Frequently Asked Questions-2011/09

Author: Bob Aberle

Edition: Model Aviation - 2011/09
Page Numbers: 82,83,84

Frequently Asked Questions — Bob Aberle | [email protected]

PLEASE WRITE in with your questions; that is the only way we can keep this column format going. When referring to already published questions and answers (for follow-ups), always provide the number as a reference.

Also note that references to addresses and websites are placed in a group, separate from the text, at the end of this column under "Sources." A "Tips" feature is provided in addition to frequently asked questions; these hints are numbered in the same sequence as the questions and answers.

Q-514: Circlip retainer washers

Q-514: AMA member Al Schmidt asked, "Where can I purchase the small circlips that are used on the shafts of our brushless outrunner motors?"

A-514: This was a basic and simple question, but read on carefully because there is much to learn from this answer. A circlip is actually a retaining washer.

Most modelers would be more familiar with the "E"-shaped retaining washer. These washers are common and are pressed into position using ordinary pliers. As many have discovered, installing these "E" washers can be a problem, especially if one flies across your shop and is lost forever. A circlip's shape is similar to that of an "E" washer, with one exception: there are two holes at each end of the "C"-shaped washer.

What makes the circlip unique is that those two holes accept the tips of a special pair of pliers. Attach these pliers to the two holes and, as you squeeze the pliers, the circlip will expand, allowing it to be easily installed on a motor shaft (or for many other applications). Because the circlip is attached to the pliers, it won't "fly" away from you. Because of this feature, many modelers have abandoned the "E"-shaped retaining washers and gone to circlips.

One of the best sources for circlips is McMaster-Carr. I've listed the company's website in the "Sources" section. I have included sources for the circlip washers as well as the special pliers.

Al Schmidt ordered his washers and pliers and was happy with the fast service. He explained how he replaces worn-out bearings on his brushless outrunner motors. Al's techniques seem simple.

He found that the Boca Bearing Company can supply a variety of tiny ball bearings that fit most of our brushless outrunner motors. I've listed contact information for Boca Bearing in the "Sources" section. With Al's permission, I have also included his personal email address. Al indicated he would be happy to describe his motor-rebuilding process to any reader who might be interested. Thank you, Al, for making that offer.

Circlip retainer applications are not limited to electric motors. Many of the carburetors on our fueled engines employ this type of retainer, so keep that in mind.

Q-515: Help understanding computer-controlled RC transmitters

Q-515: "I'd like to get the most out of my new computer-controlled RC transmitter but I'm having a tough time understanding the detailed manual that came with it. Are there any books that take you through the basics, without requiring a degree in electrical engineering?"

A-515: There are probably many such books available. They tend to change throughout the years as new technology comes available. It is smart to buy a new book on the subject every few years.

One book I discovered recently was written by the editors of Model Airplane News, published by Air Age Inc. The 30-page reference book is titled Radio Programming Essentials.

It is available in printed or digital format for $17.95 plus postage. The book describes the main transmitter screen and graphic displays. Then it gets into the system menu, which includes model type and model name, switches, knobs and buttons, wing type, and tail selection.

Then it delves into the functional menu, which includes exponential and dual-rate controls, servo travel, reversing, and trims/subtrims. Finally the book describes advanced programming such as V-tail and elevons, aileron differential, and rudder-to-elevator mixes.

The book uses a Horizon Hobby Spektrum DX8 transmitter in all the photographs, but you will find it applicable to most other system brands. The Air Age website is listed in the "Sources" section.

Q-517: Twin electric motors not starting together

Q-517: "I have an electric-powered twin aircraft. In other words it has two motors. Why does it take two or three tries to get the motors to start together? It's random; one will start normally while the other struggles."

A-517: I consulted Tom Hunt, one of the foremost electric power experts in the country. Tom provided a checklist of questions; the answer to any one of them might point to the cause of your motor start-up problem:

Are both your motors and ESCs the same brand/model/type?
Were they bought at the same time?
Is it always the same motor that starts late?
Try swapping ESCs and see if the problem moves with the ESC or stays with the motor.

If, after following these checks and making substitutions, you still have the start-up problem, you may have to live with it. But swapping in a different motor and/or ESC of the same brand and type might correct the situation. This isn't a definite answer, but it should get you into the ballpark.

Follow-up to Q-474 (from the December 2010 Model Aviation): In that issue, a reader showed an interesting aircraft storage rack made from PVC tubing and Tee connectors. The problem is that I didn't mention the Tee connectors were a special kind and not the same as the more-common variety you might find at Home Depot or ACE Hardware.

The kind of Tee connector you want snaps onto the support tubing. After snapping the Tee to the support pole you just slide it into position to accommodate your particular size aircraft.

Along these same lines, another reader showed how he makes storage racks to support his aircraft while being transported in his van or SUV. I've included a photo of that idea. In this instance, the suggestion was to use adjustable shelf brackets and standards. It's a different approach, but interesting.

Tip 515: I couldn't resist mentioning this YouTube presentation of the Cosford 2007 large model aircraft show in the United Kingdom. We are familiar with our large aircraft shows throughout the US. This video provides a perspective from another country.

The site is listed in the "Sources" section. I thank Frank Korman for providing this reference. After viewing the YouTube video you might also want to visit the Large Model Association's website.

Tip 516: AMA member Frank Pisano offered this suggestion after reading a construction article I had published. The airplane was made from sheet foam. I had suggested that a carbon tube, much like an arrow shaft, be placed on the bottom of the wing at mid-chord as reinforcement.

Frank had a better idea. He uses a DPP carbon-fiber pultrusion strip that he obtained from A2Z Corp. (the former Peck-Polymers Company, now based in Colorado). It comes in 1, 2, and 3 mm widths by 0.13 mm thickness on a 10-meter roll. Frank uses this material for wing spars as well as TE or LE reinforcements. The carbon fiber is attached to the structure using UHU POR adhesive.