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When the spiral angle B
m = 0, the bevel gear is called a Zerol bevel gear. The calculation equations of Table Figure 8-12 8-2 for Gleason straight bevel gears are applicable. They also should take care again of the rule of hands; left and right of a pair must be matched. is a left-hand Zerol bevel gear. Addendum Angle Fig. 8-12 Left-Hand Zerol Bevel Gear Example Pinion Gear Table 8-6 The Calculations of Spiral Bevel Gears of the Gleason System ItemNo. Symbol Formula Shaft Angle Outside Radial ModuleNormal Pressure AngleSpiral AngleNumber of Teeth and Spiral HandRadial Pressure AnglePitch DiameterPitch Cone AngleCone DistanceFace WidthAddendumDedendumDedendum AngleOuter Cone AngleRoot Cone AngleOutside Diameter Pitch Apex to CrownAxial Face WidthInner Outside Diameter 1 2 3 4 5 6 7 8 910111213141516 17181920 3 90° 320° 35° 20 (L) 40 (R)23.9568060 120 26.56505° 63.43495°67.0820420 3.4275 1.6725 2.2365 3.9915 1.90952° 3.40519° 3.40519° 1.90952° 29.97024° 65.34447° 24.65553° 60.02976° 66.1313 121.4959 58.4672 28.5041 17.3563 8.3479 46.1140 85.1224 m A
n B
m z
1 , z
2 A tan tan
–1 cos

(

–––––– A
n t B
m

)

d zm sin D –– +cos
–1

BEVEL GEARING - 11708 (

–––––––– tan 3
1 z
2 z
1 3

)

D
2 1 –––––– 2sin d R
2 e D
2 It should be less than R /3 or 10 m b
e h
a 1 1.700 m – h
a 2 h 0.390 0.460 m + ––––––––– m
a 2

(

–––––––– z
2 cos D
1 z
1 cos D
2

)

h
f 1.888 m – h
a Q
–1 f tan ( h
f /
R e ) Q
a 1 Q
f 2 Q
a 2 Q
f 1 D
a D +
a D
f D – Q
f d
a d + 2h
a cos D XX R
e cos D – h
a sin D –––––– cos b cos D
a b Q
a d 2 d – ––––––– cos b sin D
a i a Q
a SECTION 9 WORM MESH The worm mesh is another gear type used for connecting skew shafts, usually 90°. See Figure 9-1 . Worm meshes are characterized by high velocity ratios. Also, they offer the advantage of higher load capacity associated with their line contact in contrast to the point contact of the crossed-helical mesh. Fig. 9-1 Typical Worm Mesh 8.5.4 Gleason Zerol Spiral Bevel Gears

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