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Old Jan 26, 2004, 06:10 PM
Registered User
Sydney, Aust.
Joined May 2002
105 Posts
Question
Confused: Curves Vs Governor

I have read a lot of info on governor modes as well as throttle/pitch curves. But a lot of the info ASSUMES that you already know the basics or the fundamentals of these systems. But I am starting from scratch. But from what I have read so far, my understanding is:

A) GOVERNOR MODE:
A system (function of esc or as separate device) which allows the user to specify a suitable motor RPM. Regardless of changes to the main blade pitch, the device will do its best to anchor the motor at that RPM level. The main advantage of this system is the user only has to worry about the pitch of the main blades as the motor RPM will always be constant.

QUESTION:
How does one set the level of RPM? What is a suitable RPM for throttle at 1/2 way. What is suitable RPM for throttle at max?


B) THROTTLE / PITCH CURVE
Depending on the TX, the most common curve is a 5 point curve. This allows the user to dial points along the length of the throttle travel. At these points, it is possible to set an appropriate pitch for the main blades. The goal being to find the optimum motor power by balancing the effect of blade pitch at different levels of throttle.

QUESTION:
The throttle curve will only work together with pitch curve? In other words, you cannot use one without the other?

Is my understanding (very simplistic i know) of Governor & curves roughly correct Or have I got it all wrong? Please help me to understand it.

Thank you.

ps...i am desperate for this info as I am building a hornet v2 using Astro 010 10T, Phoenix10, 3s lipoly, GY240 gyro. My first heli was the hummingbird.
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Old Jan 26, 2004, 07:14 PM
Rotorhead
Spring,TX
Joined Jun 2003
228 Posts
moy71,

Well you're close .

Governor Mode: used to maintain a specific MOTOR rpm. The rpm it maintains is set by a percentage value entered in the throttle curve. For example, my Idle Up 1 position (on my TX) is used to set a throttle curve of 90%-90%-90%-90%-90%. Not really a curve at all but in conjuction with the ESC govenor mode and the proper pinion size, I am able to maintain a constant 1900 rpm headspeed regardless of the blade pitch (within reason ). As the load on the motor increases the governor provides more current to the motor to maintain it's speed. As the load decreases, the current draw also decreases again allowing the motor to maintain a steady state rpm. As for what a suitable rpm is...that will vary with different model types and flying styles. Basic hovering can typically use a lower rpm while full on 3D is going to need a much higher rpm. Generally speaking, you want to operate the motor at the upper end of its rpm range as that where it's most efficient and then set your actual rpm through the use of different sized pinions.

Pitch/Throttle Curves: Your description is pretty close if your talking nitro powered helis. The principle is the same with electric except that the motor rpm will ideally stay almost constant and you set the pitch based on the flight parameters, if that makes any sense. Electrics are most efficent in the upper end of their rpm range so you have to match the motor/battery/gear ratio to get the end result you want for head speed then adjust your pitch values on the pitch curve to get the desired result i.e. half stick hover or 10 degrees negative at bottom stick or whatever fits your needs.

Sorry to be so long winded, hope this helps some, others will probably have a lot to add .
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Old Jan 26, 2004, 08:27 PM
Registered User
Sydney, Aust.
Joined May 2002
105 Posts
hi ralph. thank you for the reply.

kindly clarify your example.... in governor you mentioned 1900rpm. does that mean that when you switch on your tx then your heli, then you apply throttle. at this point while the heli is STILL ON THE GROUND, are the blades already hitting the 1900 rpm mark? as i understand it, the heli will REMAIN on ground until you increase the throttle. but the increase in throttle merely increases the blade pitch NOT the throttle per se? if this is correct, then i think i've solved what is confusing me.
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Old Jan 26, 2004, 10:53 PM
Rotorhead
Spring,TX
Joined Jun 2003
228 Posts
moy71,

Basically thats it. In reality I have three curves that I use, the first is the "normal" curve which I use to spool up the heli on the ground. In that curve I have the throttle (starting with low stick and moving to high stick) at 0%/45%/90%/90%/90% and the pitch at (in degrees) -2 , -1 , 0 , +6, +12. Next I switch to Idle Up 1 where the throttle curve is 90% all the way across (allowing the governor to do it's thing) and the pitch curve is -4/-2/0/+6/+12. I use this for most of my general flying around. Last I have Idle Up 2 which has the same throttle value as Idle Up 1 but the pitch curve is now -12/-6/0/+6/+12. This is used for acro type flying and gives me a consistant pitch curve both upright and inverted.

There is actually one more "curve" which is the "Hold" curve. In that one the throttle is at cutoff (0%) and the pitch is -5/-2/0/+6/+12. The "Official" purpose is to allow an autorotation, but I use this mostly as a safety feature so that if I crash (or figure I'm about to ) I can easily shut down the motor and possibly minimize damage to the heli. It's also useful for connecting the battery as it prevents the blades from spooling up while I have my fingers and face close to the heli.

Hope that helps!!
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Old Jan 27, 2004, 05:04 AM
Registered User
Sydney, Aust.
Joined May 2002
105 Posts
i am a bit confused about your "hold curve". you've explained that in this mode, throttle curve is zero. Are all 5 points zero as well? if so, then why the need for pitch at all? at zero throttle, the main blades wouldn't be moving at all right?
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Old Jan 27, 2004, 05:41 AM
Crashing IS Flying
jerrysimon's Avatar
Cambridge, England
Joined Jan 2001
1,577 Posts
A very usefull thread. This stuff confuses me too

I think I understand. Basically this last setting is both an emergancy setting when he gets into problems as it cuts the motor dead (but the blades continue to rotate through their own interia) and is also usefull when first plugging in the battery.

At zero across the throttle range if he is plugging in his battery (or at the end unplugging it) and accidently knocks over his TX and the throttle goes to full then this setting would stop the blades spinning up.

When crashing, or about to, going to this setting cuts the motor dead and limits it thrashing around on the floor when it goes in. The need for the pitch curve is to try and auto/recover before that happens. If it does then if he was at any pitch, because the motor is switched off the blades will no longer turn when on the ground unlike if the throttle is set to 90 across the whole pitch curve.

Before he hits the hold switch the rotors will be turning and will continue to turn for as long at the inertia of them lets them.

One last thing to note that I onky just realised is that you need to set all points to 90% for 3D as when you are inverted you need the bottom throttle position for negative pitch. If your throttle curve was 0 45 90 90 90 then at max negative pitch (zero throttle) you motor would stop

Regards

Jerry
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Old Jan 27, 2004, 07:58 AM
Rotorhead
Spring,TX
Joined Jun 2003
228 Posts
Jerry,

You've got it right on the money. The only reason I didn't mention the autorotation aspect of the Hold curve is that with light weight (low inertia) blades an Auto is a pretty iffy thing.

About the 90% value... that is the number that works for me. Some folks will use 100% and others a bit less than 90% depending on their application and the specifics of their system.

Moy71,

As Jerry noted, the Hold curve is designed to provide an opportunity to autorotate the Heli to a safe landing should you have a problem. Therefore the pitch settings allow you to bottom out the collective which introduces negative pitch. As the heli descends, the air flowing up through the blades keeps them turning. As we approach the ground, we bring in progressively more positive pitch to arrest the descent and (if we time it right ) allow a safe, soft landing. The positive pitch portion of the descent is affected by the amount of inertia stored in the rotor system. The other benefits of Hold are safety related and work as described by Jerry.

And with that, it's time to burn some electrons !!!
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Last edited by Ralphw; Jan 27, 2004 at 08:01 AM.
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Old Jan 27, 2004, 08:06 AM
Crashing IS Flying
jerrysimon's Avatar
Cambridge, England
Joined Jan 2001
1,577 Posts
Ah this is good and has made me think a little more

Does having negative pitch at zero stick help the blades to spin faster on an auto decent ?

As I am not anywhere near 3D at the moment I have zero pitch (I think) at zero throttle and have yet to try an auto. Should I adjust that to have a little negative pitch at zero throttle before I attempt an auto ?

Actually thinking about it I may have -2 at zero throttle. I have just got Reflex and have been practising autos. Perhaps I should try messing about with the pitch settings in that to test it

Regards

Jerry
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Old Jan 27, 2004, 05:02 PM
Rotorhead
Spring,TX
Joined Jun 2003
228 Posts
Jerry,

Not so much spin faster as CONTINUE to spin. That being said, auto's on Micro helis are much harder because the blades have very low inertia. As you begin to increase pitch they slow down rapidly and leave very little "hang time" before the rotor speed decays to a point that they can no longer sustain the flight of the heli. In my THR HLD mode I use a -5 degree pitch on the lowest point and move toward maximum positive from there.

Even with the longer blades on my modified Voyager E (470mm, so not a micro by any definition), I wouldn't want to try Autos for the fun of it. I do that on my Venture nitro heli instead since it has bigger heavier blades and more inertia, plus I can increase my throttle for recovery and have the clutch take up the strain on the drive train. If I do that with the VE, it would likely strip gears (remember no clutch on e-heli) insuring that I have to take the Auto all the way to the ground no matter how out of shape it is.

As for changing your pitch curve, I like a little negative as I spool up to help keep the heli firmly planted. The other reason for negative is to help get the heli down from FF so I run a couple of degrees negative in my Idle Up 1 mode for that reason.

Hope that helps !!
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Last edited by Ralphw; Jan 27, 2004 at 10:21 PM.
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Old Jan 27, 2004, 05:37 PM
Rotorhead
Spring,TX
Joined Jun 2003
228 Posts
Just one more note...!!! If you don't have a "one way" or "auto" gear on your heli, then the auto rotation concept is kind of pointless. Once you put the motor to idle it will slow the blades as it slows and it's really unlikely you'd have anywhere near the necessary inertia to save the heli. Thats why the "auto hub" upgrades are popular for those helis that don't include one as standard equipment.
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Last edited by Ralphw; Jan 27, 2004 at 10:23 PM.
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Old Jan 28, 2004, 05:21 AM
Registered User
Sydney, Aust.
Joined May 2002
105 Posts
please, i have a couple more questions to throw your way:

1. when you are hovering, can you please tell me at what degrees your pitch is? what about at forward flight?

2. at what point do you flip the switch from Normal to Idle 1 on your tx?

many, many thanks!
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Old Jan 28, 2004, 08:03 AM
Rotorhead
Spring,TX
Joined Jun 2003
228 Posts
Hi moy71,

No problem.

For my heli the hover pitch is approx. 5 degrees. That number will vary depending on the heli you're flying, the blades, headspeed and a bunch of different factors. Your manual should have a recommended setting, if so, use it as a starting point. If not then start with 5-6 degrees at the point where you want the stick while hovering then adjust the pitch after test flying is complete. Some folks prefer a mid-stick hover while others prefer a 3/4 stick hover. Personally, I'm somewhere in the middle...more than half stick but less than 3/4.

As for the pitch position for FF, the answer is whatever it takes. Not a joke here...remember that in level FF, to go faster you'll increase pitch while moving toward a more nose down attitude with the cyclic control. So pitch in FF is variable (more pitch...faster flight).

When switching from Normal to Idle Up 1, I typically do that while still on the ground with the collective at the mid stick point. At this point the rotor is fully spun up and since my midstick pitch value is the same in all three flight modes, the heli won't jump when I switch between modes.
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Old Jan 28, 2004, 11:51 AM
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Gil Weiss's Avatar
Bensalem, PA.
Joined Sep 2001
476 Posts
Ralphw - your above information is very informative but I need to ask a question in reference to your 1/26 post. How do you switch from using throttle curves in the normal mode to using your governor function in mode 1 without reprogramming your ESC?

Gil
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Old Jan 28, 2004, 05:22 PM
Rotorhead
Spring,TX
Joined Jun 2003
228 Posts
Hi Gil,

The short answer is you don't. I use the Hacker Helimaster 40-3p ESC. The governor mode will simply maintain the rpm associated with whatever percentage I have on the throttle curve. So, if I was to hold the stick at a position in Normal that equated to let's say 82% and never moved it (not possible, just in theory), thats the motor rpm it would maintain. So, I use Normal to spool up and don't really take advantage of the GOV function there until I'm above the mid stick point where my curve is no longer curved , but a straight 90%. I do virtually all my "normal" flying in Idle Up 1 which is 90% straight across.

From what I've been told, some ESC's have a pre-programmed value that they will maintain (HIGH or LOW gov modes ?). That's not the case with the Hacker (at least as I understand it ).
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Old Jan 28, 2004, 09:46 PM
Flys with Thumbs
Danal Estes's Avatar
Frisco, TX, USA
Joined Sep 2001
1,858 Posts
For understanding of takeoff, switching, etc., etc. while in governor mode, read this:

http://www.logoheli.com/governormode.htm

Danal
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