ch 4 gears.docx - Supplemental ch 4 gears Calculations Torque Number of revs are constant Overload SF = NS oil Service factor = effect HP level = HP SF

# ch 4 gears.docx - Supplemental ch 4 gears Calculations...

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Supplemental ch 4: gears Calculations: Torque * Number of revs are constant Overload SF = NS + oil Service factor = effect HP level = HP * SF Velocity ratio = driver speed / driven speed = # teeth larger gear / # teeth pinion Gear ratio = # of teeth driven / # of teeth driver Torque ratio = torque at driven / torque applied to driver = driven dia/driver dia Overall speed ratio for idlers/speed reducers = GR(1) x GR(2) = N(first) / N(last) Ratio of gear reducer = overall ratio/ drive ratio Actual torque = theo torque/ drive ratio Normal torque = actual torque x SF Max torque transmitted = ( 63025 x HP) / N Required motor HP = ( normal torque x thermal input HP) / thermal output torque Velocity ratio = gear ratio = torque ratio Maxium torque transmitted (in-lb) = (63025 x HP)/ N (rpm) Circular pitch – p = (pi(d))/T P = circular pitch (distance between 2 teeth), d = pitch dia (dia of pitch circle), T = # of teeth Diametrical Pitch = # teeth/ pitch circle dia Module – m = d/T Terms to know: Driving gear – gear supplying effort Driven gear – moving the load Pitch cylinders – imaginary friction cylinders, transmit the same motion as the pair of gears by rolling together Pitch circle – circle corresponding to a section of the equivalent pitch cylinder by a plane normal to wheel of axis Pitch diameter – diameter of pitch cylinder Pitch surface – surface of pitch cylinder Pitch point – point of contact of the pitch circles Pressure angle – angle between the normal to the tooth profile at the pitch circle and tangent to the pitch circle (the larger the angle, the higher the load capacity, but lower speed) Line of centers – line through center of rotation of a pair of mating gears Pinion – smaller, usually the driver gear Addendum – radial height of the teeth above the pitch circle Addendum circle – circle passing through the tips of the teeth Dedendum – radial depth of the teeth below the pitch circle Dedendum circle (root circle) – circle passing through the roots of the teeth Clearance – radial diff between the addendum and dedendum of a tooth Full depth of teeth = addendum + dedendum Working depth of teeth – max depth to which a tooth penetrates into the tooth space of the mating gear Space width – width of the tooth space aliong the pitch circle Tooth thickness – thickness measured along the pitch circle Backlash – diff between space width and the tooth thickness along the pitch circle Face width – length of the tooth parallel to the gear axis Top land – surface of the top of the tooth  • • • 