eCalc: Q&A for propCalc, fanCalc, heliCalc, xcopterCalc - Page 2 - RC Groups
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Dec 02, 2011, 10:53 PM
Registered User
hga77's Avatar
Hi,

Great tool!

On propCalc, why cant i add the air frame weight too?
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Dec 03, 2011, 03:35 AM
electric power,what else!
eJets's Avatar
Hi hga77,

on the heliCalc and xcopterCalc the AUW is required to calculate the hover figures and does directly influences them.

on the propCalc and fanCalc the AUW has no influences at all on the calculated values....

cheers markus
Dec 03, 2011, 06:15 AM
Registered User
hga77's Avatar
Thanks!

So propCalc helps finding the best (most effecient?) prop for a given motor? I'm trying to figure out how it's useful.

I have an air frame that has a dry weight 1.4kg and AUW ~3kg. I'm trying to find a suitable power system. I'd like a ratio of 300watts per 1kg...

I want to know how to use the above data with my results:
Code:
http://www.ecalc.ch/motorcalc_e.htm?castle&elevation=500&airtemp=25&batteries=lipo_4500mah_-_45/60c&s=4&p=2&chargestate=normal&esc=cc_phoenix_ice_100&motor=scorpion&type=sii-3026-710&propeller=apc_electric_e&diameter=10&pitch=7&blades=3
Is that system effecient for my needs?
Last edited by hga77; Dec 03, 2011 at 06:34 AM.
Dec 05, 2011, 08:04 AM
get your drive right...!
if you want to have a power/weight ratio of 300W/kg you have to do this:

Basic Weight: calculate your Modell weight (incl. RC but without battery, motor, ESC)

how to determin power/weight ratio?

Take the figure "el.Power (In)" from the line "Motor" and "Entire Drive" - "Weight". then calculate the ratio:

el.Power / (Basic Weight + Entire Drive Weight)

your example:
401.5W / (1.4kg + 1.398kg) = 143W/kg (far away from your needs!)

in other words: if you expect a AUW of 3kg you need 900W to get a ratio of 300W/kg.

cheers markus
Dec 05, 2011, 10:51 PM
Registered User
hga77's Avatar
Thanks for your help!

Also

1. el.power is on several lines. What is different?
2. When would we need to use the (in) values versus the (out)?
3. Is it safe when the graph shows a shaded area "over Limit" and what does it mean?
4. What is considered a good Efficiency value on the Entire Drive line?

Thanks
Last edited by hga77; Dec 05, 2011 at 10:59 PM.
Dec 06, 2011, 02:59 AM
get your drive right...!
Hi,

plese read the Help Section: http://www.ecalc.ch/calcs/help/motorcalchelp.htm

cheers markus
May 09, 2012, 10:42 AM
get your drive right...!

eCalc Release 5.16


...is now available: www.ecalc.ch

for detailes release notes see http://www.ecalc.ch/#release

cheers Markus
Mar 15, 2013, 12:34 PM
get your drive right...!

eCalc Release 6.00 has arrived


Dear eCalc Users,

eCalc Release 6.00 has arrived - visit www.ecalc.ch

What's new with V6.00:
This major Redesign does now allow easy translation into other languages and better adaptation to the corporate design of commercial users. Ploting the Motor Graph is still missing and will be available with a next release.
Note: Press the button [calculate] to initiate a calculation (no more automatic calculation upon leaving an entry field).

cheers markus
Mar 17, 2013, 01:45 PM
This is your brain on heli's
rhodesengr's Avatar
I am getting a big differencebetween the calculated and measured values on a setup I have.

NTM 3536-1800 motor, Castle Talon 90 ESC, APC 9x6 prop, WR Inspector Wattmeter, Fully charged Nanotech 4500 3S 35C.
measured:
Peak current80 amps
Peak Power 870 watts

propcalc:
I: 50 amps
Electric power:550 watts.

Am I doing somthing wrong? Is this issue that this was a static ground test and not in the air?
Mar 17, 2013, 01:55 PM
get your drive right...!
Hi,

Of which calculator are you talking about?

Cheers markus
Mar 17, 2013, 06:57 PM
This is your brain on heli's
rhodesengr's Avatar
Quote:
Originally Posted by eCalc
Hi,

Of which calculator are you talking about?

Cheers markus
http://www.ecalc.ch/

propcalc
Last edited by rhodesengr; Mar 17, 2013 at 06:57 PM. Reason: edit
Mar 18, 2013, 01:37 PM
get your drive right...!
Hi,

first of all - there is a typo: the Kv should read 1800 (iso 1700). sorry this will be corrected with the next update.

...but this does still not explane the entire difference.
the reason for such big difference is mostly based on wrong Kv labeling or inaccurate measuring instruments. what is your RPM at this test?

cheers markus
Mar 18, 2013, 02:24 PM
This is your brain on heli's
rhodesengr's Avatar
Quote:
Originally Posted by eCalc
Hi,

first of all - there is a typo: the Kv should read 1800 (iso 1700). sorry this will be corrected with the next update.

...but this does still not explane the entire difference.
the reason for such big difference is mostly based on wrong Kv labeling or inaccurate measuring instruments. what is your RPM at this test?

cheers markus
I did not measure RPM but I will and get back to you. I just bought an RPM meter so I can do it. A lot of guys are using this motor/prop combo The NTM 3536-1800 with a 9x6 APC prop because it is the suggested setup for the popular Deep Reaper by Crashtesthobby.com. I think the high current is real. I was flying it today and had an over power fault on my Talon ESC. Also the motor was pretty hot on a cool day. The owner of CTH admitted that he has burnt out some 60 amp ESC's with that combo.

I'd like to figure out the dependency because I do want to optimize my power setup. Is there an alternate program I could compare the results with?

Thanks for your help with this.
Mar 18, 2013, 03:42 PM
This is your brain on heli's
rhodesengr's Avatar
I found another program that has the same motor in its database; dcalc

here is the compcarison
ecalc:
motor: NTM 3536-1800
prop APC 9x4.5
Battery: 5000 35C 3S full
I= 42 amps
P=481 watts

dcalc
motor: NTM 3536-1800
prop APC 9x4.5
Battery: 5000 35C 3S full
I=70A

dcalc will not accept the 9x6 prop (says use smaaller prop, correctly I think) so I used the 9x4.5 for comparison. The dcalc numbers are consistent with what I measured with the 9x6 (I=80, P=870) so either the motor data in wrong in ecalc or the calculation is not working right.
p=777W
Mar 18, 2013, 04:03 PM
Suspended Account
Hi,

Interesting...

the graphs available at hobbyking with 3S and 4S torque measurements suggest a Kv between 1850 and 1900 rpm/V. Using drivecalc like method I find kv = 1870 or 1890, depending on the number of data points.

The guy that puts the data into drivecalc found kv = 1850. He used a 7x7 sport for his measurements and I find a little less amps and a bit more rpm using some 7x7 sport propeller coefficient I used to measure, with the NTM 35-36 1800 model computed from hobbyking's data. This suggest I overestimate the resistance in comparison to drivecalc.

Anyway... with an APC 9x6, I find around 70 A for a thin electric to 72 for a sport prop. This can vary with air density, timing setting, etc...

Your 80 A are peak current ?
so might be a bit above what can be expected, because the voltage drop from the battery is not instantaneous, and there can be a peak of the current when the prop start spinning (inertia).

Obviously, the Kv is higher than just 1800.

80A, I can believe... that's a lot for a 120g motor BTW.

Also 9x6 is good, don't worry about stalled blades with this prop.


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