How do you compare electric motors to Nitro engines?

Is there a comparison of electric motors to the typical RC aircraft engine? With the Nitro motor we have .40, .46, .61 and
1.2 (I think). What would be the equivalent electric motors?
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Here's a good rule of thumb:
Take the price of a typical glow engine - let's say a .40. Take the price that it sells at - let's say $80. Triple the price - $240.
Find an electric motor that is $240. There is your equivalent! Don't let people confuse you with complicated formulas. It's really very simple. Although you will need those formulas to calculate what the appropriate battery, prop and gear ratio should be.
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On 24 Feb 2004 05:06:32 GMT, snipped-for-privacy@aol.comnospam (mike tully) wrote:
|Here's a good rule of thumb: | |Take the price of a typical glow engine - let's say a .40. Take the price that |it sells at - let's say $80. Triple the price - $240. | |Find an electric motor that is $240. There is your equivalent! Don't let |people confuse you with complicated formulas. It's really very simple. |Although you will need those formulas to calculate what the appropriate |battery, prop and gear ratio should be.
That does not tell what size, power or amps are equivalent.
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Well, take that same .40 engine and figure it will be over 1hp. IIRC, 1hp is about equivalent to 770 watts. Divide that by 8.4 volts (fairly standard pack) and you will have to deliver almost 92 amps! Remember that in anything electric, there are losses in energy conversion so you have to add maybe 10-20% to get the power to the prop. Use a geabox and add 5% or more to that.
As you can see, standard packs are going to rapidly fry trying to deliver this kind of current. The better way is to go up in volts (more cells). There is a very good program for estimating electric needs called Motocalc. If you want more precise answers, download that and play around with it.
(mike tully)

price that

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| Here's a good rule of thumb:
^^^^ obviously you meant to say `bad'. Hope this helps.
| Take the price of a typical glow engine - let's say a .40. Take the | price that it sells at - let's say $80. Triple the price - $240.
Ok, 0.049 glow engine. That's pretty typical, right? Price is about $50. Triple that is $150. Except that I can get similar performance out of a $10 motor. If the $10 motor can't do it, a $40 cobalt motor certainly will.
| Find an electric motor that is $240. There is your equivalent!
Actually for a larger electric, it's the battery pack that really costs a lot of money, not the motor. The motor prices tend to taper off, but the battery price doubles when you double the price, and the ESC price goes up as well, but not quite double.
| Although you will need those formulas to calculate what the appropriate | battery, prop and gear ratio should be.
I think that's what they were after.
--
Doug McLaren, snipped-for-privacy@frenzy.com you forth love if honk

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.049s are not typical and in the extreme minority in RC modeling. The sales figures I read in the trade mags say that the .40-46 clss is by far the largest.
you forth love if honk
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Paul McIntosh wrote:

BUT in te elecricworld, speed 400 ios the largest. Why? Because its teh cheapest way to go flying, like a 40 is with IC power.
Concluson. Don't compare electric to glo. Its a futile waste of time. Power is developed differntly RPM wise, teh motors are not fixed power devices either, the props are more efficient, and the pack is at least 60% of the equation. And the cost/performance/size graphs are completely different. And the airframes built to different standards.
If you want to just wrote a cheque, and get a 5lb ARTF into the air, then et a 40 engine and don't ask silly questions.
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