Protech ZOOM 425 ccpm Specifications download pdf (Page 200)

Better quality motors usually have a lower Io because they are more efficient and expend less

power just idling the motor.

High-power motors usually have a higher Io because the are designed to run efficiently at high

loads and therefore run much less efficiently at low loads.

30.2.1.3. Motor efficiency

Motor efficiency is important because the power not used to fly the helicopter is wasted as

heat. For example, you might compare two motors, one with 80% and 90% efficiency. The dif-

ference appears to be only 10%.

In terms of heat generation, the 80% efficient motor will generate almost twice as much heat

as the 90% efficient motor. If a helicopter requires 150 watts to hover, then the 90% efficient

motor will use 166.7 watts of power and waste 16.7 watts as heat.

The 80% efficient motor will use 187.5 watts of power, and waste 27.5 watts as heat. This gen-

erates 65% more heat than the 90% efficient motor. So, motor efficiency is very important be-

cause efficient motors run much cooler.

30.2.1.4. Motor rated RPM

Some motors are rated for a very low maximum RPM, such as:

• JETI motors have a maximum rating of 15k-20k RPM

• Older Kontronik Tangos have a maximum rating of 25k RPM

If you use the motor past its rated RPM, then motor failure will probably occur (most likely the

magnets will loosen from the rotor).

30.2.2. Physical characteristics

30.2.2.1. Motor size

Some motors are too large to fit in the some helicopters. For example, the C50-13L is too large

to fit in the ECO 8.

30.2.2.2. Motor weight

A quick guide to suitable inrunner motors is to allocate 10-15% of the helicopter's AUW to the

motor So, the inrunner motors suitable for an ECO 8 (AUW ~1600 grams) will be between

160-240 grams in weight.

Outrunner motors can be lighter because they are more efficient at dissipating heat. For out-

runner motors, it is only necessary to allocate about 7-10% of the helicopter's AUW for the mo-

tor.

If you are not experienced with selecting motors, then you should select a motor in the 13-15%

of AUW range. Motors in the 10-12% AUW are somewhat small and must be selected carefully

to fly the helicopter well and avoid overheating.

30.2.2.3. Motor mounting holes

Some motors are unsuitable for helicopter use because the motor mounting holes are non-

Technical Appendix

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Protech ZOOM 425 ccpm Specifications Page 200