# Help with electric choice

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**Help with electric choice**

I am in the process of building a 1/4 scale se5a from balsa usa. I am considering makeing it electric. Plane weight will be around 22 pounds with a 80" wing span. What would be recomended for electric flight? motor? battery types, size...? speed control?

I am new to electric so anything will help.

I am new to electric so anything will help.

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Location: Long Island, NY

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**RE: Help with electric choice**

SIZING POWER SYSTEMS FOR ELECTRIC AIRPLANES

by Ed Anderson

aeajr on the forums

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

abreviated as V.

Amps = the quantity or flow of electricty 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 abreviated 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 purspose 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 abreviated as W.

If you want more depth on this, visit this thread.

http://www.wattflyer.com/forums/showthread.php?t=1933

MOTOR EFFICENCY - Brushed vs Brushless

Whether brushed or brushless, the motor's job is to convert electricty into

mechanical motion to turn the propeller to move air. Efficency 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 efficency motor delivers more energy to the motor, and wastes less.

A typical brushed motor, say a speed 400, is only about 40-50% efficent. Only

about half the watts delivered to the motor actualy 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 $35. A comparable brushless motor/ESC combination would

typically cost 3 to 4 times

that much.

Brushless motors tend to be more efficent. 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 you

battery will last longer. Or you can use a similar size and weight brushless

motor and get much higher performance because the motor turns more of the

watts from the battery into useful work of turning the propeller.

So, 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 electic 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 misture to

the engine which allows the engine to produce more power to turn the wheels of

the car. Higher voltage pushes more electicity into the motor to produce more

power.

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 electricty is

being

delivered) to spin a certain propeller. We would say that the battery is

delivering, or that the motor is drawing 84 watts, ie: 8.4V x 10A. If you

bump up the voltage to 9.6 volts, the battery can ram in more amps deliveing

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 a speed 280 motor will have a short life with the same

combination of

volts and amps.

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 diamater and pitch.

The diamater of the propeller determines the volume of air the propeller will

move, producing thrust, or pushing force. Roughly speaking the diamater 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

diamater 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

reveloutions per minute, that prop would move 7000 inches forward 70,000 inche

per minute. If we do the math, that comes out to a little over 66 miles per

hour.

By changing the diamater 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, steeper

pitched propellers will require more energy, more watts, more horsepower, to

turn them. Therefore we need to balance the diamater 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 attched 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,

acceloration will be slow, but over time you will hit a high top end!

Typically direct dirve propellers on a given motor will have a smaller

diamater.

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 acceloration, 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.

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 = agressive aerobatics and mild 3D

150 watts per pound = all out performance.

Remember that Watts = Volts X Amps. This is a power measuremet.

In case you were wondering, 746 watts equals 1 horsepower, .

AN EXAMPLE!

This should be fun. Let's see where these forumlas 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 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 - GWS has good charts!

http://www.gwsus.com/english/product...tem/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.

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. 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. Spining a bigger prop gives me more thrust but a

lower top speed typically.

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 1100 -1500 mah capacity, depending on the

quality of the cells.

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 clearence to spin that big prop so I have

to go for the smaller but faster prop combo.

If this is a puller, then I can choose my prop by grond clearence or some

other criteria and match a gear box to it.

See, that was easy, right? 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 combinatin 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 differnet 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

Brushed Motors

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

Brushless Motors

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

Battery Packs - NIMH

http://www.cheapbatterypacks.com/mai...=445976&ctype=

http://www.hobby-lobby.com/hydride.htm

Battery Packs - LiPo

http://www.cheapbatterypacks.com/mai...gid=tp&sort=PL

http://www.hobby-lobby.com/lithium-polymer.htm

Gearboxes - Speed 400 & 480 examples

http://www.hobby-lobby.com/gear400.htm

http://www.hobby-lobby.com/gear480.htm

by Ed Anderson

aeajr on the forums

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

abreviated as V.

Amps = the quantity or flow of electricty 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 abreviated 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 purspose 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 abreviated as W.

If you want more depth on this, visit this thread.

http://www.wattflyer.com/forums/showthread.php?t=1933

MOTOR EFFICENCY - Brushed vs Brushless

Whether brushed or brushless, the motor's job is to convert electricty into

mechanical motion to turn the propeller to move air. Efficency 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 efficency motor delivers more energy to the motor, and wastes less.

A typical brushed motor, say a speed 400, is only about 40-50% efficent. Only

about half the watts delivered to the motor actualy 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 $35. A comparable brushless motor/ESC combination would

typically cost 3 to 4 times

that much.

Brushless motors tend to be more efficent. 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 you

battery will last longer. Or you can use a similar size and weight brushless

motor and get much higher performance because the motor turns more of the

watts from the battery into useful work of turning the propeller.

So, 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 electic 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 misture to

the engine which allows the engine to produce more power to turn the wheels of

the car. Higher voltage pushes more electicity into the motor to produce more

power.

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 electricty is

being

delivered) to spin a certain propeller. We would say that the battery is

delivering, or that the motor is drawing 84 watts, ie: 8.4V x 10A. If you

bump up the voltage to 9.6 volts, the battery can ram in more amps deliveing

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 a speed 280 motor will have a short life with the same

combination of

volts and amps.

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 diamater and pitch.

The diamater of the propeller determines the volume of air the propeller will

move, producing thrust, or pushing force. Roughly speaking the diamater 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

diamater 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

reveloutions per minute, that prop would move 7000 inches forward 70,000 inche

per minute. If we do the math, that comes out to a little over 66 miles per

hour.

By changing the diamater 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, steeper

pitched propellers will require more energy, more watts, more horsepower, to

turn them. Therefore we need to balance the diamater 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 attched 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,

acceloration will be slow, but over time you will hit a high top end!

Typically direct dirve propellers on a given motor will have a smaller

diamater.

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 acceloration, 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.

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 = agressive aerobatics and mild 3D

150 watts per pound = all out performance.

Remember that Watts = Volts X Amps. This is a power measuremet.

In case you were wondering, 746 watts equals 1 horsepower, .

AN EXAMPLE!

This should be fun. Let's see where these forumlas 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 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 - GWS has good charts!

http://www.gwsus.com/english/product...tem/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.

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. 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. Spining a bigger prop gives me more thrust but a

lower top speed typically.

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 1100 -1500 mah capacity, depending on the

quality of the cells.

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 clearence to spin that big prop so I have

to go for the smaller but faster prop combo.

If this is a puller, then I can choose my prop by grond clearence or some

other criteria and match a gear box to it.

See, that was easy, right? 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 combinatin 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 differnet 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

Brushed Motors

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

Brushless Motors

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

Battery Packs - NIMH

http://www.cheapbatterypacks.com/mai...=445976&ctype=

http://www.hobby-lobby.com/hydride.htm

Battery Packs - LiPo

http://www.cheapbatterypacks.com/mai...gid=tp&sort=PL

http://www.hobby-lobby.com/lithium-polymer.htm

Gearboxes - Speed 400 & 480 examples

http://www.hobby-lobby.com/gear400.htm

http://www.hobby-lobby.com/gear480.htm

#

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Posts: 8,567

**RE: Help with electric choice**

I am way out of my league here, but let me play with this a bit, just for fun. Please don't take any of this to the store and buy. But this may give you some ideas.

Based on what I posted above, a 22 pound plane X 75 W/pound = about 1650 watts to get into the sport plane power band or about 2 horse power.

I have not done a plane like that but will toss out some ideas. Others with more experience can tune this.

Perhaps something from Actro: Actro 40 will do 1700 but you would be right at the top of its scale

Motor and speed controller would be around $530

http://www.hobby-lobby.com/actro-brushless.htm

Maybe something like a pair of AXI 1520s in a belt or gear drive arrangement

http://www.hobby-lobby.com/brushless_axi.htm

Hacker B50 or C 50 series, again, you may wish to look at a pair in a belt arrangemet, especially if you are going to be going into high perfoormance aerobatics.

http://www.hackerbrushless.com/motors.shtml

If we look at about a 60 amp range, you are talking about 10S2P , or 8S3P type Lipo packs to hit the power range you need.

If you want to go NIMH, you will need about 30-32 C cells that can handle 50+ amps to hit the wattage and account for the extra weight.

Have not taken flight times into account here, just wattage. If you are trying to go competitoin pattern or 3D I would expect you would have to go to twin motors for sure.

This is all very very rough and again, I have never approached anything this large. I am just working the numbers But this might be a starting point for order of magnitude. This ain't gonna be cheap! For a plane of that size, unless you are driven to electric, fuel power is still the most economical approach by a long shot.

For example, if you use make up a 10S 3P 6000 Mah pack of 2 of the 5S3P packs shown here from Thunder power cells, will run about $700

http://www.hobby-lobby.com/thunderpower.htm

9S2P 8000 MAh packs made up of six 3 cell 4000 mah packs of these would be about $700

http://www.hobby-lobby.com/polyquest.htm

However this is just for estimation. You would probably have custom packs made for a plane like that.

Based on what I posted above, a 22 pound plane X 75 W/pound = about 1650 watts to get into the sport plane power band or about 2 horse power.

I have not done a plane like that but will toss out some ideas. Others with more experience can tune this.

Perhaps something from Actro: Actro 40 will do 1700 but you would be right at the top of its scale

Motor and speed controller would be around $530

http://www.hobby-lobby.com/actro-brushless.htm

Maybe something like a pair of AXI 1520s in a belt or gear drive arrangement

http://www.hobby-lobby.com/brushless_axi.htm

Hacker B50 or C 50 series, again, you may wish to look at a pair in a belt arrangemet, especially if you are going to be going into high perfoormance aerobatics.

http://www.hackerbrushless.com/motors.shtml

If we look at about a 60 amp range, you are talking about 10S2P , or 8S3P type Lipo packs to hit the power range you need.

If you want to go NIMH, you will need about 30-32 C cells that can handle 50+ amps to hit the wattage and account for the extra weight.

Have not taken flight times into account here, just wattage. If you are trying to go competitoin pattern or 3D I would expect you would have to go to twin motors for sure.

This is all very very rough and again, I have never approached anything this large. I am just working the numbers But this might be a starting point for order of magnitude. This ain't gonna be cheap! For a plane of that size, unless you are driven to electric, fuel power is still the most economical approach by a long shot.

For example, if you use make up a 10S 3P 6000 Mah pack of 2 of the 5S3P packs shown here from Thunder power cells, will run about $700

http://www.hobby-lobby.com/thunderpower.htm

9S2P 8000 MAh packs made up of six 3 cell 4000 mah packs of these would be about $700

http://www.hobby-lobby.com/polyquest.htm

However this is just for estimation. You would probably have custom packs made for a plane like that.