Herringbone Gears have the advantage of transferring power smoothly because more than two teeth will be in mesh at any moment in time. Their advantage over the helical gears is that the side-thrust of one half is balanced by that of the other half. This means that herringbone gears can be used in torque gearboxes without requiring a substantial thrust bearing. Because of this herringbone gears were an important step in the introduction of the steam turbine to marine propulsion.
The logo of the car maker Citroen is a graphic representation of a herringbone gear, reflecting André Citroën’s earlier involvement in the manufacture of these gears. Early Mors and Citroen cars used a herringbone bevel gear final drive in the rear axle. Panhard Dyna X and successor cars (1948-67) used double helical gears in the transaxle and for t he camshaft timing gears in the engine. You can see a Citroen Type A final drive herringbone pinion and crownwheel.