Variable head speed, or fixed?

[SurfCity]

The Gaui manual recommends a head speed of at least 3,200 rpm and suggests that less may yield an unstable hover. So are you guys running at a fixed head speed -- and if so, how high -- or do you have blade pitch and rpm lashed together?
:fly

[jimgrant]

I dont see how you could seperate the throttle and pitch, they both work off the same stick. I think the thing is to get the throttle setting at or above 3200 before the heli lifts into the air, then the head rpm increases further as the pitch is increased. It's all done by adjusting the throttle, and pitch curves in the transmitter

[stoatnchips]

Surf,

I've looked into this a bit since Paul posted about Gaui govenor mode and although i know a bit about Helis, i'm a noob when it comes to Electric power and ESCs. If anyone else can give me more info on how ESC govenor Mode works, or correct me if i'm wrong, i'd be grateful.

Full scale and RC nitro Helis aim for a constant engine RPM\Head speed, mainly for fule efficiency and also for response - It takes time to speed up /slow down a heavy rotor head, thats the reason CP was invented and i guess govenors are sold to the Nitro owners! As you know, altering pitch changes the torque or load put on the Engine/Motor. For Gas powered heli's, its easy, its like cruise control on a car when you get to a hill, it just gives more throttle to maintain the RPM/Speed.

A brushless ESC uses PWM to control speed. It switches the power to the motor on and off very quickly and by altering the relative amount of time the current is on vs. off, that controls the Motor RPM. This is where my knowledge falls down..i'm not sure how an ESC with Govenor mode, really ties to maintain a constant RPM with varying Load...changing the voltage, altering the amount of current drawn... Frequency of pulses???:confused: I could understand if the Brushless motor had sensors for direct RPM feedback to the ESC, but i can see no way the ESC can tell the actual RPM of the Motor.

My guess is it doesn't. I think it just varies the RPM (PWM) slightly and so you get a slight lag of output torque when pitch is altered. I think this is why some people have complained about tail wag... the ESC continually osscillates the RPM up and down about the goverened figure to try and maintain it approximetly. The HH Gyro and tail servo ends up working its nuts off to try and control this ever changing RPM!!??

So I'm guessing to use the Gaui Govenor Mode, you first need to choose a motor pinion that will give you the approx desired head speed for your 2s/3s setup at throtle stick of about 90%. (If you set cruise control at full speed on a car, there's nothing in reserve for when you get to a hill!!)
You then set your throtle curve to 0-90-90-90-90 and enable Govenor mode on the ESC.

On a Heli this size, the rotor hub is so light that inertia or changes in hub speed will be very quick and you will probably get better perfomance by not using govenor mode and just varying the RPM using standard throttle/pitch curves as Jimgrant suggests.

Is this all :bs or can someone tell me exactly how govenor mode works?

Stoat

[t-driver]

Variable head speed would be a better choice i think.
fixed would be a waste of battery IMO.

[psindrup]

I dont see how you could seperate the throttle and pitch, they both work off the same stick.

Yes, but they are "operated" by two different curves - pitch and throttle - so they are indeed operated/controlled "separately"

Peter

[hammerfall77]

Hi Surf,

my pitch curve is: -11 0 +11
throttle: 100-90-100

with stock motor and ESC, kokams 2s 740 mAh

I found out, that with lower head speeds the heli is somehow easier to control during hover in small places. I think with lower RPMs it doesn't react so quickly to stick inputs and it flies a little bitb smother.

So the above setting is for 3d and 75-70-75 on the ESC for hover and normal flight.

Osprey

[ICCA]

Hi Surf,

my pitch curve is: -11 0 +11
throttle: 100-90-100

with stock motor and ESC, kokams 2s 740 mAh

I found out, that with lower head speeds the heli is somehow easier to control during hover in small places. I think with lower RPMs it doesn't react so quickly to stick inputs and it flies a little bitb smother.

So the above setting is for 3d and 75-70-75 on the ESC for hover and normal flight.

Osprey

Do you change your pitch curve for your hover-normal flight?

Dave

[hammerfall77]

Hi ICCA...
no pitch curve remains the same.