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Nitro to Electric conversion Empty Nitro to Electric conversion

Post  RK Flyer on Thu Dec 03, 2015 6:12 pm

My winter project is the Lazy Bee from Clancy Aviation & so far the build is going fine but I need some help sizing the electric motor. The plans call for 049 to 15 & I would like to stay in the middle to upper power range. Is there a chart that shows gives this kind of info. Also I need info on the ESC battery, servos, this will be my first venture into the "Other World".
Not much help from the RC Forums that I've checked.

Thanks RK Flyer
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Post  Marleysky on Thu Dec 03, 2015 9:06 pm

blasphemy we speak of Nitro, CastorOil and Methanol. Electric is only used to get us started glowing......RK you are being drawn over to the DARK side..unspeakable terms of ESC, mAh, Watts of power, ( watts of power not LOTs of power. ) RPM governors, 4cell, 2cell, programmable thingys that I have no idea how to program.    Like most others, I am afraid of things I do not understand. I have looked at them like all the evils of "Pandora's Box" ( that's going to be the name of my 1st electric plane, if I, oh, if I, ever succumb to the dark side)    This is the COX ENGINE FORUM.  We like ICE,  so, I don't mean to be rude, insulting, attacking or inflammatory. I'm certain that there are members here who know that stuff ( electric ) and will happily jump in with the info you require, otherwise I'll tell you where to go:

http://stunthanger.com/smf/esc-settings/norm-whittle's-excellent-cookbook/?action=dlattach;attach=89029
Then go here:
http://stunthanger.com/smf/esc-settings/norm-whittle's-excellent-cookbook/?action=dlattach;attach=89030
If your still here, go here:
http://www.rcgroups.com/forums/index.php

I've been there and came back here, cause I didn't understand any of that weird wired
Stuff. I wish you success in your quest for electric flight. RC Plane

Yeah, I know....they're clean, they're quiet and they start 1st time every time.....what's the fun in that!?
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Post  duke.johnson on Thu Dec 03, 2015 9:51 pm

Here's a good starting point, this is how I sized my Akromaster. And it work great..

First figure out what motor to get:

You'll need about 11 watts per ounce of airplane weight.  So for a 20 ounce airplane, that's 220 watts.  So look at motors that are rated for no less than 220 watts peak power
For this sized airplane you want to spin the prop between 10000 and 12000 RPM (that drops to about 9000 for a "full sized" stunter)
For this sized airplane you probably want a 3-cell pack (bigger airplanes = more cells).  This isn't a general rule -- you could probably make this work with two cells, or with four, if you size your motor and ESC right
A 3-cell pack is an 11.1 volt pack (there's 3.7 volts per cell, and it adds up -- 3.7V/cell * 3 cells = 11.1V)
You want to spin 12000 RPM at the end of the flight and at full current -- this means you can only count on 8.3V or so (that's 75% of full voltage -- (11.1V)(0.75) = 8.3-ish volts)
The motor speed is the motor Kv times voltage.  So you want to find Kv from Kv = (target speed) / (voltage).  In our case that's (12000 RPM) / (8.3V) = 1450 RPM/volt
Now you know enough to go motor shopping -- woo hoo!  Look for motors that can handle 220W peak, and have a Kv of 1450 or better
If you just can't find a suitable motor, go back to the step where we decided on the number of cells, and try it again with four

Now figure out what ESC to get:

power equals current times voltage.  We can turn that around: current equals power divided by voltage.  So when we're asking for 220 watts from the motor, we need a current of (220W) / (11.1V) = 19.8-ish amps -- call it 20A (more cells means higher voltage, which means less current for the same power -- this is why bigger planes have more cells)
So you know that you need a 20A ESC that can handle three cells
If you are using a KR timer, or if you don't care about a "perfect" run, then almost any ESC will work (there's some really cheapo ones that the KR timer doesn't like)
If you are using a Hubin timer then you need to get an ESC that has a governor mode (the KR timer has a governor -- the Hubin timer depends on the ESC)
Go select an ESC

Now you need a battery pack:

You're going to use about 0.6 or 0.7 watt-hours per flight if you do a full six minutes.
Watt-hours can be calculated like power: watt-hours = amp-hours * volts.  You can turn that around: amp-hours = (watt-hours)/(volts)
You have a 20 ounce plane, so you need about 14 watt-hours.  You have an 11.1V battery, so that works out to (14W-h)/(11.1V) = 1.26 amp-hours, or 1260 mA-h (1 amp = 1000 mA, so 1 amp-hour = 1000 mA-hour)
You only want to discharge the battery by 75%, so you need more than 1260 mA-h: (1260mA-h) / (0.75) = 1680 mA-h
So you need a 3-cell pack with better than 1680 mA-h capacity.  1800 would be plenty.  You could probably squeak by with 1600, because the Acromaster will probably fly the whole pattern in less than six minutes
You want at least a 20C discharge rate, and mo is betta
Go buy a 20C or better 3-cell pack with more than 1680mA-h of capacity
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Post  larrys4227 on Fri Dec 04, 2015 4:56 am

I as well don't know a thing about the electrics .... but I've seen a few full size stunters fly ..... and they are impressive in a lot of ways.

If it weren't for lack of funds to buy all the bits needed, I would probably try it.

Funds .... plus Duke's excellent post above ... would get me started. Nice post Duke. Smile
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Post  Oldenginerod on Fri Dec 04, 2015 7:04 am

duke.johnson wrote:Here's a good starting point, this is how I sized my Akromaster. And it work great..

First figure out what motor to get:

You'll need about 11 watts per ounce of airplane weight.  So for a 20 ounce airplane, that's 220 watts.  So look at motors that are rated for no less than 220 watts peak power
For this sized airplane you want to spin the prop between 10000 and 12000 RPM (that drops to about 9000 for a "full sized" stunter)
For this sized airplane you probably want a 3-cell pack (bigger airplanes = more cells).  This isn't a general rule -- you could probably make this work with two cells, or with four, if you size your motor and ESC right
A 3-cell pack is an 11.1 volt pack (there's 3.7 volts per cell, and it adds up -- 3.7V/cell * 3 cells = 11.1V)
You want to spin 12000 RPM at the end of the flight and at full current -- this means you can only count on 8.3V or so (that's 75% of full voltage -- (11.1V)(0.75) = 8.3-ish volts)
The motor speed is the motor Kv times voltage.  So you want to find Kv from Kv = (target speed) / (voltage).  In our case that's (12000 RPM) / (8.3V) = 1450 RPM/volt
Now you know enough to go motor shopping -- woo hoo!  Look for motors that can handle 220W peak, and have a Kv of 1450 or better
If you just can't find a suitable motor, go back to the step where we decided on the number of cells, and try it again with four

Now figure out what ESC to get:

power equals current times voltage.  We can turn that around: current equals power divided by voltage.  So when we're asking for 220 watts from the motor, we need a current of (220W) / (11.1V) = 19.8-ish amps -- call it 20A (more cells means higher voltage, which means less current for the same power -- this is why bigger planes have more cells)
So you know that you need a 20A ESC that can handle three cells
If you are using a KR timer, or if you don't care about a "perfect" run, then almost any ESC will work (there's some really cheapo ones that the KR timer doesn't like)
If you are using a Hubin timer then you need to get an ESC that has a governor mode (the KR timer has a governor -- the Hubin timer depends on the ESC)
Go select an ESC

Now you need a battery pack:

You're going to use about 0.6 or 0.7 watt-hours per flight if you do a full six minutes.
Watt-hours can be calculated like power: watt-hours = amp-hours * volts.  You can turn that around: amp-hours = (watt-hours)/(volts)
You have a 20 ounce plane, so you need about 14 watt-hours.  You have an 11.1V battery, so that works out to (14W-h)/(11.1V) = 1.26 amp-hours, or 1260 mA-h (1 amp = 1000 mA, so 1 amp-hour = 1000 mA-hour)
You only want to discharge the battery by 75%, so you need more than 1260 mA-h: (1260mA-h) / (0.75) = 1680 mA-h
So you need a 3-cell pack with better than 1680 mA-h capacity.  1800 would be plenty.  You could probably squeak by with 1600, because the Acromaster will probably fly the whole pattern in less than six minutes
You want at least a 20C discharge rate, and mo is betta
Go buy a 20C or better 3-cell pack with more than 1680mA-h of capacity

I like simple.  That ain't simple, or cheap. Blow up Mad!
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Post  duke.johnson on Fri Dec 04, 2015 9:39 am

As far as cheap, if you want cheap, you can buy a Hobby King set up for a 1/2a (Tee Dee) for about $50 or less. Which is about the cost of a Tee Dee. As for simple, after you figure out the formulas and do the math, you can figure this out in minutes. Electric is and/or can be very simple. Some like glow, some e-power, some gas, some rubber, and some like me who like everything. It's all fun, it's all modeling.
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Post  fredvon4 on Fri Dec 04, 2015 10:03 am

Duke

You hit the nail with that last post!
Futaba Radio Biplane Flying a Plane Jeep
Babe Bee .049 RC Plane Fishing
Flying Airplane

I Agree With Above
Clapping

I am fascinated by all other aspects of the hobby.
I personally have not planned to do Free Flight, slope soaring, rubber power, indoor, 3D, nitro boats, but would enjoy any of these if I had the time and or other resources (like a proper body of water close enough to do boats)
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Post  Marleysky on Fri Dec 04, 2015 10:19 am

Duke- Someone already beat me to it, by giving you greenies for your most excellent response. Clearly written so that even I can comprehend what (watt) you're saying!
11watts per ounce of airplane, never would have thought to start there. Thanks for taking the time to share your knowledge and experience.
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Post  RK Flyer on Fri Dec 04, 2015 11:07 am

Many thanks to Duke!!
I don't think electric power is something "New" just another way to build & fly like RC, Its all about FUNN!

I'll do the math and buy the gear to finish up the "Lazy Bee" but it will take some time before flying! Sometimes I think I like the building more than flying!!

RK Flyer Flying
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Post  fredvon4 on Fri Dec 04, 2015 11:36 am

A few of the pre packaged systems and from what I read on other forums all are pretty good place to start if not rolling your own

That said keep eye hard to the sizes and configurations and shop HobyKing usa warehouses for very good prices on most all of the bits needed

RSM distribution is on vacation until 14 dec

http://www.rsmdistribution.com/rsmmain.php?osCsid=2rpsn3rvs6as6dl9lm50s20j64

Brodak
http://brodak.com/electric-accessories-1/complete-power-packages.html
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Post  duke.johnson on Fri Dec 04, 2015 3:05 pm

Thanks guys. I can't take credit for the above info though, that came from a friend that flies out of Portland and is a electrical engineer. He was trying to help a dumb plumber (plumb dumber) understand sizing electrical systems without having to call someone everytime I wanted to build a E-model. In RC I've heard said, 150 watts per pound for slow gentle flight, 200 watts per pound for sport flight, and 250 watts per pound for high preformance stunt flying. Now all this weather RC or CL is based on all up weight. And I sure just one of many ways to figure it out. I have used the figure out 1/2A and .15 size CL models, and large RC gliders. It's work well for me and they preform as I wanted.

RK-Ironic, you're a SMART plumber getting this info. I say smart because you're retired and I'm still working.

I enjoy way too many aspects of modeling, but I can't seem to limit myself to one thing. I'm just finishing an RC parachute jumper.
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Post  crankbndr on Fri Dec 04, 2015 3:16 pm

Yes the way you explained it even a caveman could do it!!
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Post  duke.johnson on Fri Dec 04, 2015 3:26 pm

Right, one step below a plumber. I just carry a pipe wrench.
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Post  crankbndr on Fri Dec 04, 2015 3:41 pm

I didn't mean you I'm a carpenter and always enjoyed the company of plumbers now electricians they were an uppity bunch lol
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Post  RK Flyer on Fri Dec 04, 2015 3:55 pm

Duke.... I don't know about being smart, At 65 & 40 years in, I looked around & didn't see any see any plumbers my age so I figured it was time !

I did the numbers & some checking around & found a Turnigy G10 with a 3 cell battery, 1200 rpm max. current 52A, max v 15, 375 watts, KV1200. How does this sound? Its at Hobby King for $26.50.

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Post  Oldenginerod on Fri Dec 04, 2015 3:59 pm

crankbndr wrote:Yes the way you explained it even a caveman could do it!!
Ugh !
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Post  getback on Fri Dec 04, 2015 5:06 pm

FRed said;:



A few of the pre packaged systems and from what I read on other forums all are pretty good place to start if not rolling your own
That's were I would start if you don't have a compatible system , I got to do some plumbing in my kitchen, 1200 Rs or 12,000 Rs ? that's low but may get the job done? getback Very Happy
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Post  duke.johnson on Fri Dec 04, 2015 6:54 pm

crankbndr wrote:I didn't mean you I'm a carpenter and always enjoyed the company of plumbers now electricians they were an uppity bunch lol
I din't take it that way.
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Post  duke.johnson on Fri Dec 04, 2015 6:58 pm

RK Flyer wrote:Duke.... I don't know about being smart, At 65 & 40 years in, I looked around & didn't see any see any plumbers my age so I figured it was time !

I did the numbers & some checking around & found a Turnigy G10 with a 3 cell battery, 1200 rpm max. current 52A, max v 15, 375 watts, KV1200. How does this sound? Its at Hobby King for $26.50.

RK Flyer Flying
What's the spec on the plane? all up weight? 375 watts seems like a lot for something that could use a 1/2A
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Post  duke.johnson on Fri Dec 04, 2015 7:08 pm

RK
Look up Lazy Bee on RC Groups. I did a quick search and found tons of stuff. Recommend motors and such.
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Post  KariFS on Sat Dec 05, 2015 2:33 am

One way to do this would be to check what size glow engine the plan calls for, then find out what kind of horsepower a typical engine of that size puts out and then get an electric motor / ESC combo with a similar output.

Many of the engine reviews on

http://sceptreflight.com/Model%20Engine%20Tests/

have the engine brake horsepowers listed. I think 1.34hp equals to 1kW.

For example, according to one of the reviews, our beloved Babe Bees have a power output of around 0.056 bhp, or about 42 Watts Smile
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