Focus on Competition
Technically Speaking ...
Greg Hahn Technical Director [email protected]
Tech Stuff, Part One: This month I'm going to change direction a little and explain (in my layman's terms) some issues and my own tried-and-true methods of combating common problems pertaining to onboard radio setups.
Lately I've had some conversations in the office with members and during some of the FAA workgroup sessions about common problems with servos, wire, BECs, and so on. I'm often asked to troubleshoot electrical problems sight unseen, which can be challenging. I hope I've helped at least some of the time.
Aircraft modeling requires many skill sets, and you often need much more than elementary knowledge to accomplish many of the required tasks. Even in today's ARF environment you need to be fairly knowledgeable in basic electricity.
You might not have to build and cover the airframe, but you still have to get the radio system installed cleanly and in working order. The power system, if you're using electric, also needs to be the same carefully organized installation.
Organization can't be overemphasized; having things in their places makes fixing problems much easier. You haven't had fun until you've been asked to find a bad connection in a well-built bird's nest.
I like to centrally locate the receiver and bring the wires in grouped in the proper direction. I use many zip-ties to keep the wires in their proper sequence and place.
If you have more than one control lead grouped together, marking them with a Sharpie will help you remember where they go. This is extra important with complex aircraft, because keeping 15 or 20 servo leads in the right places can quickly turn into a nightmare.
Wire is one of the most important and overlooked aspects of radio setup. I dare say that the majority of physical problems with radios and power are directly caused by the quality, size, and care of the wire used.
Your servo might be rated to deliver 300 in. oz. of torque at the specified voltage. But if the wire running from the receiver to it isn't of adequate size or has too many mechanical connectors for its length, that voltage will not be there—and in extreme cases the lack of needed voltage can cause damage to the servo.
I won't bore you with specifics, but the voltage drop for each mechanical connection added to the length per foot of the lead wire can be amazing. Especially in larger models, in which servo leads are routinely longer than 3 feet, the voltage drop is unbelievable and will render your system inadequate.
Keep in mind that the wire lead that comes on the servo from the factory is sized adequately to be used at the factory length. If you add to the factory lead with an extension or hard-solder an extension, the added wire needs to be significantly larger to deliver the proper voltage. I have witnessed voltage drops of 1–1.5 V over the length of 3–4 feet, which severely limits the performance of your system in all parameters.
To combat this situation I normally use lead wire that is at least one size—and preferably two sizes—larger than what comes with the servo. Overkill in this circumstance is not a bad thing, other than adding a little weight.
Also keep the number of mechanical connectors to a minimum. I usually hard-solder the extensions rather than use a connector, so that the only mechanical connection is at the receiver or, at most, the wing root and receiver.
I'll continue with the second part next month. Until then, be safe and have fun. MA
Transcribed from original scans by AI. Minor OCR errors may remain.
