Frequently Asked Questions
Bob Aberle | [email protected]
Sanyo Eneloop battery cells
Q344: "I read your Q/A #316 concerning the use of Li-Poly batteries in RC transmitters. I recognize that allowing the battery voltage to fall too low will ruin that type battery. But a technically inclined friend of mine just mentioned a new Sanyo battery type that might have application for our RC systems. I believe it is known as 'Eneloop.' What can you tell us about this?"
A344: The new Sanyo Eneloop cells are AA in size and, if my information is correct, have a capacity of 2000 mAh. They are charged the same way NiMH cells are.
Eneloop cells are interesting because of their characteristics; I can see them being well suited to RC transmitters, and they could also be used in a four-cell configuration for airborne use. The cells come ready for use—at the time of purchase they are fully charged and can be put into service immediately.
Their primary feature is that they retain their stored energy for exceptionally long periods. You can return from flying, charge your pack, and then let it sit until you are ready to fly again. Eneloops maintain a full or near-full charge for months, so if you want an RC transmitter battery, or even an airborne pack, to be ready whenever you get the urge to fly, it will be waiting.
The average cell price is approximately $4 each. An eight-cell transmitter pack for about $32 isn't much more than a regular NiMH pack and probably less than a three-cell Li-Poly pack.
Pete Rissman, an AMA member, told me he purchases packs of individual Eneloop cells from Amazon.com and then makes his own packs. He also said Robotic Power Solutions offers premade packs. I haven't pursued any of this yet, but I wanted readers to know about this battery technology. Be aware that several battery experts don't think there is anything particularly special about these cells.
Most recently I learned Eneloop cells are available in AAA size, with a stated capacity of 800 mAh. This might be interesting for four-cell airborne battery packs.
Freeware motor-selection programs
Q345: "I've heard you refer many times to two different electric power motor selection programs, namely Moto-Calc and Electri-Calc. In fact, MA's Electric Columnist, Greg Gimlick, in the December 2007 issue, described the basic Moto-Calc program in depth. Both of these programs must be purchased, although for a very reasonable price. I've heard that there are some 'freeware' programs available that can do close to the same job. Can you tell me how I could access such programs?"
A345: I can refer you to three freeware programs that can help with motor selection. A problem with any of these programs is they don't include all data for every motor, propeller, or battery pack, but you can add your own information. If you have several programs, you can "jump around" to find one with the data you need.
The commercial programs are quite detailed and sometimes provide more data than necessary, which can add complexity. A free program I use a lot is provided by Diversity Model Aircraft, which has been supplying batteries for our hobby for many years. In this instance you don't need to download the program; it is available on the website and I have it stored in my PC under "Favorites." I find it easy to use: select the motor, propeller, and battery, then make changes to parameters until you can "fly" your aircraft.
There is a downloadable freeware program from France, though it isn't exactly easy to navigate. When the home page comes up, go to "Moteurs," then select "MM_Calc_v212 (zip) english version." From there you are on your own. I found it somewhat difficult to use, but many modelers report success with it on forums.
A freeware program from Germany you can download is the Drive Calculator. Select the English version and proceed with the download.
I use the purchased ElectriCalc program along with the Diversity Models freeware. You can also read my two-part article about motor selection posted to the Sport Aviator AMA webzine.
Soldering: holding wire to connector
Q346: "In a column several months back you talked about soldering irons and soldering techniques. One of the problems I've had is running out of hands when attempting to solder wire to connector pins. Got any ideas?"
A346: Marshall Smith, an AMA member, came up with a simple idea that requires only two clothespins mounted to a board or a scrap piece of balsa. A clothespin grips the wire, and another clothespin holds the connector. Position the wire so it touches the connector pin, and your hands are then free to hold the soldering iron and the solder.
Micro models: printing plans on balsa
Q347: "Over the past year or two I've seen references to micro size model aircraft whose full-size plans could be downloaded from the internet and then printed in color directly on to balsa sheeting. I'm sorry to say that I lost track of the reference sources. Can you get me back on track?"
A347: Several modelers use this technique; one is MA's "Small-Field Flying" columnist Paul Bradley. He and his brother Ralph maintain an interesting website broken into three categories: FF models (primarily rubber powered), electric-powered RC models, and "Ralph's Micro R/C Models."
The site is extensive and features building techniques, reference material, and links to related sites. Paul has produced reproductions of some old 1950s Top Flite Jigitime models and Carl Goldberg sheet-balsa rubber-powered free flight aircraft. Any of those designs could be converted to micro indoor electric-powered models.
Paul developed a technique using an ink-jet printer to print in color directly onto 1/32" balsa. You can download plans and templates from the website. He included this information in one of his columns several years ago; it would be worth searching back for it. In a sense, what Paul does with balsa is similar to what Fiddlers Green is doing with paper, as I explained in last month's column.
Securing thin landing gear wires
Q348: "One of the problems I have when building parking lot and indoor RC aircraft is attaching the landing gear strut wires. DuBro offers nylon landing gear straps (No. 238-B) and several other distributors sell 'J' bolts, but generally the smallest diameter wire these straps and bolts can handle is 1/8-inch. That's still much too big for my application. What does a person do with 1/16-inch (.062) diameter wire landing gears?"
A348: I found a simple solution. Common nylon zip ties (ties) available in large quantities from home-improvement stores such as The Home Depot will do the job.
For parking lot and indoor aircraft, nylon ties approximately 4 inches long by 3/32 inch wide work well. Cut slots in the balsa or plywood fuselage structure. The nylon ties wrap around the wire and anchor it to a firm crosspiece, usually made from spruce or basswood. Pull the tie tight and cut the excess length.
You can cut off the tie if you need to remove the landing gear; it can be easily replaced when remounting the gear.
I used this technique in two recent micro designs featured in construction articles in the January and February 2008 issues of RC Micro World online magazine. One model is a stick trainer I call the "Mita," and the other is a 75%-size Profile Dakota biplane.
I also use these nylon ties to keep wiring neat. With new 2.4 GHz spread-spectrum radios, it's important to dress the cabling inside your aircraft. Loose or scattered wiring can affect radio range.
Please write in with your questions because that is the only way we can keep this column format going. When referring to previous Q/As (for follow-ups), provide the number as a reference. — MA
Sources
- Diversity Model Aircraft motor-selection program
(858) 693-8188 http://brantuas.com/ezcalc/dmal.asp
- Drive Calculator
- French motor-selection program
http://electrofly.free.fr/download.php?lng=fr
- Paul and Ralph Bradley's Model Airplane Page
- Robotic Power Solutions
(502) 525-2964 www.battlepack.com
- Sanyo Eneloop batteries
- "Selecting Electric Power Systems" by Bob Aberle
www.masportaviator.com/ah.asp?CatID=2&ID=76 www.masportaviator.com/ah.asp?CatID=2&ID=77
Transcribed from original scans by AI. Minor OCR errors may remain.
