Worms and Worm Gears3 ME350— .Disadvantage: >Relatively low efficiency compared to other gear sets. .The relative motion at the teeth is sliding rather than rolling >Generates significant heat. .Heat transfer from the gearbox,rather than the stresses in the teeth,can limit a worm set's life. .The oil temperature in the mesh should be kept below about 200 degree Fahrenheit for long tooth life. 26
ME 350 26 Worms and Worm Gears 3 •Disadvantage: ¾Relatively low efficiency compared to other gear sets. •The relative motion at the teeth is sliding rather than rolling ¾Generates significant heat. •Heat transfer from the gearbox, rather than the stresses in the teeth, can limit a worm set’s life. •The oil temperature in the mesh should be kept below about 200 degree Fahrenheit for long tooth life
Worms and Worm Gears3 ME350 worm gear Worm gear (pinion) wor 你 Worm Worm t Wormgear Wormgear 27
ME 350 27 Worms and Worm Gears 3
Gear Trains ME350 .Gear trains are mechanisms which are very widely used to transfer and transform rotational motion. .Rotary motion can be transferred from one shaft to another by a pair of rolling cylinders >However there is a possibility of slip. .Transfer of motion between two cylinders depends on the frictional forces between the two surfaces of contact. .Slip can be prevented by addition of meshing teeth to two cylinders >Result is a pair of meshed gear wheels. 28
ME 350 28 Gear Trains •Gear trains are mechanisms which are very widely used to transfer and transform rotational motion. •Rotary motion can be transferred from one shaft to another by a pair of rolling cylinders ¾However there is a possibility of slip. •Transfer of motion between two cylinders depends on the frictional forces between the two surfaces of contact. •Slip can be prevented by addition of meshing teeth to two cylinders ¾Result is a pair of meshed gear wheels
Gear Trains ■ ME350 .Action equivalent to action of two smooth wheels rolling on each other without slipping >With diameter of two wheels equal to pitch diameters of two gears. (a) (b) Transfer of rotatory motion:(a)rolling cylinders, (b)meshed gear wheels 29
ME 350 29 Gear Trains •Action equivalent to action of two smooth wheels rolling on each other without slipping ¾With diameter of two wheels equal to pitch diameters of two gears
Tooth Nomenclature5 ME350 Face width Top land Addendum circle Face Addendum Circular pitch Tooth Width Pitch Dedendum thickness Flank of space circle Bottom land Clearance 《《 Fillet radius Dedendum circle Clearance 30 circle
ME 350 30 Tooth Nomenclature 5