Differences Between 3D Throttle Curves

Posted on December 15, 2009 by aaronredbaron

Throttle CurveQ: What is the difference between 3D Throttle Curves?

Hello, I’ve seen and read that the Idle Up or 3D Throttle Curve is supposed to be at a constant RPM like 90 or 100% to have a consistant power band. That makes sense to me, but when I try it with the Throttle Curve at 50% at mid stick, its not as responsive as it is at the higher RPMs. I don’t want to start doing loops and rolls with my heli’s and have my Throttle Curve way off. Should I keep the same Throttle Curve or lock it in at one RPM?  What do you think about the differences between the two Throttle Curves? I’ve only been flying for about 8-9 months now & all of the 3D stuff is wicked!! Alan Szabo, Wow!!

 Life’s Short… Just Do It!!!!

Question submitted on YouTube (edited for clarity)

 
A: 3D Throttle Curves
 
Thanks for submitting a great question. Lets see if I can explain this without causing confusion. You want to know why some people talk about a throttle curve that looks like a “U” or “V” and dips to a lower % in the middle, and others have a constant flat line set at a high percentage. Both attempt to accomplish the same thing. Basically in Idle-Up mode the goal is to keep the headspeed consitant, and there are two ways to do that. A Throttle Curve can be used to reduce the throttle value at certain points that will have less load (close to zero degrees pitch). Without a load, the head will need less throttle % to keep the same RPM, so the curve ends up looking like a U or a V with the lowest value being at half stick, which is also where its at zero pitch. As you demand positive or negative pitch, the throttle curve gives more throttle to correspond.
 

But throttle curves are imperfect. You may be at zero degrees collective, but your cyclic inputs around zero collective could load the head and slow it. You could use additional mixes, ie cyclic to throttle mixing to compensate, but it starts to get overly complicated and still isn’t perfect at keeping a constant RPM when you really start to hammer on it. That is where a Governor comes in. Most of the time, an electric heli’s governor is integrated into the speed control and uses the throttle % to tell the speed control what RPM you want it to maintain. If you used a U or V shaped curve in governor mode it would actually try to bring the RPM down in the middle. We use a straight, constant Idle-Up curve to tell the speed control to maintain that certain RPM (when in governor mode, a normal V curve is used otherwise). Usually these setups are set somewhere below 100% to leave headroom for the governor to do its job. In a nitro, the governor is another gadget you can add and the throttle curve is usually only there for backup when the governor is activated. Nitro governors use a separate auxillary channel to tell them what RPM to hold.

On a nitro heli its normal to have to bring the curve down to around 50% in the middle if you don’t have a governor, but electrics are usually much higher. You are right that you will get more power with more headspeed, so go ahead and crank that Throttle Curve up to whatever you need to keep the power where you want it, that’s why its there! Hope this helps.

-Aaron

If you have a question you’d like answered, please email me at BaronsHobbies@gmail.com and I’d be happy to tackle your issue!

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