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From the Milwaukee Are Radio Kontrol Society, Franksville, Wisconsin

Vibration: How to Keep it Out of Your Radio

by Dennis Vollrath, Editor of The Flightline

One of the real problems with our hobby is inevitable, the heartbreaking crashes that can occur with our flying models. Once our club members have some experience flying these airplanes, pilot error becomes less and less of an issue. What is a real concern is when the model suddenly fails to respond to the pilot’s command.

Several of these crashes at our field have involved the larger, and more expensive, models. When these are lost, they can involve possible safety issues before the crash, along with potential total loss of all airborne equipment.

For what it’s worth, I’ve been flying electric models for 25 years, and outside of one or two issues where the electrical noise from the electric motors interfered with the receiver, I’ve never had a total loss of control with these electric jobs. Don’t know, maybe I’m just lucky, but one big difference exists between the electric models and the glow/gasoline powered models—vibration.

I wrote an article in the defunct RCM magazine on vibration, and how to keep it out of our radios. This article required the entire airborne radio system to be installed inside a plywood box, with nyrods connecting all servos to their respective model surfaces. The plywood box could then be isolated from the fuselage with a few small, soft foam blocks. The effectiveness of this setup was easily verified by removing the wing, and running the engine. Just place your fingers on the fuselage near the radio system, and compare vibration levels at the fuselage to that of the receiver. If done right, the vibration levels at the radio/battery/servo box will be near zero.

Yes, this type of setup does have drawbacks, such as added weight, extra size of the radio box and whether it will fit inside the fuselage. And, obviously, no one in their right mind will connect a servo of a 50cc gasoline-powered model to the rudder/elevator with a nyrod.

Please read the following and determine for yourself if it would useful for the models that you fly.

What options do we have? It’s a given that we can’t change how the servos are mounted. They absolutely have to be solidly mounted with very stiff linkages to the elevator/rudder/ailerons to prevent soft control of these surfaces, or even worse, flutter of the surfaces. At any rate, most of the larger models have dual servos on the elevator and ailerons. Failure of one servo hopefully will allow enough control by the other servo to get it safely back on the ground in one piece. Even still, servo failures are rather unusual in modern radios, even with larger models.

This leaves the receiver, battery, and on-off switch. Try building a plywood box out of Lite Ply, maybe a ¼-inch bottom, and 3/16-inch sides. Size this box to allow room for the receiver, battery, (or batteries in dual battery installations) and the on-off switch. The receiver/battery mounts can be hook-and-loop or Velcro.

Mounting this inside a model with foam will allow a considerable reduction in vibration levels to these components. The box should be mounted with soft foam, such that it is free to move perhaps 1/4 or 1/2 inch or so. Placing the on-off switch on the box gives it vibration protection as well. Try this for a vibration-free connection of the switch to outside the fuselage: drill a small hole through the plastic tab of the switch slide. Then insert two lengths of fish-line-type cord through the small hole, one pulled through the right fuselage side, and the other the left. Just pull one for on, and the other for off. Using this setup should hopefully make this portion of the on-board system at least as reliable as my electric models.

Note the illustrative photo above. Normally of Lite Ply wood, the photo model is balsa to show the concept. It could even have a lid. All the wiring between the switch, receiver, and battery can be placed inside of the box. All that would exit the box would be the servo leads. One way to mount this thing would be to construct another larger box with clearance on all sides. Then insert small pieces of foam between the large box and smaller box. The larger box would be solidly mounted to the model. It’s worth thinking about. Q

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