Micro-Flying
Route 4, Box 369, Farmville VA 23901; E-mail: [email protected]
GREETINGS, fellow modelers. I wish you a merry Christmas and a happy new year as we start 2002.
My focus this month is propulsion. Most of us are using some form of electric power, but I am going to briefly discuss a couple of alternatives.
A photo shows my Perky model (August 1994 Model Aviation) with a throttled Cox .010 mounted. The carburetor is a home-brew unit that is one of a kind. (I will be glad to furnish a sketch of the construction if you send a self-addressed, stamped envelope.)
The principal benefit of using a fuel-powered engine is a much higher power-to-weight ratio than normally seen in micromodels. I was pleasantly surprised by the range of throttle ability available as well as the general dependability.
Naturally, there are all the drawbacks of an IC (internal combustion) engine, including noise, fuel mess, and limited flying sites. Still, this is a workable option if maximum performance is the issue.
Of course, the standard engine without throttle does a fine job if you can handle full-speed operation only.
A different photo shows my Pepper model (March 2000 RC MicroFlight). The motor is the workhorse DC 5-2.4 fitted with Kenway 4.2:1 gearing.
Of the various choices for a micro Electric project, the DC 5-2.4 has shown the best power/weight performance available; most likely because of the coreless construction, this motor's efficiency is superb.
The normal battery complement is seven 50 mAh Ni-Cds, although many fliers are reporting excellent results using "Double Time" 120 mAh NiMH cells that John Worth sells (Cloud 9 Micro RC).
Fitted with the 4.2:1 gears, the most useful propeller is a six-inch Peck-Polymers rubber power prop trimmed to 5.25 inches. This motor is also sold with higher ratio gearing, which will drive larger propellers at lower rpm for very effective indoor performance.
Another picture shows my micro Volksplane Scale model (a future Model Aviation project). The power unit fitted is the MPS-1 sold by DJ Aerotech. Furnished complete with propeller and spinner, this is a very attractive choice for budget-minded builders.
The power is a little less than the DC 5-2.4, but the unit is lighter and runs on fewer cells (typically six 50 mAh Ni-Cds). This is the same power unit that DJ Aerotech furnishes with its very popular Roadkill kit series.
Shown are some offerings from the prolific manufacturer GWS (Grand Wing Servo). The geared motor came from the popular Lite Stik and is designated GWS IPS DXA.
This rugged motor is very well-suited to somewhat larger and more robust projects with wing areas ranging from 150 to 400 square inches. GWS offers this power unit in a variety of gear ratios and with several different motor options. Many designers of excellent Indoor models as well as plenty of outdoor fliers are working with this power unit.
The battery requirements of the GWS IPS DXA are greater than the smaller motors; 120-150 mAh Ni-Cds are a popular choice. Other modelers are fitting packs of 270 mAh NiMH cells without a weight penalty.
The ducted-fan unit in the picture is so new that I have not had a chance to build a model for it or to really wing it out. The fan diameter is two inches and the whole unit weighs slightly more than an ounce.
This is also a GWS product, and it uses the same motor as the geared propeller drives. Who will be the first to launch a micro ducted-fan project?
I've included a photo of the geared GWS propeller drive and a few of the propellers suitable for use with it. GWS sells the plastic propellers on the left, and those on the right are APC blades. I tossed in a few of my carved wooden props as a reminder that this is still an option.
For most, the plastic blades will do a fine job; they are sturdy and economical. My foray into making custom blades has been very encouraging, in that the propellers cut from pith or basswood are lighter and can be matched to the models' requirements.
The motors and gear drives I have shown are the tip of the iceberg when it comes to the full list. One that comes to mind for the really small and light models is the Kenway KR-1 drive, which uses the popular Mabuchi N20 low-voltage motor and 4.2:1 gearing.
Several other manufacturers offer a similar package using this same motor and gears. There is even a unit that mounts two of the N20 motors driving one shaft for still more output.
The small KR-1 runs nicely from three to four 50 mAh Ni-Cd cells; of course, the larger twin requires more battery capacity.
Other larger options include the very popular coreless DC 1717, which is generally sold with a concentric gear system mounted on the motor.
Considering how rapidly the market is expanding, keep an eye on the advertisements and notice what the successful fliers are using.
Another area of rapid growth is propellers. GWS has an extensive line of plastic propellers at very economical prices. The props that Landing Products (APC) offers are very high quality, and there are sizes that fit the indoor flier's needs nicely.
Several vendors are offering imported carbon-fiber props that are of the highest quality, and the sizes are suited to many indoor projects.
Another possibility is the propeller line sold under the label of ARC. These economical props are made with tough, laminated fiberglass blades bonded to carbon-fiber shafts, which are then mounted in a universal hub.
Many pitch angles and several blade shapes are available to meet a wide range of interests. Check out the ARC props at Anything RC (www.anythingrc.com). The people there are very accommodating.
I had intended to go deeper into the battery possibilities, but it looks as though that will be a future topic. The choice of batteries of various chemistries and the chargers suited to them is just too involved for the space available.
I received a delightful letter with pictures from James R. Florini, 7179 Frank Long Rd., Jamesville NY 13078-9450. He is active with the Central New York Indoor Flying Society and is especially enthusiastic about the Little Larry model featured in the September 2000 Flying Models.
James feels that this rather large and quite light model is an excellent project for someone who is just starting in indoor flying.
Apparently the Little Larry has an unusually low cruising speed and very tight turning capability. These qualities are the result of a very low wing loading—a desirable feature of an indoor model.
James relates that all of these models they have built use the GWS "A" drive and usually the GWS 10 x 4.7 propeller.
The most popular battery choice are six- to seven-cell packs of NiMH cells. The most popular choice of covering is Reynolds® Crystal Wrap, and they adhere it with a UHU®-brand glue stick.
A photo shows a portion of the models flown by this obviously talented and active group. Note the size and quantity of the Little Larry models. All of the machines seen are very well done.
Another photo shows a few members of this active group with their Little Larry models. From the left are Dick Green, Larry Vogt, Gordon Wheler, Gary Good (he is the son of the Radio Control pioneers), and Ray Armstrong.
Thank you, James, for the report on your group's activities and the fine pictures. If it were not for the weather in your neighborhood in the winter, I would be sorely tempted to come join in the fun.
Now that the rest of you have seen what one group is doing, how about sending some pictures and reports of your activities? It would be especially nice to see some material about all the neat custom equipment and models out there.
This really is your column, and I would appreciate getting some more pictures and letters (sketches, whatever) about what you are up to.
The same message goes out to you manufacturers who would like to spread the word about a new product. If you will get the material to me, I will try to see that word gets out.
Thank you to all of you who have written with words of encouragement; I appreciate that. Do you have a topic you would like to see covered? Let me know.
Meanwhile, I will see you out flying. MA
Transcribed from original scans by AI. Minor OCR errors may remain.
