Frequently Asked Questions 2010/07
Bob Aberle | [email protected]
Installing small servos
PLEASE WRITE IN with your questions; that is the only way we can keep this column format going. When referring to questions and answers that have been published (for follow-ups), provide the number as a reference.
References to addresses and Web sites are placed in a group, separate from the text, at the end of this column under "Sources."
Q453: "I noticed in many of your construction articles that you use double sided tape to attach the servos to the inside of the aircraft's fuselage. How safe is this technique and are there any 'tricks' I should know about?"
A453: The basic "trick" is knowing the limitations of this process. I use double-stick tape on all of my small or micro-size servos, such as the Hitec HS-50s, HS-55s, and HS-65s; Blue Arrow types; and even Horizon Hobby E-flite S60s.
One might use these small servos in a model weighing as much as 10–12 ounces total. For higher weights, I use the time-honored wood bearers and screws that are usually provided with the servos. It's a matter of common sense.
As the airplanes get heavier, more loads are placed on the servos. Those higher loads might cause double-stick tape to come loose. If that happens you will have no control at the control-surface end. However, I'll share some of the tricks I employ to make tape-mounting servos as safe as possible.
To begin with, you need a good, dependable tape. I have successfully used 3M Scotch Double Sided Mounting Tape for many years. In particular, I like catalog item 214DC, which is a 1-inch-wide variety that comes on a roll measuring 1.52 yards. (It is available nationwide at stores such as The Home Depot, Lowe's, ACE Hardware, and many others.) This tape has a protective backing on one side. I've found that once the package is open, the tape has a certain shelf life; it eventually dries out. So when I open a new package, I date it with a marker. Regardless of what is left on the roll after a year, I discard it in favor of a new roll. This doesn't happen often since I use so much of this tape, not only to attach servos, but also to affix receivers and ESCs.
The next important item is surface preparation. If you stick the tape to raw balsa or plywood, the adhesion will be poor. Doing it that way, I have had servos almost immediately fall off of the fuselage.
The trick is to seal the surface of the wood, using either a coating of CA glue or even five-minute epoxy. Once this is done, the double-stick tape will adhere with no problems and the joint will last for at least several years without the servo working itself loose.
Watch that carefully! If the servo moves, the likelihood is that it will come loose from the tape after a while.
There is one problem that might arise if your control rod or hinges cause a binding effect. If those parts are not moving freely, you will notice that the servo case will shift slightly as the servo arm is rotated.
Some modelers still worry about the long-term use of double-stick tape. At times they add a silicone adhesive to it. I've even seen this adhesive used on some ARFs and RTFs.
However, some silicone adhesives can give off a corrosive vapor that raises fits with electric wiring and even connectors. A specific type of noncorrosive silicone adhesive is intended for use with electrical wiring.
I found many such adhesives, such as ASI and Permatex, by using an Internet search engine. See the "Sources" section for those companies' contact information.
One last caution! Some modelers cover a servo with masking tape and then apply the double-stick tape or silicone adhesive. By doing this, they can more easily remove the servo when the time comes. But then the adhesion depends strictly on the tape used. I would not take that chance.
Q454: "I have an old glow engine that really looks like it is in sad shape, but I still wonder if it might be rejuvenated in some way. I can't even turn the engine over. What might I do to bring this old engine back to life?"
A454: A longtime friend and fellow AMA Hall of Famer, Dave Gierke, came to my rescue with this problem. There are probably many solutions, but following is an easy process as Dave related to me.
- Remove any non-metal engine components, such as O-rings, plastic carburetors, fuel lines, and plastic fuel tanks. Once you get the engine running, you will have to consider obtaining a new set of gaskets.
- Put an old propeller on the engine shaft.
- Obtain an oven-type glove to use to protect your hand.
- Get a heat gun, which you would normally use with covering material. This is actually a hot gun—not a hair-dryer type.
Holding the engine with your oven-gloved hand, apply heat uniformly while rotating the power plant to warm all sides. After approximately a minute of heating, try rotating the propeller (shaft). Initially you will feel a lot of resistance, but don't give up; continue applying heat.
Don't be alarmed if you see smoke coming from the engine. This is residual castor oil decomposing. It also indicates that you have reached the limit with heat application.
Try flipping the propeller. When it snaps back against the compression, you have reached your goal.
Let the engine cool, and then add after-run oil. Dave likes Marvel Mystery Oil.
The last step is to run the engine several times with your normal fuel. This will flush the remaining castor oil residue from the internal components, especially the ball bearings. That should do it.
Dave Gierke has written two excellent books about model engines, and you can obtain copies from the AMA. Check them out in the "Shop AMA" section of the Academy's Web site.
Q455: "Like most modelers today, I'm into mostly RC model aircraft. But I did get my start years ago with Free Flight, Rubber Powered models.
Is there a Web site you could refer me to that carries most of the supplies that I would need to once again build some Rubber Powered scale models?"
A455: I've mentioned several sources for FF rubber-powered model supplies, including rubber, special propellers and propeller shafts, thrust bearings and washers, DT fuses, and more. One I haven't mentioned is TailSpin Aviation.
I've listed the company's contact information in the "Sources" section. There is a place on the Web site where you can click on a box that will allow you to download a PDF of the complete TailSpin Aviation catalog. This site is most impressive.
Q456: "Bob, my husband has been involved with the model aviation hobby for many years. I have at times read some of his magazines and in fact occasionally read your FAQ column.
With Father's Day coming up, I was trying to find some item that reflects an interest in aviation to give to my husband. Might you have any 'shopping' suggestions?"
A456: I have to at least plug our fine AMA store, which you can access online from the AMA homepage by clicking on "Shop AMA." There are many items there, such as shirts, hats, ties, books, etc.
Awhile back, Irene Shurson sent me information about an aviation apron she makes and sells for $19.95. I included a photo of it in this column. It would be perfect as a barbecue or cooking apron, which your dinner guests would certainly appreciate.
Irene sells products under the name All Occasion Aprons. The contact information is in the "Sources" section.
Follow-Up to 412 (September 2009, Model Aviation, page 78): After making reference to solid scale models, I received a nice e-mail from Bill Hannan, a noted Rubber Scale modeler who has had columns in the aeromodeling press and has written many books. Bill is an expert in rubber-powered Scale, with a concentration on Peanut Scale—the tiny aircraft.
His book, Model Builders & Their Models International, contains a fairly comprehensive article about solid scale models. When I looked up this book on his Web site, I found many other interesting subjects and items.
I've listed Bill's contact information in the "Sources" section. Please do yourself a favor and look him up.
Sources:
- ASI
(800) 325-7040 www.americansealantsinc.com
- Permatex
(860) 543-7500 www.permatex.com
- AMA
(765) 287-1256 www.modelaircraft.org
- TailSpin Aviation
301 E. 11th St. Saint Elmo, IL 62458 www.tailspinaviation.com
- All Occasion Aprons
(319) 338-2259 www.alloccasionaprons.com
- Bill Hannan's Runway
(530) 873-6421 www.hrunway.com
Transcribed from original scans by AI. Minor OCR errors may remain.
