These motors are by far the most popular ones in the 22mm series. They are designed to provide the maximum performance in 400 to 480 size electric helicopters. Because these motors are so popular, we will spend a little more time here giving specific application notes on each one. In addition to use in Helicopters, the HK-2221 series are also used very successfully in Airplane applications such as Pylon Racers and Hot-Liners that require a high power, high RPM motor. More recently, they have also become very popular for powering 65 to 75mm ducted fan units that are capable of utilizing a motor that is 28mm in diameter. For the purpose of this article, we will stick to Helicopter applications.
For operation on 3 Li-Po cells, there are 3 different motors that can be used, the HK-2221-6, -8 and -10 models. The most versatile model is the HK-2221-8 motor. This motor can utilize a wide range of pinion gears, and this allows the motor to "Grow" with the pilot as their flight skills improve from beginner up through moderate 3D type flying. Here are some common applications of the HK-2221-8 motor. These numbers assume a main gear with 150 teeth, which is very common for the 450 size machines.
HK-2221-8 with an 11 tooth pinion, providing a head speed of around 2800 RPM: This is good for entry level flying, hover practice and basic aerobatics
HK-2221-8 with a 12 tooth pinion, providing a head speed of around 3050 RPM: This is good for advanced Sport flying and beginning to intermediate 3D Flight.
HK-2221-8 with a 13 tooth pinion, providing a head speed of around 3300 RPM: This gives enough power for just about any 3D maneuvers, but still allows the use of a 20C 2200mah battery back, without pulling too much current.
The next most popular motor is the HK-2221-6 motor. This is THE motor for people that want maximum performance from their 450 class helicopter. Use of this motor requires a minimum of a 25C 2200mah battery and a 55 amp ESC, and carbon fiber blades are a MUST. Don’t even try running wood blades with this motor! The Scorpion 60 amp Heli Edition ESC is also a very good choice for this motor for pilots that want an ESC that has a 6.0 volt BEC circuit for more speed and torque from their servos. Here are a couple common set-ups for this motor:
HK-2221-6 with a 10 tooth pinion, providing a head speed of around 3150 RPM: This is a good place to start with this motor. You have all the power needed for just about anything except for the most extreme 3D type flying.
HK-2221-6 with an 11 tooth pinion, providing a head speed of around 3400 RPM: This will get you all the power that most helicopters can handle, and will allow for any type of 3D flying out there.
If you do try to go to a 12 tooth pinion with this motor, you will get a head speed approaching 3700 RPM. This is bordering on insanity, but some pilots will try it. There are only a couple helicopters on the market that will stay together
