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Old May 04, 2012, 04:48 PM
VOLTS > AMPS
stgdz's Avatar
United States, MN, Buffalo
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Changing gears a bit, does anyone have numbers for the omega 130?

On 4s it make 700watts but I am kinda curious about its efficiency and amps.
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Old May 04, 2012, 05:05 PM
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Quote:
Originally Posted by Aeroplayin View Post
...........some said APC was more aggressive than the Xoar, some wanted to know about non-electric props, new electrics from other brands, etc,.
Lemmee ax you sumphin...I tried the Vess 15X8 and it was really good power....but the thing that was the most noticeable...was how quiet it was. Even in a Knife edge spin....really quiet. Does/could that translate into a better prop?
The Vess wasnt a prop you guys had in the test. Ive had the Xoar, APC, and the Vess...the Vess was loaned to me by a friend and I ended up keeping it....until it broke.
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Old May 04, 2012, 06:34 PM
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United States, IL, Glen Carbon
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Originally Posted by Aeroplayin View Post
No problem here either, JC. [- - -] I suggest that 1.03 for the APC and 1.08 for the Xoar is as close as you'll get for the 15 and 16, but I will not argue with other coefficients in the same proximity.
Thanks!
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Old May 04, 2012, 08:58 PM
Not as Good as The Kid
Aeroplayin's Avatar
South Pasadena, FL
Joined Sep 2009
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Quote:
Originally Posted by Cabledawg1 View Post
Lemmee ax you sumphin...I tried the Vess 15X8 and it was really good power....but the thing that was the most noticeable...was how quiet it was. Even in a Knife edge spin....really quiet. Does/could that translate into a better prop?
The Vess wasnt a prop you guys had in the test. Ive had the Xoar, APC, and the Vess...the Vess was loaned to me by a friend and I ended up keeping it....until it broke.
I've always been a fan of the Vess and you can see the high tech design in the profile:

http://rcwebclub.com/Portals/rcwebcl...e_10-26-11.jpg

The Vess WAS a prop that we had in the test, as was the Falcon and the EMP. It did perform well at the 15x8 size level but the Amps were a bit higher than what I considered comfortable for a prop this size. It's also not an electric prop.
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Old May 05, 2012, 08:19 AM
VOLTS > AMPS
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United States, MN, Buffalo
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5s results today Jim?

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Old May 05, 2012, 09:43 AM
Not as Good as The Kid
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South Pasadena, FL
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Originally Posted by stgdz View Post
5s results today Jim?

Even if I have to run it up in the back yard.
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Old May 05, 2012, 03:24 PM
VOLTS > AMPS
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Double post
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Last edited by stgdz; May 05, 2012 at 03:39 PM.
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Old May 05, 2012, 03:38 PM
VOLTS > AMPS
stgdz's Avatar
United States, MN, Buffalo
Joined Jul 2011
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Originally Posted by Aeroplayin View Post
Even if I have to run it up in the back yard.
Just be aware little movements with them packs really affect cg.

I bumped my pack by about 1/3 inch on the mxs and it was damn near impossible to fly. I got it down in one piece but bent the tail wheel, broke a sfg off and dinged my cowl. No structural damage though.


These packs are short and fat compared to the long skinny 4s.
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Old May 05, 2012, 03:40 PM
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okay, we just pulled the meter off the 48 Edge:

Motor: DM2820-750
638Kv custom
13x6.5e APC
5S 2200mAh 30C Sky Lipo
Starting volts: 20.90v
Volts under load on first WOT: 19.48v
Amps on first WOT: 42A
Watts on first WOT: 818 Watts-in
RPMs on first WOT: 9540
RPMs on third and last WOT: 9500
Volts on third and last WOT: 19.10v
Watts on third and last WOT: 800 Watts-in
Standing volts of the battery in the plane after three tests to WOT: 20.67v

9500 RPMs with a 13x6.5e APC requires 650 Watts-out and 34 Amps at 19.10v.
9500 RPMs on 19.1v and 638Kv is a 78% Kv efficiency (-22%).

150W and 8A are consumed in producing 9500 RPMs with the 13x6.5e APC (-23%).
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Old May 05, 2012, 03:44 PM
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Thanks for the warning... we didn't fly it today because the Watt meter for the 27% came and I'm about to solder the 6.5mm bullets so we can run it up and see if we're going to get what we're expecting... hoping for 6800 RPMs with the 24x10 Xoar and under 130A.
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Old May 05, 2012, 04:06 PM
VOLTS > AMPS
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United States, MN, Buffalo
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So if I am reading this rite.

That extra 40kv really makes a difference on the efficiency standpoint. I am producing about 70 less watts and 5 less amps but we care getting the same rpm.




Wonder what the 14x7 is going to pull, hope to get toms feedback soon but enjoy the new Godfrey.
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Old May 05, 2012, 04:31 PM
Not as Good as The Kid
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South Pasadena, FL
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Originally Posted by stgdz View Post
So if I am reading this rite.

That extra 40kv really makes a difference on the efficiency standpoint. I am producing about 70 less watts and 5 less amps but we care getting the same rpm.




Wonder what the 14x7 is going to pull, hope to get toms feedback soon but enjoy the new Godfrey.
Thanks... I still have to get the soldering stuff out and get off my azzz.

The bottom line here is that if we are all swinging the 13x6.5e APC to the same RPMs, we're all getting the same power-out. The difference will be the efficiency. From 800Watts-in to 650 Watts-out, and 42 Amps-in to 34A needed to deliver the 650W, I would say that this is a good setup.

Tom is getting the same 650 Watts-out with his 4 cells swinging a 14x7e APC to 8350 RPMs and 47 Amps on his 683 Kv DM2820-750. This is considerably more efficient, I think. I have to dig out the Watts reading off the meter, but I think we're talking about 100W and 4.5A consumed if I remember correctly.
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Old May 05, 2012, 08:11 PM
VOLTS > AMPS
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United States, MN, Buffalo
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On my 600kv with 14x7 I got
875 watts
45amps
8800 rpm


I'm kinda wondering if I could run this setup even though ken says no. When I talked to him about my current setup and my 9500rpm his response was a whistle "phew"

I talked to him about a 14x7 on 5s and he still worries about the magnets hitting the stator. I started to inquire as the 4s 750 14x7 rpms and he figured 7700-7800rpm was what it would be. So the guys running the 14x7 setup at 8800rpm should be fine for my 5s setup as that is what I got.


I'm undecided at the moment if i want to step up to the bigger prop. Ken believes tha I'm really at the edge with my setup.
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Old May 05, 2012, 08:39 PM
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South Pasadena, FL
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Quote:
Originally Posted by stgdz View Post
On my 600kv with 14x7 I got
875 watts
45amps
8800 rpm


I'm kinda wondering if I could run this setup even though ken says no. When I talked to him about my current setup and my 9500rpm his response was a whistle "phew"

I talked to him about a 14x7 on 5s and he still worries about the magnets hitting the stator. I started to inquire as the 4s 750 14x7 rpms and he figured 7700-7800rpm was what it would be. So the guys running the 14x7 setup at 8800rpm should be fine for my 5s setup as that is what I got.


I'm undecided at the moment if i want to step up to the bigger prop. Ken believes tha I'm really at the edge with my setup.
The bigger 14 inch prop over 9000 RPMs seems like an imminent disaster to me with this light of a motor. The first blender or wall should be enough to pop a few magnets. But 8600-8700 RPMs is only 200-300 more RPMs than Tom is getting, and all you have to do is watch his last 48 Edge video to think, as I do, that if his motor can hold up to that the way he flies, another 300 RPMs is not going to be a problem the way I fly. In the end, it's all about RPMs and if we're not doing blenders at WOT, then 8700 with a 14 inch prop may never be a problem. I'm saying 8700 because that's what I would expect if I'm getting 9000 with the 13x6.5 APC and don't expect to maintain this RPM with the bigger prop with more pitch.

I'm going to try it on my motor because the worst thing that can happen is that I have to buy a new 750Kv and go back to 4S and a 14x7 Xoar. I don't fly at WOT much anyway. Of course, I may have to buy a new Edge too, but I've been beating this one up for a year now and it may be time anyway.
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Old May 05, 2012, 09:21 PM
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I ran up the Hacker Q80-7M and the Castle Ice V2 HV160 a few hours ago and finally got around to running some numbers. On the 2x 5S 40C Sky Lipo’s and the 24x10 Xoar electric, this is what we got if anyone is interested:

We got 6635 RPMs and were expecting about 6800 RPMs
We got 4037 Watts and were expecting about 4500W
We got about 109A and were expecting about 120A

The efficiency was very good, as advertised, and we got 85.9% Kv efficiency.

The voltage did sag more than I expected and it may have something to do with new batteries. I have been told more than once that new batteries need to be broken in (cycles five to six times) before I’ll see their optimal performance.

We’ll cycle them again and I expect that we’ll need four or five more static runs before we start seeing better voltage, unless this is a myth and I'm just going through denial that I'll need more expensive batteries.

We opened up at about 41.67v, we sagged to 36.81v, and the final at rest reading was 40.80v. If we can maintain 3.8v per cell, the math says we will get the numbers we were expecting… 6800 RPMs, 4500W, and 120A.

After the third run up, we help WOT for about 45 seconds and took some static temp readings. The motor was 109 degrees (F) and the ESC was 99 degrees. The batteries were barely warm at 88 degrees, which was a few degrees more than the air temp.

I put the fish scale on it, and although I really don’t trust the readings, I did get 32 pounds or 14.5kg (1.7-to-1 thrust to weight). I ran the numbers through the online static thrust calculator and got 38 pounds and 4700 Watts, so my reading is probably closer.

I ran the numbers through the mechanical Watts formula that I use and the readings from the meter were right on, which is a rare occurrence, and means a very efficient system because Watts-in and Watts-out are about equal.
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