Table 3.4

Standard values of m_n

Note: Series 1 is preferable to Series 2

3.5. Determine the total number of teeth

Obtained value of z_Σ we should be rounded off to the nearest integer number.

3.6. Determine the number of pinion teeth

In our case ,

where z_min=17 for straight spur gears.

Obtained value of z^p should round off to the nearest integer number. If z^p < 17 it is necessary to decrease the module or to use nonstandard toothed wheels

.

3.7. Determine the number of teeth of the gear

3.8. Specify the velocity ratio of the gearing

u_act= .

The error ε = should be less then or equal to 4%. Otherwise the number of teeth z^p, z^g and z_S must be rounded down.

3.9. Determine the nominal pitch circles diameters for the pinion and the gear

d^p = m· z^p=2∙ 30=60 mm,

d^g = 2· a _w d^p=2∙ 180-60=300.

3.10. Determine the addendum circles diameters for the pinion and the gear

= d^p + 2· m=60+2∙ 2=64 mm,

= d^g ± 2· m=300+2∙ 2=304 mm.

3.11. Determine the dedendum circles diameters for the pinion and the gear

= d^p-2.5· m=60-2.5∙ 2=55 mm,

= d^g 2.5· m=300-2.5∙ 2=295 mm.

3.12. Determine forces that act in the engagement of the straight spur gears:

- turning force ;

- radial force ,

where α _w=20˚ is the pressure angle for the pitch circle.

3.13. Determine the maximum contact stress that develops in the contact zone of teeth

where T^p is the torque at the pinion shaft in N× mm; K_H is the design load factor that is determined as K_H=K_Hb× K_HV where K_Hb is the load concentration factor; K_HV is the dynamic load factor.

The load concentration factor K_Hb is specified in table 3.2. It depends upon ψ _bd= .

In order to determine K_HV it is necessary to find the peripheral gear speed V^g

m/sec,

and the gearing accuracy of manufacturing (table 3.5), where ω ^g is the angular velocity of the gear.

The dynamic load factor K_HV is determined according to table 3.6.

Table 3.5