This is 4th generation of TMCR - twin motor contra rotor. First generation was successfully build and tested in 2015. Only a small initial series of 20 motors was built. All of them are still in service!
Current design is superior in terms of weight, power and efficiency. Stator and rotor design is carefully optimized with FEMM software to obtain maximum torque density. This is the lightest outrunner in its class.
TMCR’21 uses standard Falcon propellers. Ultra light 3d printed spinner used with TMCR’21 may be printed with any diameter to match the user plane. Drive is controlled with two dedicated D3 F3A ESCs, which are smaller and lighter version of standard well known D3 controllers. Max current measured in flight 97A, max rpm in flight 4450 (limited with ESC to this value), max rpm in vertical flight with full power 4250 (with a pair of 23x20). Weight of the bare drive is 585g. With a pair of 23x20 current is distributed equally to both motors and this is the recommended setup. With light monoplane a pair of 22x20 is more than enough power.