Confederation Marine Modellers
Building tips - Radio & Electrical
There will be occasions when you want more than the 90° rotation that manufacturers set their servos to. Most of the servos I have come across are capable of more than the 90° rotation that we normally use. In fact, many are capable of as much as 180° rotation.
One method of getting the extra rotation uses a feature found in some modern radios. You may discover that it has an "end point adjustment" facility. If you only need a little more than 90° rotation this facility may be all you need.
If you need more than the radio can provide, or your radio does not have the facility, the second method is to connect a "servo stretcher" between your radio and the servo.
There are two varieties of servo stretcher, with and without end point adjustment. Some servos cannot rotate the full 180°, and a stretcher without end point adjustment may try to make your servo rotate the full 180° or more. If your servo rotation hits an end stop and cannot get the rotation that the stretcher calls for, then the servo motor stalls, keeps trying to reach the set limit, gets hot, and may burn out. To ensure you don't face this situation, you have to limit the amount of rotation.
You may be able to limit the rotation using your radio's end point adjustment, otherwise a stretcher with the facility is necessary. Robotzone make a stretcher with adjustable endpoints, currently available from Servocity and Active Robots. Stretchers without end point adjustment are available from a number of suppliers.
Here are four servo plug and wire lead diagrams. We've included these for all those
pilots and modelers who like to swap radio gear between airplanes, or who like to mix
and match receivers, servos, and battery packs. Note that the plus (+) and minus (-)
leads are common across the receiver bus.
However, make certain that these leads are not reversed in the servo plug! as such a
situation will likely cause damage to the servo, resulting in a trip to the repair shop. Also, you should know that while in most cases the signal to the servo is interchangeable between brands, there are certain brands that utilize a different shift on the signal—either positive or negative.
Information from 3-D Flyer magazine.
Hints & tips - Servo plugs
Stick a piece of Velcro to a suitable place on the hull or frames, then arrange the wires across it. Trap the wires by pressing the matching Velcro piece over them.
Have you struggled trying to hold a couple of wires together while you solder them? There are a number of tools to help you.
The most commonly-advocated tool for doing this is the “helping hands” or "third hand" tool which has a couple of crocodile clips, at the end of a bar, which can be rotated to different positions. This tool is great if the wires are looped and twisted together so they're locked mechanically before you apply solder, which is the method most professionals recommend. It works well if you are soldering a wire to a connector, if you can mechanically fasten them together.
However, many of the connectors we use have no provision for a mechanical connection, you simply lay the wire on the terminal and apply solder. Many of our wire-to-wire joints work fine when they are only held by solder. A disadvantage of the above tool is that, if you just want to hold the bare wires together for a simple, low-strength, soldered joint, you can't get the clips near enough to each other to hold the wires firmly close together, without a lot of fiddling. You could use two 'helping hands', then you can position two clips as close as you want. This is better but suffers the problem you have with all crocodile clips. The jaws of the clips are serrated, and the grooves don't line up neatly. So the wire goes off at an angle you didn't expect. The wires themselves can be bent and twisted to line them up; sometimes they don't want to stay where you want them to. With patience you can juggle around with the wires and clips and line them up.
Yet another tool, no clips this time, has a set of tapered slots set in two vertical ribs. You push the wires down until the slots grip them. There are no clips to rotate, so you can only bend the wires to get them into position. It works, but not a lot better than the other options.
All of the above will work, some require more patience than others. My near-perfect solution works quickly every time. I have two pieces of tacky putty (blue or white, whatever you can find), set 1/4” to 1/2” apart, attached to a base. You press each wire into the putty, or a wire and a connector, so that the bare ends are in contact in the space between. It's easy to get the two ends in line. Simple ! What's more, this simple little fixture lets you solder wires in tight spaces where none of the other tools would fit. This 'tool' can be made very easily from scrap wood, shown here, or scrap styrene.
Even if you can hold the wires firmly in position, don't forget the other criteria for making a reliable joint.
- make sure the wires are in contact; with stranded wires you may be able to push them end to end into one another a little way
- make sure the iron is up to full temperature
- apply just enough solder to the tip of the iron to wet the surface
- touch the iron to one side of the joint and the solder to the opposite side; when the solder melts you're sure that both wires are hot enough
- the finished joint surface should be shiny; if it's not you probably moved the joint as it was cooling. So reheat it.
A number of members have looked enquiringly at the version of this radio that I own.
Some years ago it was available from Harbor Models in the USA, but not recently.
It is now available from two suppliers in the UK, Howes Models and Cornwall Model Boats.:Howes Models F14 and Cornwall Model Boats F14. This version contains one twin-stick, ideal for twin-prop control, and one single stick. It is an 8-channel radio. The single stick could be replaced with another twin-stick if desired, available from Robbe in Germany.
These versions operate at 40MHz so they must be converted to 2.4GHz for use in North America. Fortunately this is fairly easy to do using the Assan 2.4GHz hack module available from Hobbyking: Hack module., a conversion that I have already done. Step-by-step instructions can be found on Youtube.
That's the good news. The bad news is that the radio will set you back £200 (~CDN$330) and the Assan hack module US$50 (~CDN$63).
Roy C. Aug 2017
Resistor values for LED's.
Save your servo wires from chaffing on bulkheads and when passing thru fiberglass holes by making little grommets out of scrap fuel tubing. Slit them length wise and slide over servo wires. Keep them in place with wire ties or a little Zap glue.
Do take care to install neatly arranged, easy-to-trace wiring throughout the model. Solder all connectors to insure current flow and keep all wires up out of the bilge area to prevent exposure to normal bilge water.
Affix two brass bolts so that they protrude from the transom. Connect these to your battery terminals, if desired via a changeover switch, with the positive (red) terminal on the port side, and the black (negative) terminal on the starboard. These become convenient charging terminals. They could also be placed on deck and take the form of brass bollards or cleats. This idea eliminates the need for another terminal in the radio box, where a charging socket would usually be. Use alligator clips to connect the charger.
If you are fitting LED lighting to your model, and need to work out what value of resistor you need, refer to the quick reference guide here.
Building Tips - Radio and electrical
All you need to know about LIPO's
Member's tip from Garth: Use an empty Tylenol (or similar) bottle to house your receiver and to make doubly sure it doesn’t get wet, seal it with tape or Silicone.
External charging terminals
Protecting your radio receiver