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Everything You Wanted To Know About Electric Powered Flight

Old 11-29-2011, 03:38 AM
  #226  
mred
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Originally Posted by Turner View Post
The risk of fire has more to do with the charger used than with whether or not you balance. A charger like the Triton, that cannot balance, has no way to monitor the voltage in each cell, and ends charge based on pack voltage alone is a real risk. Using a balance charger with the balance lead connected will stop the charge if any cell exceeds 4.2 volts, for LiPo, even if you choose a charge mode that does not balance. This is much safer.

Yes, a knowledgable person can use the Triton with a balancer and close attention and do so safely but when buying a charger for LiPo batteries always look for a balancing charger and always connect the balance lead for best safety.
I never said the charger would cause the fire, I said the battery being out of balance would cause it, because the charger cannot tell that one cell is way out of balance and will continue to charge it until it reaches cut-off. There is a possibility that the battery can catch on fire IF the balance is off far enough and the cells get over charged enough. That's why I said to use a balancer on that type of charger.

That's also why I said to buy a Cell Pro 4S or something like that if you can afford one. It is always best to charge with a balance charger when charging a LiPo battery and ALWAYS monitor a battery and never leave it unattended while charging. Simple precautions will stop problems before they happen.

Ed
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Old 11-29-2011, 03:59 AM
  #227  
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Originally Posted by repinfl View Post
mred "You didn't say what kind of battery you got. What is the "C" rating of the batteries you bought from China??"

I tried to order the same as I purchased from Great Planes i.e. 3200 mah 11.1V 20C but one is
a "NANO-TECH" 3300 mah 35C and it does the same thing. I might just purchase another battery from GP and see but I assume there batteries come from China also. Thanks for the help...Robert
How is your timing set on the ESC? The battery should not have anything to do with the way it starts up unless it is underrated for that motor and prop. That battery should work just fine and I have used them in a few of my planes and never had a problem with them. Your timing should be set to low for most flying and props and that is where my .32 is set, but I am using a Turnigy Plush ESC and not the Great Planes. I have a couple of their motors, but never buy their ESC's. I always buy Turnigy Plush for mine. You could try changing the timing and see if that helps you, but I have never heard of this problem before unless it was trying to pull to much out of the battery and it was pulling the battery down to far. If you have a watt meter, check and see what the battery voltage is doing when you try going to high on the throttle. It should drop down, but not very much.

Your plane calls for a .25 or .32 motor, so that one you have is fine. It will fly much different on the .32, but the .25 you have is fine for that plane.

Ed
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Old 12-02-2011, 04:27 PM
  #228  
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Hooray! I can now say with certainty, I have found my problem.
The instruction for my ESC say to set the throttle channels End
Point adjustment to 100%, which I did. However there are two
EPA’s, High and Low, which I left at 100% each….WRONG!
The correct setting turned out to be 50% High and 100% Low.
AGAIN, thanks for all the help and interest with my problem.
And I want to say “Where there is a Will….I want to be in it”

Robert
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Old 12-03-2011, 06:46 AM
  #229  
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Originally Posted by repinfl View Post
Hooray! I can now say with certainty, I have found my problem.
The instruction for my ESC say to set the throttle channels End
Point adjustment to 100%, which I did. However there are two
EPA’s, High and Low, which I left at 100% each….WRONG!
The correct setting turned out to be 50% High and 100% Low.
AGAIN, thanks for all the help and interest with my problem.
And I want to say “Where there is a Will….I want to be in it”

Robert
Glad to hear you found your problem. I'll join you in wanting to be in that will too. Can't hurt anyway.

Ed
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Old 12-18-2011, 01:39 AM
  #230  
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Question. Still trying to get this e-thing stright in my mind.
1. IF YOUR ESC matches up with your motor. Does it matter what size of battery you have.
Example.
I have an UNKNOWN size e-motor. Smaller type, was not in the box. Do not even know what make it is. Guy I got it from sold me a 18amp ESC to go with the motor.
a. He told me that a 2c 500/800 lipo batt. would be enough.
b. I have several 3s 2100 Batt. that I could use.

Is there any problem???
Thanks
SARG5
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Old 12-18-2011, 03:09 AM
  #231  
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Originally Posted by SARG5 View Post
Question. Still trying to get this e-thing stright in my mind.
1. IF YOUR ESC matches up with your motor. Does it matter what size of battery you have.
Example.
I have an UNKNOWN size e-motor. Smaller type, was not in the box. Do not even know what make it is. Guy I got it from sold me a 18amp ESC to go with the motor.
a. He told me that a 2c 500/800 lipo batt. would be enough.
b. I have several 3s 2100 Batt. that I could use.

Is there any problem???
Thanks
SARG5
Question number

1) Yes battery size matters in relation to how much amperage it can provide. The battery must be able to deliver the amps that the motor demands. See these chapters

2 ............Amps vs Volts vs C
3 ............Sizing Power Systems


2) You can use a larger battery than required. In this case he says a 2C 800 mah pack will do it. Yours are much larger than that so they are OK, though the may be kinda big and heavy for the plane if an 800 mah pack is what is expected.

Again, see chapters 2 and 3.


Also see chapter 7 on Wattmeters. Since you don't know anything about this motor you don't know what kind of amps/watts it is going to draw. A wattmeter will help.



Chapter/Post# ..... Topic

1 ............Preface
2 ............Amps vs Volts vs C
3 ............Sizing Power Systems
4.............Props vs. Amps
5 ............What is an Electronic Speed Control - Updated 11-2008
6 ............The LVC, Low Voltage Cut-off
7 ............Who Needs a Wattmeter?
8 ............Why Use a Gearbox?
9 ............Extended Flight Times and Balance
10 ...........Battery Basics
11 ...........Lithium Batteries, Chargers and Balancers
12 ...........Six Keys to Success for New Pilots
13 ...........Things to Check on an RTF
14 ...........Now its Your Turn!
23 ...........The Role of the BEC in your ESC
24 ...........The Mythical Best First Plane
33 ...........What You Need to Know About Receivers
36 ...........The AMA Park Pilot Program
39 ...........What goes on which stick?
65 ...........WHAT DO THE KV RATINGS ON MOTORS MEAN?
108 .......... A .pdf compiled and reorganized verion of the book
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Old 12-18-2011, 08:32 AM
  #232  
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Originally Posted by SARG5 View Post
Question. Still trying to get this e-thing stright in my mind.
1. IF YOUR ESC matches up with your motor. Does it matter what size of battery you have.
Example.
I have an UNKNOWN size e-motor. Smaller type, was not in the box. Do not even know what make it is. Guy I got it from sold me a 18amp ESC to go with the motor.
a. He told me that a 2c 500/800 lipo batt. would be enough.
b. I have several 3s 2100 Batt. that I could use.

Is there any problem???
Thanks
SARG5
First of all, you should be able to get this information from the guy you bought this motor from. He should know how to set it up and run it.

If you can't get the information from him, then you are really asking for trouble if you don't have a watt meter. It's not just the battery, it's the prop too. You can over prop that motor just as easy as putting the wrong ESC on it and burn something up. Did he tell you what size prop to run on that motor?? If not, then you need to talk to him and you also need a watt meter to protect yourself against making a mistake in the prop you put on. I always check my amps even if I put the prop on that they call for in the instructions. I want to know for sure that my setup is good.

I have never heard of a 2C battery except for a 1S battery. If it is a 2C battery, it will only put out 1A on the 500 battery, so you are way to big on that ESC he sold you, but it would work. As for going to a 2200MAh battery, that is way over kill too, but the motor will run fine on it. You really need to get a small battery for this thing, because you are talking about a small plane and they will not like you at all for adding all that weight. More then likely you could use a 7A ESC too.

Ed
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Old 12-19-2011, 03:44 PM
  #233  
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Thank you again EVERYONE.
It sure is great to have your knowledge out there to help us along.
THANK YOU AGAIN
MERRY CHRISTMAS
Back to the const. table
PS/ The F-16 is startng to look great. Starting the cut out on F-22.
SARG5
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Old 01-02-2012, 11:23 AM
  #234  
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Hi AEAJR,
This is the singularly most helpful post I have read on the subject of electric flight. I am an ex-wet fuel pilot and slope soarer now converted to volts as my wife says that burned out ESCs still smell better than castor dripping models. Your info on taking the throttle trim to zero has just saved the canning of an ESC which was previosly recalcitrant.
Thank you and please may I pre-order the hard copy.
Cheers
Sean
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Old 01-02-2012, 12:26 PM
  #235  
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Glad you found this helpful. No hard copy, but you can print out the PDF version.

I will be going slope soaring today.
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Old 02-17-2012, 10:28 PM
  #236  
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I'm an old retired RADAR design engineer trying to learn something about E-flying. I have a HP 2208/09 Brushless Motor (Turns: 9T, Kv: 1920, Max Cont.: 12A, Max Burst: 16A/60S, Max Efficiency: 80%, Resistance: 78mohm), running on a Castle Thunderbird 18 ESC, with a 7X5 prop. I have tried it on both a 2S and a 3S LiPo. It doesn't take much throttle to reach Max. current. What is the downside of simply adjusting the high end of the "Throttle Adjust" to a safe RPM point for this setup? If I knew something about the Torque/Speed curve or the Speed/Efficiency curve I might know whether this is a good idea or not. Can you help me understand how to trade this alternative against going with a smaller prop?
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Old 02-17-2012, 11:26 PM
  #237  
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Originally Posted by Shoeless_Joe View Post
I'm an old retired RADAR design engineer trying to learn something about E-flying. I have a HP 2208/09 Brushless Motor (Turns: 9T, Kv: 1920, Max Cont.: 12A, Max Burst: 16A/60S, Max Efficiency: 80%, Resistance: 78mohm), running on a Castle Thunderbird 18 ESC, with a 7X5 prop. I have tried it on both a 2S and a 3S LiPo. It doesn't take much throttle to reach Max. current. What is the downside of simply adjusting the high end of the "Throttle Adjust" to a safe RPM point for this setup? If I knew something about the Torque/Speed curve or the Speed/Efficiency curve I might know whether this is a good idea or not. Can you help me understand how to trade this alternative against going with a smaller prop?
Greetings and welcome to watt flyer. Now then, as to your question, you can't do that at all. That's the easy answer. The other answer is this. The output of the ESC is a square wave and you can check the amp draw for a given setup by going to full throttle and reading the amp draw on a watt meter. Now that output is showing what the motor is pulling with a given prop load and that is the peak of the square wave. Throttle back and the max amp reading you had before is still the same, but the duration of the square wave has changed. The shorter the duration the slower the motor runs, but the peak is still running at the same reading you had. I'll give you an example. Say the full power reading was 18 amps and you are only allowed to run the motor at 16 amps. Now IF the ESC is able to take this current, then you can use the throttle adjust to keep the motor from seeing more then 16 amps. That will keep the motor from burning up. IF however the max reading is 20 amps and you adjust the throttle adjust to read 16 amps, the ESC is still seeing 20 amps on that peak and it will burn out the ESC. It's a bad habit to get into adjusting the throttle adjust to read lower watts for this reason. IF the max amp reading for the ESC is 18 watts, then never go over that amount at full throttle and you will be fine. If you are going to adjust the throttle adjust to keep the readings down for the motor, then don't go over the Peak Amps for the motor anyway. It's really a bad idea to do this as you can forget and try to adjust the ESC reading for the max amps and you can't. It is still seeing that 20 amps on the peak and that alone will burn it out. In short, if you are running the motor over it's max reading then the best thing to do is just put a smaller prop on it. That will lower your amp draw and save you burning out the ESC. Hope this helps. If you have any more questions ask away.

Ed
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Old 02-17-2012, 11:44 PM
  #238  
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I looked up your motor and couldn't find any data on the operation of this motor, so I checked a different motor that does give this data. On 3S you should be able to run about a 6X5.5 and on a 2S you should be able to run your 7X5, but it may be right on the border of the max constant. What are you getting for an amp draw on 2S and 3S with this prop. Maybe we could help you a little more if we had that data too.

Ed
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Old 02-18-2012, 12:45 AM
  #239  
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I greatly appreciate your response and help. I hope you appreciate the fact that I'm trying to learn a new field for me. I once tutored a fellow in math. He told me he didn't care how I worked the problem. He just wanted the answer. I'm not like that. I don't remember the power reading (it was around 100 watts). I was watching carefully to make sure I kept the current below 12 Amps (RMS) going into the ESC. I was reaching that level at about 40% throttle on the 3S and about 70% throttle on 2S (rough estimates).

I understand that the ESC is delivering a pulse width modulated square wave. However, there is still a lot I don't know. Please correct me if I'm wrong. I believe that when an ESC is spec'ed at 18 Amps, that this is 18 Amps RMS (not Peak). I definitely know that it is the RMS value of the current that determines the heating in the motor. They don't spec the power rating of the ESC but it has to be considerably higher than the 18 Watts you mentioned. From my limited perspective I can't see how it makes any difference to the ESC if I reach 12 Amps with a bigger prop and lower speed or a smaller prop at a higher speed. I will certainly try a smaller prop and your point about forgetting later "that I made that adjustment", is well taken. But again I'm trying to learn some of the nuances. For an old retired guy it scratches my technical itch.
Thanks
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Old 02-18-2012, 02:02 AM
  #240  
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Here is what Castle Creations says about the ESC and using the throttle adjust to limit the current going to the ESC;

A speed controller controls power to the motor by turning full throttle current on and off really fast, 11 to 13 thousand times per second (Pulse Width Modulation or PWM). The percentage of each on/off pulse that is off compared to the part that is on determines how much power the motor sees. I.E. With a pulse that is 50% off and 50% on the motor will see 50% power*. Because each on pulse is 100% of full throttle current, a system set to pull 20 amps at full throttle through a Phoenix 10 will not last if you are throttled back to the point where you only see 10 amps on a wattmeter. The ESC in this case is still switching 20 amps, which it can’t do for long. Actually it is worse than the simple example above. Because an electric motor will always to try to pull as much power as is available to get to its rpm (volts times Kv), when you are running the motor below its Kv speed by switching power on an off, each on pulse will actually be way over the full throttle amp draw. That is why ESCs work harder at partial throttle than full throttle and why we underrate our ESCs. We underrate not so they can handle more current than their rating at full throttle, but so they can handle extended partial throttle operation with no problems.

* Actually, electric power is not linear as in this example, but you get the idea.

Now the motor can handle more current then what it is rated for in the max constant current and it will not burn out if kept below the RMS value and can take quite a bit of abuse by running them over the constant rating, but depending on the motor you are taking a chance with this. As long as you keep the average current in check it will be fine, but the ESC being a solid state device is different. Solid state devices can burn out rather fast if hit with to much current and they can only take so much. The ratings on the ESC are somewhat low to allow for the part throttle settings and still survive. It also must be able to take that spike on the leading edge of the square wave without burning out too. These are taking into account in the design, but over amp one and it will burn out, unlike a motor that will heat up before burning out. So if you have an ESC that is rated for 18 amps, never go over that amp draw at full throttle and you will be fine. A good reading of the amp draw would help. The watts are not telling me a lot since the amps can change with voltage. It's not the watts you need to watch, it is the amps and the rest will take care of themselves. The ESC has a watt rating in a way, because it is listed as 2 to 3 cells and 18 amps. That tells you that it is going to take about 200 watts of power, but as you get near the max, you need better cooling. Run them at 12 amps and they do fine with little cooling, but run one at 18 amps and you better have good airflow or it will still burn out. Hope this helps some........

Ed
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Old 02-18-2012, 09:33 PM
  #241  
Shoeless_Joe
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I appreciate your help. I was inspired to dig out an article, "Inside the Electronic Speed Control", by Lee Estingoy ([email protected]), published in the November 2010 issue of Model Aviation. It is an enlightening article and fully supports the ideas you presented. Especially the idea that the ESC works harder at partial throttle.

To summarize: most of the ESC dissipation (thus heating) takes place during the switching time of the FET's and the closer one gets to full throttle the less the FET's are switched. There was nothing new from what you presented but I gained a better understanding of what the circuits are doing.
Thanks.
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Old 02-19-2012, 12:51 AM
  #242  
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Yep, it's old data, just like me, but I do try................

Ed
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Old 02-25-2012, 04:51 PM
  #243  
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Ed,

I recently bought a styrker (c version). It came with a Himax 2825 3600 inrunner and venom v series 120A ESC. It has a 5.7x3 prop on it.

Motor Specs: HA2825-3600 Kv = 3600,
Rm = .025,
Io = 1.4,
Efficient Operating Current = 15-35A

I purchased one 11.1V 4000mah 20c and two 11.1V 4400mah 30c batteries.

After skimming this thread I think I may have screwed up purchasing those batteries. What are you thoughts?

Dave
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Old 02-26-2012, 03:42 AM
  #244  
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Originally Posted by davecal View Post
Ed,

I recently bought a styrker (c version). It came with a Himax 2825 3600 inrunner and venom v series 120A ESC. It has a 5.7x3 prop on it.

Motor Specs: HA2825-3600 Kv = 3600,
Rm = .025,
Io = 1.4,
Efficient Operating Current = 15-35A

I purchased one 11.1V 4000mah 20c and two 11.1V 4400mah 30c batteries.

After skimming this thread I think I may have screwed up purchasing those batteries. What are you thoughts?

Dave
Are you going to tell me what your concern is? What is it about these batteries that you think you screwed up? I can't read your mind buddy.
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Old 02-26-2012, 01:29 PM
  #245  
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I initially misunderstood what the "C" discharge rate meant. For example I thought a "20C" discharge rate meant 20A continuous. That's what the guy I bought if from told me. So my concern was that the motor operates at 15-35A and since the battery was rated at 20A then I might ruin both the motor and battery. After re-reading the sticky I know that "C" discharge rating really means mah/1000 multiplied by the "C" rate. So the 11.1V 4000mah 20C is capable of discharging 40A continuous.

Thanks Dave
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Old 02-26-2012, 03:55 PM
  #246  
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Originally Posted by davecal View Post
I initially misunderstood what the "C" discharge rate meant. For example I thought a "20C" discharge rate meant 20A continuous. That's what the guy I bought if from told me. So my concern was that the motor operates at 15-35A and since the battery was rated at 20A then I might ruin both the motor and battery. After re-reading the sticky I know that "C" discharge rating really means mah/1000 multiplied by the "C" rate. So the 11.1V 4000mah 20C is capable of discharging 40A continuous.

Thanks Dave
Closer but still not there.

The amp rating X C Rating = max amp continous

In your case that is 4 X 20 = 80 amps.

So your packs will not be working hard at all to support your motor.
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Old 02-26-2012, 04:48 PM
  #247  
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Thanks for replying. If the weather is cooperative I'll give it a try next weekend. I'll let you know how it goes. The fuse is white so I'm going to put some highlights on it so I don't loose it.

Dave
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Old 02-27-2012, 02:06 PM
  #248  
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Dark bottom and light top is what works for me.
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Old 08-13-2012, 07:26 PM
  #249  
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Great info, for someone who has been away for 20 years
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Old 10-27-2012, 12:42 PM
  #250  
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hello Ed,

Thank you for this awesome mini book for beginners. I'm new to this, i'm into cars not planes but it seems everywhere on the Internet the best guides and tutorials are written by the planes and heli communities.
After reading this and a couple of other articles and guides i'm still left with some questions.

1) You say that the Amps are a measure of how much water flows through a pipe at a given time. Just so that I can understand it better let's continue this analogy a bit.
So if I keep the same A let's say for a value of 10A and 10V the pipe will have a certain diameter. But if I up the value and go up to 40V will the pipe have the same diameter to keep the same 10A ? I believe it should be a much smaller diameter to keep the same amp flow and I understand that is how you define Resistance for a given electric system.
So for batteries that have the same capacity but different voltages and for the sake of simplicity the same C rating the battery with the higher voltage should also have a higher internal resistance am I right ?

2) I've recently bought a brushless motor that the manufacturer says it handles voltages up to 8.4 V. So I assume that if I give it a higher voltage than this, for example a 3S LiPo pack 11.1V it will turn it beyond its capabilities and it will start to heat up right and probably the bearings wil be overstressed ?

I think I have a couple of other stuff to ask but I'll first read your posts again to see if I still have them.

Thanks,
Mike
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