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Old 12-07-2017, 07:31 PM   #1 (permalink)
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Default Question on throttle curve

I just bought a slightly used 250 CFX. In doing research on setting up my DX6G3, some recommend creating a new model with the settings from the manual, some recommend using the Spektrum SPM file for the 230S.

Comparing the two heli setups they are almost identical, except for the throttle curves. This is my first CP heli (have a 120SR now), could someone explain the difference between these two curves?

From the 230 manual:
N: 0-25-50-75-100
1: 100-80-75-80-100
2: 100-90-85-90-100

From the 250 manual:
N: 0-25-50-75-100
1: 80-80-80-80-80
2: 100-100-100-100-100
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Old 12-10-2017, 06:49 PM   #2 (permalink)
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So for the normal curves 0 - 100, this is what you would have been used to on the 120 SR, basically with the throttle stick fully down you have zero power, with the throttle stick fully up you have full power. This is the usual setup for fixed pitch heli.

Collective pitch helis can fly upright with the normal curves but require an alternative throttle curve for 3D flight. This is where curve 1 & 2 come in. We generally refer to these as idle up 1 & idle up 2 (IU1 & IU2)

So with any of the curves from 1 & 2 the blades are always spinning, this is necessary for 3D flight. The five figures from the throttle curves represent the requested power in relation to stick position. So the first number is the power applied when throttle stick is at 0, second number represents power applied when stick is at 25%, third number = mid stick, fourth = stick at 75% and last number is power with stick at full.

So for example if we take the 250's curve 2 of 100,100,100,100,100 we can see that no matter where the throttle stick is placed we will be requesting 100% power at all times. This is called a flat curve.

If we take the 230's curve 2 of 100,90,85,90,100 we can see that with the throttle stick at zero we are requesting 100% power, however at mid-stick we are requesting 85% power, then back to 100% at full stick. This is called a U-curve.

So in short the 230 is using U-curves and the 250 flat curves. It's important to remember though, wether it's a U-curve V-curve or flat curve, it's up to you what you use. You can adjust the curves to suit you. For instance I use flat curves with the 230.

To be honest as this is you're first CP heli you probably wouldn't notice the difference in flight. As such I would advise to stick with the 250's recommended settings to start with. You can always adjust in future should you need to.

Hope this helps
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Old 12-10-2017, 07:46 PM   #3 (permalink)
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Here's a picture from My DX9's 250CFX TC Menu...

IU2 is 100-95-90-95-100

Notice the graph forms a variant of the letter V...

Therefore it's known as a V-curve

I've used 10-15-20 point v-curves on various heli's to allow some headroom for the main motor during hard collective changes

10 = 100-95-90-95-100
15 = 100-92-85-92-100
20 = 100-90-80-90-100
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Old 12-11-2017, 06:19 AM   #4 (permalink)
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Thanks guys, makes sense now. I'm a pretty mellow flyer and won't be doing inverted for a long while if ever, I'm thinking a V curve would work just fine for me, and get me a bit more run time as the throttle won't be pegged at 100% constantly. I'll try both and see which I prefer.
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Old 12-11-2017, 09:48 PM   #5 (permalink)
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Sounds good to me. Always best to find what works for you. As another example, for lower head speed, you could try a gentle V-curve of 80,75,70,75,80. You could even try a flat 60,60,60,60,60.
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Old 12-12-2017, 05:43 AM   #6 (permalink)
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Quote:
Originally Posted by Lotus 7 View Post
Sounds good to me. Always best to find what works for you. As another example, for lower head speed, you could try a gentle V-curve of 80,75,70,75,80. You could even try a flat 60,60,60,60,60.
I'll try that as well, thanks.
One more question. If I take the throttle and pitch curves from normal mode and use them in stunt mode 1, that will give me the same characteristics as normal mode but without the stability mode correct?

[EDIT] Scratch the above. As I currently have no desire to do 3D I'm going a different route. Going to move the self level to switch C, then create 3 flight modes with different flat curve head speeds and matching pitch curves.

Last edited by Davejb; 12-12-2017 at 09:14 AM..
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Old 12-12-2017, 03:25 PM   #7 (permalink)
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Just to confirm, your first statement was correct.

Yes moving the self levelling onto a seperate switch can be useful. Many of us do this, it offers more flexibility.

Just a quick heads up - if you do set flat curves on all three flight modes, you will be relying on throttle hold to start and stop the blades spinning. This can be a problem, if the ESC doesn't have a soft start function, as the motor may turn on instantly with lots of power possibly causing damage to main gear. Just done a quick search and I don't believe the 250 has a soft start function.

So you can still seperate the self leveling to a switch of you're choice but I would advise to keep a linear type throttle curve for take off, normal mode. It doesn't have to be 0,25,50,75,100 ..... it could be 0,35,70,70,70 this would match up nicely if you had stunt 1 set to 70,70,70,70,70....... do you see how it would give a smooth transition when switching from normal to stunt 1?
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Old 12-12-2017, 03:55 PM   #8 (permalink)
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Thanks Lotus. I should rephrase. Not doing a completely flat throttle curve, just flat above 0 pitch.

I have the following TC set up (for the reasons you mentioned with startup)

N 0 25 60 60 60

1 0 30 80 80 80

2 0 45 95 95 95

With a pitch of

N 40 45 50 65 80

1 40 45 50 75 100

2 40 45 50 75 100

I think this will give me some variations to play with without having large negative pitch to accidentally drive me into the ground, and also allow me to power off the motor with 0 throttle if I end up crashing without fumbling for a switch. I don't want to use the stock Normal settings as that seems to fly it like a FP heli, and I want to learn to fly like a CP.

Does this look like it'll work?

I appreciate the input by the way
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Old 12-12-2017, 05:41 PM   #9 (permalink)
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You're welcome. I don't see any issues at all with those settings. For what you're trying to achieve I'd say they look pretty good
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Old 01-09-2018, 07:06 PM   #10 (permalink)
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Quote:
Originally Posted by Lotus 7 View Post
Just to confirm, your first statement was correct.

Yes moving the self levelling onto a seperate switch can be useful. Many of us do this, it offers more flexibility.

Just a quick heads up - if you do set flat curves on all three flight modes, you will be relying on throttle hold to start and stop the blades spinning. This can be a problem, if the ESC doesn't have a soft start function, as the motor may turn on instantly with lots of power possibly causing damage to main gear. Just done a quick search and I don't believe the 250 has a soft start function.

So you can still seperate the self leveling to a switch of you're choice but I would advise to keep a linear type throttle curve for take off, normal mode. It doesn't have to be 0,25,50,75,100 ..... it could be 0,35,70,70,70 this would match up nicely if you had stunt 1 set to 70,70,70,70,70....... do you see how it would give a smooth transition when switching from normal to stunt 1?
Just thought I would add to this post with some recently learned info. If you have a Spektrum computer radio it has the ability to perform the same function as a soft start ESC. There is an option to add a delay in the throttle cut setting, this will actually slowly ramp up the throttle when you switch off your throttle hold switch.
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Old 01-10-2018, 10:05 PM   #11 (permalink)
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Quote:
Originally Posted by Davejb View Post
Just thought I would add to this post with some recently learned info. If you have a Spektrum computer radio it has the ability to perform the same function as a soft start ESC. There is an option to add a delay in the throttle cut setting, this will actually slowly ramp up the throttle when you switch off your throttle hold switch.
Hey Dave, can't thank you enough for coming back with that usefull info I thought I knew my DX6 inside out but that was one function I wasn't aware off

Cheers
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Old 01-11-2018, 05:52 AM   #12 (permalink)
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Quote:
Originally Posted by Lotus 7 View Post
Hey Dave, can't thank you enough for coming back with that usefull info I thought I knew my DX6 inside out but that was one function I wasn't aware off

Cheers
You're very welcome. I'm now debating if I want to change to a completely flat TC, will probably leave it as is for now, still haven't flown the thing.
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Old 02-11-2020, 12:53 PM   #13 (permalink)
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Quote:
Originally Posted by Lotus 7 View Post
Hey Dave, can't thank you enough for coming back with that usefull info I thought I knew my DX6 inside out but that was one function I wasn't aware off

Cheers
If you do the soft start I'm thinking you will have to deal with the chicken dance problem. Although if you are in sport 1 or 2 it doesn't do the chicken dance so maybe a good idea. Just thinking out loud.
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