From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Calculations and diagrams for gear hobbing, including setup, modification, and teeth contact.
| Identifier | ExFiles\Box 136\5\ scan0345 | |
| Date | 15th January 1940 guessed | |
| TO FIND THE EXTREME END POSITION FOR SETTING A HOB WHEN CUTTING SPUR GEARS. Fig. #5 Rь = BASE RAD. R = PITCH RAD. R₀ = OUTSIDE RAD. C = DISTANCE BELOW PITCH LINE ON HOB TO LAST POINT OF CONTACT Φ = PRESSURE ANGLE Cos α = Rь / R₀ C = R₀ Cos(α - Φ) - R D = R₀ Sin(α - Φ) *F MUST BE SUBSTANTIALLY LARGER THAN D TO PROVIDE PROPER STRENGTH OF LAST TOOTH --- TO FIND START OF MODIF. ON HOB FOR KNOWN MODIF. OF GEAR Fig. #6 Φ = PRESSURE ANGLE R = PITCH RAD Rь = BASE RAD. A = RAD. TO START OF MODIFICATION ON GEAR H = DISTANCE BELOW PITCH LINE WHERE SECOND ANGLE STARTS ON HOB FOR MODIFICATION OF GEAR Cos β = Rь / A δ = β - Φ H = A · COS δ - R --- TO FIND Nº OF TEETH IN CONTACT Fig #7 Φ = PRESSURE ANGLE C = CENTER DISTANCE R₁ = PITCH RAD. OF PINION R₂ = PITCH RAD. OF GEAR (Rь)₁ = BASE RAD. OF PINION (Rь)₂ = BASE RAD. OF GEAR (R₀)₁ = OUTSIDE RAD. OF PINION (R₀)₂ = OUTSIDE RAD. OF GEAR Pₙ = NOR. CIR. PITCH AT BASE Y = Nª OF TEETH IN CONTACT Y = (√(R₀)₁² - (Rь)₁² + √(R₀)₂² - (Rь)₂² - C · Sin Φ) / Pₙ For External Gears | ||