How to improve speed by changing gears?

When I drive my RC car in the park, I often get surrounded by many children, who always cheer for the speed of the car. When I ask them, “Do you know how to get this car to higher speeds?” I usually get the answer: “Change to a more powerful battery!”

Obviously, even children know that a stronger power system will bring faster speed to RC cars. However, professional RC players can also achieve greater transmission ratios by changing gears, allowing the car to achieve greater speed without changing the electronic system.

The transmission ratio represents the ratio of the rotational speeds of the driving gear and the driven gear.

Transmission ratio=driving gear rotation speed/driven gear rotation speed=teeth number of driven gear/teeth number of driving gear

The maximum speed of an RC car is affected by two sets of gear ratios, the first being the Motor Pinion Gear and the Spur Gear, and the second being the Input Gear and the Main Diff Gear.

For Motor Pinion Gear and Spur Gear, their transmission ratio=teeth number of Spur Gear/teeth number of Motor Pinion Gear

For Input Gear and Main Diff Gear, their transmission ratio=teeth number of Main Diff Gear/teeth number of Input Gear

The product of the two sets of gear ratios is the final transmission ratio.

Without changing the electronic system and wheels, the lower of the final transmission ratio, the greater of the maximum speed of the RC car, the smaller of the torque;

The higher of the final transmission ratio, the lower of the maximum speed of the RC car, the greater of the torque;

However, not all gears can be properly combined. The power of the motor determines how large a gear can be driven, and two gears can only fit correctly when the module is the same.

Taking the carbon fiber version of AK-917 as an example, with the support of the original motor, the correct combination can only be achieved when Teeth Number of Pinion Gear + Teeth Number of Spur Gear（Adjustable Range）>97T

The carbon fiber version of AK-917 is originally equipped with a 40T Motor Pinion Gear, a 63T Spur Gear, a 13T Input Gear, and a 39T main diff gear. Without changing the gear and electronic system, it can reach a maximum speed of 86.2km/h;

At the same time, the carbon fiber version of AK-917 includes additional 34T、45T Motor Pinion Gear, 78T、52T Spur Gear. If the 45T Motor Pinion Gear and 52T Spur Gear are replaced, without changing the electronic system, the maximum speed can reach 117.5km/h;

If you replace the 45T Motor Pinion Gear and 52T Spur Gear, and use the F3660-2460KV upgraded motor and 6S battery, you can achieve a maximum speed of 220+km/h!

In summary, if you want to increase speed by changing gears, you need to pay attention to the following two points:

1. Pay attention to whether the selected two gears can match;
2. With the electronic system unchanged, the smaller of the final rotation ratio, the fasterofthe RC car’s maximum speed and the smaller of the torque;