Dark Horse - Helicopter Power & Setup Calculator

Battery Pack:	mAh	->	Amps (estimate)	Watts avg... mA/min
	V \| Full Flat	->	minutes avg.	pack drain mAh used

Main Gear Teeth:			Metric	Imperial	--(convert units)
Motor Pinion:	:1	->	g AUWeight	oz AUWeight
Motor RPM/V:	Kv		Watts/kg	Watts/lb
Efficiency Factor:		->	mm rotor	inch rotor
Motor RPM:			kg/m² disk load	oz/ft² disk load
Rotor RPM:			KM/H tip speed	MPH tip speed
Try the Advanced Calculator prototype			KMH max FF	MPH max FF

Quick reference guide v1.5b

\|	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	thread1 thread2				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	thread1 thread2				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				97	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				Advanced
	---------------------------------------------------------											Custom memory presets
			96	1400	220	500	2.5	thread				9 level			last

or Spawn New Calculator

- Internet Explorer must 'allow blocked content' to use calculator scripts.

- 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.
- 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.

- When using the pack voltage radio button Full to Flat you will notice that Amps and Watts are also recalculated to show a lower Amp draw at higher voltages. Note the effect is exagerated as the rotor RPM also increases at higher voltages and would use more Amps to over come drag, something not modelled in this simple version. The the Advanced Calculator prototype tries to do this more accurately.

- Some text fields can be typed into and auto update when clicked, tab'd away or just press return.

- Edit the average Amp consumption rate to estimate maximum battery pack runtime.

- Alternatively, if you know your setup's flight time when hovering then enter the number on mins and calculate back the average Amp draw (if 100% capacity could be used).

- 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.

- 'Efficiency Factor' means you can use the drop % as a throttle if you wish but remember to drop at least 10 to 20% for real world losses. 90% is about the best zero load performance your going to ever see (eg. 90% = (100% throttle)-(10% efficiency factor)). Note that ESC's throttle % are not normally as linear. Also the resulting RPM figure is meant to be a guide value under load like in hover. Zero pitch loading at 100% throttle may be a lot higher RPM. You just got to juggle what you know from your experience of your particular heli setup.
Given that the Kv of your motor may vary +/-10% from manufactures spec, the true condition of your batteries under load, if your belt tail drive is a bit too tight, any tail rotor demands or your ESC motor timing is set aggressively etc. etc. etc. all can significantly impact real life numbers. You get the picture though right ;)... ball park estimates.
For motor efficiency info try www.fastelectrics.com and www.peakeff.com

You can just about verify the actual RPM by taking low frequency sine wave audio measurements like the method described here. All you need is a good audio editor that can give you accurate sample lengths like Sony Sound Forge. eg. Low frequency EQ filter Hornet X-3D (27T on fresh charge) audio recording revealed a max of (44100/880 samples)*60 = 3006 RPM with hover loading.
Also check out grnbrg's $10 (Or less!) rotor tach, or try this thread ;).

Formula:

Rotor RPM = (Motor RPM/V * Battery Voltage) / (Main gear Teeth / Pinion Gear Teeth) * (% Efficiency /100)
Runtime max without losses = (Battery Capacity Ahrs) / (Amps average) * (60 mins)
Or Amps average = (Battery Capacity Ahrs) / (Runtime) * (60 mins)

- 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.

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