Blade CP Tail Motor

Many Blade CP pilots have noticed an unacceptable reduction in motor life after switching to a 3-cell li-po battery. We have investigated into this issue and are working on several solutions; Better Motor We have tested several other motors that will fit on the Blade CP, this testing is currently ongoing. Most of the motors that are rated for 11.1 V Pulse Width Modulation do not provide enough RPM for adequate tail control. Changing Electrical Properties The tail motor is controlled using Pulse Width Modulation. PWM is an efficient way to control motor speed by changing the length of time the voltage is on/off at a specific frequency. Earlier speed controllers use a network of resisters to supply a constant varying voltage. These resisters had to be large to dissipate the heat and the heat is wasted power that could have been used, resulting in reduced flight time. In the Blade CP, the 4-1 sends a 1.66 kHz PWM signal to the motor; the voltage amplitude is the same as the battery. The tone you hear as you initially apply throttle is the PWM, normal human hearing is 20Hz-20 kHz, 1.66 kHz is in this range. At half throttle with the stock 9.6 V battery, the 4-1 sends 9.6 V for about 200 µs and then 0 V for about 400 µs in the ideal case. As you increase the throttle, the 200 µs increases and the 400 µs decreases, but there is always the same time between pulses, about 600 µs. When you switch to the the 3 cell li-po, the voltage is now 11.1 V instead of 9.6 V for each of these pulses.

The basic idea is that if we can change the voltage at the motor's terminals when using the 11.1 V li-po to be more like the output of the 9.6 V Ni-MH, the motor life will be increased. We tried several RC circuits and found ways to limit the voltage, but there was always an inital voltage peak equal to the full voltage before our circuits. Also, if we limited the peak voltage too much, there was a rapid reduction in performance that was also unacceptable. We finally developed a circuit using a zener diode and resistor that worked very well. The oscilliscope for the before and after are shown below: Original Setup (3 cell li-po) Zener Diode And Resister

As you can see the overall voltage during each pulse is reduced to a max of around 9 V, even less than with the stock 9.6 V battery. Our tests have found the performance to be identical with and without this modification. We have noted that the temperature of the tail motor is also reduced. The details of how to make this can be found on our Blade CP Tail Motor Fix page. If you can't find the components or want us to make one for you, that page also includes our pricing.