Pitch & Throttle Curve Calculator

[Mart61]

Hi guys

Just put together another little useful (useless) calculator.

If you enter your max and min pitch figures (assuming a linear curve) in the two white boxes, and then enter your throttle and pitch curves, it will plot the curves for you and, perhaps most importantly, calculate the true blade pitches at any given stick position.

You can also see by reading off the pitch scale on the right hand vertical axis approximately where you will reach the hover point (5-6 degrees) on both actual throttle speed and stick position.

Hope this is useful and, if you can think of any additions/improvements, let me know.

Cheers.

[tourerjim]

Thats ya home work done but how will that help me!

[Tom Burgess]

with a 0 50 80 80 80 TC
and 0 25 50 75 100 PC

I get 27.5* pitch????

[Mart61]

Thats ya home work done but how will that help me!

Well, it may not help you Jim. However, a newbie such as me sat here wondering "I wonder what effect a certain pitch curve will have on my actual blade pitches?"

So I put this together to do some rough calcs. I was trying to see whereabouts the blades would be, pitch wise, for any given set of curves or stick position.

A guy at my heli club got me to thinking that my current curves may have compressed around 50% of the positive pitch range to about 20% of my stick movement.

[Mart61]

with a 0 50 80 80 80 TC
and 0 25 50 75 100 PC

I get 27.5* pitch????

Did you put the min and max pitch figs in OK - i.e. if your full linear range goes from -12 to +12 then you should enter -12 in the top box and +12 in the other.

[Tom Burgess]

A guy at my heli club got me to thinking that my current curves may have compressed around 50% of the positive pitch range to about 20% of my stick movement.

Why Martin? If everything is linear that cant be the case.

[Tom Burgess]

Did you put the min and max pitch figs in OK - i.e. if your full linera range goes form -12 t0 +12 then you should enter -12 in the top box and +12 in the other.

aah i see, i didnt use the -

[Mart61]

I'm not running linear. I was advised that, to dumb it down for a newbie, I'm running pitch at 40,45,50,75,100 and throttle at 0,40,75,87.5,100.

I think you may be right but I wanted to plot it and see.

As it turns out, if I assume that I hover between 5 and 6 degrees (let's say 5.5 for arguments sake), I'm getting hover pitch at just over stick position 3 which also gives me just under 90% throttle.

Thus I proved the guy at the club wrong.

Might have been a long winded way of proving it but hey, I had the time...

[Tom Burgess]

I'm not running linear. I was advised that, to dumb it down for a newbie, I'm running pitch at 40,45,50,75,100 and throttle at 0,40,75,87.5,100.

I think you may be right but I wanted to plot it and see.

As it turns out, if I assume that I hover between 5 and 6 degrees (let's say 5.5 for arguments sake), I'm getting hover pitch at just over stick position 3 which also gives me just under 90% throttle.

Thus I proved the guy at the club wrong.

Might have been a long winded way of proving it but hey, I had the time...

Yeah, if you are getting 50% pitch travel over 20% of stick travel, then your PC is not linear.

I got you now Mart

[Steve]

My radio has 7 point pitch and throttle curves, not 5. Some have more. Many radios also have a curve smoothing option as well.

Few more things to think about.

Also, I'd be careful of the 'actual pitch angle' value because of the whole rotary servo motion to linear transfer thingy gobbledegook. If you have a pitch range from say 0 to 10 deg and a pitch servo range from 0 to 100%, then 50% on your Tx represents 50% of the rotary movement of the servo. This does not necessarily represent 50% of the linear movement of the swash plate, which could be up to 71% for the same amount of servo rotation, depending on the total amount of servo travel used.

In real life, I think you might find that maybe 0% servo gives 0 deg pitch, 50% servo gives 6 deg pitch and 100% servo gives 10 deg pitch or something like that. The linear Tx output gives a curved pitch output. This effect is much less pronounced (if at all) on mechanically mixed machines - i.e. not CCPM.



That's far too much gumph for one lunchtime.

[Mart61]

I have much to learn.

[tourerjim]

I'm not running linear. I was advised that, to dumb it down for a newbie, I'm running pitch at 40,45,50,75,100 and throttle at 0,40,75,87.5,100.

I think you may be right but I wanted to plot it and see.

As it turns out, if I assume that I hover between 5 and 6 degrees (let's say 5.5 for arguments sake), I'm getting hover pitch at just over stick position 3 which also gives me just under 90% throttle.

Thus I proved the guy at the club wrong.

Might have been a long winded way of proving it but hey, I had the time...

In theory it works but you would have to be in ildle up as the setting you've just given are not linear so + & - will differ.
But its good how you've made it & the way it works althrough dont know how many of us have Excel.

[Steve]

With CCPM helis, you tend to find that the geometry of the linkages means that the servos don't have to move very far away from centre to give us plus and minus 10 degrees, so by limiting the rotational movement of the servo, you are reducing the curving error massively. My recollection of mechanically mixed helis in the past is that I needed a huge servo disc and massive travel adjustments to get this kind of pitch range, but the effect in a mechanically mixed heli is cancelled out since the rotational effect is carried from the servo throughout the head all the way to the blade grip. That's one of the reasons why FAI fliers like mechanically mixed helis, along with the lack of interaction etc. The downside is the large servo movements required mean the servo takes longer to reach its destination when compared to a CCPM setup.

Life's a compromise.

[callum]

I found this spreadsheet quite useful :P



Thanks for it

[tourerjim]

With CCPM helis, you tend to find that the geometry of the linkages means that the servos don't have to move very far away from centre to give us plus and minus 10 degrees, so by limiting the rotational movement of the servo, you are reducing the curving error massively. My recollection of mechanically mixed helis in the past is that I needed a huge servo disc and massive travel adjustments to get this kind of pitch range, but the effect in a mechanically mixed heli is cancelled out since the rotational effect is carried from the servo throughout the head all the way to the blade grip. That's one of the reasons why FAI fliers like mechanically mixed helis, along with the lack of interaction etc. The downside is the large servo movements required mean the servo takes longer to reach its destination when compared to a CCPM setup.

Life's a compromise.

Nicely quoted.