# How To Find Out The Gear Ratio Of The Gearbox

## Video: How To Find Out The Gear Ratio Of The Gearbox

The gear ratio is one of the main characteristics of any gearbox - a mechanism for transmitting torque. The gear ratio is greater than one in reduction gears and less than one in increasing gears, called multipliers.

## Necessary

• - calculator;
• - locksmith's set of keys;
• - roulette;
• - tachometer.

## Instructions

### Step 1

By the type of transmission, gearboxes are classified as follows: cylindrical, bevel, worm, planetary and combined. According to the transmission of gearing, gear, hypoid, chain, belt, screw, wave transmission and frictional transmissions are distinguished. For any type of gearbox, the gear ratio is equal to the ratio of the rotational speeds (or angular velocities) of the drive shaft and the driven shaft.

### Step 2

For gear, belt, chain and worm gears, the gear ratio can be determined by the type of gearbox elements. Open the gearbox cover in order to gain access to its elements.

### Step 3

Gear Count the number of teeth N of the driven gear and the number of teeth Q of the drive gear. Divide N by Q. The resulting value is the gear ratio (number) of the gearbox.

### Step 4

Belt Drive Measure the diameters of the drive and driven pulley. The ratio of the larger diameter (leading) to the smaller one (driven) is the gear ratio of the gearbox with a belt drive.

### Step 5

Chain Drive Count the number of teeth on the drive (large) and driven (small) sprocket. The gear ratio of the chain drive gearbox is equal to the ratio of the number of teeth of the large sprocket to the small one.

### Step 6

Worm Gear Determine the number of starts J on the worm and the number of teeth G on the worm wheel. The ratio of G to J is the gear ratio of the worm gearbox.

### Step 7

The gear ratio can be calculated from the rotational speed of the drive and driven shafts. Measure with a tachometer the speed N of the drive shaft - the one that is driven by the power plant (electric motor). It is equal to the rotational speed of the motor shaft.

### Step 8

Measure the number of revolutions n of the driven shaft - that which drives the working body.

### Step 9

Divide the drive shaft speed N by the driven shaft speed n. The resulting number is the gear ratio of this gearbox.