Cobra CM-4008/36 Multirotor Motor, Kv=400

Cobra Brushless Multirotor Motors offer performance and value for Your RC Models. They are built from high quality components, and are designed to give years of top-level performance. All Cobra Motors are shipped in a custom designed package that features protective foam on all sides, with separate compartments to protect the motor and accessory pack.

The Cobra CM-4008 series motors have a 4.0mm motor shaft for extra strength, as well as oversize ball bearings to support the shaft and provide a long life. The stators are made with 0.20mm laminations for maximum efficiency and minimum Eddy Current losses. Since these motors are typically soldered directly to the speed controller for reliability, and often need to be cut to length for the specific installation, the CM-4008 motors come without bullet connectors and feature extended pre-tinned motor leads that are 17 inches (430mm) long. These motors also have 3mm threaded holes in a 19x25mm pattern on the back plate for easy installation on your model.

The CM-4008 series motors allow for multiple propeller mounting options. They have a set of four of 3mm threaded holes located on a 12mm circle for directly mounting carbon fiber props that use two 12mm spaced holes, or to mount the included bolt-on style prop adapter. This prop adapter has an M6x1.0mm thread for holding traditional multirotor props that have a 6mm center hole. The included prop washer and nylon insert prop nut provides a solid attachment for your propellers that will not loosen up and slip during use.

Included with every Cobra CM-4008 Series Motor is a complete accessory package which contains the following items:

● Two M3x10mm Prop Mounting Screws
● Four M3x8mm Prop Adapter Mounting Screws
● Machined Aluminum Bolt-on Style Prop Adapter
● Machined Aluminum Prop Washer
● Locking Prop Nut with Nylon Insert
● Machined Aluminum Top Plate for Carbon Fiber Props


Click here for the Cobra CM-4008/36 Propeller Data Chart

Cobra CM-4008/36 Motor Specifications
Stator Diameter	40.0 mm (1.574 in)
Stator Thickness	8.0 mm (0.318 in)
Number of Stator Slots	24
Number of Magnet Poles	22
Motor Wind	36 Turn Wye
Motor Kv Value	400 RPM per Volt
No Load Current (Io)	0.52 Amps @ 21 Volts
Motor Resistance (Rm) per Phase	0.075 Ohms
Motor Resistance (Rm) Phase to Phase	0.151 Ohms
Maximum Continuous Current	18 Amps
Max Continuous Power (5-cell Li-Po)	330 Watts
Max Continuous Power (6-cell Li-Po)	400 Watts
Motor Weight	106 grams (3.74 oz.)
Outside Diameter	45.5 mm (1.791 in.)
Motor Shaft Diameter	4.00 mm (0.157 in.)
Prop Shaft Diameter	6.00 mm (0.236 in.)
Motor Body Length	23.9 mm (0.941 in.)
Overall Shaft Length	33.5 mm (1.319 in.)
Motor Timing	5-10 degrees
PWM Frequency	8 KHz to 20Khz

Motor Performance Graphs

The following downloadable PDF files show the performance data curves of the Cobra CM-4008/36 motor, over its entire throttle range, with a variety of propellers. These graphs can be downloaded and printed to use as a reference for calculating power requirements at specific thrust levels, and enable the user to calculate flight times, current draw and other motor parameters.

5-Cell Li-Po Power

Cobra CM-4008/36 Performance Data with APC 14x5.5-MR prop on 5S Li-Po

Cobra CM-4008/36 Performance Data with APC 16x5.5-MR prop on 5S Li-Po

Cobra CM-4008/36 Performance Data with GemFan 15x4.5-MRW prop on 5S Li-Po

Cobra CM-4008/36 Performance Data with GemFan 16x4.5-MRW prop on 5S Li-Po

Cobra CM-4008/36 Performance Data with RC-Timer 14x5.5-CF prop on 5S Li-Po


6-Cell Li-Po Power

Cobra CM-4008/36 Performance Data with APC 13x5.5-MR prop on 6S Li-Po

Cobra CM-4008/36 Performance Data with APC 14x5.5-MR prop on 6S Li-Po

Cobra CM-4008/36 Performance Data with GemFan 14x4.5-MRW prop on 6S Li-Po

Cobra CM-4008/36 Performance Data with RC-Timer 12x5.5-CF prop on 6S Li-Po

Cobra CM-4008/36 Performance Data with RC-Timer 13x5.5-CF prop on 6S Li-Po


Performance Graph Instructions

This downloadable PDF file shows the step by step process to use for interpreting the data shown in the Motor Performance Graphs. By following this procedure, you can determine how to select a proper motor for a Multirotor aircraft, as well as calculate required power levels, determine overall prop efficiency and calculate expected flight times based on the battery size that is used. This document can be printed out and saved as a valuable reference tool to keep in your workshop for future use as well.

Motor Performance Graph Instructions



Top View




Items Included in Hardware Package


NOTE: Cross Mounts are NOT included with any multirotor motors.


For more information about this product and the rest of the Cobra Motors product line, please check out the Cobra Brushless Motors web site.