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3D Throttle EXPO

Old 08-05-2017, 06:06 AM
  #1  
dereckbc
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Default 3D Throttle EXPO

First let me say I have never touched Throttle Rate's or Expo's, just linear default. Just asking out of curiosity because I do read some 3D pilots use some Expo and Funky Rates.

What, where, and when would you use Rates and Expo on Throttle for an Electric Plane? Me thinks this might be something gassers do so they can match Travel to Power Band more linear. Electric is already linear.
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Old 08-05-2017, 07:05 AM
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solentlife
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Its about fine control in hovers and other manoeuvres - best way in fact is to use a throttle curve similar to heli guys.

Most people don't bother I would expect - but it can make a big difference in balancing power to action. The bottom end is not much use ... but as you start to get thrust - this gets important. Spreading that power band via a curve can really make a big difference. Instead of jerky hovers where power is just a little too much or too little ... you can now have a better 'feel' and band to play in.

Nigel
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Old 08-05-2017, 02:13 PM
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Throttle curve is used in 3d for focusing control around hover rpm as well as keeping the motor spinning (idle up) at closed throttle position.
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Old 08-05-2017, 05:23 PM
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dereckbc
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Originally Posted by solentlife View Post
Its about fine control in hovers and other manoeuvres - best way in fact is to use a throttle curve similar to heli guys.
You are talking using Positive Expo right?
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Old 08-05-2017, 05:29 PM
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solentlife
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Originally Posted by dereckbc View Post
You are talking using Positive Expo right?
No ... a curve ... totally different item.

Best way is to take an empty slot on your radio - doesn't matter Spek, FrSky, FlySky, Futaba ... and play with curves ...

I have options for 3, 5 and 9 point curves ...

You can basically create a sine wave of range ... concave ... convex ... line whatever suits ..

Lets say you want a throttle that quickly rises but then increases slowly through a range and then quicker to full ...

You could set points such as, using a 5 point curve ... note each point represents 20% of stick movement :

Idle Point 1 = zero
Point 2 = 35% throttle
Point 3 = 50%
Point 4 = 60%
Point 5 = 100%

A 9 point curve is even better ... you could use expo ... but with a curve you can alter at any point in the range not just around the middle ...

Nigel

Last edited by solentlife; 08-05-2017 at 08:06 PM.
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Old 08-05-2017, 05:32 PM
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dereckbc
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Originally Posted by birdDog View Post
Throttle curve is used in 3d for focusing control around hover rpm as well as keeping the motor spinning (idle up) at closed throttle position.
That is the second time you have brought up "Idle Up". First go around I think you stated when Throttle is closed to program that for a few percentage points of power to aid in landing. Does not work well for me for whatever reason. I guess my flying/landing style. This plane has so much Ground Effect makes it a bit difficult to set it down with some power on. More like you have to fly it into the ground by pushing the nose down.

When I turn final, I reduce power to about 1/8 on the stick, put the nose down and aim to fly the plane down on the end of the runway, then flare out at knee high, keep the nose up and level, slowly close the Throttle and let the back wheel touch down while I finish cutting the Throttle to let the front down.

The Hoover part I get.
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Old 08-05-2017, 08:11 PM
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solentlife
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Originally Posted by dereckbc View Post
That is the second time you have brought up "Idle Up". First go around I think you stated when Throttle is closed to program that for a few percentage points of power to aid in landing. Does not work well for me for whatever reason. I guess my flying/landing style. This plane has so much Ground Effect makes it a bit difficult to set it down with some power on. More like you have to fly it into the ground by pushing the nose down.

When I turn final, I reduce power to about 1/8 on the stick, put the nose down and aim to fly the plane down on the end of the runway, then flare out at knee high, keep the nose up and level, slowly close the Throttle and let the back wheel touch down while I finish cutting the Throttle to let the front down.

The Hoover part I get.
No ... "Idle up" is a completely different thing that has no place on fixed wing.

Idle Up is when you set throttle to be active with CENTRE at lowest rpm... but the idle and full positions have FULL throttle ...
This sounds wrong but its not - remember a Helicopter can have NEGATIVE pitch as well as POSITIVE pitch. This allows the Heli pilot to hover / fly inverted and that means he needs the bottom half of throttle stick to be active in NEGATIVE pitch ... while top part of throttle to be active in POSITIVE pitch. Throttle stick actually controls two functions on a collective helicopter .. throttle and pitch.

So ignore Idle Up .....

Nigel
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Old 08-06-2017, 12:19 AM
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Stab your throttle from closed and see how it reacts. Now stab if from a trim position where the motor is just barely spinning. This makes a significant difference on all escs I am familiar with. ZTW is a massive difference and Castle (with programmed end points) is very subtle. It makes a much more responsive throttle at the bottom. Very important for low altitude IMHO, as well as practiced by many advanced 3D pilots. I'm not talking about helicopters. This practice involves lowest throttle being set to a few percent in the throttle curve setting. Ignore it if you wish. Try it if you want to improve.

http://docaustinextreme.blogspot.com...rformance.html
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Old 08-06-2017, 05:31 AM
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dereckbc
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I knew what Throttle Up meant in the heli world, never heard it applied to Planes. Anyway I understand what you mean and found it on the radio. Used to prevent Motor Sputtering. Real simple on a DX6 Just go to Throttle Curve menu.
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Old 08-06-2017, 07:53 AM
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Originally Posted by birdDog View Post
Stab your throttle from closed and see how it reacts. Now stab if from a trim position where the motor is just barely spinning. This makes a significant difference on all escs I am familiar with. ZTW is a massive difference and Castle (with programmed end points) is very subtle. It makes a much more responsive throttle at the bottom. Very important for low altitude IMHO, as well as practiced by many advanced 3D pilots. I'm not talking about helicopters. This practice involves lowest throttle being set to a few percent in the throttle curve setting. Ignore it if you wish. Try it if you want to improve.

http://docaustinextreme.blogspot.com...rformance.html
My point was 'Idle-up' not 'Throttle up' ..... two different animals.

When I did display flying - I could flick a switch and have my Idle rpm increased - but this was glow. It avoided stuttering after prolonged idle and gave a clean rpm increase. With electrics - of course you can avoid the initial torque reaction.

Going back to Derek's op ... personally I prefer a curve to expo because models cruise points are not all same .. hover points not all same .... and rarely at 50% throttle.

Nigel
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Old 08-06-2017, 12:50 PM
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Using the voice prompts on Spektrum can reduce potential grief associated with an idle up switch.
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Old 08-06-2017, 01:34 PM
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Originally Posted by birdDog View Post
Using the voice prompts on Spektrum can reduce potential grief associated with an idle up switch.
Sorry BD ... I'm losing the point of Idle Up in this discussion ..... Throttle Up I understand with Fixed Wing as I posted after yours ... but Idle Up means FULL throttle at Bottom stick as well as Top stick - with centre as minimum. Why would you apply a Helicopter Idle Up setting to a Fixed Wing ?

Throttle up where you flick a switch and it applies a minimum idle throttle - yes agreed ... and I agree a warning would be nice ... don't really like the thought of that meat cleaver churning away on the ground at closed throttle !!

My old JR Propo has a dedicated Throttle UP momentary switch ... designed to be pressed and held when needed ... as soon as you release - throttle goes back to normal ...



(mine had a couple extra switches added .... but that's another story).







And that was in the days before digital programmable .... but of course it cost an arm and a leg to buy !!

Nigel
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Old 08-06-2017, 01:46 PM
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Call it what you want. I started RC flying with Trex and I though we were talking about planes? The Idle line in your above listed throttle curve should be increased by a few percent.

Last edited by birdDog; 08-06-2017 at 06:59 PM.
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Old 08-09-2017, 09:26 PM
  #14  
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I've never used throttle curves with electric airplanes because as long as you set your end points exactly the same, and you calibrate the throttle range with these end points, the throttle response will be perfectly linear, I.E. 50% throttle stick is 50% power output. With gasoline engines, even if you use a perfectly linear setup so that the arm on the throttle servo is at 50% with 50% stick, and the carburetor throttle arm is at 50% with 50% throttle stick, the engine will not really be running at half throttle. With the way the powerband on 2 stroke engines works, this setting on the carb will give you closer to 5/8 throttle response out of the engine. There are some tricks we can use to get the engine response to act more linear with regards to linkage geometry but generally the mid-range is really peaky still so a throttle curve will come into play to help smooth that out.

Regarding 'Idle Up', we actually use this all the time with gasoline engines on our airplanes as it keeps the RPM's up high enough to prevent the engine from stalling during high g-maneuvers at idle. Flip to Idle Up on takeoff and turn it off before landing. I personally still use an Idle Up with electric setups as it gives a faster throttle response when the ESC and motor are already running together in sync (rather than having to throttle up from zero input on the ESC- not such a big deal with smaller models, but on big power systems this is almost mandatory).
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