Helicopter Power & Setup Calculator :

Dark Horse RC

Prototype v1.6b or try the simple Calculator version. Select static Modeling:

Battery Pack:
   
mAh capacity
Main Gear Teeth:
 
Eg Volts:
V
V | Full Flat
Motor Pinion:
:1  
AUW:
 g Amps avg. (convert units)
Motor RPM/V:
Kv
Thrust:
g
 Watts avg| :Watts/kg of mass | :mA/min
Efficiency Factor:
ref
 
Sys Eff:
%
 mins avg. | :pack drain | :mAh used
Motor RPM:
ref
 
'Real'
   mm rotor | :kg/m² disk loading
Rotor RPM:
ref
RPM:
MPH / KMH tip speed
Try the simple
Calculator version
Thr%
Pitº
-
MPH / KMH max FF
Try the simple
Calculator version
gov
crv
Quick reference guide v1.6b
|
Snap in stock values
Modified
 Gear RPM Weigh/g Rotor mm Amps Data source |
Snap in stock values
Modified
   Gear RPM Weigh/g Rotor mm Amps Data source |
 
120 3500 200 330 5.0  
150 2800 700 700 12.0 forum
site		  
 
120 4000 265 430 4.5 thread2  
145 2700 1800 1070 18.0  
 
180 2600 360 560 5.2  
110 2000 1575 1060 17.0 thread
thread 		 
 
110 2500 375 620 4.8 thread
thread 		 
180 2000 1800 1040 18.0 thread  
 
140 2100 300 527 3.6 thread  
93 2500 1600 950 15 thread  
 
140 2500 410 550 6.0 thread  
96 2000 2600 1200 20.0 thread  
    140 2500 385 556 6.0 thread  
170
2000
3050
1350
30.0
 
 
140 2500 474 600 10.0 thread  
164
1800
6000
1622
30.0
  
 
         
Simple  
  ---------------- All Micro Heli Resources -------------------  
Custom memory presets
 
 
96 1400 220 500 2.5 thread  
9 level
last
 
Motor:
Motor:
unsorted
RPM/Volt:
Kv
Weight:
g
Resistance:
ohms
Io current:
A (@~10v)
Max rated:
A
Kt:
 milli-Nm/A
ESC:  
ESC:
Not used yet...
Resistance:
ohms
Weight:
 g
Max rated:
 A
Battery:
only lithium 3.7v supported
Cell:
Cell Capacity:
mAh
Num Cells:
Cell Resistance:
 ohms
Parallel:
 
V per cell:
 V
Cell Weight :
 g
Pack Voltage:
 V
Pack Weight:
g
       
       
Rotors:
    
 
Main Rotor Tail Rotor
 
Diameter span:
 mm mm
Boom:
 mm
Chord:
 mm mm
 
Blades:
 (bugs)
 
Profile drag:
 (0.01)  
 
Lift Coefff:
Torque:
 Nm
Drag Coeff:
Tail:
 º
Lift/Drag:
 
Ratio:
 :1 gear :1 rotor
 
RPM:
Reynold's:
 main
Power:
 W +> W
Total Power:
 W  
Thrust:
 g g
Stats:
  
 
Heli Weight:
 g
Motor RPM:
Battery Weight:
 g
Eg Volts:
 V
AUW:
 g
 
Thrust:
 g
Pitch:
 º
   
Throttle:
 %
Power
 
 
IN:
 W
 
Out:
 W
Watts/lb:
 of thrust
System Eff:
 %
Watts/kg:
 of thrust
Amps:
 A
g/Watt:
Duration:
 mins
       
Select static Modeling:
Throttle & Pitch Mixing:  
  Use govenor
OR Use mix curves
  RPM to hold     Thr% Pit% Rangeº
   
Point 5:
 º
   
Point 4:
   
Point 3:
 º
  Balance output:          
  Lock this Thrust, balance throttle & pitch changes  
  Lock this Power, balance throttle & pitch changes  
 Air:    
Metric
Imperial
Temperature:
 ºC ºF
Altitude:
 m ft
Pressure:
 mbar inHg
Air Density:
kg/m3
inflow velocity
 m/s
   
   
Spawn New Calculator or Email to a friend ;).

Tips:
- Internet Explorer must 'allow blocked content' to use calculator scripts. Looks, runs miles faster and better in Opera9 or Mozilla Firefox browser. Or try google's Chrome which is surprisingly fast for jscript.

- NOTE that the physics modeling is only a guide for a static model and doesn't cater for the rotor moving through the air climbing, falling or in forward flight. A reasonable guide for 0º pitch and hover pitch situations (where the heli isn't moving) but depending on the modeling physics selected. I currently prefer the Tweaked modeling for 0º and hover scenario estimates for micro's and may be the Von+ modeling suits some for mini sized heli's better. The full pitch numbers at say full 12º pitch are better reflected at 8º (use 8º as an estimate of full pitch climbout when you really use 12º in real life) as rotor in-flight inflow and air recirculation aren't modelled yet (which is very complicated stuff, have a search for blade element momentum theory). See the spread sheet in this post.

- The four static modeling buttons are slightly different math models, some of which may describe reality closer than others under certain conditions or may be more accurate for Amps but wildly out for RPM predictions etc. You just got to juggle what you know from experience and consider that a 600mm rotor on a light efficient electric will not look like a 600mm rotor on a heavier belt drive heli. Flybar drag is not modeled.

Or try changing the rotor's Blade profile drag from 0.0035 (for micro's) to 0.005 or 0.01 (for mini's) and the numbers might be even closer... who knows the actual profile drag of a particular blade anyway? You may also notice better predictions with a smaller blade chord number for larger heli's (e.g. 30mm chord instead of 40mm may give a more realistic Amp draw). Note that the profile drag number will be reset and possibly change when you click or change modeling buttons.

- Max safe Forward Flight speed estimate = Tips speed * 0.3, before the onset of uncontrollable cyclic handling from retreating blade stall (violent 'pitch up' effect 90º rotor offset to retreating blade), may occur between 0.3000 and 0.3333 of tip speed. Read the theory by Colin Mill, more here.
Remember that the rotor rpm will probably bog down under load and the heli may not be performing at full pitch for max FF. So with conventional curves the throttle may not be at 100% unless you run a flat 100% throttle curve. Try it and you'll see that it can be a fine balancing act between main rotor pitch and forward rotor tilt.

- Brushed motor are in the 60-70% efficiency range and brushless may achieve 75-90% efficiency.
- An FP is normally geared to hover at 65-75% throttle.

Using tips:
- To easier compare setups, define two Restore buttons, use 'undo' and 'redo' buttons or launch 2 versions of the calculator page
- Things to be taken into consideration when assessing the calculator results:
Whether you aim for RPM at zero pitch or at hover pitch loading (at what flying weight?)
How accurate is the motor kv (rpm/v) rating, eg. some justgofly winds seem to vary.
Operational battery voltage under load, so try out the middle three radio buttons (pack voltage) for a better guide range.
The actual efficiency of the motor and other drag factors such as gear mesh and blade profile drag.
The calculator should really be thought of as an estimator at best.
- Some text fields can be typed into and auto update when clicked, tab'd away or just press return. E.g. type 2400 into the 'Real' RPM text box, which will set the throttle governor on and try to maintain the desired RPM.
- 'Efficiency' 'ref' means reference guide values for information comparison purposes. Info here
- 'Efficiency' 90% is about the best zero load performance your going to ever see. Info here
- Note that you can shift the pack voltage with the radio buttons, just a guide to Amp draw ranges, not for true runtime calculations as there is no way to correspond a pack voltage to remaining capacity under unknown loads.

- There are 3 custom memory slots to save and restore custom model setups into your browser's cookies. Makes it easier to compare custom setups with one click and save model setups for another day (valid until the year 2022). There may be other malfunctions that crop up as old data is restored on a future modified web page, so may look odd. If this happens refresh the page and overwrite the old saved data with the newer format. Or try using one of the older versions. Note that the following link formats to the same page will save and restore different cookies (different domains): http://www.dhrc.rchomepage... or http://dhrc.rchomepage...

- If your Internet connection is not that reliable then you can always File->SaveAs this page to your hard drive and use a local copy when ever you like. Except calcAdvanced.htm that requires slider.js in the same folder and sldr5v_bg.gif and sldr2v_sl.gif in a 'img' subfolder.

- Problems with metric Kg and mm? Try this online unit converter ;)

Need more battery and motor data? Try these other calculators and resources:

- Progressiverc.com plenty of motor, ESC and battery data.
- Estimate Electric Motor & Prop Combo from the useful Beginners' Guide to Model Aircraft, who's creator has kindly contributed the Motor, Cell and ESC data on this site ;).
- Electric Motor Calculator good for planes and props etc.
- KC's Power System Comparison Spreadsheet, useful Excel tool for heli's
- www.peakeff.com/ test motor efficiency and generate online graph data.
- Drive Calculator, or download for extensive motor prop modeling
- Mmotocalc.com download 30 day trial, good for flexible airplane data modeling.
- Colorado Gliders.com has a wide variety of useful plane related Tools & Calculators
- NASA's FoilSim II is a great applet to play with.
- Aerodynamics for Model Aircraft learn about Airofoils.
- WebOCalc, in the software section for a good plane setup estimation tool for motors and props etc.
- MrMel's Headspeed calculator
- e-Motor Calculator for Helicopter (Prototyp)

- Excellent spread sheet for rotor dynamics, uses blade element/momentum theory and includes tip loss and flybar. Very good stuff!

Other info:
- Helicopter physics: Colin Mills Practical Theories parts 9,10 and 11(other parts here), a must read!.

Credits & model development: Please see this thread
and special thanks to Martyn McKinney and RCG friends.

Copyright ©2007. Free for noncommercial use only.
We take no responsibility for any damage caused as a result of any predictions etc.
Email Dark Horse
darkhorseenigma@hotmail.com
Try the simple Calculator version

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