Thread Tools
Aug 11, 2020, 04:35 PM
Registered User
Fourdan's Avatar
Thread OP
Mini-Review

Dualsky GA 8000-8S


Hi
I have received from Dualsky one motor GA 8000-8S (single shaft edition).
One card box containing the motor and the provided accessories in foam lodgings:
** 3 pairs (M/F) of gold 6 mm connectors + red & black thermo-tubes.
** 4 spacers 64mm equipped with wafers and M5 screws
** one flat wrench (13mm, 11mm and special claw)
** and one dimensions drawing (picture)

Configuration is 24N28P dLRK
Stator size 80x30 mm, 0.2 mm japanese laminations
Windings : 4 turns per tooth (8 conductors per slot), 19 strands of 0.41 mm wire, terminating delta

Weight is 1321g (motor + integrated prop adapter and integrated stator mount)
Outer diameter = 90 mm
External shaft diameter = 10 mm fine pitch, 50 mm free, wafer and collet nuts (auto-lock)
Overall shaft length = 146 mm (internal diameter 12mm)
End bell with a drum 25mm high, opening for the prop hub = 18 mm
Stator mounting 4 holes for M5 screws on circle 100 mm

As usual for my tests, I first make only no-load tests.
I have used a 130A 50V opto ESC equipped with 4mm gold connectors
First rapid checking, running under 12V, on a wood-multiply support
All is OK, very smooth rotation, low noise.
Then, I fixed on the drum four adhesive black patches (leaving four bright alu parts) to use my favourite and accurate DT2234A optical tach.

First testing is phase-phase resistance (3 DMM measurements under 4.987A CC: 92 , 95 , 90 mV dc)
Average Rm = 0.0185 ohm @ 22.5C, that is around 0.0183 ohm @ 20C
Secondary testing is no load, WOT, under my Mastech PSU 60V 5A + ESC + servo tester LETON (powered by external 5V)
I fill a table voltage, no-load current and rpm, from 12V up to 40V steps 2V
Two DMM are used (Vdc and I /10A)
* 11.68 V ; 2.200 A, 1869 rpm, peakeff 88.3 %
* 14.18 V ; 2.370 A, 2273 rpm
* 16.24 V ; 2.500 A, 2601 rpm
* 18.13 V ; 2.622 A, 2903 rpm
* 20.18 V ; 2.745 A, 3234 rpm
* 22.04 V ; 2.852 A, 3532 rpm
* 24.14 V ; 2.990 A, 3867 rpm
* 26.17 V ; 3.122 A, 4198 rpm
* 28.18 V ; 3.284 A, 4518 rpm
* 30.10 V ; 3.400 A, 4828 rpm
* 32.12 V ; 3.600 A, 5150 rpm
* 34.39 V ; 3.720 A, 5530 rpm
* 36.58 V ; 3.850 A, 5874 rpm
* 39.26 V ; 3.980 A, 6308 rpm, peakeff = 91.3 %
Then my usual EXCEL template to finish the no load analysis:
Zero current Kv is 161 rpm/V
Picture : no-load losses (W) versus rpm

To complete the analysis, I have embedded the data in Dualsky Calc 3.82
I recommend a voltage range 40V ... 50V (10S ... 12S LiPo)
Examples (by computing) on generic propellers
10S; 28x12; 37V; 121A; 4400W; 5250 rpm; static thrust 20 kgf; pitch speed 26.7 m/s
11S; 25.5x13; 40.7V; 114A; 4600W; 5880 rpm; static thrust 19.1 kgf; pitch speed 32.4 m/s
12S; 26x10; 44.4V; 123A; 5400W; 6400 rpm; static thrust 21.8 kgf; pitch speed 27.1 m/s (picture)

In the future, I have to see what props I could test with my friend Olivier (in the real world).
I plan to use a glider carrier to make power and static thrust measurements (on batteries)
Finally, the GA 8000-8 is devoted to power a giant RC glider ASK21, 6.8 m span, 26 kg, prop could be a 24x12 CF folding.

Louis
Last edited by Fourdan; Aug 12, 2020 at 03:53 AM.
Sign up now
to remove ads between posts
Aug 11, 2020, 05:12 PM
nsg
nsg
Registered User
nsg's Avatar
Louis, thank you for your review.

What, in your opinion, would be the max power for a typical 3D setup, 82% efficiency, very short bursts of full throttle?
Aug 12, 2020, 02:45 AM
Registered User
Fourdan's Avatar
Thread OP
Quote:
Originally Posted by nsg
Louis, thank you for your review.

What, in your opinion, would be the max power for a typical 3D setup, 82% efficiency, very short bursts of full throttle?
Hi nsg
Dualsky infos are
** Power (cruising 8 min) 4100W
** Power (bursts 15 s) 8200W
** Max current (bursts 160A)
It is very difficult to answer your question
A lot of parameters are acting : ambient temperature, cooling ... ESC algorithms ...

12S 150A seems acceptable for short bursts ... that is 5800 ... 6000W
Louis
Aug 12, 2020, 03:50 AM
Registered User
why choose such a big motor for about 4kw setup
Aug 12, 2020, 06:54 AM
nsg
nsg
Registered User
nsg's Avatar
Quote:
Originally Posted by Fourdan
Hi nsg
Dualsky infos are
** Power (cruising 8 min) 4100W
** Power (bursts 15 s) 8200W
** Max current (bursts 160A)
It is very difficult to answer your question
A lot of parameters are acting : ambient temperature, cooling ... ESC algorithms ...

12S 150A seems acceptable for short bursts ... that is 5800 ... 6000W
Louis
Louis - thanks.
It looks like the data posted by Dualsky is consistent with your measurements - that's good to know.
Last edited by nsg; Aug 12, 2020 at 07:23 AM.
Aug 12, 2020, 08:00 AM
Registered User
Aeroplayin's Avatar
Quote:
Originally Posted by bartk
why choose such a big motor for about 4kw setup
Because power-in (Wi) and power at the shaft (Wo) is not a true measure of force and thrust. The advantage of electric power has nothing to do with horsepower either and more about torque, which is simply angular force.

As a good example of this, if you give me 8 horsepower to play with, or about 5965 Wi, most electric motors will translate that to about:

7.6 lb-ft of torque and 54 lbs of thrust with a 29x12 to 5490 RPM
7.3 lb-ft and 52 lbs of thrust with a 28x12 to 5757 RPM at the same current and voltage
6.9 lb-ft and 51 lbs of thrust with a 278x12 to 6045 RPM at the same current and voltage
6.6 lb-ft and 49 lbs of thrust with a 26x12 to 6365 RPM at the same current and voltage
6.3 lb-ft and 48 lbs of thrust with a 25x12 to 6705 RPM at the same current and voltage
5.9 lb-ft and 47 lbs of thrust with a 24x12 to 7100 RPM at the same current and voltage

So it's really what we do with power-out and both Kv and Kv efficiency will dictate the potential.

So the reason why we test these motors is to know what they are capable of from an efficiency perspective. When I tested the GA6000.8, we could get as much as an 86.5% efficiency with a 51g 23x10 electric carbon prop to about 4770W on 44.4v, but the efficiency dropped to 76.84% by the time we got to the 119g 25x12 beechwood electric.

Since the mass is the same between these two motors -- GA6 and GA8 -- my guess is that the difference will only be about the Kv. Lower Kv mathematically MUST result in lower current since Amps = (( {lb-ft} * 192) / 1352.266) * Kv

So at 5 lb-ft of torque and the 180Kv GA6000, we should see 128A
At the same 5 lb-ft of torque and the 161Kv GA8000, we should see 114A

This means that if both motors operate at the same efficiency, then we should be able to increase the propeller size to gain more torque and thrust when we achieve the same current.

This concept is SO VERY important to understand in electric power RC airplanes.

It is also important to understand that since we are maintaining the same propeller pitch in my HP versus Torque example above, we are also trading thrust for speed. This actually must happen since this is all about Work vectors in physics. The work we put in must equal the work we result from the system, and since we are gaining force, we must give up distance.

Work = Force x distance

In our electric power example, the force is angular force, which is torque, and the distance is measured in RPM. You can see how the two trade-off in the above example.

Bottom line -- if you want more thrust at the same current, drop the Kv and increase the prop diameter. If you want speed, increase the Kv drop the prop diameter. In some cases, you can use props that inherently load less. For example, a C2E Falcon will load less than a beechwood PJN of the same size. So there is a potential to increase Kv, decrease the prop diameter, and also increase the pitch as well while still maintaining the same current.
Aug 12, 2020, 09:12 AM
Registered User
> Since the mass is the same between these two motors -- GA6 and GA8

The GA6000-9S weighs 1020gr is also 160KV
Aug 12, 2020, 10:15 AM
Registered User
Aeroplayin's Avatar
Quote:
Originally Posted by bartk
> Since the mass is the same between these two motors -- GA6 and GA8

The GA6000-9S weighs 1020gr is also 160KV
Here are the ones I know up close and personal. 155g was my test motor that ran to about 179 RPM/v unloaded. Scales are different, an the heaviest in the right has no prop hardware. Looks like Louis is saying his GA8 is 1321g.

My Hacker Q80-6L was 1359g all up and did 6500W at 145A with a 26x10TH Mejzlik -- 180 Kv and 183 RPM/v unloaded. It also did 171A with a Falcon gas carbon 27x10.
Last edited by Aeroplayin; Aug 12, 2020 at 10:20 AM.
Aug 12, 2020, 10:28 AM
Registered User
Aeroplayin's Avatar
And then there is this from the Dualsky GA8000 product page. The prop hardware is 26g and 3 male 6.5mm bullet connectors are 8g.
Aug 12, 2020, 03:49 PM
Registered User
dualsky side is complytly wrong

the weigth of the ga8000 = 1321g
and the ga6000 = 1150 g

https://www.rcgroups.com/forums/show...A6000-8-rewind
Aug 12, 2020, 07:29 PM
Registered User
Aeroplayin's Avatar
Quote:
Originally Posted by Fourdan
Stator size 80x30 mm, 0.2 mm japanese laminations
Louis, do you have the stator size of the GA6? So this is not just a 160Kv option to the GA6.... more like competing with the Hacker Q80-6L which is 1359g.
Last edited by Aeroplayin; Aug 12, 2020 at 07:42 PM.
Aug 13, 2020, 03:56 AM
Registered User
Fourdan's Avatar
Thread OP
Hi
GA 8000-8 stator is ~80x30 mm
GA 6000- stator is ~80x25 mm
both are 24N28P config
I have no GA 6000
I have one GA 8000-8S (but not dismantled)
Louis
Aug 13, 2020, 01:29 PM
nsg
nsg
Registered User
nsg's Avatar
Louis,
Would it be possible to use your DualSky calculator? Or is it the same as Scorpion?
Aug 13, 2020, 01:42 PM
Registered User
Fourdan's Avatar
Thread OP
Hi nsg
Dualsky Calc is a cousin of Scorpion Calc (same basic kernel)
It is not updated since some years and the motor library is old.
I have just added the new GA 8000-8
You can contact me via a RCGroups PM
Louis


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion 93" long PC-21 (Sebart PC-21XL) + Dualsky GA 6000.8 Eddie P Giant Electric Planes 402 Sep 08, 2020 10:05 AM
Help! ESC Settings of Castle Edge and Dualsky GA Combo - your experience? eJets Giant Electric Planes 9 Dec 08, 2017 10:59 AM
Discussion ESC Settings of Castle Edge and Dualsky GA Combo - your experience? eJets Castle Creations 1 Dec 01, 2017 09:03 AM
Discussion Lady Ga Ga 100 Swarm Drones @ Half Time dragbikebam Multirotor Drone Talk 9 Feb 06, 2017 04:27 AM
Discussion Radio ga ga bierhaus31 Sailboats 3 Apr 09, 2009 07:46 PM