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Offline rclad  
#196 Posted : Wednesday, October 17, 2018 12:41:23 PM(UTC)
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Is that the GRU that Aeroplayin is developing? A 35% Extra with that setup is what I want as well for my next plane, but that may be another year down the road. It looks very promising!
Greg Hladky
Flying on a wing and a purpose...
and physics, power, practice, preparation, plans...
and pioneers who pushed the envelope!
Offline Suds  
#197 Posted : Wednesday, October 17, 2018 1:32:38 PM(UTC)
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Originally Posted by: rclad Go to Quoted Post
Is that the GRU that Aeroplayin is developing? A 35% Extra with that setup is what I want as well for my next plane, but that may be another year down the road. It looks very promising!


Yes, this is the Aeroplayin GRU.
I’ve been in contact with him for a couple of months and have agreed to do some 3D torture testing on the GRU as well as providing some videos during the beta testing. He hopes to eventually release for sale.
thanks 1 user thanked Suds for this useful post.
rclad on 10/17/2018(UTC)
Offline Steve Stanton  
#198 Posted : Thursday, October 18, 2018 9:40:59 AM(UTC)
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Nice looking piece of machinery but curious to know: There is always an efficiency loss through an RPM reduction
system. In something like a "gear box" it can be as high as a 10% Loss.
What's the advantage of taking the efficiency hit with the RPM reduction to gain a lower RPM on the prop.?
Offline rclad  
#199 Posted : Thursday, October 18, 2018 9:58:25 AM(UTC)
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The big advantage is the ability to swing a larger diameter prop at a slower speed. Also the the loss in a belt drive GRU vs. gear box is less. But Aeroplayin is better at explaining this with real world numbers from tests he has made. Here is a post he made back in June:

Quote:
There are [a] few advantages here, so let me try to hit on all the ones I know right now.

First, yes, the efficiency is better. What this means is not that simple.

When I put the Rapala on the drive unit one day with the 26x12 on 14S, the 27x10 in 14S, the 27x12 carbon on 13S, and 28x12 on 12S, while the meter was connected, the results were not exactly what I expected. I actually tested them again, then when I mounted the unit and brought the plane to the field, my buddy Frankjp helped me test them again on the plane with the Rapala connected to the airframe. Same results.

I did what I normally do and went to the math. I knew the RPM because I had already taken the current and RPM reading simultaneously on the test stand, so when I calculated HP, torque, and Amps using Kv_Kt, I realized that the higher thrust on the lower Amps and Watts at the correct voltage meant that there was a much smaller margin between Watts-in and Watts-out. This means there was more power being developed at the shaft per Watt going into the system with the GRU.

To explain this mathematically....

((28" diameter / 12)^4) * (((5865 RPM) / 1000)^3) * 1.066 pK * (12 pitch / 12) = 6375 Watts-out

The Amps were reading 156A at nominal voltage on the meter at peak RPM. 156A times 44.4v is 7006 Watts-in.

6375Wo / 7006 Wi = 90.99%

44.4v times 145.16Kv times 91% = 5865 RPM

So everything here makes perfect mathematical sense, and taking this another step further...

6375 Wo / 745.7 = 8.55 HP

((8.55 HP *5252 RPM) / 5865 RPM) = 7.66 lb-ft or 1470.7 oz-in of torque

(1470.7 oz-in / 1352.4) * 145.16 Kv = 157.8 Amps

So 157.8 calculated Amps and 156 measured Amps means we're certainly close enough to suggest a confirmation.

So the first thing to assume here is that the drive unit is operating at a 91% efficiency while my Q80-6L 180Kv was operating at a 79.8% efficiency on 12S and my SII-6540 155Kv was operating at a 75.8% efficiency on 14S.

The second thing that must be stated here too is that my Q80-6L could not spin the 28x12, had trouble with the 27x10, liked the 26x12 better, but was cooler and smoother with less ripple and commutation loss with the Mejzlik 26x10TH. It was going right around 6500 Wi with that prop on 44.4v.

My SII-6540 155Kv on 14S loved the 26x12 but lost a magnet on flight #19.

The bottom line is that none of these direct drive motor setups were able to pull more than 48 lbs, and that was at 171A on 12S. My guess is that we'd have to go to the Hacker Q100 motors before we start to see 8.55 HP at the shaft, and they are twice the price of the GRU at $1,000, but they also weigh about 1900g. Plette's that can do it are about $300 more than that and will be about 1500g.

So not only are we talking about a GRU being more efficiency as far as power-in to power-out, but they cost and weigh less too when we compare prop and power potential.

I have been talking about Amps and RPM, and the difference between Wi and Wo here for a long and there is no better illustration of why that was, than this example. Some people will look at the 171A on the 27x10 and consider it to be more power than the 156A with the 28x12 on the same voltage, but it's not. More power is going into the system but less power is being developed at the shaft.

So using the GRU means more prop for more thrust with less current and more flight time.

The images illustrate the weight trade-off by showing the 1360g Hacker, the 1380g Scorpion, and the 611g GRU and 768g motor, which combine for basically the same 1379g weight.

I can't wait to see what the shop is doing with my modified shaft and prop mounting design with the 5mm pitch gears and belt. I'm expecting to hear about a time estimate for delivery early next week. Once I get it, I'll test if for efficiency, make sure the mesh count is acceptable, and make mods if either are not what I'm expecting. Getting my plane the way I wanted it took three prototypes and almost a year, but I'm hoping to get this right the first time. But we'll have to see.
Greg Hladky
Flying on a wing and a purpose...
and physics, power, practice, preparation, plans...
and pioneers who pushed the envelope!
thanks 1 user thanked rclad for this useful post.
Suds on 10/18/2018(UTC)
Offline Suds  
#200 Posted : Thursday, October 18, 2018 12:02:10 PM(UTC)
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Originally Posted by: Steve Stanton Go to Quoted Post
Nice looking piece of machinery but curious to know: There is always an efficiency loss through an RPM reduction
system. In something like a "gear box" it can be as high as a 10% Loss.
What's the advantage of taking the efficiency hit with the RPM reduction to gain a lower RPM on the prop.?


rclad listed the measured info in his post above.

It appears that any efficiency losses from the gear reduction are offset and then some by the higher efficiency that the 700-gram heli motor is providing at higher rpm versus the stock efficiency of an equivalent 1600-1800-gram low kv outrunner. The GRU also takes all the force of the prop and angular momentum which the large outrunners would normally need to be engineered around - this and the higher rotating mass weight of the large motors may be the reason they are less efficient.
The GRU also allow for different pinions to change the ratio so 27-28" props and different pitches could be utilized.
There is also the option to change motors to a lower kv to open up the potential for 14S power for some that would like to keep the amps lower.

I'm looking forward to the opportunity to test this out in practice.
thanks 2 users thanked Suds for this useful post.
Walter Royster on 10/18/2018(UTC), rclad on 10/18/2018(UTC)
Offline Brad  
#201 Posted : Thursday, October 18, 2018 12:27:50 PM(UTC)
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I'll be very curious to see what these performance numbers mean in terms of air speed for a typical 35 percent air frame. Thrust is only part of the equation, and really matters on uplines as the plane is losing air speed, but will the larger prop have enough airspeed to carry into the upline to provide the aerobatic performance pilots need? I do like the progress though!

Brad
Offline Steve Stanton  
#202 Posted : Thursday, October 18, 2018 1:00:37 PM(UTC)
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The numbers and equations are dazzling but am I getting this right.
Your taking a given size motor with a direct drive on a given prop. Now your reducing the size of the motor, adding
The weight of the timing belt, two pulleys, two bearing, a drive shaft, and the friction loading of the reduction
drive and coming up with more power and a longer flight time?
Hmmmmmmmmm.
Offline Suds  
#203 Posted : Thursday, October 18, 2018 1:17:20 PM(UTC)
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Originally Posted by: Brad Go to Quoted Post
I'll be very curious to see what these performance numbers mean in terms of air speed for a typical 35 percent air frame. Thrust is only part of the equation, and really matters on uplines as the plane is losing air speed, but will the larger prop have enough airspeed to carry into the upline to provide the aerobatic performance pilots need? I do like the progress though!
Brad


Here is what the thought on speed is from the designer:
"The airspeed will not be as good as a 27x11 on a DA-120 releasing RPM in the air, The pitch speed will be a very good 67 mph and the tip speed is nowhere near Mach 0.70 at 0.634, so every bit of WOT is efficient prop power."

If I had to guess, the speed will be similar to a DA120 on a 28x9.5 which is a fun prop for me.

Originally Posted by: Steve Stanton Go to Quoted Post
The numbers and equations are dazzling but am I getting this right.
Your taking a given size motor with a direct drive on a given prop. Now your reducing the size of the motor, adding
The weight of the timing belt, two pulleys, two bearing, a drive shaft, and the friction loading of the reduction
drive and coming up with more power and a longer flight time?
Hmmmmmmmmm.


Fairly sure the 'Hmmm' portion was a thought going into this project but the testing has born out a different result than one might theorize. Also for comparison at the output being measured, the nearest direct drive is the Hacker Q100-6M which is a 1830g motor. So the GRU unit all up is >300g lighter. But as they say, the proof is in the pudding and time will tell how the unit work in real life. Guessing it will work pretty well, as this project was intended to be a beefed up version of the Flitework GRU (who's 100cc version is just their 50cc version with a larger heli motor).
Here is the Flitework on what is likely a 31-32# Sebart.
Offline rclad  
#204 Posted : Thursday, October 18, 2018 1:19:58 PM(UTC)
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Originally Posted by: Brad Go to Quoted Post
I'll be very curious to see what these performance numbers mean in terms of air speed for a typical 35 percent air frame. Thrust is only part of the equation, and really matters on uplines as the plane is losing air speed, but will the larger prop have enough airspeed to carry into the upline to provide the aerobatic performance pilots need? I do like the progress though!
Brad

Good question! I'm sure Suds will be testing that, but I suspect that as long as the airframe is kept light enough and thrust to weight is sufficient that will not be an issue. Aeroplaying is getting 55 lbs of thrust from this setup. That is more than enough for a 30 lb plane to maintain airspeed on a vertical line, even with reduction of voltage toward the end of a second sequence.
Greg Hladky
Flying on a wing and a purpose...
and physics, power, practice, preparation, plans...
and pioneers who pushed the envelope!
Offline Steve Stanton  
#205 Posted : Friday, October 19, 2018 10:50:11 AM(UTC)
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It will be great if this does provide an improvement on electric competition planes. Especially on extending
flight times. While the concept doesn't quite look right to me, I'll be the first to applaud if it works. Every
improvement, big or small, helps..
Seems like this concept would work well on airplanes that need the prop. shaft up closer to the top of the nose.
Also for planes like an SE 5 that have the prop. down low on the nose. Some of the War Birds don't look right
with small props so this would allow for using a bigger prop.
Offline Krzy4rc  
#206 Posted : Saturday, October 20, 2018 3:05:09 AM(UTC)
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That looks like a great project. If another tester is needed I would be happy to put together a Laser or maybe a JTEC Giles to try it.
Rich
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Offline Suds  
#207 Posted : Thursday, October 25, 2018 10:50:12 AM(UTC)
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Here are the results from the GRU (belt drive) prototype unit on 12S-5000 swinging a Xoar PJR 28x12 (from the designer):

"The RPM at WOT peaked at 5945 RPM at 43.45 volts and 173.77 Amps. To make the RPM reading work perfectly by the math, I need a 91.2% efficiency at 43.454 volts. To make the Amps work perfectly for the prop to 5945 RPM, I would have expected 167.6A from the Kv-Kt calculation. I was thinking about the 8.5A I was seeing the unit use while running at full throttle unloaded. Maybe, but there are so many things happening here that a 3.4% error is arbitrary.

The RPM settled in at 5905 RPM at 43.16v. This was a static test,

During the 5 minutes, I spent several episodes at WOT for 5 seconds, a few at 50% and 75% throttle, and the rest pulsing the throttle between 25% and 75% to 80% throttle and spaces the pulse until I felt a good pull from the power system. I’m going to guess there were 1.5 second pulses from 25% to 75% to 25% again.

After the timer went off, I raised the throttle to half, and left it there for about 10 seconds. I shut the idle switch and checked the Watts meter and saw a peak of 167.23A. This is almost exactly what I was looking for during the RPM test, and what I saw during my preliminary test over the weekend.

The thrust was once again settling in right around 55.1 pounds and the throttle response was about what I was seeing on the Xpwr60 with a 24x10 PJN, which is incredibly crisp. That’s about as good as I could ask for. I should have gotten a video of the throttle response and will try to do so the next time I have that prop spinning on the GR unit again. Just not enough hands to do everything today, and plenty of other things to think about.

The math says a 28x12 to 5905 RPM is 55.6 pounds.

I tend to trust the math for a specific understanding because there is no way to line up all the electrical variables at the same time with RPM, but the math says 165.3A at 55.6 pounds at 86-88 degrees at sea level. This is also a pitch speed of 67.1 mph and a prop tip speed of Mach 0.64."


He's going to move forward and produce 4 units and I'll be receiving one of those four. Once the beta testers have completed some time testing in flight, he will consider a small production run.

Edited by user Thursday, October 25, 2018 2:35:45 PM(UTC)  | Reason: typo correction (underlined)

Offline Curtis Cozier  
#208 Posted : Thursday, October 25, 2018 1:42:08 PM(UTC)
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Originally Posted by: Suds Go to Quoted Post


[i]"The RPM at WOT peaked at 5945 RPM at 43.45 volts and 173.77 Watts. .


Umm...Hope the plane doesn't weigh more than about a pound and a half................
......
Offline rclad  
#209 Posted : Thursday, October 25, 2018 2:04:56 PM(UTC)
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Looks like a typo there. It was 173.77 amps, not watts.
Greg Hladky
Flying on a wing and a purpose...
and physics, power, practice, preparation, plans...
and pioneers who pushed the envelope!
thanks 1 user thanked rclad for this useful post.
Suds on 10/25/2018(UTC)
Offline rclad  
#210 Posted : Friday, January 11, 2019 8:37:05 PM(UTC)
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I've been playing with various configurations for my latest electric project, the Extreme Flight 104" Extra 300 V2. It's very hard to find a good compromise between weight, thrust and flight time. Fortunately, eCalc makes it easy to try various configurations before spending any money on components.

The three numbers that mean the most to me are Wing Cubic Loading (WCL), Thrust-Weight (T/W) ratio, and Estimated Flight Time (EFT). When all three line up nicely in the green, and don't over stress any components, then I can be confident the plane will perform well. Getting there is not so easy for a 35% scale electric plane, especially when it must compete against gas powered planes that are 2-3 lbs lighter!

To get a good idea of expected performance, I found it necessary to go back to planes I know fly well and calculate or measure these three numbers:

EF 95" Extra 330SC-E
WCL: 9.3
T/W: 1.8:1 (calculated - I still need to measure actual static thrust)
FT: 9.5 min. (flying 2 Intermediate sequences + practice)

JTEC 2.7M Extra 300CS - Greg Marsden
WCL: 8.7 (@ 28 lbs); 8.0 (@ 26 lbs)
T/W: 2:1 (12S 13000 mAhr, Q80-6L, MGM250 ESC, Mejlik 26x12)
FT: enough for 2 Advanced sequences (calculated time is 7.5 minutes)

For comparison to the latest gold standard in gas-powered planes:
Kam-Aero Extra 300
WCL: 7.4 (@39.5 lbs); 7.9 (@ 42lbs)
T/W: 2:1 (30x13 CF @6300 RPM on DA200)
FT: 15 min.

Here are the weights, components, and performance numbers from eCalc, for the EF 104 V2:

Model/subject: Extreme Flight 104" Extra 300 V2
Airframe Weight (no motor, batteries or electronics): 15.58 lbs

Motor: Scorpion HKIII 5035-410
Speed Control: HW Platinum Pro 200A Opto
Cell type/count: Glacier 35c LiPo 12s 10,600 mAh
Prop/fan: Xoar 28x14 PJN
Reduction method and ratio: Aeroplayin GRU 3.158:1

Radio Electronics weight: 1.67 lbs
Power System weight: 4.96 lbs
Battery weight: 6.92 lbs
Weight Read to Fly: 29.14 pounds

Performance:
Amps: 132A Max
Watts: ~5600
RPM: ~5100
Wing Loading: 35.93
Wing Cubic Loading: 9.98
Estimated Flight Time (IMAC): 9.63 min.
Static Thrust: 46.6 lbs
Thrust-Weight: 1.6
Pitch Speed: 109 mph
Est. Speed: 67 mph
Vert. Speed: 33 mph

Bottom line: the 104V2 will not perform as well as my 95" or Greg Marsden's 105" JTEC. That's disappointing from a numbers-only perspective. If I move forward with this project, I will have to practice more to get the most performance possible out of the plane. Maybe some magic will happen in the air?
Greg Hladky
Flying on a wing and a purpose...
and physics, power, practice, preparation, plans...
and pioneers who pushed the envelope!
thanks 1 user thanked rclad for this useful post.
Vicente Bortone on 1/12/2019(UTC)
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