The low cost glider type RC planes are driven by small brushless DC coreless motors (its coil is wound on itself and not on iron – there is no iron core in the rotor). They are usually 3.7V (can go up to 4.2V). Very importantly, they can and will get overheated since there is no heatsink nor cooling fan for them!
When there is a need to replace them, you want to know there are variations in the motor size, length, shaft diameter (even same size motor can have different shaft diameters!) and rotation directions (it is either red/blue wires or white/black wires). Different motors need to work with different prop too (due to difference in motor rotation directions). It is getting popular for different props to be colored differently for easy identification.
Replacement is straightforward if the size gives a perfect fit. You simply unplug the bad motor and cut the wires, then put in a new one and solder the wires. Keep in mind, motors on both sides should rotate in exact opposite directions (how you wire them will make a difference here). You want to hold the plane and test to see if both “blow” towards the end and not the other way around.
You need to know that for the coreless motors, clockwise motors use red and blue wires while anti-clockwise motors use black and white wires. Make sure the motor and prop combination is pushing air to the back (if the prop is facing the back like most Jet Fighter gliders).
The 3 most common variations are 614, 716 and 720.
614 means motor diameter 6mm, motor length excluding shaft 14mm.
716 means motor diameter 7mm, motor length excluding shaft 16mm.
720 means motor diameter 7mm, motor length excluding shaft 20mm.
For 614, shaft diameter is mostly 0.8mm. For 716 and 720 it can be either 0.8mm or 1mm.
720 motors can be upgraded to 820 for even more power. 820 means motor diameter 8mm, motor length excluding shaft 20mm.
Also keep in mind, these motors have no cooling and they will get overheated! Give them enough rest after each fly!
If there is a need to connect a replacement motor to the plane’s control unit and the wire colors do not match, keep in mind that red should be wired with black and blue should be wired with white. The motor will not spin in the proper direction if you get this wrong. And use hot glue to protect the wire connections (so to secure them).
Glider running on 614 motors:
Glider running on 820 motors: