Approximate value of mechanical transmission efficiency

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Approximate values of mechanical transmission efficiency
Category | Transmission type | Efficiency η
Cylindrical gear transmission | Gears with excellent running-in quality, 6th-grade precision or higher, lubricated with thin oil | 0.98–0.995
General gears with 8th-grade precision, lubricated with thin oil | 0.97
Gears with 9th-grade precision, lubricated with thin oil | 0.96
Open gear transmissions with machined teeth, lubricated with dry oil | 0.94–0.96
Open gear transmissions with cast teeth | 0.90–0.93
Bevel gear transmission | Gears with excellent running-in quality, 6th- and 7th-grade precision, lubricated with thin oil | 0.97–0.98
General gears with 8th-grade precision, lubricated with thin oil | 0.94–0.97
Open gear transmissions with machined teeth, lubricated with dry oil | 0.92–0.95
Open gear transmissions with cast teeth | 0.88–0.92
Worm gear transmission | Self-locking worms | 0.40–0.45
Single-start worms | 0.70–0.75
Double-start worms | 0.75–0.82
Three- and four-start worms | 0.82–0.92
Torus worm gear transmission | 0.85–0.95
Belt transmission | Open transmission using flat belts without tensioning wheels | 0.98
Open transmission using flat belts with tensioning wheels | 0.97
Crossed flat belt transmission | 0.90
V-belt transmission | 0.95
Synchronous belt transmission | 0.96–0.98
Chain transmission | Welded chains | 0.93
Plate-type link chains | 0.95
Roller chains | 0.96
Serrated chains | 0.98
Sliding bearings | Poor lubrication | 0.94
Normal lubrication | 0.97
Excellent lubrication (pressure lubrication) | 0.98
Liquid friction | 0.99
Rolling bearings | Ball bearings, lubricated with thin oil | 0.99
Roller bearings, lubricated with thin oil | 0.98
Friction wheel transmission | Flat friction wheels | 0.85–0.96
Sagged friction wheels | 0.98–0.90
Pulleys | 0.95
Couplings | Floating couplings | 0.97–0.99
Gear couplings | 0.99
Elastic couplings | 0.99–0.995
Universal couplings (α≤3°) | 0.97–0.98
Universal couplings (α＞3°) | 0.95–0.97
Half-shaft couplings | 0.97–0.98
Composite gear sets | Sliding bearings | 0.98–0.90
Rolling bearings | 0.99–0.95
Conveying rollers | 0.96
Reducers | Single-stage cylindrical gear reducers | 0.97–0.98
Two-stage cylindrical gear reducers | 0.95–0.96