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Author Topic: Which number is the "Power"  (Read 442 times)

Offline Ken Culbertson

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Which number is the "Power"
« on: December 13, 2019, 07:43:56 AM »
The more I learn about electrics, the less I seem to know!  I have finally got the relationships under control but I still don't have a clue how to figure out which motor to buy for a new ship.  For simplicity and budget I am sticking with the Cobra line.  Within a particular size, the physical dimensions are the same (2820, etc.) and it is the windings ("/xx" number) that changes.  What little I know about motors tells me that more windings means more power but RPM's and the ability to hold them is all that matters to the flight.

To oversimplify the question - I have a ship using a 2820/12 and I want more power but I cannot change the size of the motor.  So what does changing the "/xx" number actually mean in real terms.  Getting IC to perform is pretty straight forward once you get the hang of it but electric is like playing "Wack a Mole".  Guess I will get it eventually.

Thanks - Ken
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Offline John Rist

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Re: Which number is the "Power"
« Reply #1 on: December 13, 2019, 08:43:33 AM »
The /xx in the Cobra P/N has nothing to do with power.  For this discussion lets assume that you have a setup that provides constant RPMs.  either a KR timer that controls RPMs or a speed controller that does the same.   To increase the amount of power (or more pull if you will), all you need to do is install a bigger prop.   The way electric motors work is that when you install a bigger prop the motor will  output more power in order to achieve the set RPMs.  It does this by drawing more current from the battery.  The problem is that electric motors are basically dumb.  They will keep pulling harder to maintain the RPMs, you are asking for, until they explode.   Cobra provides prop charts detailing what props are suitable for a particular motor.  If you are using a constant RPM setup you can go to the upper extreme because you are running the motor at less than wide open throttle.   However too much prop will smoke the motor.   Of course you can also demand more power out of a motor be increasing the RPMs.

The Cobra motor you specified, Cobra 2820/12,  is a 590 W motor.  If you need more power the Cobra 2826/10 is a 660 W motor.  It mounts in the same place as the 2820/12.   However it is longer.  You may or may not have clearance in your airplane for a longer motor.

Anyway the bottom line is more prop or more RPMs means more power until the smoke comes out.  Unfortunately you can't put the smoke back in!   y1   #^   LL~
« Last Edit: December 13, 2019, 09:09:01 AM by John Rist »
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Online Steve Berry

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Re: Which number is the "Power"
« Reply #2 on: December 13, 2019, 09:20:39 AM »
....until the smoke comes out.  Unfortunately you can't put the smoke back in!   y1   #^   LL~

All electronics work via magic smoke. Don't believe me? Do some thing wrong, let out the magic smoke, and the electronic whatever will stop working. Magical smoke makes electronics work.

The opposite is true of internal combustion engines. They can't stand the magic smoke, that's why they get rid of it as fast as they can. They run, instead, on magic elixirs formulated by crafty elves who live deep underground. As long as they have a steady supply of this magic elixir, they run just fine. The only real issue is that the elixir puts out magic smoke when heated, and i.c. engines don't like it, so they blow the smoke away.

Offline John Rist

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Re: Which number is the "Power"
« Reply #3 on: December 13, 2019, 09:47:19 AM »
All electronics work via magic smoke. Don't believe me? Do some thing wrong, let out the magic smoke, and the electronic whatever will stop working. Magical smoke makes electronics work.

The opposite is true of internal combustion engines. They can't stand the magic smoke, that's why they get rid of it as fast as they can. They run, instead, on magic elixirs formulated by crafty elves who live deep underground. As long as they have a steady supply of this magic elixir, they run just fine. The only real issue is that the elixir puts out magic smoke when heated, and i.c. engines don't like it, so they blow the smoke away.
"They run Just fine"  as long as the needle is set just right, the fuel is clean, the plug isn't blown, the filter isn't clogged. the tank is in the right place, you have the right number of head gaskets, ETC.   And that smoke they are belching gets goop all over my airplane.  IE  all form of power have problems and all work well if you know what you are doing.  y1
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Offline Shorts,David

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Re: Which number is the "Power"
« Reply #4 on: December 13, 2019, 09:49:44 AM »
I don't think this was mentioned. But check your batteries C rating. If your motor wants 50amps but the battery can only squeeze out 40 amps at a time you will think you've reached your max motor power. Switch to a battery able to deliver more amps and you've got more power.

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Offline Ken Culbertson

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Re: Which number is the "Power"
« Reply #5 on: December 13, 2019, 10:24:20 AM »
The /xx in the Cobra P/N has nothing to do with power.  For this discussion lets assume that you have a setup that provides constant RPMs.  either a KR timer that controls RPMs or a speed controller that does the same.   To increase the amount of power (or more pull if you will), all you need to do is install a bigger prop.   The way electric motors work is that when you install a bigger prop the motor will  output more power in order to achieve the set RPMs.  It does this by drawing more current from the battery.  The problem is that electric motors are basically dumb.  They will keep pulling harder to maintain the RPMs, you are asking for, until they explode.   Cobra provides prop charts detailing what props are suitable for a particular motor.  If you are using a constant RPM setup you can go to the upper extreme because you are running the motor at less than wide open throttle.   However too much prop will smoke the motor.   Of course you can also demand more power out of a motor be increasing the RPMs.

The Cobra motor you specified, Cobra 2820/12,  is a 590 W motor.  If you need more power the Cobra 2826/10 is a 660 W motor.  It mounts in the same place as the 2820/12.   However it is longer.  You may or may not have clearance in your airplane for a longer motor.

Anyway the bottom line is more prop or more RPMs means more power until the smoke comes out.  Unfortunately you can't put the smoke back in!   y1   #^   LL~
So what you are saying is that to get more power you need more watts.  So my 2826/12 is more powerful because it uses more watts?

Ok, here is the actual decision tree.  I have a 2826/12 in an ARF Nobler now.  It is over powered and I can't fit anything larger than a 2200 battery in it.  That barely gets me through the pattern at 5.0 laps which is too fast for me.  Dropping the rpm hasn't prolonged the life of the battery as mush as I need.  I am converting my competition profile to electric.  It is a .46-.60 size ship (660 sq) and about 50 oz.  I was shopping for a motor for it somewhere inbetween a 2820/12 and 3520/14 that I also have.  I think you answered my question for me and that is to move the 2826 to the profile on 5s and get a new motor for the ARF.  If I am understanding all of this (which is a stretch), a 2814/16 should produce enough power for the ARF on a 4s 2200 and be a tad lighter.

And I thought IC was confusing!

Ken
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Re: Which number is the "Power"
« Reply #6 on: December 13, 2019, 12:35:31 PM »
Cobra's method of nomenclature uses the stator size.  Most other manufacturers use outside can dimensions, or some vague reference to an approximate glow equivalent. 

Cobra 2808 = 3530 = Park 480
Cobra 2815 = 3536 = Power 10
Cobra 2820 = 3542 = Power 15
Cobra 2826 = 3548 = Power 25
Cobra 3520 = 4250 = Power 32

Handy cross reference chart: http://innov8tivedesigns.com/docs/Airplane-Motor-Chart.htm
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Offline John Rist

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Re: Which number is the "Power"
« Reply #7 on: December 13, 2019, 12:45:55 PM »
Lets start with your 2826/12 motor in the nobler.  Per the Cobra chart this is a 760 KV motor.  Typically the "/xx" in the cobra PN refers to the KV of the motor.  KV is the number RPMs per volt that the motor is designed for.  IE  Volts applied times the KV number equals expected RPM.

For your Cobra 2826/12 with a KV 760 for a 4 cell pack (14.4 volts) it would be 14.4 x 760 = 10900 RPM.  5 cell pack (18 volts) is 18 x 760 = 13680 RPM.  6 cell pack (21.6 volts) is 21.6 x 760 = 16400 RPM

If you are going to set the motor RPMs at around 10,000 RPM the 4 cell pack would not be an acceptable choice.  You need head room for the governor to work.  Also you need room for voltage drop as the battery gets discharged.

The 5 cell is probably OK but the 6 cell would be better.  Looking at the Cobra prop chart for the 2826/12 it says that an APC 10x7-E should turn at 12,495 RPM using a 6 cell pack.  However this is pushing the limits of the motor.  If you are planning to set RPMs at around 10,000 RPMs this prop should work.   Just a word of warning: Do not run the motor on the ground for more than a minute or so.  The motor will unload when the airplane is launched and the current will drop to a safe level.

My point is that it is necessary to match the KV of the motor to the number of cell you are planning to use.  Target max RPMs should be around 12K to 15K  for a set RPM of 9K to 10K RPM.

For the most part I run 4 cell packs.  I chose motors with a KV of around 930 giving an RPM rating of 13,400.  I run my KR timer at around 9,500 to 10,000 RPM.  So far this has worked for me. D>K
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Offline Fred Underwood

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Re: Which number is the "Power"
« Reply #8 on: December 13, 2019, 12:52:50 PM »
So what you are saying is that to get more power you need more watts.  So my 2826/12 is more powerful because it uses more watts?

The motor is able to use more watts and can be more powerful, but the prop load will determine.  On the same prop, it may not change much.

I don't think this was mentioned. But check your batteries C rating. If your motor wants 50amps but the battery can only squeeze out 40 amps at a time you will think you've reached your max motor power. Switch to a battery able to deliver more amps and you've got more power.


We fly at about 20 amp/h as an average. For a 2200 mah pack, 10C would about suffice.  25C could output about 50 amps, more for short bursts.  For our use, C is not usually a problem.  More "C" is usually heavier for same capacity.
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Offline Tim Wescott

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Re: Which number is the "Power"
« Reply #9 on: December 13, 2019, 01:27:10 PM »
... Within a particular size, the physical dimensions are the same (2820, etc.) and it is the windings ("/xx" number) that changes.  What little I know about motors tells me that more windings means more power ...

You have something to unlearn then.  Sorry.

Here is some theory

For a given motor geometry, less the windings, the best-case power capability of the motor is pretty much constant.  That's because if you put in more windings you have to use thinner wire, so as the current needed to get a certain torque goes down, the voltage needed to get a certain speed goes up.  Assuming that the windings are packed efficiently into the motor, which is a pretty big assumption, for any given motor speed and torque output its efficiency (and hence the heat it generates) will be constant across different windings and winding styles, and it's ability to dissipate heat will be constant, too.

What does vary is the voltage and current that are needed for that speed and torque point -- if you compare a 12-turn motor against an 8-turn motor, the 12-turn motor will need 2/3 the current and 1 1/2 times the voltage to do the same thing as the 8-turn motor.

Onward to facts

The facts are that, first, that assumption about efficient winding packing isn't always true -- but I suspect it's more true for the model motors we use than the industrial servo motors I've worked with professionally.  Second, motor manufacturer's don't seem to be very motivated to compare apples to apples -- they're more interested in making a motor look good for the market segment it addresses, without being accused of false advertising.  So your friendly local professional motor-picker gets frustrated reading their marketing foof, because it's hard to unwind what they say into hard engineering data.

There are some details having to do with how efficiently an ESC/battery combination can be used by the motor -- the most efficient case is when the motor is perfectly loaded and using 100% of the pack voltage, but that doesn't work for us because we must have overhead, so we don't run out of poop in the overheads.  So you need to choose a motor/ESC/battery combination that gives you enough overhead, without going overboard.

Note that DC motors are very obedient: Two motors with roughly the same Kv, prop, and voltage/ESC setting, will do their damnest to turn the same speed -- the difference is that a great big motor will (probably) be more efficient and will (definitely) be better at dissipating heat.  So the little motor may well burn itself up trying to make you happy while the big one loafs along and keeps its cool.

The bottom line is

If you have two motors from the same manufacturer made in the same case with different winds, there is no free lunch.  Given the same prop, a 2826/8 may handle fractionally more or less power than a 2826/12, but the biggest difference will be the best battery voltage (and hence ESC current and wire size).

If you need more power and your motor is already as hot as it can stand then you either need to find a better prop for the motor you have (i.e. spin it faster) and either adjust the battery voltage and ESC or adjust the number of turns, or (far more likely) you just have to bite the bullet and get a bigger motor.
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Offline Ken Culbertson

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Re: Which number is the "Power"
« Reply #10 on: December 13, 2019, 03:40:35 PM »
Tim, going electric has been the biggest "unleanin" exercise in my life but worth it.  However, now I am more confused than when I started.  So let's make this simple.  I am trying to find the right motor to put in a Nobler ARF that will last 5.5min on a 4s 2200 25c battery and it needs to be smaller (dimensions) than the Cobra 2826 in there now. I KNOW I NEED A LARGER BATTERY, there just isn't any place to put it.

Is there another 2820 in my future?

Help - I need to click on a "Pay Now" button here pretty quick.

Ken
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Offline Tim Wescott

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Re: Which number is the "Power"
« Reply #11 on: December 13, 2019, 03:52:24 PM »
Let's go back to your original post -- what do you mean by "I need more power?"

  • Is your motor burning up (landing hot enough to fry eggs)?
  • Is the plane just too slow?
  • Is it running out of poop in the overheads?
  • Why can't you run a higher pitch prop?

If you just want the motor to turn faster on the same voltage, then you want a higher Kv (i.e., fewer turns).  But if it's already running too hot then you'll just burn it up faster.  And more power out means more power in, so if it's already sucking the battery dry it'll just do that worse.  So -- clarification is needed, so that we answer the right question.

And if the thing is running out of battery before the end of the flight then you just need to find a home for a larger battery.
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Offline Ken Culbertson

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Re: Which number is the "Power"
« Reply #12 on: December 13, 2019, 04:10:44 PM »
Let's go back to your original post -- what do you mean by "I need more power?"

  • Is your motor burning up (landing hot enough to fry eggs)?
  • Is the plane just too slow?
  • Is it running out of poop in the overheads?
  • Why can't you run a higher pitch prop?

If you just want the motor to turn faster on the same voltage, then you want a higher Kv (i.e., fewer turns).  But if it's already running too hot then you'll just burn it up faster.  And more power out means more power in, so if it's already sucking the battery dry it'll just do that worse.  So -- clarification is needed, so that we answer the right question.

And if the thing is running out of battery before the end of the flight then you just need to find a home for a larger battery.
The original post was seeking a motor that had more power to put into my competition profile.  The answer to that came with the revelation that the 2826 I had in my Nobler ARF was the right choice on a 5 or 6s battery.

From there the question became what to I put into the ARF since the 2826 was overkill.  What can I put in that will use a battery that will fit and since I have 6 relatively new 2200's, that would be where I want to start.
More power is not the issue now, it is simply that "size matters".

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Offline Fred Underwood

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Re: Which number is the "Power"
« Reply #13 on: December 13, 2019, 04:38:04 PM »
So the number of watts or mahs is the limit.  A smaller motor could make it the limiting factor - smoke getting out.  What about using less power?  I realize that you mentioned slowing it down not helping much - slower might mean running longer to finish the pattern. 

A different prop pitch might hit the sweet spot where the motor uses a few less mah.

You didn't mention line length, but shorter lines could help if you can slow the motor and get the required laps.  Of course slowing the plane may adversely affect line tension.  If you try to keep everything the same, battery prop, and speed, then motor may not help much. 

An interesting search of Nobler,  in "list your setup" gave a variety of battery information and different size packs.  I also realize that you have the 2200 packs and that would be an expensive change, motor not so expensive.  2200's were used by some, so may work if you can change something else.

Then maybe Tim has a better answer.
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Offline Ken Culbertson

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Re: Which number is the "Power"
« Reply #14 on: December 13, 2019, 04:58:14 PM »
So the number of watts or mahs is the limit.  A smaller motor could make it the limiting factor - smoke getting out.  What about using less power?  I realize that you mentioned slowing it down not helping much - slower might mean running longer to finish the pattern. 

A different prop pitch might hit the sweet spot where the motor uses a few less mah.

You didn't mention line length, but shorter lines could help if you can slow the motor and get the required laps.  Of course slowing the plane may adversely affect line tension.  If you try to keep everything the same, battery prop, and speed, then motor may not help much. 

An interesting search of Nobler,  in "list your setup" gave a variety of battery information and different size packs.  I also realize that you have the 2200 packs and that would be an expensive change, motor not so expensive.  2200's were used by some, so may work if you can change something else.

Then maybe Tim has a better answer.
I am on 60' lines so I could go to 58' and back off of the RPM's  Prop is probably my best bet.  Right now it has an APC 11.5 x 6 on it.  That got me the best battery on the 2820/12.  I know where I can get a light 11 x 5.5 three blade to try.  Then there is always that useless wing center section.  I think I have about an inch before I hit the leadouts.  It's "Dremmel Time".... ~^

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Offline Tim Wescott

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Re: Which number is the "Power"
« Reply #15 on: December 13, 2019, 05:41:51 PM »
The average power of an electric stunter tracks strongly by the airplane weight, until you start flying with the big boys who use active timers and purposely use inefficient props.  It's about 7 watts per ounce.  That, plus some physics, will get you hard numbers on the battery regardless of the motor.

Weigh it, with the battery in.

Multiply the weight in ounces by seven -- that's the average power it'll use, more or less, assuming a constant motor speed (i.e., Hubin or KR timer).  Assuming 48 ounces, I get 340 watts.

Multiply the watts by 0.1 for a six minute flight (six minutes is 0.1 hour).  That's the energy used in watt-hours.  I get 3.4 watt-hours.

Divide that by 3.7 (the cell voltage) times 4 (the cell count).  That's the charge taken from the battery.  I get 2.3 amp-hours, or 2300 mAh.  That's bigger than 2200mAh, so I get a "no pass" on a 2200mAh, 4s pack.  If you go by the rule that you want 20% left over, you want 2300mAh / (0.8) = 2800 or 3000 mAh.  A 5S pack would land with a bit less than 20% left.

I just don't see you getting there from here, unless you do something extreme like rebuilding your packs into 5S, or making your flights scary-short to come in under the wire on the energy in the pack.

This is all pretty much regardless of the motor used.  You could try thrashing it to find a more efficient prop/motor combination, but I think it'd be a losing proposition.

Going in the other direction, a 4S 2200mAh pack should be just about ideal for a 35-38 ounce airplane -- I suspect that's right where a Skyray would fall all up with battery, or maybe something very slightly larger.
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Offline John Rist

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Re: Which number is the "Power"
« Reply #16 on: December 13, 2019, 06:07:52 PM »
You might look at a Cobra 2814/16.  According to the prop chart it will turn a APC 9x6-E prop at 11880 RPM. (14.4 V - 4 cell battery).  AT this RPM it is pulling 26 amps (close to the max allowed).  The Nobler originally flew on a FOX 35 turning a 9x6 at around 8K to 9K RPMs.  If you set the RPMs to around 8,500 rpm it should get the amp draw down to around 20 amps.  This should give you a 5 minute run time.

This motor can't handle an APC  11 x 5.5-E on a 4 cell battery.

Unless my math is off to get a 5 minute run times from 2200 MAH battery you need to keep the current around 20 AMPS.

I am guessing for a given prop size and set RPMs the amount of power (AMPS) needed will be the same no matter what motor you pick. So first pick a prop/RPM needed to fly a Nobler. Then pick a motor.

The fly in the ointment  is your battery.  At 2200 mah  I think the magic number is around 20 amps to get a 4 minute flight.  Others with more experience may have a better handle what is maximum amp draw allowed to get a 5 minute flight out of a 2200 mah battery.
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Offline Tim Wescott

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Re: Which number is the "Power"
« Reply #17 on: December 13, 2019, 06:44:04 PM »
Unless my math is off to get a 5 minute run times from 2200 MAH battery you need to keep the current around 20 AMPS.

Unless you're absolutely draining it dry, yes.

I am guessing for a given prop size and set RPMs the amount of power (AMPS) needed will be the same no matter what motor you pick. So first pick a prop/RPM needed to fly a Nobler. Then pick a motor.

Pretty close to true.  For the sizes of motors we run, bigger is usually slightly more efficient, but not a whole lot.  There's an efficiency sweet spot, but it happens at a motor weight that's way heavier than anyone would want.

The fly in the ointment  is your battery.  At 2200 mah  I think the magic number is around 20 amps to get a 4 minute flight.  Others with more experience may have a better handle what is maximum amp draw allowed to get a 5 minute flight out of a 2200 mah battery.

Well, 5A from 2200mAh works out to 0.11 hours, or 6.6 minutes -- but that's sucking the battery absolutely dry.  Leaving yourself with 80% capacity is more like 5.3 minutes in theory, probably more like 5 minutes.

I have it stuck in my head that you need six minutes to fly the pattern -- can you do it in five?
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Re: Which number is the "Power"
« Reply #18 on: December 13, 2019, 06:57:22 PM »
5:20 or so will easily do the pattern with some extra laps.
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Offline Tim Wescott

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Re: Which number is the "Power"
« Reply #19 on: December 13, 2019, 07:01:42 PM »
5:20 or so will easily do the pattern with some extra laps.

Thanks Brent!  I re-dood my calculations for a 48 ounce plane, and came up with 90% battery usage.  So Ken, if you want to use up those packs, draining them down to 10% each flight ought to work well -- and you can fly.  You still need a the right motor, though...
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Offline William DeMauro

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Re: Which number is the "Power"
« Reply #20 on: December 13, 2019, 07:11:15 PM »
I have a Gieskie nobler with the cobra 2814/ 16 in it and it fly's great with a 10x6 xoar E prop and a 4 cell 2800mah thunderpower battery. I've flown it on a 4s 2200 and it barely makes it to the end of the pattern and is a little tail heavy. Another option that we have used in the ARF Noblers is the cheaper exceed motor  https://www.hobbypartz.com/86mb22-rocket-3015-1035kv.html  which is only 6 grams heavier You can use the same prop and batteries as the cobra. Your best bet at this point is to stop banging your head against the wall to figure out what motor prop battery will work on what plane and just copy known set ups that work well in similar sized planes. Once you put one or 2 together you will see a pattern developing just like you would choose a motor for an I/C engine. I set my motors for 5:20 run time
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Offline Fred Underwood

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Re: Which number is the "Power"
« Reply #21 on: December 13, 2019, 07:52:21 PM »
10" prop might solve it for you until the batteries get old and have only 2000 mah, not the labeled 2200.  Maybe with shorter lines.  There were 2200 batteries shown as working in list your set up with a Nobler.  Since you own the 2200's, worth a try.
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Offline Ken Culbertson

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Re: Which number is the "Power"
« Reply #22 on: December 14, 2019, 12:31:51 AM »
I have a Gieskie nobler with the cobra 2814/ 16 in it and it fly's great with a 10x6 xoar E prop and a 4 cell 2800mah thunderpower battery. I've flown it on a 4s 2200 and it barely makes it to the end of the pattern and is a little tail heavy. Another option that we have used in the ARF Noblers is the cheaper exceed motor  https://www.hobbypartz.com/86mb22-rocket-3015-1035kv.html  which is only 6 grams heavier You can use the same prop and batteries as the cobra. Your best bet at this point is to stop banging your head against the wall to figure out what motor prop battery will work on what plane and just copy known set ups that work well in similar sized planes. Once you put one or 2 together you will see a pattern developing just like you would choose a motor for an I/C engine. I set my motors for 5:20 run time
Thanks - I was about to order one of those.  My 2820's will get through the pattern on the 2200 but it sucks them pretty dry.  Looks like the 2816 would do the same.  Guess I will just get out the trusted dremmel and make a 2800 fit.  Didn't need that wing LE anyway. n1

Ken
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Offline William DeMauro

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Re: Which number is the "Power"
« Reply #23 on: December 14, 2019, 07:12:42 AM »
Thanks - I was about to order one of those.  My 2820's will get through the pattern on the 2200 but it sucks them pretty dry.  Looks like the 2816 would do the same.  Guess I will just get out the trusted dremmel and make a 2800 fit.  Didn't need that wing LE anyway. n1

Ken
I'm almost positive you can fit the 2800 in without cutting the leading edge of the wing, most likely no dremel needed!
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Offline Ken Culbertson

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Re: Which number is the "Power"
« Reply #24 on: December 14, 2019, 07:54:47 AM »
I'm almost positive you can fit the 2800 in without cutting the leading edge of the wing, most likely no dremel needed!
Wish it were true.  I may get it in there after I remove part of the bulkhead and part of the IC motor mounts in the back and maybe thin the LG mounts in the front.  If I am going to keep this plane around I need to find a way to get a minimum of a 2800 in there.  If I am going to grind away I will make a 3000 fit.  It would be simpler to replace the motor with something that would do a pattern on 2200 but it doesn't look like that is going to happen.

I have cut out the LE on Noblers before and never had a wing fail.

Ken
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Offline William DeMauro

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Re: Which number is the "Power"
« Reply #25 on: December 14, 2019, 04:06:41 PM »
Neil Beekman has set up about 3 Noblers  with 3000 mah batteries I have a few pictures that I will attach. These are early pictures from about 2012, we have since completely changed the motors (went to the motors listed above we also changed the way we mount the motors)
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Offline Randy Powell

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Re: Which number is the "Power"
« Reply #26 on: December 15, 2019, 02:08:31 PM »
Tim, I set my timer for 5 minutes 23 seconds. That give me 5 laps to start the wingover and 4 to 6 laps (depending on wind) after the clover.
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Online Dennis Toth

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Re: Which number is the "Power"
« Reply #27 on: December 23, 2019, 07:37:07 AM »
Ken,
You didn't mention the size of the battery compartment available. I have a Don Still Stuka that I converted to electric and originally flew on TP 4S-2200 packs. The ship uses an APC EP10 x 5.5 prop set at 9750 rpm at the ESC. I fly on 60' C to C lines at 4.95 lap time. One thing I found was that rpm has a big impact on amp draw. I like the speed but for the PA pattern it drew down the 2200's really low and as they got older would hit low voltage cut-off. I have switched to a Zippy Compact 4S-2450, this pack now covers the pattern with 8 laps at the end. If you want to slow the lap time you could drop rpm or add 1 foot of line for each 0.1 sec you want to slow the time. I think the 11.5" diameter prop on a Nobler is one of the factors drawing higher amps. In IC form the Nobler flew well with the old spoon Top Flite 10x6, if you take the 11" and try trimming it to 10.5" it should have similar pulling power and a pack around 2500 should work.

Best,   DennisT

Offline Ken Culbertson

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Re: Which number is the "Power"
« Reply #28 on: December 23, 2019, 08:44:15 AM »
Ken,
You didn't mention the size of the battery compartment available. I have a Don Still Stuka that I converted to electric and originally flew on TP 4S-2200 packs. The ship uses an APC EP10 x 5.5 prop set at 9750 rpm at the ESC. I fly on 60' C to C lines at 4.95 lap time. One thing I found was that rpm has a big impact on amp draw. I like the speed but for the PA pattern it drew down the 2200's really low and as they got older would hit low voltage cut-off. I have switched to a Zippy Compact 4S-2450, this pack now covers the pattern with 8 laps at the end. If you want to slow the lap time you could drop rpm or add 1 foot of line for each 0.1 sec you want to slow the time. I think the 11.5" diameter prop on a Nobler is one of the factors drawing higher amps. In IC form the Nobler flew well with the old spoon Top Flite 10x6, if you take the 11" and try trimming it to 10.5" it should have similar pulling power and a pack around 2500 should work.

Best,   DennisT
You are right, all of the "just put in a bigger battery" solutions would just create a "blivit"  I can't change the amount of room for the battery.  I like the prop idea.  I have some 10" props that I can try.  My Nobler flies comfortably on 58' lines at 5.4 (my comfort zone time).  I have only had one "power on" landing and a couple where I could feel it weakening in the clover - that was on an 11-5.5 APC.  A light 10" three blade may be the answer.  I don't care if I don't get 100 cycles out of these cheap ($$) batteries, I just don't want it "rolling over in the clover" LL~
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Offline Dan Bregar

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Re: Which number is the "Power"
« Reply #29 on: February 18, 2020, 03:25:58 PM »
FWIW our friend William DeMauro talked about using a 2800 mah "Thunder Power" batt.. My experience has been that this brand of batteries are lighter & smaller than most other brands, as well as being more expensive.  So a 3000 mah Sky Lipo or Turnigy battery may not fit, but a Thunder Power probably will. FWIW  ;)
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