General Altering Pitch Range

[Harford]

On my Trex 500 ESP (ie with flybar), I believe I have set up the head correctly according to manufacturers instructions and all is level (pitch at zero 50 in 50 out). With collective at max up, pitch both blades are +14.6 degrees, at max down -13.5 degrees. I would like to reduce the pitch range eg max pitch at high stick at say 10 degrees positive. How do I do this please on a flybarred heli ? My swash mix is at -55% for pitch. I understand you can adjust this setting to alter the pitch range but is seems to me it would have to be altered quite dramatically to reduce positive pitch from 14.6% to 10%. Your help would be appreciated.

 

[Tony]

You are correct, you just reduce the number in your swash mix, that's it.

 

[Harford]

Thanks Tony. My concern is that by changing the swash mix setting for pitch from -55% to -50%, the max pitch dropped from +14.5% to a little over +13%. Presumably then I would have to make a big alteration to the pitch value in the swash mix to bring it down to around +10%. Cannot I not achieve the same thing by just altering the pitch curve, ie reducing the max value, or am I getting confused ?

 

[murankar]

fix your pitch diferential first. Your swash is not center on the main shaft when at mid stick. shorten all three swash to servo links the same amount of turns.

I would do three full twists first then see where your at.

 

[Harford]

Will that reduce the overall pitch range ? My concern is this will make the servo to swash plate links quite a bit shorter that the Align manual specifies and that this may have other implications ?

 

[murankar]

Those link sizes are starting points. As for pitch range, no it won't. It will how ever lower your max positive and raise your negative. Basically all you are doing is splitting the difference so that your positive and negative are the same numbers.

I just looked at your numbers. Once the adjustment is done you should be around 13.75° +-. So you will not be losing anything.

Your collective travel in the radio is what will limit your pitch range.

 

[Harford]

All understood, many thanks

 

[murankar]

Your welcome.

 

[Smoggie]

As for reducing the total range. The best way to do that where possible is by using shorter servo arms (or by moving the balls in if the arms have more than one hole). This has the advantage of increasing the mechanical advantage of the servo so it needs less torque to operate and also gives more precision in it's movement. On some layouts you cant move the balls in too far because they might hit the servo body or the frame so make sure to check that isn't an issue.

PS... for differential movement (e.g. more + pitch than -) also check that when at zero pitch the servo arms are precisely horizontal. If the arms are all slightly down at zero pitch you will get more + pitch than -, and visa versa (assuming swash moves up for positive pitch)