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Unformatted text preview: 99 Chapter 7 Helical Gears 7.1 A pair of parallelaxis helical gears has 14½° normal pressure angle, diametral pitch of 6 teeth/in, and 45° helix angle. The pinion has 15 teeth, and the gear has 24 teeth. Calculate the transverse and normal circular pitch, the normal diametral pitch, the pitch diameters, and the equivalent tooth numbers. 2 15 teeth N = , 3 24 teeth N = , 6 teeth/in t P = , cos 8.485 teeth/in n t P P ψ = = , Ans. 0.523 6 in/tooth t t p P π = = , cos 0.370 2 in/tooth n t p p ψ = = , Ans. ( 29 2 2 2 1.250 in t R N P = = , ( 29 3 3 2 2.000 in t R N P = = , Ans. 3 2 2 cos 42.43 teeth e N N ψ = = , 3 3 3 cos 67.88 teeth e N N ψ = = Ans. 7.2 A set of parallelaxis helical gears are cut with a 20° normal pressure angle and a 30° helix angle. They have diametral pitch of 16 teeth/in and have 16 and 40 teeth, respectively. Find the transverse pressure angle, the normal circular pitch, the axial pitch, and the pitch radii of the equivalent spur gears. 2 16 teeth N = , 3 40 teeth N = , [ ] 1 tan tan cos 22.796 t n φ φ ψ = = ° , Ans. 16 teeth/in t P = , 0.196 4 in/tooth t t p P π = = , cos 0.170 0 in/tooth n t p p ψ = = , tan 0.340 1 in/tooth x t p p ψ = = , Ans. ( 29 2 2 2 0.500 in t R N P = = , ( 29 3 3 2 1.250 in t R N P = = , 2 2 2 cos 0.667 in e R R ψ = = , 2 3 3 cos 1.667 in e R R ψ = = Ans. 7.3 A parallelaxis helical gearset is made with a 20° transverse pressure angle and a 35° helix angle. The gears have diametral pitch of 10 teeth/in and have 15 and 25 teeth, respectively. If the face width is 0.75 in, calculate the base helix angle and the axial contact ratio....
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 Spring '11
 Jung
 gear, Helix Angle

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