Electric highlights of the 2006 Weak Signals (Toledo) Show
Greg Gimlick | [email protected]
Toledo Weak Signals Show
In the last column I got into some technical thing and building motors isn’t for everyone, so this month I’ll cover a wide variety of topics including Toledo impressions, data acquisition, and random thoughts of an “old guard” electric-power modeler.
The big question I’m asked when I return is always, What’s the one highlight of the show this year?
Although there were some cool things again, the highlight had to be the pure quantity of electric stuff available. Almost every booth had something for the electric-power flier, and the proliferation of tiny indoor electrics was a marvel. Just as impressive was the advancement in Giant Scale Electrics, as evidenced by visits to AstroFlight and Castle Creations booths.
Last year I whined loudly about the demise of the indoor fly the Perrysburg Electric River Flyers (PERF) group used to put on at Bowling Green State University during Toledo Show weekend. It was swallowed up by the more commercial indoor Electric Tournament of Champions, and the regular ol’ indoor fliers with micro-sized airplanes were left without a place to have fun.
Big kudos to the PERF group for coming up with a gym near downtown that allowed us to have a great evening of relaxed micro indoor flying. We had a blast, and even my 0.75-ounce Air Hogs Aero Ace spent most of the night in the air. This is a great little airplane, and I think half the people in attendance must have taken a turn at the sticks. Thank you, PERF, for putting on this event!
Eagle Tree Systems — Data Acquisition for the Rest of Us
For a few years there have been in-flight data-acquisition systems for remotely controlled vehicles, but you needed to bring your whole wallet if you wanted one. I’ve lusted for one to use with product reviews so I could give real-time results with accurate numbers when I evaluated a system in an airplane. In the past I’ve done the math and the projected performance calculations with the help of ElectriCalc and MotoCalc. It’s been useful and pretty accurate, but nothing can really tell you what’s going on unless you can get the data during the flight. Eagle Tree Systems to the rescue!
The company’s Seagull Pro system is the ultimate but is beyond the reach of many modelers, and quite frankly most don’t need something that is that expandable. If you’re a competitor, it’s certainly the way to go, but the average flier will be more than happy with the new MicroPower system. Following are the MicroPower’s key features:
- Logs pack current to 100 amps and voltage to 45 volts.
- Software computes wattage, mAh, etc., for complete electric-flight data.
- Accepts optional inexpensive sensors for temperature and rpm (magnetic or optical).
- Supports simultaneous temperature and rpm sensors or two temperature sensors.
- Weighs approximately 0.5 ounce (17 grams). Version with wire leads weighs slightly more.
- Supports USB Live Mode, which lets you see what is happening in the model live on your PC.
- Has an adjustable logging rate (one to 10 samples per second) and lossless data compression for long log times.
- Comes with state-of-the-art Windows virtual playback display and graphing.
- Features powerful graphing software with advanced charting features, such as amps vs. volts.
- Has Internet-updatable firmware. As Eagle Tree adds new features (or needs to fix a firmware bug), the update is just a download away — there is no need to ship hardware back and forth.
I grabbed this list off the Web site so I wouldn't have to type it myself, and every bit of it is true to the letter. I've used my system several times, and it's extremely helpful.
Would I like to have airspeed? Sure I would, and it's available on the Seagull system if I want to spend that much. We want to know what our current, voltage, and rpm is doing, along with some temperature information, and every bit of that is available on the $70 MicroPower system. The additional sensors you might want are inexpensive, ranging from $10 to $15.
The system also features a "live mode," so if you're working in the shop you can read everything on your computer screen while it's happening. I normally just use the memory buffer of the unit and download it to my laptop after my model lands, but the live feature is neat when you're trying different propellers and gearing combinations because you can get the static info instantly.
There are several options for sampling rates, which will extend the record time of the unit while reducing the number of readings per second.
If you're still wondering if having a data system is worthwhile, let me tell you a story. While setting up my 1/4-scale Gee Bee R-2 I ran all the static numbers and found the setup that worked well.
I called Pete Peterson at Model Electronics Corporation (www.model-electronicscorp.com) and bought a Merlin 2000 motor geared 5.5:1 with an MEC Monster Gearbox, Castle Creations HV-85 controller, and two "Twenty" PolyQuest 45-3700 Li-Poly packs in series. This setup spins an APC-E 20x10 propeller at 5,500 rpm and draws approximately 43 amps, giving me roughly 90 watts per pound.
Every now and then I heard a strange sound from the Gee Bee, and each time I checked things out everything seemed fine. It was momentary, but clearly a change in sound.
I mounted the MicroPower system with the optical rpm sensor reading the propeller and a temperature sensor on the motor. The system automatically logs the voltage and current. I ran the system until I heard the sound and then repeated the run. This gave me enough data to see whatever was happening twice.
I downloaded the data, which is a simple matter of hooking the special USB cable to the unit and my laptop. When you run the data playback, you can see the gauges and numeric readings in real time as the clock runs, and you can pause it at any time. My two runs accumulated almost five minutes of data, and the buffer wasn't nearly full.
As I watched the data run, I suddenly saw the rpm drop and the voltage rise while the current dropped. It recovered within a couple seconds and ran along fine until it suddenly did it again. There were my two data points for the sound I heard!
What does it tell me? My guess was that something was allowing the propeller, pinion, or spur gear to slip momentarily. This would account for the sudden drop in rpm which was reading from the propeller and the reduction of load that would cause the battery voltage to increase.
I had checked the propeller for tightness before and all seemed fine, but this time I tore into the system knowing one of them was slipping, so I paid close attention as I disassembled it.
It turned out that when I fitted the propeller bushing it protruded out the back of the propeller a tiny bit, and that affected its tightness under loads. It could slip and then be okay again. I trimmed the bushing and made sure all was tight, and then I reran the tests. All was fine.
Having a preliminary data log gives me a base point to keep on file. When I think something is not the way it used to be, I can easily run another test and compare it to the first. This tells me if anything is changing and just what it is.
I highly recommend the little MicroPower if you're going to do electrics seriously. It's light and quick to install; I can hook it up on one of my airplanes in approximately 10 minutes anytime I want data.
Improving Your Model the Easy Way
I've been accused of being "old guard" because I've been flying electrics for quite a while and remember when accomplishing an aerobatic four-minute flight at the KRC Electric Fun Fly was an achievement.
Those days are long gone, but the desire to improve my setups continues. I'll bet I get three or four E-mails each month with the following type of question:
"I'm flying an electric [model] with a cobalt motor, [a certain] controller, with 10 1700 mAh Ni-Cd cells and love it. The performance is fine, but I'd like more duration, so I guess I have to bite the bullet and buy a new brushless motor, controller, and a Li-Poly pack.
Since it's going to be so expensive, I'm looking for advice. Can you help me?"
The key is the sentence about being happy with the performance but wanting more duration. There's nothing wrong with the new brushless-motor setups and Li-Poly batteries. If you're happy with performance and want only more duration, why not look at your batteries first?
Replace your sub-C Ni-Cds with something such as GP-3700 NiMH cells, and suddenly you've doubled your battery capacity and increased duration. If you really want the Li-Poly packs, you can have them too without replacing the whole system.
Get a Li-Poly pack that will handle the current you're drawing and either replace the controller or go the more economical route of getting an Automatic Cell Detect, Low Voltage Cutoff Device (item AVC1AIR) from FMA Direct (www.fmadirect.com). This will allow your old controller to use the new Li-Poly packs, and since you're going to lighten the model with the Li-Polys, you'll increase your duration even more because it won't require as much power.
Don't throw away good equipment if you're happy with the way your airplane is flying. Some of the cheap brushless motors flooding the market are no more efficient than a quality brushed motor such as the ones AstroFlight has produced for years. Spend your money carefully and wisely, but don't get caught up in "upgrade fever" — unless you just feel like it.
Sources
- AstroFlight Inc.
13311 Beach Ave. Marina Del Rey, CA 90292 (310) 821-6242 Fax: (310) 822-6637 [email protected] www.astroflight.com
- Castle Creations
402 E. Pendleton Ave. Wellsville, KS 66092 (785) 883-4519 Fax: (785) 883-4571 [email protected] www.castlecreations.com
- Spin Master Ltd. (Air Hogs)
450 Front St. West Toronto, Ontario, Canada M5V 1B6 (800) 622-8339 Fax: (416) 364-8005 www.airhogs.com
- Eagle Tree Systems, LLC
4957 Lakemont Blvd. SE Suite C-4 PMB 235 Bellevue, WA 98006 (888) 432-4744 (Ordering) (425) 614-0450 (Technical information) Fax: (425) 484-4131 www.eagletreesystems.com
Transcribed from original scans by AI. Minor OCR errors may remain.
