Spur and Helical Gears

Who is credited with introducing the foundational equation for estimating bending stress in gear teeth in 1892, which considers the tooth form?

In the AGMA stress equations, which factor is used only in the pitting resistance equation and accounts for surface finish, residual stress, and plastic effects?

What is the primary purpose of the Hardness-Ratio Factor (CH) in the AGMA equations for gear analysis?

According to the Barth equation for a gear with a cast iron, cast profile, what is the velocity factor Kv if the pitch-line velocity V is 900 feet per minute?

What type of failure, which is a form of wear due to lubrication failure, is distinguished from pitting in the discussion of surface durability?

In the AGMA methodology, how should the safety factor for pitting (SH) be defined to make it linearly comparable to the bending safety factor (SF)?

For a through-hardened steel gear of grade 2, calculate the gear bending strength (St) in psi, given a Brinell hardness (HB) of 250. The relevant formula is St = 102 HB + 16 400 psi.

What is the gear contact strength (Sc) in psi for a grade 1 through-hardened steel gear with a Brinell hardness (HB) of 300, using the formula Sc = 322 HB + 29 100 psi?

The AGMA factor J (Bending-Strength Geometry Factor) for spur and helical gears is a modification of the Lewis form factor Y. What two other factors are included in its calculation according to Equation (14-20)?

What is the AGMA definition for the face-contact ratio (mF) for helical gears?

For what range of oil or gear-blank temperatures can the Temperature Factor (KT or Y-theta) be taken as 1.0?

What is the recommended value for the Rim-Thickness Factor (KB) when the backup ratio (mB) is greater than or equal to 1.2?

The AGMA strengths for bending and contact stress are based on a standard number of load cycles and reliability. What are these standard values?

What is the reliability factor KR for a requirement of fewer than one failure in 10,000, according to Table 14-10?

The dynamic factor Kv is calculated based on a quality number Qv. Using the formula B = 0.25 * (12 - Qv)^(2/3), what is the value of B for a gear with a quality number Qv of 8?

What is the recommended range for the face width (F) of spur gears as a general rule?

The load-distribution factor Km is composed of several sub-factors. Which component, Cpm, accounts for the pinion proportion?

For a nitrided through-hardened steel gear of grade 2, what is the gear bending strength (St) in psi for a material with a core Brinell hardness (HB) of 300? The relevant formula is St = 0.749 HB + 110 MPa, which is not directly usable. The figure must be referenced. Figure 14-3 shows St = 108.6 HB + 15 890 psi.

What is the AGMA recommendation for the allowable bending strength (St) value when dealing with two-way (reversed) loading, such as in an idler gear?

For a gear set with a quality number Qv = 11, what is the maximum recommended pitch-line velocity in ft/min? Use the formulas A = 50 + 56(1 - B), B = 0.25(12 - Qv)^(2/3), and (Vt)max = [A + (Qv - 3)]^2.

What is the primary physical interpretation of the AGMA elastic coefficient, Cp (or ZE)?

The load-distribution factor, Km, is calculated as Km = 1 + Cmc(Cpf * Cpm + Cma * Ce). For a gear set with uncrowned teeth, what is the value of the load correction factor, Cmc?

Calculate the value of A' for the hardness-ratio factor (CH) when a pinion with Brinell hardness HBP of 300 is mated with a gear of hardness HBG of 200. The applicable formula is A' = 8.98(10^-3)(HBP/HBG) - 8.29(10^-3).

The stress-cycle factor for bending strength, YN, is used to modify the gear strength for lives other than 10 million cycles. For a gear made of 160 HB steel, what is the formula for YN for a number of load cycles (N) between 10^3 and 3x10^6?

What is the primary reason that a designer might choose to use a harder pinion than the gear in a through-hardened gearset?

In the context of the AGMA Stress Equations, what do the symbols 'sat' and 'sac' represent?

What are the two fundamental failure modes that the AGMA stress equations are designed to analyze for spur and helical gears?

Calculate the reliability factor KR for a gear design requiring a reliability of 0.995. Use the formula KR = 0.50 - 0.109 * ln(1 - R), which is valid for 0.99 <= R <= 0.9999.

For a spur gear, what is the value of the load-sharing ratio (mN)?

What is the surface-strength geometry factor I for a spur gear set where the pinion has 17 teeth, the gear has 52 teeth, the transverse pressure angle is 20 degrees, and the load sharing ratio is 1?

What is the primary role of the Overload Factor (Ko) in the AGMA stress equations?

For a commercial, enclosed gear unit, what value of the mesh alignment factor (Cma) would be selected from Figure 14-11 for a face width (F) of 2.0 inches?

In the original Lewis equation, the Lewis form factor 'y' is related to the AGMA form factor 'Y' by which substitution?

What is the face-contact ratio (mF) for all spur gears?

For a gear with an AGMA quality number (Qv) of 5, calculate the dynamic factor (Kv) if the pitch-line velocity is 1000 ft/min. Use the formulas A = 50 + 56(1 - B) and B = 0.25(12 - Qv)^(2/3), and Kv = ((A + sqrt(V))/A)^B.

Which factor in the AGMA equations is intended to adjust the estimated bending stress to account for the potential for fatigue failure to occur through the gear rim rather than the tooth fillet in thin-rimmed gears?

What is the primary difference in how the AGMA analysis treats life predictions for cast-iron gears compared to steel gears?

The Lewis form factor Y for a 20-degree full-depth tooth is 0.296 for a 16-tooth gear. What is the value of Y for a 20-tooth gear according to Table 14-2?

According to the AGMA design of a gear mesh outlined in Section 14-19, what is typically the first design decision made after all the 'a priori' decisions (function, tooth system, etc.) are established?

For a steel-on-steel gear pair with Poisson's ratio of 0.30 and a Young's Modulus of 30 x 10^6 psi for both, what is the value of the elastic coefficient Cp in units of sqrt(psi)?

What is the relationship between the normal base pitch (pN), the normal circular pitch (pn), and the normal pressure angle (phi_n)?

The AGMA factor Ks can be viewed as incorporating Lewis's geometry into which other factor from fatigue analysis?

For a gear with a life goal of 10^9 cycles, what is the stress-cycle factor for pitting resistance (ZN)? The relevant formula is ZN = 1.4488 * N^(-0.023).

What is the value of the overload factor (Ko) for a gear drive with a uniform power source (e.g., electric motor) and a driven machine with moderate shock (e.g., reciprocating pump)?

For a steel gear, what is the repeated-use gear bending strength (St) in psi for a material with a surface hardness of 55,000 psi according to Table 14-3?

In the AGMA design process, why might a designer choose a material like Nitralloy 135M and nitride the gears?

What is the AGMA definition of the gear ratio (mG)?

For a steel pinion with a normal diametral pitch (Pd) of 10 teeth/in, what is the calculated size factor for bending (Ks) using the formula Ks = 0.4867 + 0.2132/Pd, which is valid for 0.5 <= Pd <= 16?

When comparing the results of Example 14-4 (spur gear) and Example 14-5 (helical gear), which were analyzed under nearly identical circumstances, what was the primary reason for the helical gearset having larger factors of safety?

According to the analysis in Example 14-6, if a 300-Brinell, 18-tooth, grade 1 steel pinion is to have the same bending factor of safety as its mating 64-tooth gear, what is the required Brinell hardness of the gear?