Simply Airsoft Guns

In this post, we’ll be opening up an airsoft guns gearbox and learning the name of the gearbox parts.

If you’ve seen a gearbox for airsoft guns before you’ll know there’s quite a few gearbox parts that can appear very complicated. Unfortunately, building an airsoft gearbox is not as simple as 1-2-3, but becoming familiar with the parts will give you a strong understanding of how they function and how to identify possible problems.

The gears

At the bottom of the airsoft electric guns gearbox you’ll see the bevel gear which is driven by the motor coming up from the bottom of the gearbox. The bevel gears teeth are cut at a 45 degree (or ‘bevelled’) angle to give maximum friction between the gears and reduce slippage.

On top of the bevel gear you’ll see a small gear with several ridges cut into it. This gear is used with the anti-reversal latch (a piece of metal sprung against the casing) to prevent the motor from spinning in the wrong direction.

Connected to the bevel gear is the spur gear, a large flat gear which bridges the gap between the bevel gear and the piston, and specifies the correct torque ratio for the gearbox. The spur gear has two sets of teeth – the outer gears connect with the bevel gear and the inner gears connect with the sector gear.

The sector gear sits to the right of the spur gear and is so called because it only has a ’sector’ of teeth rather than teeth all the way round. The sector gear drives the piston backwards, releases it, and repeats the action on the next rotation.

The axels of all the gears are kept in line and spinning freely with bushings. Washers are also used to align the gears correctly.

The cylinder and piston

On top of the sector gear sits a long piece of plastic with a triangle pointing down – this is the tappet plate, which moves the nozzle (at the top right of the gearbox) backwards to allow a bb to be loaded in front of it. The tappet plate is also connected to a small spring which returns it to its original position between shots.

To the right of the sector gear is the trigger, which starts and stops the motor when pulled.

Sitting above the tappet plate is the cylinder and cylinder head. The cylinder holds the piston and intakes air through the nozzle as the piston is drawn back. When the piston is released, it compresses the air in the cylinder and forces it through the nozzle, creating a short sharp blast of air which propels the bb from your airsoft bb guns.

The piston is a cylindrical piece of plastic that sits inside the cylinder and forms an air tight seal using a rubber o-ring at the piston head. The piston has teeth along its length, allowing it to be drawn back by the sector gear and released.

At the top left of the gearbox you’ll see a large spring, used to push the piston back down the cylinder to compress the air quickly and return it to its original position. The spring is held against the casing and kept straight using a spring guide – a small metal cylinder that sits inside the side.

That’s it!

So there you have it. You can now identify the parts in an airsoft gearbox and have made the first step towards identifying problems in your own automatic airsoft guns.

Later in the series we’ll be looking at how to perform specific repairs and upgrades, so stay tuned!