Friday, October 20, 2017
Home » Product Reviews » Scorpion HKIII Motor Series

Scorpion HKIII Motor Series

Scorpion HKIII Motor Series

Instant Power and Efficiency Boost

Since breaking into the hobby scene in 2006 with its line of brushless outrunner motors, Scorpion has continually evolved their products. Utilizing improved manufacturing techniques and design fed by field testing, Scorpion mass-produces highly efficient and powerful motors at a reasonable price. Scorpion motors are distributed exclusively by Innov8tive Designs. The HKIII series of motors is the latest incarnation of these outrunners for use in model helicopters.

Scorpion HKIII Motor Series
Scorpion HKII motor on the left with longer output shaft installed, Scorpion MKIII on the right with shorter shaft installed. Also note the cooling grooves on the exterior of the HKIII’s rotor.

Specifications
HKII-4020-910
Included in the Box
(1) Scorpion HK-4020-910Kv motor
(3) Female connectors
(3) Heat shrink
(4) M3 screws

STATOR DIAMETER: 40mm (1.56 in.)
STATOR THICKNESS: 20mm (0.79 in.)
NO. OF STATOR ARMS: 12
MAGNET POLES: 8
MOTOR WIND: 10-turn delta
MOTOR WIRE: 24-strand 0.25mm
MOTOR KV: 910Kv rpm/volt
NO-LOAD CURRENT (IO/10v): 1.95 amps
MOTOR RESISTANCE (RM): 0.015 ohms
MAX CONTINUOUS CURRENT: 65 amps
MAX CONTINUOUS POWER: 1820 watts
WEIGHT: 284 grams (10.02 oz.)
OUTSIDE DIAMETER: 48.9mm (1.9 in.)
SHAFT DIAMETER: 4.98mm (0.19 in.)
BODY LENGTH: 46.5mm (1.81 in.)
OVERALL SHAFT LENGTH: 78.7mm (3.10 in.)
MAX LIPO Cell: 8S
MOTOR TIMING: 5 deg.
DRIVE FREQUENCY: 8kHz
WEIGHT: (including packaging) 434 grams
PRICE: $149.99

HKIII-4020-890
Included in the Box
(1) Scorpion HKIII-4020-890Kv motor
(3) Female connectors
(3) Heat shrink
(4) M3 screws
STATOR DIAMETER: 40mm (1.57 in.)
STATOR THICKNESS: 20mm (0.79 in.)
NO. OF STATOR ARMS: 12
MAGNET POLES: 10
MOTOR WIND: 4T/5T delta
MOTOR WIRE: 21-strand 0.29mm
MOTOR KV: 890Kv rpm/volt
NO-LOAD CURRENT (IO/10v): 2.44 amps
MOTOR RESISTANCE (RM): 0.012 ohms
MAX CONTINUOUS CURRENT: 65 amps
MAX CONTINUOUS POWER: 1820 watts
WEIGHT: 302 grams (10.65 oz.)
OUTSIDE DIAMETER: 49.98mm (1.97 in.)
SHAFT DIAMETER: 4.98mm (0.20 in.)
BODY LENGTH: 46.8mm (1.84 in.)
OVERALL SHAFT LENGTH: 78.7mm (3.10 in.)
MAX LIPO CELL: 8S
MOTOR TIMING: 5 deg.
DRIVE FREQUENCY: 8kHz
PEAK CURRENT: 75 amps (5 seconds)
PEAK CONTINUOUS POWER: 2100 watts (5 seconds)
WEIGHT: (including packaging) 460g
PRICE: $189.99

The new motors use a different alloy in the stator laminations that have a higher efficiency and lower hysteresis for less internal losses and less internal heating. The shape of the stator was also changed to concentrate more of the magnetic flux fields towards the magnet faces for greater efficiency and higher torque. The rotor is now constructed of a new alloy that retains more of the magnetic fields and also assists in increasing the motor’s efficiency. The rotor’s exterior features a unique spiral-cut cooling pattern that increases the internal flux pattern for the magnetic fields and increases the surface area, which improves cooling. Unlike other motors that use a series of circular grooves on the rotor can, the HKIII motors use a continuous cut from one end of the rotor can to the other. This design pulls air down the sides of the motor for increased cooling and lower operating temperatures.

Scorpion HKIII Motor Series
Data plot showing the current used during hovering by the HKII.
Scorpion HKIII Motor Series
Data plot showing the current used during hovering by the HKIII.

All of the changes to increase the efficiency in the motor cause a drop in Kv value. In order to get the Kv back up near its original rating, the motors are wound with fewer turns of heavier gauge wire. This allows for lower internal resistance (Rm) and also increases their current handling capability.

To illustrate these changes I tested both generations in a Gaui X5 FES loaded with MKS HBL servos under the command of a MicroBeast flybarless controller. The collective pitch was set to a 20-degree range. This model comes stock with a Gaui branded Scorpion HKII-4020-910 motor which puts out gobs of power and comes down cool to the touch. If the HKIII can best the stock motor, that would put an exclamation on an already fantastic performing model! I installed a Castle Creations Phoenix ICE 100 ESC for data logging, setup in Fixed-End-Point mode, Medium Timing, and 8 KHz pulse width frequency. I ran the electronics off of a Venom LiFe 2S 1200mAh receiver pack so the data would be purely indicative of the drivetrain demands. I used a Thunder Power 6S 3850mAh 65C LiPo that had 12 flights on it as the main flight battery for its solid power delivery.

In order to illustrate the power characteristics of each motor, I performed a timed schedule of hovering and pitch pumping. Since forward flight and 3D have substantially more variables involved, I wanted to compare apples to apples as best as possible. On a freshly charged battery, I hovered at eye level for 10 seconds after liftoff and then progressively increased pitch, allowing the model to climb for five seconds before reversing pitch to bring the helicopter back down to eye level. I repeated this sequence several times to insure a good data set.

Scorpion HKIII Motor Series
Data plot showing the current used during full pitch load by the HKII.
Scorpion HKIII Motor Series
Data plot showing the current used during a full pitch load by the HKIII.

Scorpion equipped the HKIII motor with a 78.7mm long, un-notched output shaft, but the stock Gaui motor came with a shorter notched shaft that is better suited for the X5. Before having a shaft swapping party, I measured the weight of the stock HKII motor without the pinion at 286.5 grams. Then I swapped the shorter notched shaft into the HKIII motor and it weighed in at 309.5 grams. The additional weight is primarily a result of the increased number of magnets and heavier gauge stator wire. After weighin, I installed the pinion, popped the motor back into the X5, hooked up the wires and went out for round two of flight testing.

After my flight, I downloaded the log and culled the pertinent data. I took averages from ten hovering and full pitch cycles to determine how the motors differ from each other. Compared to the HKII, the HKIII pulled 10-percent more current in a hover (22 amps vs. 20) and 20-percent more current during the peak amp draw under full pitch (72 Amps vs. 60). The HKIII pulling more power than the HKII for comparable flying may seem to be a letdown, but where this motor takes it also gives. The newer motor’s increased efficiency is realized in its ability to convert more of the electricity into work (wattage). The HKIII produced 8.25-percent more power (512 watts vs. 473 watts) in hovering and 5.2-percent more power (1313 watts vs. 1248 watts) in pitch pulls. The peak wattage during my flight on the HKII was 1776 watts; the HKIII was 4.1-percent higher at 1849 watts.

Scorpion HKIII Motor Series
The overall dimensions are nearly the same between the HKII on the left and the HKIII on the right.
The obvious difference between the two are the HKIII’s ribbed can with the etched Scorpion motif.

The HKIII’s head speed sag from a hover to full positive pitch was 45-percent less than the HKII (110 RPM vs. 201 RPM). While my setup was rather conservative, on a geared up ballistic X5, the additional power and reduced head speed sag would produce shattering performance. This motor also came down cool to the touch and the battery was barely above ambient.

The HKIII motor definitely felt like it had more guts than the stock motor during my climb outs. If you’re thinking about a motor upgrade from a previous generation Scorpion motor, the HKIII is equivalent to swapping in an engine that has been stroked and topped with polished and ported heads. Compared to its predecessor, the HKIII makes more efficient use of your battery’s power and gives extra oomph for a minimal increase in current draw. If you have a sweet tooth for a real performance improvement, the Scorpion HKIII motors are the spiked cherries needed to top your cake! 

Contact
INNOV8TIVE DESIGNS innov8tivedesigns.com, (760) 468-8838

Leave a Reply

Your email address will not be published. Required fields are marked *