Get your rear in gear! Greg Gimlick >>

The rear of your helicopter might not actually use a

gear, but is it working? Our little machines are marvels of technology, but preventative maintenance is paramount to success. We tend to ignore the tail-rotor drive systems until there is trouble, and by then it’s often too late. The price for ignoring this is usually a crash. Let’s get ahead of it.

TYPES OF DRIVES If you have several helis, chances are that you have an example of all of these types of tail drives. Each one serves its purpose well if it is properly maintained.

• TT:Torque tubes drive

the tail rotor with a shaft from the main gear to the tail rotor gearbox. It might be a wire, tube, or shaft made of plastic, carbon fi ber, or aluminum, using a gear on each end. They provide the tightest tolerance and performance, but they require careful setup and are easily damaged if the tail rotor contacts the ground. • BD:Belt drives were common for years and remain popular. It’s a simple setup, with the belt making a twist inside of the tailboom to change the direction of the drive without requiring gears. They are more forgiving when a beginner makes contact with the ground or tall grass, but they are still good for 3D fl ying and are used by some 3D experts. They require occasional

32 PARK PILOT [Summer 2018]

This direct-drive tail uses a motor connected to the blade. Check to make sure that the motor bolts and the blade retaining bolt are secure.

tensioning and should be sprayed sporadically with silicon to reduce static electricity. • DDVS:Direct-drive variable-speed tail-rotor drive systems are now more common because dual speed controls can drive them effi ciently. Some claim they still “blow out” during hard 3D maneuvers, but they are certainly capable of performing good 3D fl ight. They use a separate motor on the tail, driving fi xed-pitch tail-rotor blades and providing anti-torque by varying the rpm. Simplicity and ease of maintenance make them popular.

What is required to maintain a tail drive? Not a lot, but some attention is needed to ensure safe operation of your machine. Let’s begin with the easiest.

DDVS tail-rotor systems have a motor mounted at the end of the tailboom that is connected directly to the tail-rotor blades. The wires run up the tailboom and connect to the control board or secondary ESC. These wires, depending on the motor/heli size, can be anywhere from 22 grams to tiny wires akin to motor windings. Check the connections and ensure that they are routed away from any gears that might chafe them. Turn the motor to see if it’s still smooth. After a fl ight, check the temperature of the motor with a temperature gun, log it, and occasionally check to see if it’s beginning to run hotter. That’s a sign of bearings going bad in the motor. Check the bolts and screws holding the motor to its mount,

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