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Old Jan 26, 2015, 04:44 PM
crash tester
United States, NV, Reno
Joined Dec 2014
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Beginner Question, dual rate

I have a simple beginner question about transmitter setup. I see the term "dual rate" used a lot and I don't really understand what that is. I read an explanation somewhere and thought I got it, but I didn't. I don't use "dual rate" at this point, I just have my pitch and throttle curves set where I like them and that's where I leave them.
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Old Jan 26, 2015, 05:46 PM
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Joined Jan 2011
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Dual rates, also known as low rates, refer to the ability of the radio to reduce servo throw.

Taking the rudder as an example, at "high" rates moving the rudder stick to the extents of its throw causes the rudder servo arm to move 100% of its maximum travel distance. On a heli, that of course causes the pitch of the rail rotor to be as aggressive as possible, leading to a fast piro rate.

Now toggle the rudder rate switch to "low", and the rudder servo arm will travel say 60% of its maximum angle, even though the rudder stick is still being pushed hard-left or hard-right. The pitch of the tail rotor is thus not as aggressive, and the maximum piro rate is slower.

The term "low rate" is just a concept. It simply means "lower than maximum", and it does not refer to any particular percentage. Depending on skill and heli setup, one pilot might want the "low" rate to be 40% (of max) while another prefers "low" to be 80%. There is no _correct_ value.

Many transmitters feature "triple rates" - low, medium, and high. How that capability is configured and used is again up to the pilot. Some may like to have three different rate settings for each of the primary controls (ailerons, elevator, and rudder). The high (max throws) rate might be used for "smack" 3D, the low rates are for precision flying, and the medium setting is for some sort of personal in-between compromise. Others will completely ignore the rates switch(es) on their transmitter, and always stick to a particular setting. Again, it's a personal thing, just like "expo" (exponential) - there's no "right answer".

By the way, rates are not directly linked to throttle and pitch curves, although a gentle curve (avoiding the max values) is conceptually similar to a low rate.
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Old Jan 27, 2015, 03:05 AM
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Originally Posted by H2SO4 View Post
Dual rates, also known as low rates, refer to the ability of the radio to reduce servo throw.
I always have wondered where the term "dual rates" originated? It seems like calling it "dual range" would fit better.

Anybody know the history behind the term?
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Old Jan 27, 2015, 04:37 AM
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Denver, CO
Joined Dec 2005
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I don't know the history of the term, but I do know that the term was used by the late 70's. I bought a new Futaba transmitter that had them. Thought it was the greatest thing for my car. If it was on dirt it could use full rates. Indoors on tile it was much faster, and slide around. Low rates made it much easier to drive.
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Old Jan 27, 2015, 05:25 AM
crash tester
United States, NV, Reno
Joined Dec 2014
63 Posts
Thanks, sounds simple enough, just couldn't find a good explanation. At this point I don't need it since I'm always in "low rate". But yeah, not really a rate more of a range. But I suppose it could be called a rate considering it makes the stick more or less aggressive.
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Old Jan 27, 2015, 05:48 AM
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Latvia, Ventspils pilsēta, Ventspils
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Quote:
Originally Posted by CraigHB View Post
Thanks, sounds simple enough, just couldn't find a good explanation. At this point I don't need it since I'm always in "low rate". But yeah, not really a rate more of a range. But I suppose it could be called a rate considering it makes the stick more or less aggressive.
Someone I am sure will corect me ... but as I understood it ... Rates comes from the days when radios changed from amplitude of signal to Pulse Code ... that the command was dictated by the RATE of pulses ...

Anyway - just to add to previous :

Dual rates : The ability of user to program in two or more servo travel settings to suit required style of flying. It allows User to connect up servo and surface at maximum movement and then by altering the % in the Dual Rate programming to set desired amount of servo movement and so the amount of surface movement.
To be able to switch from HIGH to LOW rate during flight.

Most radios today allow this % to be altered in both FULL rate and LOW rate positions. Personally I only alter the FULL rate % if a model is difficult to set up mechanically to desired max rate.

(I agree with Wargo's advice about having maximum SERVO ARM movement to have maximum resolution of movement and control actual surface movement amount by using inner / outer holes on arms / horns. Even though its advice primarily intended for Fixed Wing flyers - it still in my view has merit in Helis).

On a Heli - it is actually really good to be able to 'tame' down those control movements .. in my opinion. I have the full range at HIGH and about 60% at LOW .. means I can select LOW and get into hover, smooth flight and stay without all that twitching about that full rate gives me ... (I'm not very good at Heli's never have been !! )

Nigel
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Old Jan 27, 2015, 04:39 PM
crash tester
United States, NV, Reno
Joined Dec 2014
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I limit the range on the collective through the transmitter, but I limit range on the cyclic through the extent adjustment on the receiver. I could do it through the transmitter, but it's more convenient for me to turn a pot on the receiver. Right now I run with zero to 12 degrees collective pitch and -6 to +6 degrees on cyclic at zero collective. I'm using zero expo with that. My micro heli feels quite tame to me. It's actually easier for me to control than any of the 500 class helis I've been able to set up in the simulator.
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