Planetary Gear Tooth Count

Check up the net there are several thumb rules for the number of teeth for the three (planets Vs Sun Vs Ring) for different types of combinations.

As far as I remember Roymech too has a page on it. Or try SDP-SI that also has one.

78 - 30 = 48 / 2 = 24 teeth for the planets. How did you get 23?

Further, what ratio do you want to achieve? Which of the three components is stationary?

You can check yourself considering the fact that the distance between two neighbour planets should be > than the outter diameter of the planet + a gap.

Assuming not shifted profiles the distance is D=m*(Zs+Zp)*sin(180/n)/2

Dep= m*(Zp+2) The gap shoiuld be >0 in order to avoid contact.

There are other conditions for assembly but you do not ask for them and it is better for more complex aspects to look in a book about planetary drives.

As Floram writes usually the number of teeth of the outter gear is Zout= Zs+2*Zp which is not the way you seem to think.

Zout - number of teeth for the gear with internal teeth

Zs- same for the sun gear

Zp- same for the planet gears

The gap can be for instance (0.5...1) m, the smaller "m" the bigger j/m.

m= module of your gears

n- number of planets in same plane.