Electrics - 2009/02
RDRC Fly for Tots charity fly-in
TAKING OFF: It hardly seems possible that this is the February issue already, but I guess that's a sign of old age. The election is over and we may have another month or two before the 2012 campaign begins, so let's talk airplanes!
Fly for Tots: The Raleigh-Durham Radio Control club (RDRC) held its Fly for Tots Children's Charity Fly-In in late September here in North Carolina. This has been an annual event for the last 18 years or so, and Larry Lewis, along with the rest of the club, does an outstanding job. The gathering has grown each year, and the club gives 100% of all profits to charity, which for the last two years has been the Victory Junction Gang Camp.
Exactly 219 pilots attended and brought more than 700 aircraft of all shapes and sizes. Although this isn't an electric meet, the number of electric-powered airplanes at the event continues to grow. This year's fleet included everything from park models to Bob Violett Models jets. With factory pilots from Horizon Hobby and other competition teams doing demonstrations, there was never a dull moment. Jeff Foley brought his full-scale Stearman and raffled off rides; his profits were donated to the charity as well.
Robert Vess of Vess Aero did his part as the master of ceremonies and kept the action moving along nicely with many RDRC members' help. He also gave demos with his KingCat jet and offered his usual high level of expertise to anyone needing or asking for help.
Robert is the brain behind Vess Propellers. He taught at North Carolina State University's aerospace engineering school before moving on to aerodynamic development for some of the top teams in NASCAR.
A moving event within the event was the re-enlistment of 15-year Army Sergeant Roger Flannegan from Bravo Company 3rd VSTV in Fort Bragg, North Carolina. He re-enlisted for the fourth time Saturday at show center, with all veterans who were present standing on the flightline. Extreme Flight JR Team member Lee Morey hovered his 110-inch Extreme Flight Yak-54 in the background.
As a retired Army veteran, I was thrilled that Sgt. Flannegan chose the Fly for Tots event as the place of his re-enlistment and requested all of us old vets to stand behind him. He will serve his fourth tour of duty in Iraq later this year, and I wish him luck and another safe return.
The real magic this weekend was the final tally for the charity: $25,000. All that money goes directly to the Victory Junction Gang Camp.
If you can work it into your schedule this fall, you owe it to yourself to attend this event. The AMA was well represented there by its president, executive vice president, district vice president, and several others.
Thanks to Dustin Hedrick for his photos and all the RDRC gang for putting on a great event!
Arming Switches
Several months ago, I wrote briefly about arming switches, mostly referring to larger electrics. Instead of going into depth, I referenced Greg Covey's article on RCUniverse, because it was so thorough and I know him well enough to know he's dead on with his information. See the "Sources" listing for the website address.
That generated several e-mails and many great ideas and suggestions. I heard from people who hate the idea of arming switches and those who wouldn't fly without one.
In the latter group were some who bought commercially available units and others who wired their own. One reader who makes his living doing failure-mode analysis provided some excellent food for thought on the various methods.
The bottom line is that there is no consensus. That's okay, and ESC manufacturers have left the issue up to the end user after years of making various arming devices, only to have users cut them off or bypass them.
The method I like most in my airplanes is the version available from Maxx Products International (MPi). Model 6970 comes with Deans Ultra Plugs installed, and model 6980 comes with Anderson Powerpoles. The cost is $10, and it can be built into a hatch or scale accessory so that it's hidden and accessible.
The beauty of this setup is its pure simplicity. There are no switches to fail or get knocked. The model can have its motor battery plugged in and assembled while the airplane is in the pits or on display, but there is no way the motor can be activated until the plug is physically pushed into the connector.
You can make one if you're so inclined or don't want to spend $10. But these switches from MPi are nicely made and well worth the price by the time you purchase all the connectors separately to make one.
One great suggestion and method for arming came from Mark Qvale. He was concerned about the safety of his electrics and, being an engineer, he took it upon himself to do some research.
After coming up with his idea, Mark ran it by the people at Castle Creations because he was going to alter one of the company's controllers to use his method. They told him they didn't see any problem with it, and he has used it successfully for months since doing the modification.
One of the things we discussed was the need to check with the ESC manufacturer before altering the radio wire. This technique depends on the ESC allowing no signal from the radio to the ESC and programming the speed control to disengage any signal to the motor without a proper radio signal.
With Mark's switch placed where it is, the signal from the radio is blocked and the ESC won't arm the motor. This allows him to check all of his controls, etc., without the motor armed.
Not all controllers are so solid in their performance when a radio signal is lost or blocked, and that's why you need to check with the manufacturer before using this method. Prudence would suggest thoroughly bench-testing your system.
Thanks for your suggestions about arming switches. I believe in them and use them in all of my large models.
Keystone Indoor Electric Fly (KIEF)
MA technical editor and longtime friend Bob Aberle wrote me the other day to report on the KIEF event held in Pennsylvania in late October. It came along at a great time, since many indoor fliers were left without a venue when the JR Indoor Electric Festival had to be canceled because of a windstorm that blew down and destroyed the dome.
For a full report on the KIEF, point your browser toward the RC Micro World Online Magazine. The "Sources" listing contains the address.
I'll be adding this to my list of places to go this year, because the flying facility looks perfect. It's huge and sectioned off into three areas, to keep the micros from being eaten up by the larger models and 3-D flyers.
I asked Bob what the restrictions were, and he said:
"Basically the ground rule was that the park flyer type and 3-D models were limited to a 16-ounce flying weight. But in several cases a few very slow flyers were allowed to fly at 20 and 21 ounces at the discretion of the CD. On the micro end we set 6 ounces as the max limit.
"Keep in mind that there are two floor-to-ceiling nets that separate the larger models on one end and the micro airplanes at the other. That still leaves the center stage at 300 by 200 feet with an 85-foot ceiling."
This could become a big event, and one of the things I like about it is that it's not a commercial gathering. Although those are fun to attend, sometimes the regular ol' pilots get lost in the production and it's no longer a flier's event. Since the KIEF had 80 pilots its first time, it looks like it will be popular.
Check out the Cloud 9 website and take a look at the RC Micro World Online Magazine while you're there. There is lots of good info if micro-flying is your thing.
How Many Poles Are in a Motor?
Since writing about my Eagle Tree Systems data logger a few months ago, I've gotten some e-mails asking how a user is supposed to determine how many poles a motor has. This information is required when you set up your computer program so it will interpret the data correctly.
The easiest way to determine the number of poles is to read the documentation for the motor; it is hoped that the information will be there. If it isn't, a method is described in the instruction manual from Eagle Tree.
That's a kind way of saying, "Read the instructions closely." But in case you missed it, following is the section of the manual describing how.
"To calibrate the RPM sensor, you need to know the number of 'poles' your brushless motor has. This information is normally supplied by the motor manufacturer. For outrunner motors, the term 'poles' refers to the number of magnets in the motor (not the number of stator teeth, 'legs,' or 'hammerheads'). For example, if you have an outrunner with 10 teeth on the stator and 14 magnets in the flux ring, the motor has 14 poles. For inrunner motors with a central magnet, the term 'poles' refers to the number of magnetic poles present on each magnet (always 2, so enter a '2' for poles).
"If you are uncertain about the number of poles, or want to verify you calculated correctly, a hand-held tachometer can be used to compare the RPM value displayed real-time by your recorder, in a bench test (assuming it is safe for you to do this). Real-time display is available in Recorder USB Live Mode, on the MicroPower PowerPanel, or with the Seagull Wireless Dashboard. If the value displayed is incorrect, you can change the poles setting to adjust the displayed RPM value. For example, if your handheld tachometer reads 4000 RPM, and your Eagle Tree data shows the maximum RPM of 8000, you would need to double the number of poles by 2."
There you have it, easier than most of us try to make it.
Eagle Tree Systems has great support, and of all the data loggers I've tried, I find this company's to be the easiest to set up and use. Nothing against the others, but the support available from Eagle Tree has proven to be great when I've asked questions.
Final Approach
That's it; the space is gone and it's time to head for the shop. I hope to see many of you at the WRAM Show and Toledo R/C Expo in the near future. MA
Sources
- Fly for Tots
- Victory Junction Gang Camp
(877) 854-2267 www.victoryjunction.org
- Vess Aero
- Greg Covey's article in Amp'd Issue 2: "Arming the Big Boys"
www.rcuniverse.com/magazine/article_display.cfm?article_id=950
- Maxx Products International
(847) 438-2233 www.maxxprod.com
- Keystone Indoor Electric Event coverage
- Eagle Tree Systems
(425) 614-0450 www.eagletreesystems.com
Transcribed from original scans by AI. Minor OCR errors may remain.
