Which of the following gear system have minimum axial thrust?

Option 2 : Double helical gears

Explanation:

Helical Gear:

[ alt="helical" src="https://storage.googleapis.com/tb-img/production/19/01/helical.PNG" style="width: 200px; height: 208px;">

• They have curved teeth, each being helical in shape.
• Two mating gear have the same helix angle but have teeth of opposite hands.
• At the beginning of the engagement, contact occurs only at the point of the leading edge of the curved teeth. As the gear rotates, the contact extends along a diagonal line across the teeth. Thus load application is gradual, low impact stresses and reduction in noise.
• Helical gears have the disadvantages of having end thrust as there is a force component along the gear axis. The bearing and mounting must be able to withstand the thrust load.

Double Helical Gear:

• A double helical gear is equivalent to a pair of helical gear secured together, one having a right-hand helix and the other has a left-hand helix. The teeth of the two rows are separated by a groove i.e. used for tool run out.
• In double-helical gear, the helix angle is 45°.
• Axial thrust occurs in the case of single helical gears eliminated in double helical gears. This is because the axial thrust of two rows of teeth cancels each other.
• These gears can be run at high speeds with less noise and vibrations.

[ alt="F1 Ashik Madhu 17.09.20 D7" src="//storage.googleapis.com/tb-img/production/20/09/F1_Ashik_Madhu_17.09.20_D7.png" style="width: 155px; height: 166px;">

[ alt="spur" src="https://storage.googleapis.com/tb-img/production/19/01/spur.PNG" style="width: 180px; height: 256px;">

Bevel Gear: Bevel gears are used to transmit motion between shafts at various angles to each other and their axis intersects each other. The teeth profile may be straight or spiral.