Pitch angles and percentages

[ShinySideUp]

I've looked everywhere but can't find an answer so I'll have to post.

I am rebuilding my Blade 400 and want to set the pitch correctly; something like +10 and -4.
I believe that 50% on the transmitter should equate to 0 degrees of pitch if all is set up OK but what percentage equates to -4 and +10. In other words the percentage on the transmitter is a percentage of what?

I'm using a DX6i.

Sorry if this has been answered in another form somewhere.

Cheers

Martin

[adieuk]

hi martin
you need to set it up around 30% and that will give around 4%

[millerman]

hi martin
you need to set it up around 30% and that will give around 4%

+1 what i was gonna say ;0)

[Mslater]

Should be about right but you really need a pitch gauge to be certain.

If you don't have one there is a method of laying the heli on its side and allowing the blades to hang over the edge of the table.

Turn the head so that the feathering shaft is parallel to the table top and let both blades hang side by side.

You will notice that as you apply pitch the blades will move, when they are together (viewed from the side) that is zero pitch.

If you are cleaver enough and can remember your triangles theory from school then you can measure the separation at any point with a ruler and from that calculate pitch very accurately.


If you have an android phone their is a free app that does the calculation for you
RC-Heli-Pitch - Android

[adieuk]

+1 what i was gonna say ;0)

i use a pitch gauge on my setup and with 30% gives me - 4%

[adieuk]

31.5% to be exact

[adieuk]

+1 what i was gonna say ;0)

forgive me if im wrong but that is the way it says on my pitch gauge which isnt a cheap one

[ShinySideUp]

Thanks for input everyone and I appreciate the actual readings that have been given but how are they worked out? 50% is zero pitch but 50% of what? What is 100%? I am so confused .

[adieuk]

i'll leave the rest to tell you mate but the best thing is to get a pitch gauge and work from bottom stick and set the pitch you need

[Mslater]

In other words the percentage on the transmitter is a percentage of what?

Sorry just re-read the thread and noticed the question.

The TX shows a percentage of movement. Depending on your servo's and the arm lengths your movement may be more, less or the same as other similar setups.

Really you should set Idle up 2 first and work from there. In idle up 2 you should have a range somewhere like -12 to +12. So when the stick is at the bottom you see -12 pitch. By setting a straight line on the TX from 0 to 100 you should find zero degrees is centre stick.

You will probably find that your links are the wrong length or you may need to increase the pitch setting on the TX to get this correct.

The quick and best solution is to get a pitch gauge or use the method in my previous post.

When you have this correct you should find 4degrees is 31% of the travel from zero to +12.

[bolders]

Thanks for input everyone and I appreciate the actual readings that have been given but how are they worked out? 50% is zero pitch but 50% of what? What is 100%? I am so confused .

Ok so the bit of information you are missing here is that there are to places where you adjust pitch on a helicopter.

on the DX6i these are the swash mix and pitch curve menus - these can both be found in the adjust list.

The swash mix will effectively set the maximum (and minimum pitch) you will get from the heli if you set your pitch curve to 100% (or 0%).
So what this means is that your pitch curve is dependant on your swash mix value.

What we will do first is set the pitch curve to a linear line using the values

0 - 25 - 50 - 75 - 100 (we will come back to these later)

Now we go into the swash mix menu. There will be 3 items in this menu. For pitch adjustments we are only interested in the PIT setting

You will notice the PIT setting is a single value shown as a percentage. 100% in this menu effectively denotes the maximum travel you have available from the servos to control the pitch. This value works from the servo mid position (this should be your 0 degree pitch) therefore setting this value adjusts the amount of positive and negative pitch you get equally.
The PIT value can also be +ve or -ve. This enables you to reverse swash direction (i.e. up is down and down is up - remember for the blade 400 the swash moving down (from the mid point) gives positive pitch)

On my blade 400 I had to set the PIT value to around 80% to get +/- 11 degrees of pitch (this is much higher than stated in the manual). However the best thing is to put a pitch gauge on and adjust PIT value until you get the required pitch.
To do this (motor always disconnected when setting pitch btw) set your pitch gauge to say 11 and put your collective stick on your radio to its maximum (remember we set a linear pitch curve earlier so full stick equates to 100 on the pitch curve)

Adjust the PIT value until the pitch gauge aligns with the flybar (tip - you can use a 3mm allen key to lock the flybar on the blade). The heli is now set to give a maximum of +11 degrees pitch. If the head is set-up correctly you should get -11 degrees of pitch with the collective stick at its minimum position and 0 degrees at mid stick position.

OK so now we have set our heli to give us a maximum of +/- 11 degrees of pitch but we may not always want this setting. For example when taking off and landing we may want a different pitch range to when doing acrobatics and 3D manoeuvres. We accomplish this with the pitch curve menu (we have 3 modes on the DX6i, normal mode, Idle up mode, and throttle hold - i think idle up is called stunt on the DX6i menu).

So now we have established a max available pitch range of +/- 11 degrees in the swash mix menu, we can equate a pitch value to the percentages in your pitch curve menu (it is important to recognise that the pitch curve values are dependant on the max pitch you set in the swash mix menu)

At 0% in the pitch curve menu we have -11 degrees of pitch.
At 50% in the pitch curve menu we have 0 degrees pitch
At 100% in the pitch curve menu we have +11 degrees pitch

Therefore a 50% change on the pitch curve equates to 11 degrees or 1 degree = approx 4.5% change on the pitch curve menu.

so if we want -4 degrees then our first point on the curve is going to be

4 x 4.5 = 18 (18% change required to go from 0 degrees pitch to -4 degrees pitch)

50 - 18 = 32 (remember we are going from 0degrees which is 50% so we need to subtract the above value from 50)

Note this is very close to the value Adie provided earlier.


So this gives us a pitch curve of

32 - x - 50 - 75 - 100

This gives us -4 degrees at low stick, 0 degrees at mid stick and 11 degrees at full stick with a linear change between mid and high stick.

Obviously the value X must be larger than 32 and less than 50. You could use a value that is halfway between these values i.e. 39 or you could adjust it to give you a smoothly changing slope by looking at the graph when adjusting the value.

[Planehazza]

It all depends on the model and setup. If the max physical pitch is say +-15, then you need to use swash mix (or the FBL controller menu or equivalent) to electronically lower the pitch amount. So once that's done, +100% should be the max positive pitch you want (+11 for me) and 0% (or -100% depending on the radio) should be the max negative pitch. Then it's just a case of working it out what equates to what - 40% of 11 is 4.4.

Hope that makes sense.

EDIT: Didn't see bolder's post. He explained it in a lot more detail

[gazza131]

i know this is a stupid question, where abouts do you stick the allen key to lock the flybar ?

[ShinySideUp]

Thank you all very much, especially bolders for your description of exactly what I needed to know.

Cheers

Martin

[bolders]

i know this is a stupid question, where abouts do you stick the allen key to lock the flybar ?

Use the short end of the allen key and push it in the hole in the head block so it sits above the flybar see-saw. Make sure it goes right through and pokes out the hole on the other side

Thank you all very much, especially bolders for your description of exactly what I needed to know.

Cheers

Martin

Happy to help mate