Mostro recommended control throws

[Hawk404]

Got around to setting up the FBL and noticed that at 12 degrees pitch and 10 degrees cyclic throw I get servo stall at full negative pitch / elevator throw.

What would be some normal numbers for the Mostro on pitch and cyclic deflection? I just pulled 12/10 out of my last 600 and I'm by no means wedded to those numbers.

I could get 12/10 with longer linkages but I'd rather not go through that unless the 9/6 that cures the servo stall is too anemic (I fly anemic so big issue in any event)

Thanks!

[kumar2494]

Which flybarless unit are you using? Some fbl units have an adjustable cyclic ring that automatically limits cyclic throw at high and low collective. With this enabled, you should be able to use at least 10 degrees cyclic and 13 degrees collective without any issues. On my nitro, I have 12 cyclic and 13 collective with no issues (using vbar).

[Clarence Creer]

In addition to what was just asked, how long are your servo arms?

[Pitch-Itch]

Originally Posted by Clarence Creer

In addition to what was just asked, how long are your servo arms?

Yeah that's what I would look at first. When I first set my heli up I used 14mm spacing and I didn't get nearly enough travel before the servos stalled out.

At 17mm I get *just* enough travel for 13/10.

[Clarence Creer]

Please give me details on your entire setup. Something doesn't seem right. I am using 17mm Seacraft horns on mine. I get plenty of throw on the CGY 750. Many other team members are running the same horns with vbar and get plenty of throw.

[Pitch-Itch]

Originally Posted by Clarence Creer

Please give me details on your entire setup. Something doesn't seem right. I am using 17mm Seacraft horns on mine. I get plenty of throw on the CGY 750. Many other team members are running the same horns with vbar and get plenty of throw.

You referring to OP or me?

[Hawk404]

I was unclear in the OP - my problem isn't insufficient throw. I can easily set limits in the FBL that provide 12+- collective 10+- cyclic or more.

But when I do the swash binds when given full elevator at full negative pitch.

So I kept reducing the limits until the servos stopped buzzing at full elevator / collective and 9 collective 6 cyclic was where the servos stopped buzzing.

At 12/10 I can have full negative pitch or full elevator - I just can't have both due to the swash binding at that point.

I'm guessing the linkages are too short - I don't get similar binding at full positive pitch / elevator deflection.

The arms are 17mm Secraft, the FBL is Spirit and it's been dialed down to reduce collective and cyclic travel but this was intentional to stop the servos from stalling when the swash bound up. The servo linkages are about 36mm center to center - kind of hard to measure mounted so that might be off some.

Sorry about the lack of clarity in the OP.

[kumar2494]

As long as there is a 4mm gap between ball links and the head is at 0 degrees when the servo arms are centered, your mechanical setup is fine. It sounds as though it is a setting in the fbl unit that is causing binding at full cyclic/collective.

[jrwalte]

Something wrong in your setup. With spirit and 13mm servo horn i could get 13/11 without issue. You gain more mechanical throw with 17mm. When i went to 17 i could do 14 and 12 without binding, though i kept it at 13.

I'm on bx now with 13mm horn and have 13/11.

[Hawk404]

I'll run the setup again. It does seem physical as it's hard to push the swash into that position even with the links disconnected.

I've got a BD3SX laying around not doing anything - maybe I'll sling that thing into build and see what gives.

[jrwalte]

Or swash is bad

[Hawk404]

Originally Posted by jrwalte

Or swash is bad

That seemed plausible except that a bad swash would presumably be just as bad irrespective of its position on the main mast but it's fine at zero and full positive pitch positions.

Ditto with FBL settings - if it could stall servos at full elevator and full negative pitch it should also stall them at zero and full positive pitch.

It's like the swash is bottoming on something at full negative / full elevator but visually it's still clear of the bearing so I'm working on a class A mystery at the moment.

[mdu6]

When you first put the swash on the main shaft - did you manually slide it from top to bottom of the main shaft ?

On my machine I had 2 rough spots that I needed to polish (on the main shaft) so the swash would slide freely from top to bottom.

[Hawk404]

Originally Posted by mdu6

When you first put the swash on the main shaft - did you manually slide it from top to bottom of the main shaft ?

On my machine I had 2 rough spots that I needed to polish (on the main shaft) so the swash would slide freely from top to bottom.

There is a noticeable "hitch in the giddyup" when the swash is close to the bottom of its travel on the main shaft.

However, wouldn't that only impact the whatever-it-is-sorta-round thing in the middle of swash leaving the outer portion free to do whatever it is it's supposed to do?

Meantime by lengthening the servo-to-swash linkages and reducing the length of the DFC arms (thanks Dremel) I've gotten the throws to "almost 11 on pitch and almost 10 on cyclic". 10/9 is probably realistic.

Which is just going to have to do - and I expect it will do quite nicely - I'm not the sort of 3D guy that will get all stressed out over less than full control deflections. To be honest I tend to fly with dual rates anyway so this will just save me the hassle of setting them up as the deflections are already a bit inhibited.

The folks on the forum will testify that I'm more than willing to accuse the parts of being sub-par but I don't think that's the case this time - the center portion of the swash graunching up against the main shaft should have no effect on travel of the outer portion - and I'm right here staring at it.

I'm guessing not Avant's fault, not Spirits fault and certainly not the 17mm servo horns fault - sometimes things are what they are.

And, yeah, I had to take a mallet to the mainshaft to get it to seat but it was, after all, a rubber mallet. Even if it was an 18 pound sledge I don't see it impacting swash travel in the elevator direction.

[Pitch-Itch]

Yes the main shaft is a bit difficult to get in, but with a little light oil it slides in nicely, just make sure your two plates are perfectly perpendicular. You want the main shaft to be this way. It's a good thing.

About your swash, can you see any burr or rough spots on the inside of the swash ball? I'm thinking just getting everything set up and then moving the collective up/down a couple hundred times will burnish the parts and make them move freely. Just a hunch.

Also, the heli will still be VERY agile at 11/10. I'm set up for 13/10 and I can do full 3d flights at those values. The heli reacts fast, and is very agile. It's a dream to fly.

In other words, you won't feel like you're flying a neutered heli at those values.

[jrwalte]

11/10 would definitely work and would be adequate for spirit rescue, but you obviously have something going on. with 17 arms you should be able to achieve 14/12.

[Hawk404]

Originally Posted by jrwalte

11/10 would definitely work and would be adequate for spirit rescue, but you obviously have something going on. with 17 arms you should be able to achieve 14/12.

I'm thinking I'll never notice a difference. And I suppose I could easily make it 14/12 because I can't think of what I'd be doing that would require full negative pitch with full elevator which is the only time it would be an issue.

I'm just looking to not stall the servo. With my luck the Spirit would figure out a use for full negative and elevator and force a brown out due to stalled servos so I'm not going to give it the chance.