Electric power for dummys......

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MadProfessor8138

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For those of us that are versed in internal combustion but are looking into the possibilities of electric power.......
Could someone post information pertaining to motors that are currently available ?
Real numbers that show motor size,prop used and thrust numbers acheived would be great.

A person can spend an endless amount of time searching the web and still not come up with usable information.

Kevin
 

tspear

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Good luck. I had very little luck getting anywhere with this a few years ago.

Tim
 

MadProfessor8138

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Hopefully,a straight forward question will produce some results.
The net seems to be full of everyone talking of electric power but no real information to show......
I'm the type of person that appreciates a straight forward answer and someone to point a finger and say "that's what I used".

Kevin
 

pictsidhe

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Our member Farfle used the motor and batteries from a Zero electric motorcycle in a Belite. Apparently they are of good quality. You'll have to cannabalise a bike as they no longer sell the bits.
I was looking at this supplier in Alibaba, though someone else here was not impressed. There are other suppliers in alibaba and maybe aliexpress.
The turnigy motors are available form Tower hobbies. Yep, they're Chinese too. But decent quality. Peter Sripol used a pair of Turnigys in his biplane

How long is a piece of string? If you want to know thrust, I suggest playing with Javaprop to get an idea of what size prop can do what. In flight thrust will depend on prop size, rpm, power and speed, static thrust is only useful when you are stationary.
 

Tiger Tim

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RCGroups would probably be a good place to ask since the specs on brushless motors seem to use such foreign units compared to how one would size a piston engine. It starts to make a little more sense when you think about how the peak output of a motor isn’t constrained to a specific power band but I still don’t understand why unloaded RPM is important.
 

pictsidhe

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Try swinging a 36" prop at 10,000rpm and it should become clear. Right along with a spot in the roof of your workshop/hangar.
Electrics motors are essentially capable of constant torque with a maximum rev limit. Peak power is up near peak revs.
 

delta

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9x5.JPG I've been looking into alternator to motor conversions with a hybred system in mind. Replace the prop on the nose with generators and get it to work without speed controllers or batteries. This single place is 18' x 13', with 30"props.
 

pictsidhe

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View attachment 86549 I've been looking into alternator to motor conversions with a hybred system in mind. Replace the prop on the nose with generators and get it to work without speed controllers or batteries. This single place is 18' x 13', with 30"props.
Alternators conversions aren't very efficient. By the time you've bought extra batteries to compensate for that, you could have bought some much better RC motors and be winning weightwise.

This is the wrong forum for free energy schemes.
 

RonL

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I still don’t understand why unloaded RPM is important.

The reason is the need to know what power the motor draws just to overcome the air and bearing friction.
This chart is an example of most things important to the motor it represents.



E105/30 HD Series
Elite 200cc 105 3D

Kv (rpm/V)
105
Max Power (W) 9000W
Max Amp (15sec) 185A
Max Efficiency 95%
Io (No load A) 4.5A
Rm (Resistance) 0.0248Ohm
Shaft Diameter 10mm
Gearbox N/A
Motor Diameter 119mm
Motor Length 93.5mm
Motor Weight 2400g
Built in Fan Yes
Max Rpm 7,000
Poles/Stator 28/24
Case Outrunner
ESC Timing 20 deg
ESC Switching Freq. 8kHz

The Kv and Io are the important things, changing these is only a matter of changing the size and length of the copper in each coil.

For each Volt, the motor will increase by 105 RPM and at 7,000 RPM with no load will require about 66 Volts X 4.5 Amps equal to 297 Watts of power to operate.

Note that max amps and power are for a 15 second time period and that a constant duty run time would make this motor seem a lot less impressive.

On the radical thought side, if one had a 2 or 3-second power need, it might be possible to transfer as much as twice the power (18,000 Watts).
In my opinion, this is where the real value of motors and generators will shine through in the near future. (sorry if I got a little carried away)
 

emir_82

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If you want anything serious you have to go with emrax, rotex or Siemens.
Depending on the motor type you need to go to a more expensive controller.

Also you can contact me, in the short term I'll start to manufacturing motors.
The first batch will be 30kw continuous for my electric self launching system for sailplanes project. Then I'll go for the paramotor power range and custom made motors.

Don't trust in Chinese motor specs. If you want to buy one anyways expect only 25% of the power rated.

Invest in controller reliability. The great source of failure is there.

And please, do not go cheap on li-ion cells.

Regards
 

emir_82

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Why only 25% of rated power from the advertised specs ???

Kevin
Because they are Chinese. They not only exaggerate the numbers, but also uses the power that goes from the battery to the motor and not the power on the Axel of the motor. And always think that they speak in peak power and peak current. Even if they said it's continuous.
 

pictsidhe

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Most of the motors with good power to weight are high rpm. Fortunately, a belt reduction is a lot easier to design for an electric motor than for an IC motor. Some of the outrunner motors may not have suitable bearings for belt drive, however.
 

RonL

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Because they are Chinese. They not only exaggerate the numbers, but also uses the power that goes from the battery to the motor and not the power on the Axel of the motor. And always think that they speak in peak power and peak current. Even if they said it's continuous.
What would you say that would convince anyone that the motor you produce will be any better than a Chinese motor?
 

pictsidhe

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Cannabalize? I don't think you should be working on your build while smoking pot.

Oh. Do you mean CANIBLIZE?:D
You nearly caught that, but fumbled it. 'Caniblize' doesn't seem to be a word in any language.

I meant cannibalise, which is the English spelling of 'cannibalize'.
 
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