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Selecting Electric Power Systems -

Old 10-05-2009, 12:41 AM
  #176  
mred
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Originally Posted by Easy Flier View Post
I'm really confused about this. I'm building the GP Corsair .40 size sport model Converting to electric power.
Here is what I figured on using.
Motor Pulso X2826/10 KV=920
ESC 80A
Batteries 2/ 2200mah 25C
Plane weight approx. 5-7 lbs with 3 servo's
Prop? would like to use 3 or 4 blade
Am I even close to getting this in the air???
Thanks
JT
I don't see why not. That motor is about a 650Watt motor and is close to a .40 size glow. Running something like an 11X8 APC on a 4 cell battery you should pull somewhere around 650 watts on this. That should be enough to get it off the ground OK. That would be around .8 HP from that motor and while you wouldn't want to try 3D with it, it should fly fine. According to the spec. sheet they give, it is the same as the AXI 28X26/10 and that should fly it no problem. You could drop down to a 10X6 or 10X7 three blade and get about the same power out of it from what I can see.

Ed
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Old 10-05-2009, 01:08 AM
  #177  
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Thanks for the reply, it makes me feel a little more at ease now.
JT
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Old 10-05-2009, 06:59 AM
  #178  
AEAJR
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Any time you ask for an evaluation of an item, please provide a link to each of the components you list so we can see the information you left out. Please don't make us run web searches to find the information. There is a very large possibility we will find the wrong motor, and read wrong specs.

A 2200 25C pack is rated for a Max of 55 amps. So I would not run it at more than 45 amps so as not to over stress the battery. That would give you about 3 minutes of run time at 45. Not very long.
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Old 10-05-2009, 02:42 PM
  #179  
Easy Flier
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Originally Posted by Easy Flier View Post
I'm really confused about this. I'm building the GP Corsair .40 size sport model Converting to electric power.
Here is what I figured on using.
Motor Pulso X2826/10 KV=920 http://www.pulsosystem.com/motor/2826.html
ESC 80A http://www.dealextreme.com/photogallery.dx/sku.13025~seQ.3
Batteries 2ea 3cell/ 2200mah 25C http://www.hobbycity.com/hobbycity/s..._25C_Lipo_Pack
Plane weight approx. 5-7 lbs with 3 servo's
?Prop? Don't know size would like to use 3 or 4 blade.
Am I even close to getting this in the air???
Thanks
JT
I think I got the right info this time. Sorry this is my first time trying to figure all this out.
Thanks
JT
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Old 10-05-2009, 02:51 PM
  #180  
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I wouldn't go with an 80 amp esc, too much probably for your battery max, I would go with a 60 amp esc with a 4s battery (3000mah or better).
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Old 10-05-2009, 05:46 PM
  #181  
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You can use an ESC with just about any ampere rating that is higher than your MOTOR will pull under load. The current pulled out of your battery is set by your motor and its prop, not the ESC itself.

That said, you could use an ESC rated for over 100 Amps for a motor that will pull 45 Amps. But, that ESC is going to be much heavier, and its cost will skyrocket.

But for the Castle Creations ESC's the weight difference between their 60 Amp and their 80 amp units is not much, the cost will be a few extra dollars though. So, if you are thinking about going to a higher powered electric model down the road, the 80 Amp unit might be a good idea.
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Old 10-31-2009, 01:13 AM
  #182  
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I don't know where this belongs so will try here.
I've been in RC for very long time and in electrics also for about 3 years. I really like electrics in many ways but a major problem exists with them, in my opinion. NOTHING, is consistent. This particularly so with motors in most every concievable way. Mounting system varies totaly,prop shaft size varies, Motor length varies, method of rating varies,etc.etc etc. I realize there will be some variables regarding specific sizes but after all if a particular size(basically) motor is suitable for specific size,weight model there should be a reasonable consistency here. To clarify somewhat. When building a 45 size glow plane Or any size glow plane I can easily find many motors available that wil work without total modification of the aircraft. I realize there are some variables but please manufactures give us a break. This is particularly existent with ARF's the manufacter builds them to accept Their products no others, propriety I guess it's called.
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Old 10-31-2009, 01:28 AM
  #183  
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Originally Posted by tedmo View Post
I don't know where this belongs so will try here.
I've been in RC for very long time and in electrics also for about 3 years. I really like electrics in many ways but a major problem exists with them, in my opinion. NOTHING, is consistent. This particularly so with motors in most every concievable way. Mounting system varies totaly,prop shaft size varies, Motor length varies, method of rating varies,etc.etc etc. I realize there will be some variables regarding specific sizes but after all if a particular size(basically) motor is suitable for specific size,weight model there should be a reasonable consistency here. To clarify somewhat. When building a 45 size glow plane Or any size glow plane I can easily find many motors available that wil work without total modification of the aircraft. I realize there are some variables but please manufactures give us a break. This is particularly existent with ARF's the manufacter builds them to accept Their products no others, propriety I guess it's called.
Well, I've built glow powered planes that require some work to get the engine to fit right and it's not all that different with electric motors. Sure they build them to mount their motors, but that doesn't mean that you have to mount theirs. I've changed most of mine to different motors and never had one that was a real hard job of changing to another style motor. I have even changed from brushed motors to brushless motors and that is much harder to do then changing to a different brushless. It's not really that big a deal and I don't think any harder then changing from a 2 cycle to a 4 cycle on a glow plane.

Ed
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Old 10-31-2009, 02:06 AM
  #184  
Sky Sharkster
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Hello Tedmo,
I understand your frustration, but am not sure the picture is as bleak as you paint it. Virtually evey outrunner I've purchased or seen recently can be mounted flat to a firewall, with an "X" mount or the circular flush mount. I've built several models that were designed for glow (originally) and when mounting an outrunner, the prop washer came out in nearly the same position. So the overall length of an equal-sized electric was nearly the same. This may not be true on larger sizes, but up to .15 glow it is.
Now inrunners are a different story; Fitting a perfectly round motor into a square box will obviously create problems. But even there, most inrunners and planetary gearboxes can be front-mounted flush to a firewall.
Offset geardrives clearly present a different problem. Again, in smaller sizes, the GWS "Stick" is as close to a standard as we have for now.
Another factor is the sheer volume of motor manufacturers. How many I.C. engine makers are there? Maybe a dozen? (Excluding specialized racing engines). There are perhaps 50 and possibly many more electric motor brands and more every day, it seems. Some are small "cottage" industries and others are companies that previously made other electric products, they're not primarily "Model Industry" companies. So, standardization is difficult, if not impossible. But I see it as a way for a small business to enter a growing market, which is good for everyone.
Anyway, the hobby rewards ingenuity!
JMO
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Old 10-31-2009, 03:11 PM
  #185  
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Originally Posted by tedmo View Post
I don't know where this belongs so will try here.
I've been in RC for very long time and in electrics also for about 3 years. I really like electrics in many ways but a major problem exists with them, in my opinion. NOTHING, is consistent. This particularly so with motors in most every concievable way. Mounting system varies totaly,prop shaft size varies, Motor length varies, method of rating varies,etc.etc etc. I realize there will be some variables regarding specific sizes but after all if a particular size(basically) motor is suitable for specific size,weight model there should be a reasonable consistency here. To clarify somewhat. When building a 45 size glow plane Or any size glow plane I can easily find many motors available that wil work without total modification of the aircraft. I realize there are some variables but please manufactures give us a break. This is particularly existent with ARF's the manufacter builds them to accept Their products no others, propriety I guess it's called.
I feel your pain... been flying RC for a long time as well (started 35+ years ago with single channel pulse proportional stuff and I remember my older brothers playing with rubber powered escapement actuators!). I started dabbling with electrics about 15 years ago, then got into it fully about 5 years back. The thing that really bugs me is the lack of standards in motor specifications and a naming convention. Back in the I.C. days if you saw "motor size .15 to .25" you had a good idea of what was required. Now you see things like "2822-32", "400T", etc., etc.... and for the most part those numbers are meaningless regarding their power output. Sometimes you'll see something a little more intelligent and they'll give a watt rating. That's a start, but it tells you nothing about how the motor should be used (big prop at low RPM or small prop at high RPM). ...and don't even get me started on LiPo "C" ratings....

What is needed is a motor naming convention that incorporates (at a minimum) Kv and an input watt limit... right now its required to do a lot of guessing based on the information available. If you're really lucky you can find data on the web somewhere that someone has measured... however, that data may not be accurate. I simply do all the measurements myself, but I realize that not everyone has the knowledge / resources / or desire to do that...

I'd also like to see some industry standardization on battery specifications and how they're measured.

The only consolation I can give is that things are much better today than they were 15 years go....

Jim.
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Old 10-31-2009, 10:50 PM
  #186  
AEAJR
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Originally Posted by tedmo View Post
I don't know where this belongs so will try here.
I've been in RC for very long time and in electrics also for about 3 years. I really like electrics in many ways but a major problem exists with them, in my opinion. NOTHING, is consistent. This particularly so with motors in most every concievable way. Mounting system varies totaly,prop shaft size varies, Motor length varies, method of rating varies,etc.etc etc. I realize there will be some variables regarding specific sizes but after all if a particular size(basically) motor is suitable for specific size,weight model there should be a reasonable consistency here. To clarify somewhat. When building a 45 size glow plane Or any size glow plane I can easily find many motors available that wil work without total modification of the aircraft. I realize there are some variables but please manufactures give us a break. This is particularly existent with ARF's the manufacter builds them to accept Their products no others, propriety I guess it's called.
Much of what you say is true. But there are lots of tools to help. If you read the first post in this thread you know that. Put in the basics about your plane and there are tools that will tell you about the specs of the motor/battery/prop that you should buy. And there are tools will even tell you what brand and model of motor to buy, what prop to use and what battery to use. I don't know how much easier they can make it.

In addition many of the brands have tools that do this, but within their product line.

So, it has gotten pretty easy. Put in the numbers, and follow the instructions.

If you want to understand the ins and outs of how the answers are derrived, I mean the background, then read the article below. But really you don't need to know any of this stuff. Just use the tools.


Now, when it comes to glow, you have exhust positions, tank pressurization, venturi position, idle problems, stalling, starting, oil content, and it goes on and on. And, of course there are different cylinder wall designs, head designs and a variety of materials. Not all .40 motors have the same power or use the same fuel, same glow head and... so many details.

Of course you have to fuel proof the plane and brace it to stand up to vibration. And let's not forget nosie and fuselage vibration and mufflers and tuned pipes and ...... So complicated. How does anyone get a plane in the air? Please! And flipping a prop with your finger, glow plug heaters, electric starters, carrying flamable fuels and cleaning that crap off your plane. You must be kidding!

After run oil What the heck is that?

And, did you know the balance of your plane can change as the flight proceeds and the fuel runs down? Make sure you position that fuel tank in the right place.


Give me electric. Put in the numbers, pop out a motor/prop/battery combo. Mount it and hit the throttle. Warm weather, cold weather, the things just run! Turn them off an on while you are in the air. Fantastic. And so quiet. I can even run mine in my shop.

I don't know how glow guys manage. Electric is so simple.


SIZING POWER SYSTEMS FOR ELECTRIC AIRPLANES
by Ed Anderson
aeajr on the forums
Revised 9/8/07

This may get a little technical but I will try to keep it as simple as I
can. I will draw parallels to cars and bicycles in many places as most
people can relate to these and know at least a little about how they work.
I will use round numbers where I can and will use some high level examples.
If you are an engineer you will see that I am taking some liberties here for
the sake of simplicity. I will go through the parts of the power system,
then, toward the end, I will show you how we tie these all together to come
up with a complete power system.


POWER = WATTS

I will be using the terms Volts, Amps and Watts throughout this discussion.
Let me define them.

Volts = the pressure at which the electric energy is being delivered - like
pounds per square inch or PSI in a fuel system or water from a garden hose.
Volts is about pressure, it says nothing about flow. You will see volts
abbreviated as V.

Amps = the quantity or flow of electricity being delivered, like gallons per
minute in a fuel system or that same garden hose. Amps is about flow, it
says nothing about pressure. You will see amps abbreviated as A.

Watts = V X A. This is a measure of the energy or power being delivered.
This is how we measure the ability of that electricity to do work, in our
case the work of turning a propeller to move our airplane through the air.
Watts is about both pressure and flow. This serves the same purpose as
the horsepower rating of your car's engine. In fact 746 watts = 1
horsepower. So if you had an electric car, the strength of its motor could
be reported in either watts or horsepower. You will see watts abbreviated as
W.

If you want more depth on this, visit this thread.
http://www.wattflyer.com/forums/showthread.php?t=1933


MOTOR EFFICIENCY - Brushed vs. Brushless

Whether brushed or brushless, the motor's job is to convert electricity into
mechanical motion to turn the propeller to move air. Efficiency is how we
measure how much of the power, the watts, that our battery delivers to the
motor is actually turned into useful work and how much is wasted as heat.
A higher efficiency motor delivers more energy to the prop, and wastes
less.

A typical brushed motor, say a speed 400, is only about 40-50% efficient.
Only about half the watts delivered to the motor actually end up as useful
work turning the propeller. The rest is wasted. Motors that have a "speed"
designation, like speed 400, are brushed motors. There are other names for
brushed motors but the "speed" term is a common one. They are inexpensive
and they work. For example, you can buy a speed 400 motor and electronic
speed control, ESC, for $30. A comparable brushless motor/ESC combination
would
typically cost 2 to 4 times that much.

Brushless motors tend to be more efficient. They typically deliver 70-90%
of that input power to the propeller, Thus you get better performance per
watt with brushless motors. Seen a different way, if you use a brushless
motor, then, for the same flying performance you will use less energy which
means your battery will last longer. Or you can use a similar size and
weight brushless motor.battery combo to get comparable performance
because the motor turns more of the watts from the battery into useful work
of turning the propeller.

As with many decisions we make, this is a cost benefit decision. Am I
willing to pay more to get more? That is up to you.


THE BATTERY IS MORE THAN JUST THE FUEL TANK

Think of the battery as the fuel tank plus the fuel pump and a supercharger
all rolled into one. It feeds/pushes energy to the motor. So you have to
look at the battery and the motor as one unit when you are sizing power
systems for electric planes. In many cases we start with the battery when
we size our systems because the motor can't deliver the power to the prop if
the battery can't deliver the power to the motor.

The higher the voltage rating of the battery, the higher the pressure, like
a supercharger on a car engine. More pressure delivers more air/fuel
mixture to the engine which allows the engine to produce more power to turn
the wheels of the car.

Higher voltage pushes more electricity into the motor to produce more power,
IF AND ONLY IF, the battery has the ability to deliver more electricity.
Again using the car analogy, if you put a big motor in a car and put a tiny
fuel line and a weak fuel pump, the motor will never develop full power. In
fact the motor might starve and stall once you got past idle. Such is the
same with batteries. We need voltage, we need capacity, but we also need to
know how many amps the battery is capable of delivering at peak.

If we compare an 8 cell AAA battery pack to an 8 cell C battery pack we get
9.6 V for both packs. However the AAA pack may only be able to deliver 6
amps. After that the cells will heat up and either be damaged or the
voltage will start to drop fast. The C pack, also 9.6 V, might be able to
deliver 60 amps without damage. So we have to size not only by voltage, but
by the ability to deliver amps to the motor. Again, think of the fuel line
and the fuel pump as your image of what I am trying to explain. If the
motor needs 12 ounces per minute to run but the fuel line can only deliver
8, the engine will starve and die.

Using our electric motors, a given motor may take 10 amps ( the quantity of
electricity flowing ) at 8.4 volts ( the pressure at which the electricity
is being delivered) to spin a certain propeller. We would say that the
battery is delivering, or that the motor is drawing 84 watts, i.e.: 8.4V x
10A. If you bump up the voltage to 9.6 volts, the battery can ram in more
amps into the motor, more energy to the motor, which will produce more power
to the propeller. In this example, if we move from an 8.4V battery pack to a
9.6V battery pack the motor may now take 12 amps. This will typically spin
the motor faster with any given propeller or allow it to turn a larger
propeller at the same speed.

However, if you bump up the pressure too much, you can break something.
Putting a big supercharger on an engine that is not designed for it will
break parts of the engine. Too much voltage can over power your electric
motor and damage it. So there is a balance that has to be struck.
Different motors can take different amounts of power, watts, volts X amps,
without damage. For example, a speed 400 motor might be fine taking 10 amps
at 9.6 volts or 96 watts. However bump it up to 12 volts and ram 15 amps
down its throat and you will likely burn it out.

Our goal is a balanced power system. If you match the right battery with
the right motor, you get good performance without damage to the motor. In
many cases airplane designers will design planes around a specific
motor/battery combination so that they match the size and weight of the
plane to the power system for good
performance.


PROPELLERS

Propellers are sized by diameter and pitch.

The diameter of the propeller determines the volume of air the propeller
will move, producing thrust, or pushing force. Roughly speaking the
diameter of the propeller will have the biggest impact on the size and
weight of the plane that we can fly. Larger, heavier planes will typically
fly better with larger diameter propellers.

Pitch refers to the angle of the propeller blade and refers to the distance
the propeller would move forward if there were no slippage in the air. So a
7 inch pitch propeller would move forward 7 inches per rotation, if there
were no slippage in the air. If we combine pitch with the rotational speed
of the propeller we can calculate the pitch "speed" of the propeller. So,
at 10000 revolutions per minute, that prop would move forward
70,000 inches per minute. If we do the math, that comes out to a little
over 66 miles per hour.

By changing the diameter and the pitch of the propeller we can have a
similar effect to changing the gears in your car or a bicycle. It will be
harder for your motor to turn a 9X7 propeller than an 8X7 propeller. And
it would be harder to turn a 9X7 propeller than a 9X6 propeller. The
larger or steeper pitched propellers will require more energy, more watts,
more horsepower, to turn them. Therefore we need to balance the diameter
and pitch with the power or wattage of the motor/battery system.
Fortunately we don't actually have to do this as motor manufacturers will
often publish suggested
propellers to use with a given motor/battery combination. We can use these
as our starting point. If we want we can try different propellers that are
near these specifications to see how they work with our airplane.


GEARBOXES

While unusual on glow or gas planes, gearboxes are common on electric
planes. Their primary function is similar to the transmission on a car. The
greater the gear ratio, the higher the numerical value, the slower the
propeller will turn but the larger the propeller we can turn. So you can
use a gearbox to help provide more thrust so you can fly larger planes with
a given motor. However you will be turning the propeller slower so the
plane will not go as fast.

With direct drive, that is when the propeller is directly attached to the
motor shaft, we are running in high gear ( no gear reduction). Like pulling
your car away from the light in high gear. Assuming the motor doesn't stall,
acceleration will be slow, but over time you will hit a high top end!
Typically direct drive propellers on a given motor will have a smaller
diameter.

With the geared motor, it would be like pulling away from the green light in
first gear - tons of low end power and lots of acceleration, but your top
speed is reduced.

So, by matching up the right gear ratios made up of the propeller and,
optionally, a gearbox we can adjust the kind of performance we can get out
of a given battery/motor combination. How this is done is beyond the scope
of this article.


NOW WE CAN START TO MATCH UP THE PIECES!

The simplest approach I have seen to figuring power systems in electrics is
input watts per pound of "all up" airplane weight. The following guidelines
were developed before brushless motors were common but it seems to hold
pretty well so we will use it regardless of what kind of motor is being
used.

50 watts per pound = Casual/scale flying

75 watts per pound = Sport flying and sport aerobatics

100 watts per pound = aggressive aerobatics and perhaps mild 3D

150 watts per pound = all out performance.

Remember that Watts = Volts X Amps. This is a power measurement.
In case you were wondering, 746 watts equals 1 horsepower.


AN EXAMPLE!

This should be fun. Let's see where these formulas take us! We will use a
24 ounce, 1.5 pound plane as our example. If we want basic flight you will
need 50 watts per pound or about 75 watts input to your motor for this 1.5
pound plane. That is, 50 watts per pound X 1.5 pounds = 75 watts needed
for basic flying performance. If you want a little more spirited plane, we
could use 75 watts X 1.5 pounds which is about 112.5 watts.

Lets use 100 watts as the total target, just to be simple, shall we? I am
going to use a lot of round numbers here. I hope you can follow.

The Battery:

If we use an 8 cell NiMh battery pack at 9.6 V it will have to deliver 10.4
amps to hit our 100 watts input target ( 100/9.6 = 10.41amps) If my
battery pack cells are NiMh cells that are rated at 10C then I need an 8
cell pack rated at 1100 mah to be able to deliver 11 amps. Sounds about
right.

Now I select a motor that can handle 100 watts or about 10.4 amps at 9.6
Volts. From experience we know this could be a speed 400, a speed 480 or
some kind of a brushless motor.

We now need a propeller that will cause the motor to draw about 100 watts. I
don't know off the top of my head what that would be. I would go to some mfg
chart as a starting point. GWS has good charts!
http://www.gwsus.com/english/product/powersystem/edp400.htm

I see that if I use a direct drive speed 400 with a 5X4.3 prop at 9.6V then
the motor will draw about 12.4 amps or about 119 watts. This would be a
good candidate motor/prop for the plane using a 9.6V pack that can put out
12.4 or more amps. This would be a set-up for a fast plane as that motor
will spin that small prop very fast.

However maybe I don't want such a fast plane but one with a really good
climb and lots of low end pull to help out a new pilot who is in training or
to do more low speed aerobatics

I can also use a speed 400 with a 2.38 gearbox and run it at 9.6V spinning a
9X7 prop and run at about 12.8 amps for 120 watts.
http://www.gwsus.com/english/product/powersystem/eps400c.htm
The larger prop will give this plane a strong climb, but since the prop
speed has been reduced by 2.38 times, it won't be as fast. Spinning a
bigger prop gives me more thrust but a lower top speed typically. This is a
common strategy for 3D planes.

Back to battery packs and motors

So if I shop for a 9.6V pack to be able to handle about 15-20 amps, I should
do just fine and not over stress the batteries. In NiMh that would probably
be a 2/3 or 4/5 A pack of about 1000 -1300 mah capacity. Some examples here:
http://www.cheapbatterypacks.com/mai...ells&chem=NIMH

We view the battery and motor as a linked unit with a target power profile,
in this case about 100 watts. We use the prop and gearbox, if any, to
produce the manner in which we want to deliver that power to the air to
pull/push the plane.

If this is a pusher, I may not have clearance to spin that big prop so I
may have to go for the smaller but faster prop combo.

If this is a puller, then I can choose my prop by ground clearance or some
other criteria and match a gear box to it.


See, that was easy, right? ( well sorta but ....)


But we are not done! Oh no!

I could try to do it with a 2 cell lithium pack rated 7.4V. To get 100 watts
I now need a pack that can deliver 13.5 amps and a motor/prop combination
that will draw that much. So if I have 10 C rated lithiums, then the pack
better be at least 1350 mah. Probably use a 1500 mah pack to be safe.

Well, when I look at the chart for the geared speed 400 I see that,
regardless of prop, at 7.4V I am not going to have enough voltage (
pressure) to push 13 amps into this motor. So the 2 cell lithium won't meet
my performance goal of 100 watts+ per pound using this gear box.

If I go back to the charts and look at a different gear boxes. I can't hit
my
power goals using 7.4V. Maybe we go back to direct drive.
http://www.gwsus.com/english/product...tem/edp400.htm

We see that the best I can get this speed 400 to do is a total of 70 watts
at 7.2V ( close enough ) so I can't hit my power goals using a speed 400 at
this voltage. but 70 watts would be about 48 watts per pound so I could have
a flyable plane, but not an aerobatic plane using this two cell pack.


REALITY CHECK!

Now, in fact that is NOT how I would do this. I would decide on the watt
target, go to the chart, find a combo that meets my goals, then select a
battery that will meet the demand and see if my weight comes up at the
target I set. A little tuning and I come up with a workable combo.

I often use the MaxxProd combos for reference. If you read the details on
each
package they have wonderful information. And, the fact is that I generally
go
with brushelss motors these days. Costs are reasonable and their higher
efficency
gives me more performance and longer flight times.
http://www.maxxprod.com/mpi/mpi-264.html

Following the example above, the combo 10 on that page would be an excellent
fit for my 1.5 pound plane for sport flying.

The Combo 049 might be a good fit for a slow flyer. Either way the package
has all I need.

If I wanted the plane to have all out performance, the 15A or 19A package
would
be my pick. Note that these would need either higher voltage or higher
amperage
battery packs. The flyers/PDF for the packages make recommendations.

For those who like to be even more analytical about it, there are packages
like MotoCalc that will allow me to play with all sorts of combinations and
make suggestions on what I should use. There is a link for MotoCalc below.


SUMMARY

So, in these few paragraphs you have taken in a basic knowledge of how
electric
power systems are sized, the factors that are considered an how to predict
the outcome. Simple, right?

Of course there is a lot more to know and time and experience will teach
you plenty, but with this basic understanding you are better prepared to
begin playing with the power systems you put in your planes.

Here are some additional resources that may be helpful.

Good luck e-pilot!

Clear Skies and Safe Flying!
Ed Anderson


Brushed Motors
http://www.hobby-lobby.com/elecmot.htm

Brushless Motors
http://www.hobby-lobby.com/brushless-motors.htm

Brushless outrunners explained
http://www.diynetwork.com/diy/rc_planes_aircraft/article/0,2033,DIY_14224_4320834_02,00.html

Battery Packs - NIMH
http://www.cheapbatterypacks.com/main.asp?pgid=packs&pid=AIR&sid=445976&ctype=
http://www.hobby-lobby.com/hydride.htm

Battery Packs - LiPo
http://www.cheapbatterypacks.com/main.asp?sid=445976&pgid=tp&sort=PL
http://www.hobby-lobby.com/lithium-polymer.htm

Lithium Balancers and Balancing Chargers
http://www.rcgroups.com/forums/showthread.php?t=599287

Gearboxes - Speed 400 & 480 examples
http://www.hobby-lobby.com/gear400.htm
http://www.hobby-lobby.com/gear480.htm

A series of posts on electric power system basics
http://www.wattflyer.com/forums/showthread.php?t=1933
http://www.rcgroups.com/forums/showthread.php?t=417868

Maxx Products has a pretty good tip sheet on coming up
with a glow to electric power comparison. You can find it here:
http://www.maxxprod.com/mpi/tips3.html

This reader says Keith Shaw originated the watts per pound rule
http://www.rcgroups.com/forums/showpost.php?p=6156600&postcount=39

MotoCalc - Fee
A commercial tool that 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. There is a fee but if you are going to do a lot of this kind of
work, it is well worth it.
http://www.motocalc.com/

Electricalc - Fee
Like Motcalc, this is a commercial tool that is very extensive. Well worth
the money.
http://www.slkelectronics.com/ecalc/index.htm

Webocalc - Free
A free calculator that can help you get close to the proper design. You put
in certain paramaters and it will give you the proper prop combo for that
motor set-up.
http://flbeagle.rchomepage.com/software/webocalc_1.05/html/webocalc_imperial.html

Motor and Prop Estimating tool - Free
A free calculator that will help you estimate your motor/battery/ESC and
prop combo
http://www.adamone.rchomepage.com/calc_motor.htm

This club has some interesting links on their home page that may be helpful
in planning props and power systems.
http://www.srcmc.co.uk/

Drive Calculator Version 2.21
Based around a Microsoft Excel spreadsheet This includes a propeller thrust
and power database, in a similar form to MotorXL, a motor database, and
tools for predicting home made motor performance. With these tools it is
possible to predict the performance of motor and prop combinations - even
with custom motors!
http://www.badcock.net/motorcalc/

The Great Electric Motor Test
http://www.flyingmodels.org/motortest/index_e.htm

Last edited by AEAJR; 10-31-2009 at 11:35 PM.
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Old 11-01-2009, 04:32 AM
  #187  
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AEJR...

That was absolutely a masterpiece!!!

Best simple analysis I have seen of the electric "rig" I have seen yet...and it needs to be posted as a sticky!

I do just a bit different. I use what chart combos i can...understanding them to be designed for a particular objective...and then I proceed to lighten and make sleeker and better the aircraft design...and then experiment with different props diameters and pitches to nail the best combo.

Its fun, fast and surprising and entertaining. Since I design all my own aircraft, I have more fun "tweeking" the design of the plane to get the most out of an already optimized combo. Depron and hot glue is somewhat cheaper and faster than making a mistake on a combo and having to re order the right one. Comes with having designed my own planes since 1969....Your method very accurate...mine , more tongue-in-cheek, but gets about the same results.
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Old 11-02-2009, 04:27 PM
  #188  
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Hey all,

I need someone to check over what I have done here. I have a plane expected to be 25 oz. Would this setup work?

Turnigy 3632 Brushless Motor 1200kv
Weight: 3.5 oz
Peak amps: 35 amps
Constant amps: around 30A , doesn’t give much info
Voltage: 11.1v
Max Power Input: 388.5 Watts
Continuous power input: 333 Watts
http://www.hobbycity.com/hobbycity/s...idProduct=8504

Battery: ZIPPY Flightmax 3S 1800mAh 20C
Weight: 5.4 oz
Max continuous amps: 36A
Volts: 11.1
Max output watts: 399.6
http://www.hobbycity.com/hobbycity/s...00mAh_3S1P_20C


Hobbyking SS Series 40-50A ESC
Weight: 1.4 oz
Max burst amps: 50A (continuous 40A)
Volts: 2-4S (will use a 3S 11.1v)
Max Power Rating: 555 watts (continuous 444 watts)
http://www.hobbycity.com/hobbycity/s...ies_40-50A_ESC

Thanks,
PA

Last edited by Don Sims; 11-22-2009 at 12:03 PM. Reason: Origional link corrupting thread, edited out link.
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Old 11-02-2009, 06:27 PM
  #189  
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Great site for more info.
I am just starting with e-flite plane. Have been nitro, still learing. Going to go elect. all the way.
Everything placed on order yesterday.
Starting with EasyStar, I am going all HYPERION, everything, charger EOSO6061, Battery G3CX2100 MAH, Motor and ESC in the 20A range, servo's are digital.
I have a NEW FRIEND, helping me to try and get it all right the first time.
Yes, My second plane will be the Mentor, then to the www.eppfoam.com F-22 Raptor.
I know that some of the above will have to be upgraded to handel the Mentor. Hope all of this will work!!!
What say all of you great folks.
SEEING AND FLYING THE COUNTRY WE DEFEND
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Old 11-21-2009, 07:24 AM
  #190  
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Default Long battery wires

Guys, I need some help please.

I am building a large model and will be using an AXI5345/14, pulling around 90 amps. It will run 12 cell 5000 mAh lipos. The plane is a twin boom pusher configuration, and I need to locate the lipos in the nose of the plane to get the CG right, and will require lipo wires of around three feet long. Can you advise me on what gauge wire to use, and will there be significant losses due to the longer wires?

Is there a chart of wire gauge vs. amps?

Thanks in advance,
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Old 11-21-2009, 12:13 PM
  #191  
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Test
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Old 11-21-2009, 12:45 PM
  #192  
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Question Advice

I thought I would post this power system I'm thinking of buying for a scratch built I've just started.
It's my first one so I'm not absolutely sure if I've got it right.

Turnigy 480L V-spec 2150Kv
Max current: 60 amp
Volts: 14.8v
Battery: 4S

Turnigy plush 60amp ESC
Continous current: 60amp
Burst current: 80amp

Turnigy 3000mah 4S 35C or Turnigy 3000mah 4S 30C.

Propeller: 6x4.

The build is loosely base on plans I have for a pylon racer.
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Old 11-21-2009, 10:51 PM
  #193  
MustangMan
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Originally Posted by Longtimeflyer View Post
Guys, I need some help please.

I am building a large model and will be using an AXI5345/14, pulling around 90 amps. It will run 12 cell 5000 mAh lipos. The plane is a twin boom pusher configuration, and I need to locate the lipos in the nose of the plane to get the CG right, and will require lipo wires of around three feet long. Can you advise me on what gauge wire to use, and will there be significant losses due to the longer wires?

Is there a chart of wire gauge vs. amps?

Thanks in advance,
According to the chart here: http://www.powerstream.com/Wire_Size.htm
you should use #7 AWG for 90 amps continuous in "chassis" wiring. That would be very heavy wire.

In our application we never run continuous maximum current so, looking down the chart a bit it looks like you could likely get by with #10. It has a resistance of 1 mOhm/ft. which means you'd see a total of 6 (2 x 3) mOhms of wire resistance. At 90 amps your total voltage drop would be 0.006 Ohms x 90 Amps = 0.54 volts. That's pretty significant but not catastrophic. You could cut the loss in 1/2 by running two parallel #10 lines for each wire.

I've seen discussions on this question and it seems that often the ESC's don't like having long lines from the battery. The recommendation from ESC vendors like Castle seems to be to shorten the battery wires and lengthen the motor wires. You might want to check their web site for application notes discussing this issue.
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Old 11-21-2009, 11:06 PM
  #194  
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Old 11-21-2009, 11:36 PM
  #195  
PaperAirplane
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Does anyone have an answer for me from a few posts back (post #188)?
Thanks

PA
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Old 11-21-2009, 11:43 PM
  #196  
MustangMan
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Originally Posted by PaperAirplane View Post
Does anyone have an answer for me from a few posts back (post #188)?
Thanks

PA
That's almost 215 watt/lb! That's huge power. What type of airplane is it? The parts should work together OK, though at full power the battery won't last 3 minutes. I'm not sure about the Flighmax but most lipo's don't really like being pushed to their specified C rating for very many flights.
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Old 11-21-2009, 11:53 PM
  #197  
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Its a Cub trainer (scratchbuilt). Thanks for checking. I wrote that post a few weeks back and I was still not very knowledgable about E-Power. I now realize that it is extremely overpowered. This is also my first plane, so slow is what I need. I will redo the research and selecting again. How many w/lb would you suggest? I want a little bit of reserve, just in case. Maybe 100w/lb?

Thanks so much,
PA
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Old 11-22-2009, 02:36 AM
  #198  
MustangMan
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Originally Posted by PaperAirplane View Post
Its a Cub trainer (scratchbuilt). Thanks for checking. I wrote that post a few weeks back and I was still not very knowledgable about E-Power. I now realize that it is extremely overpowered. This is also my first plane, so slow is what I need. I will redo the research and selecting again. How many w/lb would you suggest? I want a little bit of reserve, just in case. Maybe 100w/lb?

Thanks so much,
PA
That would be plenty I'd think. ~100 w/lb. usually gives good "sport" aerobatic performance. That generally means enough vertical for pretty big loops but not unlimited vertical climb. High powered airplanes, like high powered cars, can be tricky to control and get in trouble quickly unless you stay off the power.

I have a 3-channel balsa trainer, about 16 or 17 oz. When using it for teaching I put a 2-cell lipo in it and average about 20-25 watts for cruising around practicing turns and basic maneuvering. When I put a 3-cell in it it tops out something more than 100 watts and will climb at about a 75 degree angle indefinitely! At that power level though it becomes extremely control sensitive and can be a handful to fly.
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Old 11-22-2009, 03:05 AM
  #199  
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In conclusion, I guess about 80w/lb would be enough then.
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Old 11-22-2009, 05:32 PM
  #200  
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Originally Posted by PaperAirplane View Post
In conclusion, I guess about 80w/lb would be enough then.
I would think so, yes.
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