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  1. #126

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    RE: EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT

    Thank you very much. Finally I think I understand. Your work has been extremely helpful to me.
    Dave

  2. #127
    Moderator aeajr's Avatar
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    RE: EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT

    Glad I could be of service.

    Now that you know EVERYTHING, go help the new guys who are still lost. That is now your obligation.

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  3. #128

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    RE: EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT

    May I be allowed a follow-up question?

    So, too small a prop produces no harm except underutilization of the motor's capacity; too large a prop (in relation to the motors "desire" to turn xxx rpm/V) overloads and can burn out the motor?

  4. #129
    Moderator aeajr's Avatar
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    RE: EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT

    You have it perfectly.

    The controlling factor is the Kv rating and the amp limitation. The motor will draw more and more current, more amps, trying to hit the RPM that the KV rating calls for.  So we balance the prop size so that the motor can reach the RPM it seeks while not drawing too many amps for the windings to handle.

    When the amps get too high, the resistance in the windings produce more heat than the motor can disipate.  Either the insulation on the windings breaks down and you get a short, or the bearings swell from the heat, causing more heat.  The motor will draw more amps trying to overcome the swelling of the bearings causing more heat in the windings.  In the end you "burn up" the motor.

    If you get it hot enough but not so hot as to short the wires you can cause excessive bearing wear and the shaft gets loose, causing vibrations that lead to heat,  and ..... you get the idea.
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  5. #130

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    RE: EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT

    Thanks a million!

  6. #131

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    RE: EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT

    Hi! is this thread still active? I am late to the party, just started flying a few months ago. Tried reading the complete thread before posting and I could not find out an answer to my questions. ( I am pretty sure the answers are here, I just am unable to put it all together) I would like to have an expert opinion by writing a detailed question, but before I do I would like to know if this thread is still active.

    Thanks

    Dan

  7. #132
    Moderator aeajr's Avatar
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    RE: EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT



    There are lots of recient posts.  Why would you think it was inactive?

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  8. #133

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    RE: EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT

    Like I said, I am new to all of this, Thank you for answering.

    My problem is with my flight time. I only get about 5 minutes with my current set up. Lets start with what I have, then you can tell me what information you need.

    Airplane Neptune sea plane.

    http://www.eastrc.org/estoreneptune.htm

    Wing span 59"
    Wing area 713
    Weight 3.6 Lbs

    Motor Eflite 60 400KV
    Battery 18 volt 5Cell 4350Mah Li-Po
    ESC 60 Amp
    Porp 14 X 10 E

    The first time I tried to fly this plane it would not get off the water (had a 13 X 8 Prop. Took it to the LHS and they put a watt meter on it and it was showing about 13 amps. They changed the prop to a 14 X 10 (largest it can use for clearance.) And then it showed about 23 amps. Took the plane back to the lake and was able to take off and land twice and did not have enough power for a third take off. Put in a fresh charged battery, took off and flew about 6 minutes, landed and did not have enough power to take off again.

    Questions

    How do I calculate what my flight time should be with this set up?

    How can I extend the flight time using what I have and making the least amount of changes.

    What would be the best set up for extended times.

    I am thinking a higher KV motor and a different prop might make more sense. Should I use two smaller batteries combined to get the volts and mAh i need? How do I figure out what I need.

    Please, I am not asking for any recommendation on exact equipment to use but more how to figure everything out.

    Thank you for your time. I purchased the watt meter from the LHS so if more information is needed I may be able to get it. I appreciate any help you can give me.

    Dan

  9. #134
    Moderator aeajr's Avatar
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    RE: EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT


    ORIGINAL: DanVI

    Like I said, I am new to all of this, Thank you for answering.

    My problem is with my flight time. I only get about 5 minutes with my current set up. Lets start with what I have, then you can tell me what information you need.

    Airplane Neptune sea plane.

    http://www.eastrc.org/estoreneptune.htm

    Wing span 59"
    Wing area 713
    Weight 3.6 Lbs

    Motor Eflite 60 400KV
    Battery 18 volt 5Cell 4350Mah Li-Po
    ESC 60 Amp
    Porp 14 X 10 E

    The first time I tried to fly this plane it would not get off the water (had a 13 X 8 Prop. Took it to the LHS and they put a watt meter on it and it was showing about 13 amps. They changed the prop to a 14 X 10 (largest it can use for clearance.) And then it showed about 23 amps. Took the plane back to the lake and was able to take off and land twice and did not have enough power for a third take off. Put in a fresh charged battery, took off and flew about 6 minutes, landed and did not have enough power to take off again.

    Questions

    How do I calculate what my flight time should be with this set up?

    How can I extend the flight time using what I have and making the least amount of changes.

    What would be the best set up for extended times.

    I am thinking a higher KV motor and a different prop might make more sense. Should I use two smaller batteries combined to get the volts and mAh i need? How do I figure out what I need.

    Please, I am not asking for any recommendation on exact equipment to use but more how to figure everything out.

    Thank you for your time. I purchased the watt meter from the LHS so if more information is needed I may be able to get it. I appreciate any help you can give me.

    Dan

    Dan,

    I will helpyou understand your plane and your setup but I am not goingshoppingfor parts for you.If you want that kind of help Isuggest you start a new thread asking for help to tune up your plane. But let's see if we can help understand your current situation.

    It is usually best to post links to your components so we don't have to go looking them up to check specs.

    is this your motor?If so it appears that you are not pushing the motor hard at all, so that should not be a problem. Iwould expect you to be using a larger prop with a 5 cell pack, pulling more like 30-35 amps. Or go to a 6 cell pack on that prop to get the power up if you feel you need more power.
    http://www.horizonhobby.com/Products...odID=EFLM4060A

    As to your power system:

    First, you say you arepulling 23 amp ( measured )at 18 volts or about 414 watts on a 3.6 pound plane. That is about 115 watts/pound which is probably a good power to weight ratio for a plane of this weight. However I will say that I know nothing about water take-off and that is totally outside the scope of this discussion. A water plane would not be my first choice for a beginner plane.

    You might need more power to get off the water more easily. HoweverI would suggest you also consider your balance or your take-off technique as having something to do with your take-off problems. I presume you are taking off into the wind. If you are not, that is probably your problem.

    Using that 4350 mah pack, pulling 23 amps, I would expect you to get a solid 8-10minutes of flying time at full throttle, or about 12-16minutes in mixed flying.The fact that you say you are only getting6 minutes leads me to believe that there is something wrong with the battery. Either you have a weak cell or your charger is not charging it properly.

    You should be balance charging that pack through the balance plug. If you are not balancing it, you may have a seriously out of balance pack. What charger are you using and at what rate are you charging it?

    I don't see why you are having such a short useable time on that pack. But if you are constrained to a 14" prop, I would probably suggest you get a 6 cell pack to generate more power and maybe get off the water a bit easier.



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  10. #135

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    RE: EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT

    Dan,

    "I will helpyou understand your plane and your setup but I am not goingshoppingfor parts for you.If you want that kind of help Isuggest you start a new thread asking for help to tune up your plane. But let's see if we can help understand your current situation"

    Thank you as I said in my first post. "Please, I am not asking for any recommendation on exact equipment to use but more how to figure everything out."

    Yes, that is the motor I am using.

    I currently have an eflite apprentice as my trainer plane http://www.e-fliterc.com/Products/De...ProdID=EFL2725 Hope the link works. I won the neptune in a drawing at the local club I am training at. The person training me is a member of that club and has been flying for years. He is also the one that flew the sea plane for me after he let me help him assemble it. He has a lot of experience flying off of the water.

    My charger is a Dynamite Passport Ultra. Link below hope it works. I set it to 5 cell, 18.5 volt and a charge rate of 4.3 amps. The batteries have never been charged without the ballance plug in the correct input. They last about the same amount of time so I guess both could have a bad cell.
    When charging is complete each cell shows about 4.04 volts.


    http://www.amainhobbies.com/product_...r-Cycler-6S-8A

    This brings up a new question. How do you test a battery pack for a bad cell?

    "I would probably suggest you get a 6 cell pack to generate more power and maybe get off the water a bit easier."

    This being the case, could I wire two 3 cell 5000mAh batteries togeather to make a 6cell 5000 aMh pack with both more power and more mAh. If this can be done, how do I calculate expected flight time?

    "Using that 4350 mah pack, pulling 23 amps, I would expect you to get a solid 8-10minutes of flying time at full throttle, or about 12-16minutes in mixed flying."

    How did you calculate this? How do I calculate what my flight time should be with this or any set up?

    Again, thank you for yuor help.

    Dan



  11. #136
    Moderator aeajr's Avatar
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    RE: EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT

    I will give you the way I do quick estimates for duration.

    I will use your 4350 mahpack as the example.

    A 4300 mah pack = a 4.35 amp hourpack. If you draw 4.35 amps the pack can sustain that for an hour.

    If you draw 43.5 amps, the pack can sustain that for 1/10 of an hour, or about 6 minutes.

    You are drawing 23 amps. A little more than half the 43 amps, so you should get a little less than double 6 minutes, so I guestimated aroud 10 minutes.

    Usually you don't fly at full throttle all the time, so for mixed flying I use a 150% of the full throttle time, or about 15 minutes. Naturally your smileage will vary.

    If you want the math, it would be 4.35 amps hours/23 amps = .189 hours which equals 11.35 minutes at full throttle. In practice you get a little less than that.


    CHECKING FOR A BAD CELL

    There are a variety of ways. Many chargers will actually display the voltage of the individual cells. My Cellpro 4S shows me the voltage of the cells. When the pack is drained, I can see if one cell is low. Ican also see what the voltages are when it is fully charged.

    VOLTMETER - You can also use a volt meter to read the individual cells through the balance plug if your charger doesn't display cell voltages.


    WATTMETER - Assuming your pack charges to its proper voltage and they are balanced, next you would use a watt meter to see if the pack sustains a reasonable voltage under load.. For example, Ihave a 3 cell pack that charges to its expected 12.6V, fully charged. But under load, instead of sustaining something between 10.8 V or higher, under load, it drops under 9 V almost immediately. The reason, one cell is weak.


    6 CELL - Yes you can hook up two 3 cell packs in series to make a 6 cell. The should be of equal capacity to be sure that you don't over drain one of them.


    Using a 6S pack and a 14X10 prop you can expect 29 amps and 625 watts. My reason for suggesting this is that with more power you might be able to get off the water easier and faster. Iam assuming that you are eating up a lot of power getting out of the water, but as I said earlier, I know nothing about flying off water.

    Using 29 amps and the 5000 6S pack that you suggest, what would you expect the full throttle duration to be? You do the numbers.
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  12. #137

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    RE: EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT

    OK, thank you.

    "CHECKING FOR A BAD CELL

    There are a variety of ways.  Many chargers will actually display the voltage of the individual cells.  My Cellpro 4S shows me the voltage of the cells. When the pack is drained, I can see if one cell is low.  I can also see what the voltages are when it is fully charged."
     

    My charger does this also.  All cells are within .5 mAh when charging is complete and the voltages are the same.

    "WATTMETER - Assuming your pack charges to its proper voltage and they are balanced, next you would use a watt meter to see if the pack sustains a reasonable voltage under load..  For example, I have a 3 cell pack that charges to its expected 12.6V, fully charged.  But under load, instead of sustaining something between 10.8 V or higher, under load, it drops under 9 V almost immediately.   The reason, one cell is weak. "

    My watt meter also provides this information but I do not recall what it was.  I will charge the batteries again and test this.  If you want I will post the results in a day or so.

    "Using 29 amps and the 5000 6S pack that you suggest, what would you expect the full throttle duration to be?  You do the numbers. "

    5 amp hours / 29 =  .172 X 60 (one hour) = about 10 minutes to a dead ( and probably ruined) battery at full throttle.  150% would be aprox 15 minutes.  This being said I would not gain much if anything.

    What have I learned here so far?  My 400 KV motor with a 14X10 prop may be too large for this plane since I can not run a larger more efficient prop.  If I were to change to a 670 KV motor and the same battery Perhaps I could get more RPM for less amps and increase flight time.  Unless a 670 KV motor needs more amps.

    "
    Using a 6S pack and a 14X10 prop you can expect 29 amps and 625 watts"

    This interest me as well.  You say I can expect 29 amps.  Is there a calculation to determine aprox amp draw with a given motor and  prop specs?
     
    Thank you for your help with this.

    Dan


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    RE: EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT

    i am new to electric flying. i have a question. i have gerneral hobbies yak 54, 46" wingspan, about 2 lbs i think. i have a turnigy 35-42 1250kv motor, a turnigy plush 80 amp esc (a little over kill), and am using 11.1v 2200mah batteries from hobby king, swinging a 11x8.5 prop. i programed the esc with a turnigy card mostly default settings. the problem i am having is that i went to fly it today and when i give it full throttle it gives a load screeching sound, when i back off the throttle some the sound goes away. i tried reducing the end point travel on the futaba radio i am using. this is all brand new equipment. the motor got very hot to the touch. i didn't fly it just ran it up several times trying to solve the problem. i had a problem with my other motor when i installed it. the motor had a short in it and burned up along with my plush 60 amp esc. didnt get to fly that one either, were brand new as well. any suggestions. why is the motor get so hot and making the screeching sound at full throttle? dont want to burn this up too. seen nothing but good revievs for turnigy as well. any help will be greatly appreciated.

  14. #139
    Moderator aeajr's Avatar
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    Re: Everything you want to know about electric flight

    ESTIMATING BATTERY RUN TIME
    by Ed Anderson
    Updated 6-6-14

    Since this comes up so often it is worth posting by itself.

    THE AMP HOUR CALCULATION METHOD

    Note that a 1300 mAH pack = 1.3 AH pack

    m = mili which means 1/1000. Just two ways of expressing the same numer.

    Capacity in AH / amp draw X 60 = minutes of run time.

    1.3 AH / 8 amps = .1625 hours

    .1625 X 60 = 9.75 minutes at 8 amps.

    This assumes you use up all the useful battery capacity, not that you are running the battery to zero voltage. It also assumes that the battery can actually deliver its total rated capacity before the LVC, low voltage cut-off, kicks in to keep you from running it too low. See the end for more on this.

    Normally you don't run at full throttle all the time. For mixed flying that is probably more like 15 minutes. I usually estimate mixed flying time at 150% of the calculation but your actual experience will differ based on how you fly.

    When estimating useful flying time out of a pack, be conservative, then watch it over several flights to get your true number. This calculation is for planning purposes.

    If you are sizing a power system for a plane, part of that sizing should include the duration of the battery pack.


    THE AMP MINUTE CALCULATED METHOD

    Another approach is to convert everything to amp minutes.

    A 1300 mah battery = a 1.3 amp hour battery

    1.3 amp hours = 1.3X60 = 78 amp minutes.

    Your plane draws 12 amps at full throttle. How long will this battery last?

    78 amp minutes/12 amps = 6.5 minutes.

    Assuming you never fully drain the pack I would use about 75% of that or about 4.9 minutes. This leaves some reserve and does not over drain the pack.


    ANOTHER QUICK ESTIMATE METHOD

    Above is the more precise way to calculate run time. However I usually use this quick estimate method.

    If the battery can deliver 1.3 amps for one hour then it can deliver 13 amps for 1/10 of an hour ( 6 minutes )

    In this example, we are only drawing about 2/3 of that ( 8 amps) , so the run time will be about 1/3 longer than 6 minutes, about 8 minutes. Just a quick estimate method I use. Not as exact, just a quick approximation that I can do in my head.

    However, your actual run time will vary by battery quality, how hard you are pushing the pack, the LVC setting on the ESC and how much time you spend at what throttle setting.

    For example, if you run your 20C pack at 20C you will get greater voltage sag then if you run it at 10C. The greater voltage sag will cause you to hit the LVC sooner than if you run the same pack at 10C.

    In actual flying you will likely be flying at partial throttle at times which will reduce the draw and extend the time. You might get twice the estimated full throttle time if you do a lot of partial throttle flying.

    When working with e-gliders, where we typically only run the motor for short bursts the time could be much longer. My Radian's battery is only good for about 3 minutes at full throttle. Since I have the motor off most of the time and I know how to ride thermals, that battery typically lasts me an hour.

    THE EFFECT OF C RATING ON PACK PERFORMANCE

    While several battery packs may be "rated" at a given C rating we can see significant variation on how well they actually work at this rating. The higher priced, higher quality battery packs tend to be better at running at this extreme end of their abilty. The lower cost packs may not live up to that rating quite as well. But it can vary from brand to brand and pack to pack.

    I typically don't plan to run my packs at greater than 80% of their stated continuous C rating. So if that 1.3 AH pack I used in the example ( possibly a Radian pack for example ) is rated at 15C then you would expect it could run at 15 X 1.3 amps or 19.5 amps and maintain a good voltage of 10.5 to 11.1 Volts for most of its useful capacity. Well some can and some can't.

    I would look at that pack and say that I would plan to never run it sustained at more than 15-16 amps. This would put less stress on the pack and give me more useful capacity in the range that I want.

    If you are running in a situation where you only need full power for short bursts, like a 30 second full power climb followed by running most of the time at about 2/3 throttle, than the pack might handle 19.5 amps quite well for those short bursts.

    Some packs have sustained ratings and peak ratings. I ignore the peak ratings.

    To understand more on batteries see chapters 5 and 6.
    Last edited by aeajr; 06-06-2014 at 01:23 PM. Reason: Updated article
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  15. #140
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    RE: EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT

    Ed:

    I should have searched a bit further to find your thread. I wrote up a "quickie" as and answer to a question someone asked that was directly related to your thread, so I didn't intend to steal your thunder. Your thread is great, and I thank you for putting the effort to supply all that great info.

    I do have one question that I asked in the Beginners forum as I am a mod over there.. and this question pops up from time to time, not directly as I posted it, but often as an indirect question about motor applications on various planes.

    The question is that if there is some link to a chart that compares motors to each other.. for instance, an API to a Rimfire with similar numbers, and so on.. and another that compares a typical glow to a typical electric.. ie: OS .46 AX to it's comparable API or Rimfire motor, and so on.

    Thanks again.

    Dick... CGRetired.
    Skylark 70 - OS .75 AX; Excelleron 90 - OS 1.20 AX; Venus II - OS 1.20 AX; And, I still fly my trainer, Hanger 9 Alpha - OS .46 FX! Some electrics. Airtronics RD8000 - Spektrum DX7 - DX6i. AMA 705964.
    Semper Paratus!

  16. #141
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    RE: EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT

    ORIGINAL: garylkendall

    i am new to electric flying. i have a question. i have gerneral hobbies yak 54, 46'' wingspan, about 2 lbs i think. i have a turnigy 35-42 1250kv motor, a turnigy plush 80 amp esc (a little over kill), and am using 11.1v 2200mah batteries from hobby king, swinging a 11x8.5 prop. i programed the esc with a turnigy card mostly default settings. the problem i am having is that i went to fly it today and when i give it full throttle it gives a load screeching sound, when i back off the throttle some the sound goes away. i tried reducing the end point travel on the futaba radio i am using. this is all brand new equipment. the motor got very hot to the touch. i didn't fly it just ran it up several times trying to solve the problem. i had a problem with my other motor when i installed it. the motor had a short in it and burned up along with my plush 60 amp esc. didnt get to fly that one either, were brand new as well. any suggestions. why is the motor get so hot and making the screeching sound at full throttle? dont want to burn this up too. seen nothing but good revievs for turnigy as well. any help will be greatly appreciated.
    Sounds like your timing is out. ESC sends pulses of current to the motor to make it spin. The pulses have to be aligned with the timing of passing magnets that are glued to the spinning 'can'. If the timing is out, the motor will effectively see some demands for 'reverse', thus creating some excess heat.

    Timing is a function of both the ESC and the motor. Since it is difficult to get support from the Chinese stuff (Turnigy), you either need to search the forums, ask around, or experiment.

    There is a similar thread somewhere that just came up. OP changed the timing from low to med and the problem was solved. My motor, for example, must be on LOW otherwise I will hear noises too.

    Hope this helps.
    Joe Marri
    Enjoying all things aviation.

  17. #142
    Moderator aeajr's Avatar
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    RE: EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT


    ORIGINAL: CGRetired

    Ed:

    I should have searched a bit further to find your thread. I wrote up a "quickie" as and answer to a question someone asked that was directly related to your thread, so I didn't intend to steal your thunder. Your thread is great, and I thank you for putting the effort to supply all that great info.

    I do have one question that I asked in the Beginners forum as I am a mod over there.. and this question pops up from time to time, not directly as I posted it, but often as an indirect question about motor applications on various planes.

    The question is that if there is some link to a chart that compares motors to each other.. for instance, an API to a Rimfire with similar numbers, and so on.. and another that compares a typical glow to a typical electric.. ie: OS .46 AX to it's comparable API or Rimfire motor, and so on.

    Thanks again.

    Dick... CGRetired.
    This comes up a lot. There is no comprehensive chart or comparision. That is why people use calculators. Even the calculators are only close estimates.

    Just as two .40 glow engines from different makers will have different power, RPM and other characteristics so is the case with electric motors. Now you take that variaton of glow motors and compare it to a wide variety of electric motors and .... well it doesn't really work. too many options.

    I tell people to ignore glow motors. If you are not going to fly it with glow then forget glow and just select an electric motor based on weight and performance as outlined in chapter 3.

    However companies like Electrifly do have charts that compare their brand of motors to glow motors. Here are two resources provided by Electrifly and Hobbico.
    http://www.electrifly.com/powersyste...tem-index.html
    http://manuals.hobbico.com/gpm/gpmz0...-elec-conv.pdf


    MotoCalc
    This program will tell you everything you need to know: Amps, Volts, Watts, RPM,
    Thrust, Rate of Climb, and much more! It is a popular tool for predicting
    the proper motor, prop, battery pack for electric planes.
    http://www.motocalc.com/

    WebOCalc - A free motor modeling system
    Much more limited than Motocalc, but ... its free! I use this one a lot.
    http://flbeagle.rchomepage.com/softw.../webocalc.html

    Watts/pound is always my starting point. - See chapter 3 of this book.
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  18. #143
    Moderator CGRetired's Avatar
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    RE: EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT

    Ed: Ok, and thanks. Someone posted at least one of those Electrifly links so I have that one.

    There is no real easy way with this, is there. I've used that watts per pound for engine choices and recommended that to answer some requests for information. It is a pretty good gauge of what to use for what application.

    Thanks again.

    CGr.
    Skylark 70 - OS .75 AX; Excelleron 90 - OS 1.20 AX; Venus II - OS 1.20 AX; And, I still fly my trainer, Hanger 9 Alpha - OS .46 FX! Some electrics. Airtronics RD8000 - Spektrum DX7 - DX6i. AMA 705964.
    Semper Paratus!

  19. #144
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    RE: EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT

    UNDERSTANDING EXPECTATIONS WHEN MAKING RECOMMENDATIONS

    For glow pilots I usually target 100 watts/pound as a starting point.

    For electric pilots coming from the parkflyer space, I may start at 75 watts per pound.

    Why the difference?  Expectations. 

    Most glow planes are higher powered than the typical parkflyer, so the pilot's expectation will be higher than an RTF parkflyer pilot moving to ARFs or kits.  And their duration desires may be different than a glow pilot’s requirements.

    Also, in the world of electric we have slow flyers and indoor flyers, that don't seem to exist in the glow world.  Here we might be working as low at 40 watts/pound and have a very satisfactory experience based on low weight targets.

    We have pilots who want their planes for taking photos and videos in the air.  They may care more about duration than about speed or fast climb, so we may set-up for moderate current draw and long motor runs that might include power off gliding with many restarts.  You can’t do this with glow engines.

    We also have electric gliders. While you can put a glow motor on a glider the entire model of how that works is different as you can't restart the glow motor in the air.  So goals and objectives are different.  With electric gliders we can have many climbs before having to land.  
     
    With glow you start that motor, run it until it runs out of fuel, then you glide. If you want to relaunch, you land, refuel and do it again.  
     
    So if a glow pilot wants to know  the .25 equivalent in electric for his glider, I ask him what his performance expectations are because he could never do with glow what we do with electric. 
     
    Sometimes I have to reset and reorient their thinking to help them see what they really want, rather than what they asked for.   So the power to weight ratio expectations for electric pilots could be quite different from glow pilots.  That is why I usually ask what the pilots performance expectations are before I even consider recommending something. 
     
    What is their main goal?  Is it speed, climb rate, duration, noise, or something else?  Indoor our outdoor?  What is the budget?
     
    Hope that helps you consder your own goals and prepares you to help others.


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    RE: EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT


    This is an incredible reference for anyone interested in electric flight - as a novice who has semi-trashed more "beginner planes" than a house on fire - I would like to thank AEAJR and the other contributors for taking the time to put their knowlege and experience on paper - one thing the manufactures of radios could do, thatwould be extremely helpful to me and probably other beginners, isaddan adjustment (manual or digital) on all radios for the amount of tension in the sticks to help decrease the tendency to over-control/correct - if the gas pedals and streeing wheels in cars were as loose as as the sticks on transmitters, it would be total mayhem - I understand that the springs on some of the basic radios can be tightened (afterremoving the back of the TX etc.)and the exponential on the computer models can be programed formore or less control, but I don't think either of these solutionsare as helpful as an adjustment to put as much/little tension (maybe a rachet adjustment which would make it possible to correlate the the number of "clicks " with the amount of control) on each stick asthe pilot desires - I knowthis would decrease the amount of timeand money I have spenttrying to learn howto fly(or maybe the TX is my scapegoat) - am I missing something and/or does anybody have any ideas on the subject?

  21. #146
    Moderator aeajr's Avatar
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    RE: EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT


    ORIGINAL: PAR3


    This is an incredible reference for anyone interested in electric flight - as a novice who has semi-trashed more "beginner planes" than a house on fire - I would like to thank AEAJR and the other contributors for taking the time to put their knowlege and experience on paper - one thing the manufactures of radios could do, thatwould be extremely helpful to me and probably other beginners, isaddan adjustment (manual or digital) on all radios for the amount of tension in the sticks to help decrease the tendency to over-control/correct - if the gas pedals and streeing wheels in cars were as loose as as the sticks on transmitters, it would be total mayhem - I understand that the springs on some of the basic radios can be tightened (afterremoving the back of the TX etc.)and the exponential on the computer models can be programed formore or less control, but I don't think either of these solutionsare as helpful as an adjustment to put as much/little tension (maybe a rachet adjustment which would make it possible to correlate the the number of "clicks " with the amount of control) on each stick asthe pilot desires - I knowthis would decrease the amount of timeand money I have spenttrying to learn howto fly(or maybe the TX is my scapegoat) - am I missing something and/or does anybody have any ideas on the subject?
    Many if not most computer radios have tension adjustments for the sticks. I presume you are talking about the cheap radios that come with some low priced RTF packages. Well, you get what you pay for.

    However I don't see that as doing much to help with over control, but if your radios are that loose and sloppy, perhaps it will. None of my radios were ever so bad that it impacted my ability to fly the plane.
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    RE: EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT

    An employee at a hobby store gave me misinformation about the capabilities of most computer radios - I'll look into it again.

  23. #148
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    RE: EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT


    ORIGINAL: PAR3

    An employee at a hobby store gave me misinformation about the capabilities of most computer radios - I'll look into it again.
    Decide what you want in a radio, then look at the feature lists. Most have a manual you can download.

    Radios are not the topic of this discussion so let's not go into what you would want in a radio, but know that many have this feature.
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  24. #149

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    RE: EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT

    Wow! what a lot of great info. My sons (and now grandsons) have been encouraging me to try electric flight for quite some time. (I've been flying nitro since the 60's, starting with control-line and later R/C) I think they are a little tired of the cleaning up after glow fueled flights.  Your definitions, explanations, and patience here have been quite valuable.

    Although probably not very important to the hook-up and operation of these systems, I am still a little unclear about how the brushless motors work. Since your earlier posts indicate that there are three leads and that reversing any two of those leads will reverse direction, I am assuming that the motors are three-phase, delta connected induction motors? If so, does the ESC vary the speed of the motor by varying the frequency of the 3-phase AC supply, or does it vary some other characteristic of the input power (i.e. voltage, waveform, etc.) in order to achieve variable speed? Or, is this another type of motor with some other type of control?

    I will definitely subscribe to this post and will probably use what I learn here to try my first electric. Thanks for all you do.

    Charles

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    RE: EVERYTHING YOU WANT TO KNOW ABOUT ELECTRIC FLIGHT


    ORIGINAL: Lone Star Charles

    Wow! what a lot of great info. My sons (and now grandsons) have been encouraging me to try electric flight for quite some time. (I've been flying nitro since the 60's, starting with control-line and later R/C) I think they are a little tired of the cleaning up after glow fueled flights. Your definitions, explanations, and patience here have been quite valuable.

    Although probably not very important to the hook-up and operation of these systems, I am still a little unclear about how the brushless motors work. Since your earlier posts indicate that there are three leads and that reversing any two of those leads will reverse direction, I am assuming that the motors are three-phase, delta connected induction motors? If so, does the ESC vary the speed of the motor by varying the frequency of the 3-phase AC supply, or does it vary some other characteristic of the input power (i.e. voltage, waveform, etc.) in order to achieve variable speed? Or, is this another type of motor with some other type of control?

    I will definitely subscribe to this post and will probably use what I learn here to try my first electric. Thanks for all you do.

    Charles
    If you go back and look at the chapter on ESC you will see that the ESC controls speed via applying power on a duty cycle basis. It pulses the power.

    You may find this interesting on how Brushles motors work.
    http://en.wikipedia.org/wiki/Outrunner
    http://en.wikipedia.org/wiki/Inrunner

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