Handles & RC

Lets deal with handles first, ignoring electronic means, we are mainly talking about IC powered planes and mean 3 line systems. 

The commercially made Roberts  System is sot made anymore, but some are still in circulation. In practice it's a bit over engineered, and the handle is bit clunky with  a range of bellcranks to match.

Many self made handles of various complexity exist.

The aim of both these these types is to achieve a balanced control system. Both the throttle and elevator cranks are interconnected. Movement of the throttle can affect the elevator position so engineering out this interaction would at first glance seem desirable.

However all is not what it seems.

Unbalanced systems:

Having used both. I can say with hand on heart I can't tell the difference. The main advantage of an unbalance system is simplicity. 

A simple two line handle with the third line attached to a keyring for your finger, is all that is needed.  The bellcrank setup is  just one for the throttle and one for the elevator bolted together.  Only the pivot point of the floating elevator bellcrank is important, it helps reuce ducing any interaction to a minimum. 

The images below should give a good idea. Yes, there is some slight interaction, but in practice it's so small, I defy anyone to tell if it's affecting the model. There are far bigger forces at play, a gentle breeze will have a far greater effect than any small deflection of than elevator when you move your trigger finger.

This simple handle setup also has the advantage the ring can be used on different fingers to get different throttle responses. Iwas told by someone that always flew with this system and had some considerable success, the middle finer gives a slightly muted feel, and the first finger has the the most rapid response. I found pulling sideways always gave some very fine control.

The piece of string is just to stop the throttle line going walkabout if you put the handle down.

To this day I am still puzzled why hardly anyone else uses this setup, it's cheap, simple, foolproof; what's not to like?.

Electonic Systems:

This is quite an involved subject depending on your end goal.

First subdividing the options as basically as possible: 

1. Signal down the lines.

2. RC car controller

3. Normal RC plane controller

An RC system, if broken down to it's basic parts; think of these as boxes that do something an consists of:

1.  An Encoder [ generates signals that a servo can react to. ]

2.  A Transmitter [ sends a radio signal carry the encoder information somewhere. ]

3.  A Receiver [ receives the Transmitter signal. ]

4. A Decoder [ takes out the Encoder signal and sends it to a servo. ]

Signalling down the lines:

This does not need the receiver transmitter parts of the system, the lines do the communicating between (1) an (2) If you have ever used a servo tester, that is an encoder. if you extended the signal wires for 60 feet and had a servo on the end, in essence  that is the basic same principle.

Of course there is a bit more to it than that. However not many people use this system these days due to the ready availability of cheap RC car controllers and receivers.

RC Car Controllers:

These have been in use for CL carrier for  a number of years now and are quite popular. they can be used as-is, by just holding and controlling one in the left hand whilst using a normal handle in the right. Or the other way around if you happen to be left handed.

However should you wish to convert one into a handle, it's not too difficult. But be aware they do have some drawbacks. 

They are almost all set up for left hand use. Expensive ones can be altered. This is not so much of a problem if you hold a conventional handle in your right hand and do all the throttle controlling with your left. But, if like myself and others ,you have spent a good many years having a handle in my right hand, then using a three line system also in my right hand, there is a desire to try and modify these car Tx's to handles be used  in the same way.

Modification is usually quite easy as long as you are prepared to get your hands dirty and don't mind unscrewing things, followed by the inevitable struggle to get things back in place. It also helps if you know how to use a soldering iron to resolder any broken joints if things  get waggled about too much.  

I am lucky enough to  be able to 3D print stuff,  which means sometimes I can add a part to hold the lines without altering the body of the Tx. Even if you can't do this it's not a difficult job to use a metal bar and drill a few holes in it.

If you are keen, shifting the other potentiometers and switches to the a spare space on the  left of the body; can make life a lot easier. Space may be a bit tight but it can be done as can be seen in the images.

As these basic Tx's are normally 3 channel, some are even more! It's a shame not to use them. In Basic Class and Junior Class  the use case is throttle control, and hook release. 

Any other class,the above, plus rudder offset, adjustab;e line rake, flaps, retracts. and anything else you care to think think of. 

Recently I stumbled across and controller that was so cheap and made in such a form that it was begging to be used for Control Line. It works but suffers from the problem I will outline later. To be fair it has a boat mode which will give a different throttle setting and  disables the brake.

 So not as bad as some of the others and deserves more effort to experiment with it because of it's shear compactness, and 4 channels, which is enough for most carrier models to ever need. The instructions translated from Chinese are sometime amusing or a bit cryptic, it took me a while to work out how simple it was to change modes..???

I saved this advert from AliExpress in Sept 25. Although it's on sale, the normal price for this package averages around £17.00.

I'm lucky enough to be able to custom design and 3D print parts, like the line bar; but there is no reason this can't be made of any other readily available material.

Below are images of how I added the line bar and got access to the trigger mechanism.

The large fly in the Ointment!

Whereas most people get on fine with these controllers, 'As Is.' I personally do not. I must stress this is a personal opinion, not anyone else's.

My main reason is not straightforward, so apologies in advance for the somewhat lengthy explanation. It's also the main reason I still use my old standard RC plane Tx setup that I came up with a long time ago; whilst am I still trying to get  a car controller to behave in a similar way.

With a normal plane TX the throttle lever moves over the full range available over an angle of about 60 degrees. Change that to a trigger and it's a reasonable distance for your finger to pull. Any trembling or sweaty repositioning is not so noticeable at the plane end. 

However with Car Controllers things are different. That throttle 60 degree arc is split into two halves, the equivalent to the centre biased non throttle controls on a normal transmitter. As they are primarily aimed at land vehicles, the backwards movement controls the Throttle and forward movement controls the Brakes with the crossover point being half of the available travel; All set up for basically pull full back flatout GO! Full forward BRAKES ON! with no subtlety

At first glance one would think that  removing the centering part of the throttle mechanism would give a full range of movement. Well it does. But! The electronics still thinks that mid point exists. If you try this all that happens is first half of the movement thinks the brake is still full on and is waiting till you get to the middle, to start working the throttle. This can be partly reduced by playing with the throttle trim, but not eliminated.

In other words you need a steady finger to work over a very short distance when working the throttle. The end result is a very twitchy model especially if it's electric as the instant torque is not insubstantial To a certain extent this will not be quite so noticeable with an IC engine throttle, as they can be fast but not so instant to respond.

Some pilots  use the steering wheel or other control, usually just the potentiometer, placed  somewhere easily accessible on the handle. During the slow run they just move it to a fixed position, in other words fly with a fixed throttle setting. This can obviously be adjusted at will. I cannot fly like that, I need to feel I am always in control of the throttle all the time.

The steering (big wheel knob on the side) seems to be able to use full range of movement. Very impractical as it's physically a bigger size than the throttle pot (at least on all the ones I have a look at).

The other impediment is no access to the throttle curve settings. On my normal TX there is. Basic Tx;s don't have this, if you want to try this, check that yours has this setting.

Adjusting the curve makes it possible to fine tune the slow running throttle response to be very gentle with full throttle coming in fast if you get into trouble. Unless you have experienced the difference this makes it's difficult to comprehend or explain; unless you happen to drive an electric car when changing from Sport Mode to Eco Mode. Eco has a similar effect to the cars throttle response to that which  I have achieved with my RC set up. You can move your foot a lot further in ECO and things happen gently, without spinning wheels or scaring you to death.

I have tried various ways to get around this problem with Car Controllers because it would be far less cumbersome than what I use at present. But still no luck. 

I have come to the conclusion the only way is to use a gear mechanism to reduce the  actual throttle movement by a ratio of 2:1. I have some the gears. I just need to make a gear box that is small enough to somehow to combine with the existing handle body and still be usable? If I ever get it working, you will read it here.

Using a conventionl RC aircraft Transmitter:

Although this is the most cumbersome solution. It's the one I've had the most success with. The auxiliary switches on top, I use for the hook release, rudder offset, flaps, and  will use for retracts on my latest model (bit of step into the unknown? Decks and under carriages are not the best of friends.)

The Transmitter  was taken apart and the throttle wires disconnected from the the potentiometer (variable resistor)  and connected to a socket  fixed in the side if the case. I used a din socket and plug because they were small enough to fit the case; very small pins to solder though!. I used fairly thick standard servo wire from an appropriate plug (for the TX end) to a handle. I had made the handle out of several layers of plywood. This had the advantage of making it easier to fit a  trigger mechanism. and cut a groove to accommodate the incoming wire. Another advantage of wood was being able carve and glue bits on to make ia custom fit to the quirks of how I hold a handle. These days designing and  3D printing it would be less work, but I would still use this one as pattern.

The actual trigger mechanism was taken from an old car controller I  had tried and failed with many years before. It happened to have the same value potentiometer as the transmitter,  and was complete unit including trigger. 

This hack has stood the test of time reliably. Until I can make one of the car controllers do my bidding, I will keep using it.  

The biggest downside and inconvenience is having to wear the Tx on a belt around my waist. This is a pain as with all these Tx's I have mentioned above. If you have to walk back to the deck to do something dragging the lines there and back is almost guaranteed to snag the lines on something. Unhitching the TX and leaving it on the ground is not safe as loss of signal can cause unpredictable things to happen. It's not happened yet but it could. 

I also need to modify the transmitter so I can unplug the handle when switched on, doing that at  present will make the throttle open up full if the model is powered up. It's a simple mod I have  just never got around to. Like a lot of things, I really should pull my finger out; and just do it! Like removing the sticks and replacing them with rotary knobs, which would be more useful.

The lucky coincidence

You will notice in the image above, a lever type thing that is attached to the front of the handle and the trigger. Initially installed to act as friction device to get some feel into the  trigger movement. However I never trimmed off the excess length. This turned out to be extremely fortuitous. I found I could rest my thumb on it causing back pressure on the trigger as I pull it back with my finger,  This made  it much easier to hold it in any position. It was a very lucky find.