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| Issue 38 (August 2009) |
Words: Staff |
Almost inevitably when the question "What's the best electric motor for my ...... (anything)?" comes up, the answer that comes out is the Neu motor. And it's no wonder, since Steve Neu has been making electric motors that have been breaking world speed records since 2002. In this scope we are reviewing the 1706 1.5Y motor. This motor is ideal in most 500-size helicopters such as the Trex, Atom, or Vibe 500.
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Features and Specifications:
The 17 series In-runner motors feature a 24-slot stator and an 8-pole rotor. They have 5mm hardened steel shafts and 13mm ball bearings. The 1706 has an overall weight of 165 grams, a low internal resistance of .022 ohms, and a no-load current of 1.5 amps at 10 volts. The 1706 1.5 Y has a KV rating of 1255 RPM/VOLT, making it well suited for a wide variety of gear ratios and battery voltage choices for most 500s. The 1706 1.5Y is also rated at over 1200 watts, giving it the potential of delivering incredible power from a decent battery.
No-load current and internal resistance are key factors in determining motor efficiency. No-load current is the minimum current required to keep the motor turning at a given voltage and RPM. Large and higher-KV motors tend to have relatively high no-load currents because it takes more energy to keep them turning.
Internal resistance indicates the resistance of the wires inside the motor. High internal resistance means the greater the motor losses in the form of heat (I2R). Motors with small wires used for windings, typically found in relatively low KV motors and or relatively small motors, tend to have higher internal resistance. Both no-load and resistance losses must be subtracted from the overall power consumed by the motor when determining efficiency. For a given overall motor size, having these losses as low as possible is ideal.
Test Setup:
1760 gram flybarless(SK360) Trex 500
Curtis Youngblood RADIX 430MM blades
Eagle Tree Micro Power E-Logger with a brushless RPM sensor
Castle Creations 45 HV brushless ESC governed to 2540 RPM
8S Rhino Packs 2350 MAH
162 T main gear 13T pinion gear 12.46:1 gear ratio
Pitch +/- 13 degrees
Flight Testing
Observations:
Flight performance was excellent, with minimal bog during most maneuvers such as Tic-Tocs and full collective climb outs. Motor operation was also very quiet. Upon landing the motor temperature peaked at 120 degrees on a 70-degree day, well below any operational limit. The Eagle Tree Micro Power E-Logger collected in-flight data during testing. Peak amps, peak power, average current, RPM decay, voltage droop, and no-load current were abstracted. During in-flight testing, pitch pumping was executed for 20 seconds to analyze the system response to full load requirements.
Data charted for 20 seconds during +/-13 degree pitch pumping
Results Summary:
The charted data show the rotor head speed averaged 2541 RPM, the current averaged 20 amps, and the voltage averaged 31 volts. The minimum no-load current and power recorded at governed RPM is 2.9 amps and 92 watts respectively. The battery delivered a maximum of 70 amps and 1980 watts (2.7HP) of power at full collective.
Data Analysis:
The wave form results are typical for pitch pumping. At peak current, power follows and peaks while voltage and RPM sag and decay due to the increased load on the rotor head. The lower the sag and decay the greater the battery and motor performance. Also, the average amps during pitch pumping indicate the average current that may be expected during 3D flight.
At full power the voltage sagged to 28 volts and the RPM to 2316 RPM. The results indicate very efficient system operation at full power based on the minimal head speed decay of 225 RPM and voltage sag of only 3 volts. With a 20 amp average current, hard 3D flight could be maintained for approximately 5.5 minutes, leaving the 8s 2350 mah battery at 80% discharge at the end of the flight.
Conclusion:
The peak-delivered power during testing of 2.7 HP without significant sag and heating is extraordinary for a motor of this size. Even with rough accounting for resistive, no-load, and other losses, the motor would still deliver approximately 1700 watts (2.3 HP) to the transmission. The Neu 1706 1.5Y offers quiet, efficient power at a variety of gear ratios and battery combinations. With extreme power, combined with a weight of 165 grams, this motor is a clear performer and an outstanding choice for most 500-size helicopters.
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HITS
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• Lightweight
• Efficient
• Powerful
• Quiet
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MISSES
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• Have to trim frames to fit motor in a TREX 500
MANUFACTURER: NeuMotors
PART NUMBER(S): 1706 1.5Y
STREET PRICE: $129
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