Fly Bar Control Arm Tip

2006 Apr 2

Table of Contents:

Introduction

There are two methods described. The Unassembled Rotor Head and the Assembled Rotor Head.

The objective of this setup is very critical and will affect the flight characteristics of the model.

The alignment of this setup are to have the fly bar paddles at equal distance and level to the fly bar control arms with respect to a horizontal datum line reference.

The horizontal datum line will be define as a line perpendicular to the main mast. The term "level plane" is in reference to the "horizontal datum line".

The following are important when building the model and should be performed meticulously.

An out of alignment head will create vibrations and fatigue the components of the mechanics. It will also affect the overall flight characteristics of your helicopter.

Fly Bar Control Arm Modification

A simple modification can be done to the fly bar control arms that will counter act the applied force when tightening the fly bar control arm set screw.

This mod will prevent the ends of the fly bar rod from bending upwards from its center.

It is recommended to drill this hole by hand using a pin vise or similar to avoid damaging the aluminum threads of the fly bar control arm bushing.

Remove the fly bar control arm set screw and using a #30 or equivalent drill bit, manually drill through the plastic.

Remove the fly bar control arm bushing and enlarge the hole with a # 23 drill bit or equivalent. The enlarging hole is necessary to avoid stripping the threads of the fly bar control arm bushing when installing the set screw.

Reinsert the fly bar control arm bushing and set screw into the fly bar control arm.

CAUTION: Do not strip the threads of the fly bar control arm bushing when reinserting the set screw. If resistance is felt during installation of the set screw, remove the set screw and reinstall the fly bar control arm bushing in a different orientation. This can be accomplished by rotating the flybar control arm bushing 180 degrees or flipping 180 degrees.

To avoid an unbalanced condition, install a pair of matching set screws to both modded fly bar control arms.

Un-assembled Rotor Head Method:

Fly Bar Component Assembly:

Refer to page 11 of the manual. Assemble the fly bar control arms, fly bar rod, bushing, bearings and seesaw hub.

Gently hand tighten (snug) the control arm's set screw but just enough so that the fly bar control arms can be moved with minimal friction in order to locate the flat spot on the fly bar rod.

Verify that the flybar control arm's set screw is mated in the groove of the flat portion of the fly bar rod by sliding the fly bar control arm. It should slide back and forth the length of the flat grooved surface.

Fly Bar Rod Alignment:

Compress the fly bar control arms towards each other. Gently hand tighten (snug) the fly bar control arm set screw just enough so that the control arm does not move while taking measurements.

Adjust the fly bar rod so that both ends are at Equal distance, A = A, from the fly bar control arm bushing. Take note of the raised ridge on the fly bar control arm bushing when placing the measurement device.

Verify that there are no lateral play between the see saw hub and the fly bar control arms and the fly bar control arms rotate freely.

Fly Bar Control Arms Alignment:

Place two pieces of wooden blocks of same dimensions under the flat surface of the fly bar control arms. Verify that the fly bar control arms are level and resting flat on the wooden blocks.

If the control arms are not level perform the following steps simultaneously.

Slightly loosen the set screws, maintain compression between both fly bar control arms, press the fly bar control arms flat against the wooden blocks, and tightened both set screws evenly and equally going back and forth until they are both tightened. Do not over torque the set screws.

Control Arm's Set Screw Over Torqued:

Excessive tightening of the fly bar control arm's set screw will cause the fly bar control arms to rotate out of alignment.

Also, the force applied by the set screws, will force the ends of the fly bar rod to raise upwards from its center.

Verify that the fly bar control arms are aligned, A=A, and the fly bar control arm rotates freely while holding the fly bar seesaw hub.

There should also be no lateral play between the fly bar control arms and the fly bar seesaw hub.

Fly Bar Paddles Installation:

Do not hold the fly bar control arm assembly when rotating the fly bar paddles.

Use a pliers to grip the fly bar rod so that the rotational force applied during this installation does not un align the fly bar control arms. Insulate the fly bar rod with cloth or card board to prevent the pliers from marring the surface.

Install the fly bar paddles on the fly bar rod by rotating the paddles clockwise until the fly bar rod can be seen at the fly bar paddle's inspection widow.

Align the fly bar paddles so that they are at EQUAL distance from the fly bar control arm bushing, B = B. Ensure that the fly bar paddle's leading edge are orientated in the correct direction.

Fly Bar Paddles Alignment:

Place a fly bar paddle alignment tool on one fly bar paddle.

Using a straight edge and cloth pin (see photo), placed the straight edge on the flat surface of the fly bar control arm (see setup tools)

To avoid parallax errors, ensure that the alignment tools are at 90 degrees to the fly bar rod.

Sight the top of the fly bar paddle alignment tool to the straight edge. Rotate the fly bar paddle so that the top edge of the alignment tool is level to the straight edge.

Use a pliers to grip the fly bar rod so that the rotational force applied during this alignment does not un align the fly bar control arms. Secure the set screw on the fly bar paddles.

Place a second fly bar paddle alignment tool on the "unaligned" fly bar paddle. Sight the top of the "unaligned" fly bar alignment tool to the top of the "aligned" fly bar alignment tool.

Rotate the "unaligned" fly bar paddle until the top edge of the "unaligned" fly bar paddle alignment tool is aligned with the top edge of the "aligned" fly bar alignment tool.

Secure the set screw on the fly bar paddles.

This alignment will have the control arms and fly bar paddles, level to the horizontal Datum reference line.

Assembled Rotor Head Method:

To ensure accurate placement of the fly bar rod, A=A and B=B, remove the fly bar paddles and perform the following steps:

The photo shows a technique for aligning the fly bar control arms using two 3 x 35mm hex bolts hand tightened on the fly bar seesaw hub.

The fly bar control arms are interlocked against the 3 x 35mm hex bolts keeping both fly bar control arms on the same reference plane.

Caution: Fully loosening both fly bar control arm's set screws will result in A ≠ A, B ≠ B, and the set screws not secured to the ground flat on the fly bar rod.

Slightly loosen the fly bar control arm's set screws, maintain compression between both fly bar control arms and ensure that both fly bar control arms rest on the 3 x 35m hex bolts.

Tightened both set screws evenly and equally going back and forth until they are both tightened. Do not "over torque" the set screws as this will cause the fly bar control arms rotate out of alignment.

With no pressure applied, both fly bar control arms should rest firmly on the 3 x 35mm hex bolts.

Refer to the Fly Bar Paddles Alignment paragraph for final alignment.

References:

A datum (plural datums) is a reference from which measurements are made. http://en.wikipedia.org/wiki/ Datum

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