Chapter 15: Problem 2
What is the basic requirement of gear-tooth geometry?
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Chapter 15: Problem 2
What is the basic requirement of gear-tooth geometry?
These are the key concepts you need to understand to accurately answer the question.
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State the fundamental law of conjugate gear-tooth action.
A spur gear reducer has an 18-tooth pinion driven 1500 rpm by an electric motor and a 36 -tooth gear that drives a load involving "moderate shock." A life of \(10^{6}\) pinion revolutions is required, and the transmitted load, \(F_{t}\), is \(100 \mathrm{lb}\) (this figure includes a safety factor of 2 ). Conditions are such that \(K_{m}=1.8\) and \(k_{t}=1\). It is proposed that standard \(20^{\circ}\) full-depth gears be used, with both pinion and gear teeth being cut with a low-cost, average-quality, form-cutting process from steel of \(235 \mathrm{Bhn}\) for the gear and \(260 \mathrm{Bhn}\) for the pinion. Diametral pitch is to be 10 , and face width \(1.0\) in. Estimate the reliability with respect to bending fatigue failure.
A pair of mating spur gears with 6-mm modules and \(0.35\)-rad pressure angles have 30 and 60 teeth. (a) Make a full-size drawing of the tooth contact region, showing (and labeling) (1) both pitch circles, (2) both base circles, (3) both root circles, (4) both outside circles, (5) pressure angle, (6) length of path of contact, (7) both angles of approach, and (8) both angles of recess. (b) Using values scaled from your drawing, state or calculate numerical values for (1) length of path of contact, (2) angles of approach, (3) angles of recess, and (4) contact ratio.
Sketch in three dimensions, two adjacent involute gear teeth (using about a 1 in. tooth thickness), and identify and label the following: face width, top land, pitch circle, circular pitch, width of space, face, flank, bottom land, tooth thickness, addendum circle, dedendum circle, clearance circle (mating teeth extend to this circle), addendum, dedendum, whole depth, working depth, clearance, and filet radius.
Write definitions for the terms spur gears, involute, involute of the circle, base circle, conjugate gear-tooth action, line of centers, point of contact, pitch point, base circles, pitch circles, center distance, pressure angle, line of action, involute tooth, pinion, and gear.
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