Actuator Mods:

Improving the Rudder Actuator System
Author: Rudi48
Author Email: Rudi48 at RCGroups
Specs: Describes how to improve coil performance
Material Required: Various
Downloads available:
Notes: For my understanding the original rudder actuator is too weak in function. I the motor runs up to half speed only, the actuated rudder will stay in its position Left/Right. But at full speed of the motor the thrust will push the rudder halfway back to the center position. So what to do in order to improve that?

An analysis of the actuator system shows, that the driver electronic will not allow for more than 100 mA source current. This was found out with some measurements:
Resistor Voltage Current Power Comment
8 Ohm 0.8 V 100 mA 80 mW original coil
20 Ohm 1.6 V 80 mA 128 mW resistor
30 Ohm 2.0 V 67 mA 133 mW resistor

Data of the original coil: 176 cm wire length, 110 windings, 4.5 Ohm/m, 8 Ohm, 0.06 mm wire diameter.

I tried to improve the actuator function just by rewiring the coil, and it works.

Data of the new coil: 400 cm wire length, 250 windings, 6.7 Ohm/m, 27 Ohm, 0.06 mm wire diameter, 2.0 V, 74 mA, 148 mW.

By removing the actuator from the plane you destroy for sure the foam. But this is easily repaired by some foam plate from a fast food package (best use for a fast food package :-). For gluing the foam plate please use something like UHU-por. Quick glue (cyanaclylat) will destroy the foam material. In order to keep the coil in place, I used two thick paper plates glued to the coil holder (see the picture). Especially on the outer side it is important, because of the slits for the magnet hinge. Otherwise it is easily possible to cut one of the thin wires if you put the magnet holder in place (it happens to me, so I know :-). In the picture you can see a little PCB to allow measurements and soldering the wires. In the upper left corner of the picture you can see the magnet axis which slips with some force in the guide way of the coil bobbin.

The flight test showed that the rudder now stays in place Left/Right even at full thrust with a 50 mAh LiPo as a power source. And the current consumption is only 3/4 of the original, which extends the flight duration. But those little dimensions need calm fingers and a magnifier.

After you have removed the magnet, it may be possible to just extend the coil by winding additional 220 cm of 0.06 mm diameter wire in the same direction as the old coil has, but I have not tried yet.


Pull-Pull Actuator Design
Author: Graham Smith
Author Email: None
Specs: Describes a Pull-Pull method for actuator usage
Material Required: Various
Downloads available:
Notes: Here is a photo + drawing of the actuator showing the pull-pull system. Itís actually from the monoplane, but itís exactly the same as the bipe.
The wire is bronze, from epilot. I have modified it since this picture was taken. The thread (invisible thread used in sewing) was glued to the bronze arm this tended to impart a slight resistance and stifness to the system which reduces the throw, although the model still flew quite well. I have now glued some tiny tubes cut from electrical flex to the bronze arms so that the pull-pull cables are free to move about, and the rudder now bangs healthily from side to side. The pull-pull thread is still glued directly to the rudder horn on the fin. it probably helps give a bit of centring to the rudder, otherwise I just let it flop about in the slipstream, just like the original.


Rudder Hinging
Author: Graham Smith
Author Email: None
Specs: Describes Method of Rudder Hinging
Material Required: Various
Downloads available:
Notes: This picture shows how I have hinged the rudder, iv'e used a fine piece of wire glued to the fin and a thin piece of plastic from food packaging with a hole pushed into it with a pin glued to the rudder, its coloured red with a marker. and the bottom of the rudder is hinged in the same way.