Πέμπτη, 13 Ιανουαρίου 2011

Setting up RC Helicopter - Normal - Idle Up 1 & 2

Radio Setup by Simon Lockington

Now that you've correctly setup your mechanics (see Setting up Raptors - Mechanical) you can now start on setting up the program! This really is the easy part, I'm very much a subscriber of keeping it simple.

Normally you'll have a Normal mode for hovering and an Idle Up 1 condition for aerobatics and perhaps also Idle Up Two. Generally, for 3D machines, if I have a governor, then I'll just use Normal Mode and Idle Up One, however if I don't have a governor, I'll use Normal Mode, Idle Up One and Idle Up Two. Idle Up One would have a 'tick curve' that would allow some descents and Idle Up Two would use a full 'V Curve' for inverted, rolls and general 3D. If you have a governor, just use one Idle Up condition.

NORMAL MODE/IDLE UP SETUP
I have a very basic 3D setup, my F3C one is a little more complex, but we won’t go into that just now.

NORMAL MODE (HOVERING)
On this little Rappy, I’m just going to be keeping a straight line between 0 and 100% which is something that I’d advocate for every flight condition (ie normal mode, idle up, hold), unless you’re planning on doing quite a bit of hovering, then I’d advise dulling it down a little (ie raising the bottom end pitch).

One thing to remember here, is you should only use normal mode for hovering only. Set up your normal mode so the machine hovers well, then do all your circuits/aerobatics in either Idle Up One or Two. Don't do forward flight in normal mode.

WHERE DO I HOVER? HALF STICK OR THREE QUARTER?
No matter what the pitch values, I always keep a straight line curve. For instance on my F3C machines, where I have less top end and bottom end pitch in normal mode than idle up, I still maintain a straight line. I don’t actually care where on the stick the machine hovers at, what I do care is that the heli responds in a linear fashion when I move the stick. Having all sorts of curves in your pitch curve is just complicating things in my opinion.

WHAT ABOUT MY THROTTLE CURVE? SHOULD I USE 100% THROTTLE?
No, no you should not use 100% throttle in normal mode, you never need 100% throttle in hovering situations. All that will do is make your power delivery 'peaky' as the helicopter undergoes sudden torque changes. Instead if you look at the graph below, you'll see that the power ramps up quickly, then tapers off. You want the rotorspeed to come up to speed quickly, but then not change dramatically, instead you are just applying power to counter the increased pitch loading. As you can see, the last point is only at about 55% or so. Obviously the actual value that your heli uses will vary depending on the heli, the engine and exhaust (and tuning), the blades, pitch etc, but these are example values only.

If the graph below had it's last point set to 100%, you would see a massive jump in power as you moved between points four and five, the engine would suddenly wind up and with the increased headspeed as well as the slightly increased pitch, the heli will rocket into the sky, the gyro will lurch with the increased pitch and it'll be a bitch to fly.


EXAMPLE CURVES FOR SOMEONE WHO CAN HOVER




This is a good starting point for your normal pitch curve if you are past the point of learning how to hover (ie you can hover steadily), I would not recommend this curve for rank beginners, you might boom strike by putting in too much negative pitch.

See how the throttle ramps up early, but then tapers off? You want the engine to maintain a constant not through all the pitch changes, you don't want the headspeed to change at all if possible.

EXAMPLE CURVES FOR SOMEONE WHO LIKES A SOFTER HOVER




This curve will yield a more softer feeling heli, it won't jump around as much, however it's still a straight line curve.

See how the throttle ramps up early, but then tapers off? You want the engine to maintain a constant not through all the pitch changes, you don't want the headspeed to change at all if possible.

DUAL RATES/EXPONENTIAL
It's very rare that I wouldn't use Dual Rates or Exponential on any of my machines. Both of these functions can be really handy in settling a machine down and making it fly nicer. On this Raptor, in Normal mode I have my dual rates on both the Aileron and Elevator set to 80%. For exponential I like to have a relatively softer feeling around center and so in normal mode have this set to -20% (for Futaba, it would be +20% for JR). In this way I can have the Rappy nice and calm in hover even though mechanically it is setup for hard 3D.

I don't use any dual rates or expo on rudder, but that's just personal preference.

IDLE UP ONE - FORWARD FLIGHT, BASIC AEROBATICS
This mode is used for circuits, loops, stall turns if you don't have a governor. If you do have one, ignore this and proceed straight to Idle Up Two (but call that one, Idle Up One!).

In Idle Up one you use the full pitch range, and an increased throttle curve. You want a higher headspeed in Idle Up One and you also want to make sure the throttle curve won't allow the engine to cut back to idle when doing things like stall turns when you pull the throttle stick back.

Below is a suggested Idle Up One curve.

EXAMPLE IDLE UP ONE CURVES








The blue line (throttle) is an example of a 'Tick Curve', this allows the engine to keep up speed when the throttle stick is low (during stall turns for instance), but it won't over speed the heli as much as a proper 'V Curve' would on some descents.

IDLE UP TWO - ROLLS, INVERTED AND 3D FLIGHT
This mode is used for rolls, inverted flight and all other 3D. The main component is the straight line pitch curve and also the throttle's V Curve. Which allows you to have full power at full bottom stick.

Remember in Idle Up Two, you're hovering at about 1/3rd stick when inverted and 2/3rds stick when upright, so remember to not have too much throttle on at those points otherwise the heli will SCREAM and overspeed which you don't want. If you find that the engine speed is slowing up, we can use cyclic to throttle mixing to help that along. I'll cover that later.

Below is a suggested Idle Up Two curve.

EXAMPLE IDLE UP TWO CURVES



Notice how at points 2 and 4, the throttle curve is at about 65%, I wouldn't use any more than this at these points because you hover at around both of these points. Also, in many cases, point three will be lower than this example as well. All this ofcourse depends on your engine, exhaust system, gear ratio etc.


GOVERNOR SETUP
I have my machines with governors on them set so that they come on and off with the flick of a switch. Why do I do that? It's so that I can easily isolate the governor if I think there's a problem. Also a governor can mask a badly running engine. For instance, if your engine is running lean, it can be more difficult to identify that if your governor is going because the govenor will always be trying to reduce the throttle of an overspeeding engine. Unless you know what to listen for, you may miss the fact that your engine is running lean. Therefore, when I suspect my engine is not running correctly, I turn the governor off and see.

My governor is set to 1650RPM in Normal Mode and 2000RPM in Idle Up One.

GYRO SETUP
This Raptor is running a Futaba GY601, generally I never run more than 37-40% gain, simply cause there is no need to. I have the same gain settings for all flight modes. I always run in heading hold.

Never ever use rudder trim if you're running in heading hold! You'd be amazed at how many times I've seen guys trying to 'trim' a heading hold gyro and wonder why it drifts!

MIXES
In a future article, I'll go over how you setup some mixes to make the helicopter roll correctly.

If you have a 14MZ, you can download my setup here. Please check to make sure it works with your helicopter first! Don't just load my program and expect to go and fly.

If you have any questions, please email me at simon@littlerotors.com!

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