Oct 23, 2012

# Comparison of Gear Efficiencies - Spur, Helical, Bevel, Worm, Hypoid, Cycloid

Comparing efficiencies of different gear types across various reduction ratios will help us to make right gearbox selection for our applications. Please note that these efficiency values are for general guideline and refer manufacturers catalogue for more accurate values.

## Gear Efficiency Comparison Table

 No Type Normal Ratio Range Efficiency Range 1 Spur 1:1 to 6:1 94-98% 2 Straight Bevel 3:2 to 5:1 93-97% 3 Spiral Bevel 3:2 to 4:1 95-99% 4 Worm 5:1 to 75:1 50-90% 5 Hypoid 10:1 to 200:1 80-95% 6 Helical 3:2 to 10:1 94-98% 7 Cycloid 10:1 to 100:1 75% to 85%

## 1. Spur Gear Efficiency

Spur gearing is a parallel shaft arrangement, and these gears can achieve much higher efficiencies compared to other gear types. Its efficiency varies from 94% to 98% with lower gear ratios.

## 2. Straight Bevel Gear Efficiency

Straight bevel gearing is similar to spur gearing with perpendicular shaft arrangement. Like spur gearing these gears also only can handle lower gear ratios with higher efficiencies (93% to 97%).

## 3. Spiral Bevel Gear Efficiency

Because of tooth shape and contact spiral bevel having less noise and vibrations compared to straight bevel gears, and thus having better efficiency (95% to 99%).

## 4. Worm Gear Efficiency

Worm gear efficiency varies significantly when lead angle, friction factor and gear ratio changes.

### Worm Gear Efficiency Calculation

Use the  following gear efficiency equation to calculate efficiency of worm gears.

Where f is the coefficient of friction for worm gears normally ranges from 0.06 to 0.02, p the pitch of the worm thread and r the mean radius of the worm.

## 5.Hypoid Gear Efficiency

The efficiency of a hypoid gear is around 80-95% and can achieve very high gear ratios up to 200:1.

## 6. Helical Gear Efficiency

Helical gears can run with very high pitch line velocity and can achieve much higher efficiencies (94%-98%) with maximum gear ratios up to 10:1.

## 7.Cycloid Gear Efficiency

These gears can work in very high efficiencies at relatively high gear ratios above 30:1 and under normal working conditions cycloid gearing efficiency ranges from 75% to 85%.