DS-8417 Digital Servo

The DS-8417 servo has a very high performance and will give long reliable service if treated with respect.

Due to the high speed and hence high inertia, if the output arm hits an end stop at full speed, it is possible to break the gears. It is necessary therefore to take precautions to ensure that this does not occur. The high speed comes from the performance of the motor which consequently draws large currents from the battery supply. If the output is stalled, these large currents can damage the motor or the amplifier by overheating and premature failure may occur. Of course, stalling the servo momentarily will cause no damage.

Due to resonant vibration effects on helicopter systems, we do not recommend that the DS-8417 servo is used for tail rotor control on helicopters.

With large currents being drawn from the battery, it is essential that proper attention is paid to its capacity and state of charge.

Please note that JR servos should be used with 4 cell (4.8 volt) NiCad batteries only. 5 cell NiCads MUST NOT be used.



Known issues:

Vibration: When mounting the rudder servo at the tail rotor end of the tail boom, many users (Raptor!) mount the servo with the mounting plate above the mounting lugs. As the DS-8417 has a flange to support the mounting lugs at the top, this flange is compressed against the servo plate and feeds all vibration direct to the servo in spite of the mounting rubbers. The solution is to file slots in the servo mounting plate to clear the flanges so that the mounting rubbers can do their job.

JR servo performance is specified with a 4.8 volt supply, unlike other manufacturers who specify the performance with 5 cells. This is why JR servos have a reputation for being more powerful. Our experience is that the extra stresses induced by the extra voltage on the servo, can lead to an unacceptably reduced service life.

Solid state gyros, in conjunction with super fast rudder servos can act as a vibration damper on the tail boom. Modellers may not be aware that there is a vibration problem with their model and if the vibration is at the correct frequency, the core-less motor can resonate and fail prematurely.

As a final comment, JR servos with a "G" suffix such as the DS-8700G are designed to be used for rudder control on helicopters. Why not use a servo designed for the job!