Basic Radio / Heli Set-Up

Author: Tom Toledo
November 22, 1996 (From CRH Meeting - Workshop 96-1)

Introduction:

We will be discussing basic radio/heli mechanical control set-ups. The settings are very basic and every heli will be somewhat different (too many variables) but these settings or tips will get you pretty close. The foundation for this set-up is to strive to center the controls early on in the radio installation phase, which will allow you to get real close to linear travel at each control. The results will give you a more accurate feel in flight, not to mention, any adjustments or programming changes you might need to do later on. This will also provide a more accurate representation of the input at the transmitter closely emulating the control input at the model.

This workshop will focus primarily on throttle/pitch curves that utilize a hover point at half stick. I recommend this to beginners and intermediate flyers, but as anything goes in heli flying it is a matter of feel and preference. These are only my suggestions…

Topics:
Strive for a Tight Control System:
· Check for play at all connection points
· “Ganging” of control slop
· Ball fit
· Polishing balls
· Squeeze method (with pliers)
· New reaming tool available
· Proper arrangement to mount ball to servo arm (bolt, washer, ball, washer or nut, servo arm, washer, nut, then Loctite).

Gyro set-up:
· Try to keep gyro away from engine vibration and/or exhaust gunk
· I recommend positioning the gyro as far forward (away from the engine) as possible.
· Gyro is more isolated (from vibration) up front and allows you to turn up the amplifier gain even higher resulting in improved resolution and longevity (unless you crash nose first!).

Servo output theory / resolution:
· Centering throw
· Centering the controls around the hover point (4 degrees)
· Use proper servo arm length which allows you increased servo travel (ATV) as much as possible or at least in the 100-110% range.
· “Trail offs” occur in servo arms rotating in an arc. Most of your input occurs at the neutral point.
· Servo arm / bell crank relationships (symmetry)
· Disconnect pushrods from servos to check for limit and or control binding

Collective set-up:
· If the model is set-up accurately (centered controls), then the pitch/throttle curve relationships will be represented accurately in the transmitter/simulator.
· Erase all of the mixes/program, zero all the trims, ATV and default the curves.
· Then try and set all the travel adjusts as high as the radio will allow (minimum of 100% to ~150%) and reduce the servo arm lengths to achieve proper throw.
· Avoid asymmetrical throws (i.e. 120% Left and 80% Right).
· Once you’ve set the pitch, try to leave it alone and adjust throttle to maintain rotor rpm as needed during flight test.
· Throttle low point should always match to 0 degrees pitch (idle up).
· Basically the curves should be pretty close, not varying by more than 15 % both in percentages and in slopes of the line curves (graph).

Throttle set-up:
· Linear set-up with centered servo corresponding to half throttle.
· Servo speed should match or surpass collective servo speed. (output arm lengths are a factor, too)
· Doesn’t have to be an expensive, high torque servo, just reliable (low torque requirement)

Cyclic set-up:
· Minimize binding at extremes (corners?)
· Safer and minimizes wear on control system, servos and batteries in the long run.
· Work on other areas in the rotor system (paddles, bell/hiller ratios) to achieve more control response instead of using excessive swash plate travel.
· Control lengths can exceed 30 inches (servo to outer 1/3 portion of blade) which potentially results in excessive play (ganging).

T/R Set-up:
· Another day, another workshop…. a lot to cover here, but here are some of the basics:
· Your fastest, most precise servo should be for tail rotor use.
· This is a very active control system and therefore tends to wear out much faster.
· Higher maintenance - keep a close eye on the tail rotor system.
· A tight tail control system will give you an excellent tail rotor feel and precision and also allow the gyro to provide accurate feedback to the tail rotor. Minimizes “hunting”. Especially important with highly accurate gyros of today.

Radio Basics:
· Exponential vs. Dual Rate

· ATV - Automatic Travel Volume
    · Use a minimum of 100% to ~150%.

· Throttle Vs Pitch curves
    · See graphs
    · Throttle should lead the pitch - during acceleration (normal/idle up 1) and lag during deceleration (normal) to better maintain rotor rpm.

· Idle up - a throttle pre-set to help in maintaining rotor rpm in most flight requirements.

· Throttle Hold
    · Consider disabling during initial training stages
    · Get to know this switch!

· Receiver switches
    · Install opposite engine exhaust and protect from grit and oil.
    · Consider replacing every season.
    · Source of crashes (i.e. glitches, voltage drops, intermittent control, shorting from moisture, etc.)

· Record activation dates for each servo and “rotate” servos for improved
longevity. Some scribe the “born on date” on the servo case.

· Take your time and do a neat, clean job.
    · Mount the servos with proper hardware.
    · Carefully inspect all wiring/radio installation after a few flights to confirm proper installation. Look for chafing, and wear on radio components.
    · This attention to detail should extend the life of your radio gear as well as improve its operation and perhaps improve its protection during a crash.

· Crash protection for the radio/heli and minimizing collateral damage
    · Safety devices for retention of clevises, pushrod, etc. Use small “safety washer” between screw and ball to retain clevis (especially throttle).
    · Spring returns for throttle?
    · Battery mounting and wiring security (Velcro Vs rubber bands), zip ties / fuel line
    · Use of “strongbox” recommended

· Antenna routing
    · Base loaded antennas
    · Proper mounting
    · Minimize vibration due to harmonic/sympathetic sources. Isolation and retention.

Remember, if the control mechanism is not set up right, the heli will not fly
right, no matter how fancy the radio or heli.

The Colorado Rotor-Heads is a group of R/C helicopter pilots based in Denver, with members all along Colorado's Front Range.  Our members belong to many of the Front Range clubs from Colorado Springs to Fort Collins.  As a result, you may see our members at many of the local club fields and even the occasional cul-de-sac.  If you would like to learn more about the Colorado Rotor-Heads, or R/C helicopters in general, please visit our web site at www.coloradorotorheads.com.

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