Protech ZOOM 425 ccpm Spécifications télécharger pdf (Page 218)

for tail control with a heading hold gyro. You may need to use an external switching BEC to

avoid overloading the built-in BEC of the ESC, which will add to the weight of the heli.

Also, some servos which have high torque will have a correspondingly high current draw. For

example, the GWS Naro HP BB has the nickname of "current hog" because it draws a large

amount of current for its size.

30.6.2. Physical characteristics

30.6.2.1. Size

There are four servo sizes which are tyically used on electric helis: Standard, mini, micro, and

submicro.

The standard servos are usually 40mm x 20mm x 40mm, and are typically used on helis which

heavier than 2.5 kgs, such as the Swift and Logo 20.

Mini servos are about 30mm x 12mm x 30mm, such as the Hitec HS-81 and HS-85. These

servos are typically used on helis between 1kg and 2.5kgs, such as the Viper 90, ECO 8, Logo

10, and Robbe Spirit.

Micro servos are about 23mm x 12mm x 24mm, such as the Hitec HS-56. These servos are

typically used on helis between 500 and 800 grams, such as the Zoom 400, T-rex 450XL, and

Viper 70.

Submicros vary in size, but the Hitec HS-50 and HS-55 are in this category. These servos are

typically used for helis under 400 grams, such as the Piccolo, GWS Dragonfly, Century Hum-

mingbird, etc.

30.6.2.2. Mounting lugs

Some helis which use micro servos have four holes for mounting, and some have two.

30.6.2.3. Servo weight

Some servos are very heavy. This weight may be undesirable for a heli which is optimized for

duration flight.

30.6.2.4. Speed and Torque

Speed and torque are dependent on the gearing inside the servo. Often there will be two ser-

vos from the same manufacturer which be visually identical but have different speed and

torque specifications, such as the HS-85 and Hs-81. This difference is due to the difference in

gear ratios inside the servo.

Torque is usually more important for swashplate servos because it is important to hold the

swashplate position accurately. Speed is more important for tail servos when used with a

heading hold gyro which requires fast servo response.

30.6.2.5. Gear type

There are two main types of gears used in servos: plastic and metal.

The advantage of plastic gears is they wear slowly. However, they are easily damaged in a

crash. Metal gears are more durable and are more resistant to crash damage. However, they

wear much faster and develop mechanical slop.

Technical Appendix

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Protech ZOOM 425 ccpm Spécifications Page 218