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Mikado Modellhubschrauber . GrandRC . CanoMod

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e-Electric Motors & Controllers > Electric "Throttle Curve"
 
 
d_wheel
Veteran
Location: Deep in the heart of Texas.

After reading a few messages, and also reading the instruction sheet with my ESC, I am confused about how to program the throttle on an electric helicopter.

What are the advantages and disadvantages of leaving the ESC in airplane mode and using a standard throttle curve (like used on gas heli's), as opposed to programming the ESC to "helicopter" mode? Or do you do both?

If using the heli mode, is it necessary to separate the throttle and pitch channels? The instructions read like the throttle should be on a slider or knob, while collective is left on the normal stick. Very confusing for an old (I mean REALLY OLD) heli pilot ;o) ..

How do I know what head speed to expect if the ESC is in heli mode? For calculation purposes, use a Hacker B50-16XL motor on 20 cells, 95 tooth main gear and 7 tooth pinion, and a Phoenix 60 amp ESC. Please explain how you arrive at your head speed calculations.

TIA!

Later;

D.W.
05-17-2003 Over year old.
 
 
rscamp
Veteran
Location: Ontario, Canada

D. W.

Perhaps I can help a bit. I don't have your controller so I can only generalize.

Some people use airplane mode, but generally people use heli mode which employs a governor and sets other options more appropriate for helis such as no brake.

An electric motor has a much different torque curve than an engine. The electric motor fights to run at its set speed and develops maximum torque at zero RPM. In other words, it doesn't slow down as much as the power output increases. You can get even get away with a flat throttle curve without a governor, although a bit of a curve to compensate for load would be better if you aren't using governor mode.

It is NOT necessary to use a separate channel for throttle. Some people do this and it appears in some instruction sheets, but most find it more convenient to use the IDLEUP settings in their normal manner with the throttle on the collective stick.

You should set up the heli so you are at about 80% of full throttle with a governor to allow headroom for it to compensate for load. Much less than 80% is harder on the controller. You may need to size the pinion accordingly for a reasonable head speed. If you can find out the speed constant (Kv) for your motor, multiply this by 0.8 (governor setting), by the number of cells (1.0V X 20 in your case) and then by 7/95 (your drive ratio) to arrive at a conservative head speed estimate.

Rob
05-17-2003 Over year old.
HOMEPAGE  
 
 
d_wheel
Veteran
Location: Deep in the heart of Texas.

80% of full throttle

Thanks Rob,

When you say "80% of full throttle" do you mean that I should set the throttle ATV to 80% at hover pitch? If so, should I set it to 100% at full pitch or leave it at 80?

Later;

D.W.
05-18-2003 Over year old.
 
 
rscamp
Veteran
Location: Ontario, Canada

Depending on your controller, 80% of full throttle will mean making your set points somewhere around 80%. Your controller "should" initialize to give you 100% throttle at or very close to a set point of 100%. With most controllers you go through a routine of moving the collective stick back and forth to calibrate the controller. When you do this, you should be in NORM mode and the throttle curve should run from 0% to 100%.

Suggested throttle curves using the governor:

For NORM, you might use something like 0% - 75% - 75% - 75% - 75%

For IDLEUP, you might use something like 80% - 80% - 80% - 80% - 80%

Your actual numbers may vary.

BTW. I would have been more accurate to say "In other words, it (the motor) doesn't slow down as much as the torque load increases." in my previous explanation.

Hope this helps.

Rob
05-18-2003 Over year old.
HOMEPAGE  
 
 
d_wheel
Veteran
Location: Deep in the heart of Texas.

Thanks again Rob,

You've been a great help! You said that the radio should be started in normal mode so that the controller can learn the stick limits from 0 to 100 %. You then show a normal curve of 0 to 75%. Was that a typo, or is it necessary to start up in a third setting to get the 0 to 100%?

Later;

D.W.
05-18-2003 Over year old.
 
 
rscamp
Veteran
Location: Ontario, Canada

The 0% to 100% is required for initial calibration of some controllers - mine, for example . Afterward, you set the throttle curve to 75% (or whatever) because you want some headroom for the governor. You don't need the 0% to 100% throttle setting again unless you want to re-calibrate.

Rob
05-18-2003 Over year old.
HOMEPAGE  
 
 
Eddi E. aus G.
Senior Heliman
Location: Gerlingen. Germany.

My setup is Kontronik Tango 45-04 and BEAT 30-8-30.
I've set the throttle curves to zero, so pitch doesn't affect throttle.
Throttle is controlled by a slider.
The BEAT is setup by "showing" it where the slider on my tx is on 0 % and 100 % position, so it even won't initialize before setting the tx to 0 % throttle (for safety reasons).
In hovering and slow FF I preset throttle to 75 to 80 % and just fly. The rest is done by the governor-mode or heli-mode.
Pitch curve and the other controls are set up as usual. I only don't have to mess with the motor/engine.
You don't recognize the work of the ESC in normal flight conditions, the rotor rpm is almost constantly kept at the preset value.

BTW: even to the end of flight time the ESC keeps the rpm as high as possible and squeezes the last few electrons out of your cells. If the heli is becoming less powerful, it's maybe time to land ASAP

Born to fly. Forced to work.
05-18-2003 Over year old.
HOMEPAGE  
 
 
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e-Electric Motors & Controllers > Electric "Throttle Curve"
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