GAUI EP 100 SE Setup guide

Summary:
a compact setup guide for the GAUI EP 100 RC helicopter.
Some may be more obvious than others. A few were learned the hard way.

Introduction

The material on this page is mostly related to the GAUI EP 100 SE, also known as “EP 100 Pro” or “Mini Zoom SE-PRO”, the latter is written on the box.
Most information is relevant also to the “EP 100” (I've got one of those as well), which is known as “Pixy Zap”, or “Mini Zoom”.
At the end is a quick collection of “Pixy Zap” related comments.
The discussed setup is good for “sports flying”. So far, I have no experience with inverted flight (or autorotation, if that is possible).

Center of gravity

The COG should be along the main shaft: When lifting the heli by the blade bolts (turned left / right), the skids should remain parallel to the ground.
In the shown setup, this is the case, depending on the position of the battery on the velcro mounts.

Main blades

Balance the main blades carefully, check for vibrations with tail rotor blades removed.

Some types of wooden blades don't fit into the EP 100 SE blade holder, because there is too much wood on the inner end. This needs to be filed down.

Blade end

The circled area is important, because there the blade swings back when struck by an obstacle.
One can also file down the heads of the blade holder screws slightly.

Tail rotor blades

Balance also the tail blades carefully, and run without main blades. The reason is that main blade vibrations will also cause tail vibrations.
A badly imbalanced tail assembly may “blur” 5 mm into any direction at speed. A well-balanced setup remains essentially “in focus”.
Make sure that there is no slop for the tail blade to twist in the blade holder.
Reportedly (this post, hugovanleeuwen) a simple plastic washer can improve the situation.

Blade tracking

The EP100 pro out of the box was perfectly adjusted, but it should be mentioned here:
Both main blades should rotate in the same plane. If one is too low or too high, the rods in the rotorhead need some adjustment. The process is described here:
Blade tracking instructions (page 21)
In a nutshell, a slightly different approach below:

Usually blade tracking is off for a reason (crash?).
Common sense demands to check the rotor head etc beforehand:
Flying parts might knock out some teeth (or worse).

Cut two equal patches of tape
Put one around the front edge of one blade tip
Put one on a flat side of the other blade tip to keep it balanced
Nail the heli to the table, put on appropriate face protection and spin up
Look at the heli sideways, and identify which blade is too low / too high. The distance is greatest around zero pitch.
Adjust the pushrods to the blade holders. A longer push rod gives more pitch and raises the blade
Raise or lower? Good question. Possibly concentrate on the side that suffered most in the crash.

Flybar

I prefer to have as much control authority as I can get with the smallest possible headspeed. Therefore, the weights below the flybar paddles are removed.
The flybar should be balanced, and this is achieved by removing the ball links and turning them upwards:

Flybar balancing with the ball links removed

Tail rotor angle

Usually, one would set the tail rotor at 90 degrees to the main shaft. In practice it may be better to tilt it slightly upwards:
When hovering, the heli leans somewhat to the right to compensate the sideways push of the tail rotor by cyclic.
This angle can be set on the tail rotor, so that its thrust is horizontal to the ground, and not slightly downwards (for further study, haven't investigated too deeply).

Tail fin resonance

It can happen, that the tail fin resonates violently (+/- 4 mm at its lower end) at one particular headspeed.
A possible solution is to stiffen it with a carbon fiber rod (2 mm, for example from a training kit) that has been spliced in half.
CA glue attaches the rod on its whole length.
To determine, whether there is a problem, remove the main blades and spin up the heli very slowly.

half a carbon fiber rod to stiffen the tail blade

one half on either side

As an alternative, differently shaped tail fins are for sale, which may be less troublesome.

CF tail assembly (upgrade for EP 100, standard for EP 200)

Both bearings should be glued into the tail assembly using a drop of CA glue.
Otherwise they will be held in place by tail belt tension, but under load the tail shaft may start to wobble badly.

A drop of CA glue keeps the flanged tail rotor bearings in place

Blade bolts

The bolts that hold the blade should be tightened so that there is still some friction, but the blades can move.
In a typical setup, blades need to move because of the lead-lag effect:
When the heli moves, the blades on one side have a higher velocity relative to the air than the blades on the other side.
This holds true for both rotors.

Rotorhead / feathering bolts

"Feathering bolt" is the name of the M2x10 screws that attach the bladeholders to the rotorhead.
These screws are very important for the stability of the heli, because there is a rubber seal underneath behind a brass spacer, that dampens the blade:

If the blade rotates too easily (no friction), the heli will fly stable, but it “wobbles like jelly” for a split section when recovering from abrupt moves
If the blade is too tight (too much friction) the heli becomes hard to control and doesn't obey pilot input very well
If the bolt is bent (happens after even the slightest crasw) stability suffers

Those instructions are provided on a leaflet together with a spare CNC rotorhead, but curiously not with the heli itself.

Rotorhead drawings

Here is a manual for the EP 200, which uses the same rotorhead (this post, mahbouni).
It shows all the bearings and washers. Highly recommended!

Belt

The belt should not be slack, but not much tighter either:
During one hour of flight, the tail rotor will revolve almost a million times. Excessive belt tension will reduce the life expectancy of the tail bearings.
I use lithium grease or synthetic oil on the belt. Otherwise it may happen that the teeth of forward and backward direction interlock inside the tail assembly.
The carbon fiber tail upgrade seems to perform well.
When the tail rotor hits an obstacle, the belt may flip. If it's only between main wheel and guiding wheel, it's easily turned back.
If it flips on its whole length, it will be necessary to remove the tail assembly and easiest to remove and reinsert the belt. A belt that keeps flipping needs to be replaced.
A convenient way to insert the belt is by cutting a small notch into a cable tie:

The miraculous belt puller tool, only 9.95!

Servos

Lessons learned the hard way: “Gotcha” #1:
Small servos break easily:

if the servo arm is turned by external force, for example with a screwdriver when overtightening the screw
If the servo arm is pushed too hard “into” the servo, because the pressure acts directly on the potentiometer.
If the mechanism binds - either mechanical failure, or the motor overheats and demagnetizes
Some were even broken straight out of the box, therefore it is good to order some spares
Servos can be repaired! Replacement gear sets are cheap, and it may already help to reassemble the wheels at a random angle.

Some servo, for example Bluebird BB306BB, are held together by the labels and small plastic pins only.
It does not take much force to crack open the case, and then the plastic pins break for sure.
Some vendors even recommend to wrap it in tape.
A piece of string and CA glue on the knot does the job and is more reliable.

Left: the pins, one missing. Right: case closed!

Hint: The servos driving the swashplate should be identical to maintain symmetry.
But the tail servo can be used as temporary spare part, replace with any type.

CCPM servo mounting

Since there is not enough space inside the canopy for the servo arms, they move towards the inside.
Compared to the photo below, one could achieve slightly less offset between lower and upper ball link by moving the servos to the outermost hole, as shown by the arrows.

Front CCPM servos

For the 3rd servo, some foam tape or bicycle tube rubber is required to set a gap between the servo arm and the opposite side of the frame.

Rear CCPM servos

“Gotcha” #2, Lessons learned the hard way:
Leave some safety margin for the gap

The worst kept servo secret

Most servos are designed in such a way that rotating the servo arm by ninety degrees will result in a quarter spline offset.
Therefore, a servo arm with cross levers can be adjusted with an accuracy of a quarter spline! For a two-sided servo horn, the resolution is half a spline.

A cross servo arm can be adjusted with 1/4 spline resolution!

Make sure that servo reverse is programmed correctly, before cutting off the unused end(s)
Check that trims are neutral

CCPM servo adjustment

To my understanding, the Bell-Hiller system will give less effective pitch change for the same servo travel than it gives in collective direction.
Therefore, I set up the CCPM servo arms to meet the following two requirements:

No binding between swashplate and guiding posts at full cyclic / collective input (0.5 mm margin)
0 deg pitch at collective stick center
Maximum possible swashplate angle in both axes without binding

Since it's unlikely that the pre-drilled hole in the servo arm is exactly in the right spot, I use the outermost hole (risk of binding!) and dial down collective response in the transmitter's CCPM menu.
The blade angle at the endpoints of the collective stick may still be impractically high, and one can reduce the transmitter parameter further.
As said, the motivation is to have maximum swashplate deflection in situations, where the flight path is suddenly crossed by a planet.
Having blade angles far in excess of 12 degrees makes little sense:

Crude measurement of blade angle without a pitch gauge

Note that even for relaxed flying, it is good to have some negative pitch in reserve to deal with wind.
Most transmitters have a CCPM menu, where the servo travel is distributed between collective and cyclic. Usually it is evenly split between collective, cyclic elevator and cyclic aileron.
My current setup trades off some collective range against more cyclic (40/60/60). As said, the swashplate may bind against the main shaft, if the maximum possible angle is exceeded.

Upside-down swashplate mounts

It appears to be possible to mount the front swashplate servos upside down. As a result, the asymmetry of the swashplate pushrods reduces (haven't tried this yet).
Link (hugovanleeuwen)
It may require longer push rods, for example using a spare tail pushrod (reportedly the ball link fits tight, even though there is no thread on one end, see here).

CCPM setup for three- or five-blade heads

disclaimer: I don't own any of those
The three/five blade heads are not flybar-stabilized, and therefore extremely sensitive to cyclic input.
A way to deal with it is to set up the CCPM mixing as for example 80 on collective, and 20/20 on cyclic aileron/elevator.
Since now more servo travel is available for collective pitch, it may be possible to use shorter servo arms, giving more precise control.

Cabling

I wouldn't bother with cleaning up the cabling for the first couple of hours of flight.
Chances are high that some parts will need to be removed, and the neater the setup, the more cumbersome it gets. But they shouldn't interfere with rotating parts.
A piece of string, locked with CA glue, keeps them together.

Tying up cables isn't worth the effort, unless the setup is “stable”

Individual cables are wound up to a spiral, around a screwdriver (not antenna cables!)

Receiver and antenna cables

My two short 2.4 GHz antenna cables go whereever they like. They aren't attached anywhere.
The reason is simply that this prevents them getting pulled out of the receiver when handling the heli, or in case of a crash.

Some small pieces of foam (gyro) tape are placed between the receiver and the chassis. This might help reliability in the long run, or maybe it's just superstition.
It is held in place with string and a drop of CA glue on the knot.

Battery / motor cables

Those are soldered straight to the ESC. Any extra length of cable is bad, because of the extra resistance and weight.
Here it does matter (well, at least somewhat), because the currents are pretty high, in comparison to the low voltage.
Cable ends next to a solder joint should not be allowed to bend, because they will break sooner or later, and performance degrades.

Motor adjustment

Some motors are set up badly by the factory. If so, adjusting the bearings can make a huge difference.
Also, the spacing between the motor pinion and the main wheel is critical, if only for noise.

I use Lithium / Teflon grease on the gears to reduce noise.
The label of the GAUI motor will come off anyway sooner or later, so remove it immediately.

Rotor mechanics

Some moving parts in the rotor cause a high-pitched squeal that can get quite annoying in a small room. Some Lithium/Teflon grease takes care of that.

Accu mount

Two small patches of velcro tape keep the accu in place.

Velcro tape

Gyro mount

Two narrow “bridges” of doubled gyro foam tape attach the gyro to the frame. The more it isolates vibrations, the better.
Also, the cables should have some slack to decouple vibrations.

“Gotcha #3”, Lessons learned the hard way:
If the tail is oscillating at too high gyro gain, check main and tail blades individually for vibrations. Also, the main shaft could be bent.

Gyro mount

Rudder servo

“Gotcha #4”, Lessons learned the hard way:
Binding can occur between the rotating part of the tail slider and the fixed part that holds the 90 degree lever.
This is a truly nasty problem because

One may not notice it - flying with full rudder input is rather uncommon, unless one does it on purpose (not a bad idea, and I've seen videos where it's the first thing pilots do)
It can happen sporadically in flight, when the gyro decides to give full rudder input
It causes vibrations, instability and loss of head speed
It can cause the tail belt to slip, and suddenly the tail kicks out left
It will damage the tail belt and lead to all sorts of ugly problems (tail belt flipping etc)
The rudder servo may change its position slightly on the tail beam and even drift with temperature / voltage variations

As indicated above, there should be a small safety margin between the rotating part of the tail slider, and the turning point of the 90 degrees lever.
The rudder servo needs to be set up accordingly.

Neglecting this small gap can lead to big trouble

The rudder servo arm needs to be comparatively short, although at the time of writing I'm running mine in the 2nd hole from the center.
Everything else unchanged, a longer servo arm will require a reduction in gyro gain to obtain the same control behavior.

Lenght of the tail servo arm

Note, it would be better to move the push rod to the other side.

My tail servo is mounted using some rubber padding (cut from a bicycle tube). Some manufacturer recommended this, I can't say whether it affects servo life time.
I haven't investigated, whether it actually makes sense to run the tail rotor at this extreme pitch, because its efficiency will reduce. Anyway, that's how mine is set up at the moment and it flies well.

Frame

“Gotcha #5”:
The heli will still fly with a loose servo mount, but will tend to wobble etc.

This is actually mentioned in the manual: The frame needs to be glued, once the size of the back CCPM servo mount is known.
Glue tends to break during flight, but it's easily reinforced with some wire (I use two pieces, one wrapped, one glued).

Frame glued and wire-reinforced

Noise reduction

This brings back nostalgic memories to the days when cable TV came to town...
Enter “Airwolf: Silent mode”

Since I usually fly the only heli in the gym, it makes more noise than all the other fixed wings together. And then some...
The modification below is quite efficient at reducing the high-pitched gear squeal.
It is cut by knife from some soft RC mart packing foam. It is flexible enough to be inserted without removing any screws.

Foam shield (1)

Foam shield (2)

Canopy rubber washers

Glued to the canopy with CA glue.

ESC placement

At the tip of the frame to move the center-of-gravity forwards. Again, double-sided tape, string and a drop of CA glue keeps it in place.

ESC placement and short cables

Note: some brushless motor manufacturers explicitly forbid to cut motor cables. Therefore I leave them at their original length, they are short enough.

Throttle curve

Copying a throttle curve is probably not too useful, anyway, here's mine:
0-35-55-65-77
It gets changed often: more power outdoors, and less to prevent structural damage to my living room :)

Carbon fiber blades

The CF blades are light and short, 340 mm rotor diameter.
A disadvantage is that they cannot be easily folded back for transportation, and the heli requires more space in a case.

Carbon fiber blades folded back as far as possible. Note the flybar on the opposite end.

CNC seesaw spindle (from EP 200)

Recommended upgrade, because the plastic holding the screws may wear out.
Note that both washers are on the inside:

CNC spindle instructions

Pixy Zap / EP 100 standard related

The ugly duckling grew into ... err... a hawk? Buzzard? Vulture?

I own an EP 100 SE and a Pixy Zap with somewhat similar setup:

GAUI SAE 12A ESC
standard GAUI 4700 kV brushless motor
6 ch Rx, one Futaba, one Spectrum
Bluebird BB306BB servo on rudder

The Pixy Zap has been converted to long blades and tail, and I'm trying to keep it as light as possible.
It is a bit more challenging to fly than the smaller EP 100, which in comparison is as “squirrelish” as a freight train.

Not mentioning the original unreliable Pino MG servos, I tried cheap Pico Pro 4.3 g servos on CCPM.
However, their resolution is too coarse: It is difficult to maintain a steady hover, because usually the heli wants to go either “up” or down, but there's nothing in-between.
Now it was upgraded to 3x Bluebird BB303, and it is in comparison more precise.
That said, the cheaper servos would be perfectly adequate for outdoor flying, when accuracy is not a concern, or crashes are a cost factor.
Still, the limitations of the 303 show. Maybe this will get upgraded in the future to different servos.
The tail servo is mounted using an “upgraded” tail clamp from the EP 100 SE. In the future, the servo arm might be one hole longer, though.

Standard EP 100 SE servo mount

The other servos fit to the original mount points of the Pino MGs. Some plastic tube is inserted on the screws to set the distance (arrows). They are cut from a refill for a ballpoint pen.

servo 1, 2, ...

and 3. The frame was slightly cut out to accomodate the bigger servo.

Update: Now a fourth BB303 on the rudder, and servo arm one hole longer than shown in the picture.
It flies well (one could almost say it “floats”, since its weight is so low), no data on reliability yet.

BB303 servo

On the 100 SE, the Bluebird BMS 303 servo do not work too well. The controls are not precise (all the time, the heli wants to go “somewhere”).
The first BB303 failed after about four battery packs on swashplate, its counterpart after about 15.
It seems that the poti is broken - which is unfortunately not user replaceable.
I don't think they are being overloaded - there is no binding, and the mechanics move easily after many hours of flight time using other servos.
Still, even though the specs are almost the same as 306, they don't move nearly as swiftly.
The 303 may be recommended for “micro” helis (EP 100 is AFAIK “sub-micro”), but I wouldn't recommend them. Back to 306, which has been quite reliable so far.
Hitec HS-45 work also well and are in practice only slightly heavier, but not slower than BB306, even though the specs suggest so.

© Markus Nentwig 2007-2008
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Comments? Questions?

Please send me a mail! mnentwig@elisanet.fi