 3)
- Formulas that allow calculating their dimensions:

D x N x M, D ‘x (N + 2) x M qx 2,1666 x M, mxn + (2 x M) nxm – (2 x M0, px P xv, px P xvxrx 0.967 x M) Tg = p / (nx π), dx (D + n) / 2 = (D + m) / 2 – M

- The letters represent the following screw dimensions in the formulas above:

m, maximum diameter. n average diameter. p; He passed. q, height of the fillet. r, length of its base; inclination of the same, and, the number of principles, if it is multiple fillet.