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HomeScaleAircraftScale HeliScale Helicopter Main Discussion › Motor Sizing Guidelines
01-25-2010 01:50 AM  8 years agoPost 1
jutrast

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Henniker, NH

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I'm planning to use an electric powerplant for my Vario Dauphin, and am in the process of sizing my electric motor & pinion.

Does anyone have a good resource for sizing criteria? I understand the basics of RPM/Volt and efficiency, and I know my target headspeed. For a LiPo power system though, not sure what voltage to use... the nominal 3.7v/cell, or fully charged 4.2v/cell.

I thought ReadyHeli used to have a sizing too with a good article, but I can't find it.

Thanks,
Toby

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01-25-2010 02:17 PM  8 years agoPost 2
liljalepeno

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Dublin, Ireland

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I'm doing something similar right now and decided to go overkill on the motor because I couldn't locate an article which had this sort of info.

In the end, it was a culmination of excellent posts here on RR that I worked from.
I am open to correction (I'm not an expert by any means) but the rule of thumb "appears" to be something like this:

100W outout per pound for hovering
150W output per pund for scale FF
200W+ ouput per pound for 3D

Based on the estimated weight of your finished model, you should look for a motor that can output the required watage comfortably.

Voltage and amp draw are also a factor but as you increase the voltage, you should in theory, be drawing less amps.

So, if your budget can allow it and your project can carry the weight, use the highest voltage set up you can so less amps are drawn through the esc/motor/battery and everything runs cooler.

For your project, I'd gues you'd be looking at 12-14S LiPo.
For calculations, use 3.7v for average voltage under load.

Look at some of the threads in the conversion section, there is even a headspeed calculator and lots of good info but I think you'll have to piece a lot of it together.

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01-25-2010 05:38 PM  8 years agoPost 3
wingtip

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Indiana

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http://www.scalerchelis.com/phpBB2/...t=e+calc#p95604

link provides the software, and brief explanation of how to use with screen shots, this will get you close.

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01-25-2010 07:07 PM  8 years agoPost 4
liljalepeno

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Dublin, Ireland

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Wow Wingtip, that is an excellent resource !
Thanks so much for posting the link.

My figures were near double what the tool estimates, pretty much as I expected. I was going overkill but it's great to know that I have plenty of margin to play with and some solid, reliable calculations to compare to.

Really, really great tool, good work to the person who put it together !

Thanks again.

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01-25-2010 08:42 PM  8 years agoPost 5
wingtip

rrApprentice

Indiana

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your welcome ,

but i wouldnt go overkill...a little margin is fine but going to far can be bad too..

so tell us what kind of recommendations did it come up with for you and what did you plug into it for blades, gear ratios etc and did you play with gear ratios to get the least current draw etc..

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01-25-2010 11:16 PM  8 years agoPost 6
marc28

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new york

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Toby,what mechanics are you going to put in the dauphin? If you're using vario skyfox or benzin mechanics,it's been done numerous times and it is a very easy conversion with the motor mounts available from joe at eastcoastscale

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01-25-2010 11:28 PM  8 years agoPost 7
jutrast

rrApprentice

Henniker, NH

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Marc28,
I'm using the X-Treme mechanics, and I did get the conversion from Joe... I did the math on gear ratios, and have a setup in mind... I'd like feedback from those with experience...

Motor: Scorpion HK-4035-400Kv
Pinion: 22t
ESC: Castle Phoenix ICE HV 80
Batteries: 10s LiPo

At 90% efficiency, I think this gets me very close to the max recommended head speed and fenestron speed of 1,350/9,000.

Curious if there are advantages to going to 12s, or a higher kv motor with a smaller pinion.

Thanks,
Toby

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01-26-2010 12:46 AM  8 years agoPost 8
wingtip

rrApprentice

Indiana

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not sure on the hv80 but i can tell you on the hv110 lots of people are smoking them on 12s... we've ran them with 10s no problems for several years.. can the hv80 even take a 12s...?

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01-26-2010 12:57 AM  8 years agoPost 9
marc28

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new york

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higher voltage will give you lower amps,not sure about 12s on the ice,but your numbers on 10s look good

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01-26-2010 12:26 PM  8 years agoPost 10
garyl

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taxachussetts

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Yes the 80 HV can take 12S. Just do not run it over 80 amps, I had one and it turned off at a spike of 85 amps.

JIVE 80+ HV

16-50 V
80 A continuous current
BEC 5A continuous current
84g with cabels

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01-27-2010 01:26 AM  8 years agoPost 11
darrelluh1b

rrApprentice

Dalton Ga

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I have been flying my Vario that was converted to electric for a couple of years and having a ball. You can e-mail me a darrelluh1b@optilink.us
if you need some help.
Darrell

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