An airsoft AEG's gears determine what kind of build the airsoft gun has an how the AEG performs. Torque builds and gears are chosen for field use, giving more range to players at the cost of RPS. Speed builds are often used by players in CQB environments where range is not as much an issue as getting quick shots.
Most airsoft gears come in a set of gears designed to work together and be in a specific ratio. These sets come in a drop in pack including the sector gear, spur gear and the bevel gear. A higher ratio gear set, or a torque gear set, will enable the motor to pull back a stronger spring at reduced speed since more turns of the gears will be required to fire. A gear set is considered a torque set if the ratio is above 18:1. Super and infinite torque sets exist that can get up to a 300:100 ratio. If the ratio is lover than 18:1 such as 16:1, then the gears are considered a speed set. Speed gears require less turns to fire but put a greater strain on the motor and have to use weaker springs. Original, stock, or standard type gear sets typically are near the 18:1 ratio and often come stock on most AEGs.
Finding Airoft Gear Ratios
To calculate a gear set's ratio, count the number of teeth on the bevel gear (ex. 30) and divide it by the number of teeth on the pinion gear (ex. 10) to get the first number (ex. 3), then count the number of teeth on the outer wheel of the spur gear (ex. 40) and divide it by the number of teeth on the small ring of the bevel gear (ex. 10) to get the second number (ex. 4). Then count the number of teeth on the small ring of the sector gear (ex. 30) and divide it by the number of teeth on the inner ring of the spur gear (ex. 20) to get the last number (ex. 1.5). Multiply the three values to get your ratio (ex. 3*4*1.5:1 = 18:1).
The pinion gear is compression fit to the end of the airsoft motor's axle. Some times the gear has a set screw to hold it in place, or locktite has been used to ensure a good connection. The pinion gear drives the bevel gear and comes in two varieties, full moon and half moon. Full moon pinion gears have a full opening and can be fit on to either half or full moon airsoft motor axles, but are designed for full moon. Half moon pinion gears have an opening shaped like a half moon and are more stable. To remove and install pinion gears and airsoft motor head tool is often required.
Airsoft Helical Gears
Some gears in airsoft use helical teeth. Helical teeth provide a more even pull than regular gear teeth and are thought to be quieter. Helical gears are easier on gearboxes and motors because of the even movement and it is very rare to break the individual teeth due to the design. Occasionally, the helical teeth gear sets require half tooth pistons in order to work properly.