700N head design and travel range adjustments

[n808]

Having built and setup my 700N, and then watched Bob's video on head setup, I have a couple of comments.

When I setup everything with 90/90 and flat lower mixing arms, I ran into the same issue as Bob's video shows (but does not really comment on). The washout block will butt into the top of the head at a very low pitch mix % (54), while there is plenty of room for more movement downwards at full negative pitch.

Another problem problem here is that the resulting travel range turns out to be uneven, perhaps +13 to only -10 or so, even with 0 center. In order to remedy this, I made the arms from the flybar cage to the lower mixing arms quite a bit longer. The lower mixing arms will no longer be level, but (i) I could increase the pitch mix % to 66 without binding in either direction, and the travel is now +13.5 to -13.5 (0 center). Note that the suggested link lengths from the manual more matches my setup than Bob's setup)

I had to do the same on my Knight 3D, which has the same A lever anti-rotation mechanism, which makes the position of the swash plate fixed. When the swash center position is fixed, the only way to adjust the travel range seems to be to adjust the center position of the washout block.....

Thoughts?

Karl.

[toaster12]

I have the same problem. The A arm seems to be too long or the links to the washout block from the swash or the main shaft is not long enough!

Mine hits the head block at about +12 but I have plenty of travel left to go at the bottom.

If the test pilots did not notice this then obviously they don't know how to set up helis, which I can't believe!

So something is amiss here.

[Finless]

Guys.... this ain't a 450 or a E heli where you can get 15 pitch and get away with it... A 90 sized heli like this swinging 710's running 14 is a STRETCH! I understand the desire for fast pitch and "pop and lock" but you will find this to be a different animal! Even on my Aurora 13 was pretty much max and is more than you will ever need!

Bob

[n808]

Guys.... this ain't a 450 or a E heli where you can get 15 pitch and get away with it...
I think we all agree to this :) I reduced mine to +13/-13. However, like I mentioned, when the swash center is fixed, the only way to adjust travel range is to move the washout block by adjusting the links from the flybar cage to it, and allowing slightly non-level lower mixing arms. Both the manual drawings and suggested link lengths indicate this too. And I had to, to get the same amount of positive and negative travel.

In any case, the two videos I have watched so far have been very useful. I watched the torque tube one before building, since this was my first torque tube, and now the head setup to to this issue. In had some nice tips (4 mm allen wrench to lock flybar level, and use a suitable tool in the blade grip holes for zero pitch adjustment)

Karl.

[toaster12]

Guys.... this ain't a 450 or a E heli where you can get 15 pitch and get away with it... A 90 sized heli like this swinging 710's running 14 is a STRETCH! I understand the desire for fast pitch and "pop and lock" but you will find this to be a different animal! Even on my Aurora 13 was pretty much max and is more than you will ever need!

Bob

Yep, found that out after the first flight :oops:

This is my first 90 so what pitch should be set was based on my 50's. After reading all reports everywhere and all the test pilots saying they were running +/- 14 That's what I was expecting to set. Not that I would have used i! I set the maximum travel available and then dial it down in the pitch curves.

You only learn from experience and now I know.

[harryboe]

There is one thing i don't understand.

If everything is symmetric - as it is by design - and at 90° how can the positive and negative pitch be different ???

Any thoughts ?

[toaster12]

At 90 everything is symmetrical! (Well it is on my 700!)

Just there is more available range towards the negative, But, if you use that range the washout block hits the head block.

[harryboe]

Yep, I got that with the travel, but the one i was referring to was this ..


Another problem problem here is that the resulting travel range turns out to be uneven, perhaps +13 to only -10 or so, even with 0 center.

So again how could that be ?!

Anyhow, got my kit today and might figure it out soon :)

[toaster12]

That only happens if the length of the rods from the washout arms to the flybar cage are incorrect, I believe!

[n808]

I will try to take some photos tonight with what I ended up with.

[Espeefan]

My question might be a little off subject, but I thought I had read somewhere that the 700N's head design was pretty much the same, or was the same, as the 600N. Does that mean most of the components simply carry over?

[Finless]

Yep, I got that with the travel, but the one i was referring to was this ..

So again how could that be ?!

Anyhow, got my kit today and might figure it out soon :)

There is another reason that can happen. Some radios like Futaba, Hitech, etc have hover pitch trim knobs or pitch high/low knobs. MANY of these radios have this stuff turned ON by default and when your setting up center stick they will really mess you up!!! For sure they tend to cause a higher pitch reading on one side vs the other depending on where you have the slider or knob. So make sure you check that stuff if it's not making sense and you getting offset ppitch values like that!

Bob

[BiggerDanno]

There is another reason that can happen. Some radios like Futaba, Hitech, etc have hover pitch trim knobs or pitch high/low knobs. MANY of these radios have this stuff turned ON by default and when your setting up center stick they will really mess you up!!! For sure they tend to cause a higher pitch reading on one side vs the other depending on where you have the slider or knob. So make sure you check that stuff if it's not making sense and you getting offset ppitch values like that!

Bob

Bob, How do you re-set the hover pitch to zero (neutral) on a DX-7? I don't see anything that tells you where it is set.

[Finless]

As I recall there is a center beep sound. e.g. it beeps when you move it but when you hit center it makes a different beep. Also as I recall on the DX7 there is a trim bar graph at the very top which is horizontal. Thats what I recall from memory now sorry if I am incorrect.

Bob

[toaster12]

The vertical trims on the DX7 will move when the hover throttle and pitch trims are used and the beep is different went centred.

They return to the throttle trim and forward trim after a short while too.

When they are open squares instead of filled squares they are centred.