Multiblade rotor phasing: can it be implemented?

Hi,
As we know, model helicopter rotors need 90deg phase shift for proper flight control. This is easy to do with twin blades - all fb and fbl mechanics are like this.
Multi-blade rotors are not so simple case. they also need 90 deg, but either:
1. can be done mechanically, and the control rods are not parallel to the main shaft
2. can be done electrically, by a high priced FBL controller, where you set up the mechanics straight and enter a single number into the controller for delay correction...

#1 is cheap - but looks ugly and not scale, but works with anything.

Could #2 be implemented in Deviation?

I am thinking in a single line added to the <Heli> page, where we set the swash mixing, like "Phasing: 90deg", and we could give something like 90+-45deg...

I do not know how hard would that be to phase shift the ccpm mixing... could you guys please have a look?

(That option would make Deviation even more awesome , if it is not awesome enough already...). Scale builders (as myself) could save lot of $$$$$$$$

Thanks
bm

For example, Helicommand has an option like this, call "cyclic phase". most scalers use this device but it is very $$$

...anyone?

Can it be done? Sure. With current firmware? Probably with some complex mixers, but might be easier to change the source code to offer phase rotation.

Most modern FBL helis don't do the mixing in the radio anymore -- they send the elevator and aileron channels directly to the controller in the heli, which is programmed separately for the specific linkage you have. But deviation already has 90, 120, 120x, 140, 140x mixing predefined in the simple GUI, and even allows you to tweak the angles.

With deviation complex mixers, you could probably create a sin curve mixer and approximate sin and cos transforms for given range of inputs and then combine those to approximate a phase rotation of any given amount with fairly decent precision. Off the top of my head I don't know if you would also need arcsin or a tan/arctan curve as well, but if you can figure out the math then the complex mixers should offer enough flexibility to implement it as a sequence of mixers.

WOW. Never thought of that... but honestly, I would prefer option 2, with a simple "slider" or number

I have a 3Gx on that given model, which requires a 120deg ccpm tx setup.

But here comes the second part of your email... would that mess up the 3gx directions... ? Probably yes
That goes to all FBL's, as the phase delay is the last logical step in the control chain...

Which is bad news for me. And basically gives the answer to my question.

The only use for the Tx based phase setting would be useful if someone would use a multiblade without an FBL controller (=single, normal gyro, like an FB). ...which is possible, but not really used anymore, due to low prices of the basic FBL controllers.

Too bad, seemed to be a good idea

Assuming you are talking about an Align 3GX FBL controller, I think you should be using the 1servo (no swash mixing) in the deviation TX. At least that is what I use for my microbeast FBL controller and my walkera gyro-RX.

I'm not saying it can't be done with dumb RX and all the mixing in the TX, but all gyro-based controllers want stick inputs from the TX, not the mixed servo outputs.

Doing quick google search for 3GX and 4-blade, I ran across this:
www.helifreak.com/showthread.php?t=530451 . Sounds like the 3GX has some issues (at least in the past) with more than two blades. This thread also mentions some other FBL controllers that do allow more flexible blade setups, which I presume relates to phasing that you are looking for.

I'm certainly no expert on multi-blade rotors or phasing, or even FBL setups in general. Just trying to respond to your thread since nobody else offered any ideas.

Could someone explain to me why multiblade is so different from 2-blade? There is only one angle to control and it can be set disregarding of how many blades you use (as mentioned by tmcg).

I was curious too, and found what looks like a reasonable description here: rc.runryder.com/helicopter/t729468p1/ (6th post down by Keygrigger).

Not really the point here, but the Align 3GX does use the CCPM mixing from the radio, unlike the Beast or the V-Bar or most of the controllers...

The link with the explanation is really good, this is exactly what I was talking about.

However, it would only work with a single gyro...

1. De bird


2. De brain


3. & 4. De Head



5. De viation

So you may notice: the control rods on the head are not parallel to the main shaft - to properly set the mechanical 90 deg. phase advance (= the attachment point of the control rod on the swash is 90 deg forward to the blade)

That looks awful

...and keeps the main shaft unnecessary long. Parallel rods could be much shorter, head could go lower, bird would be more scale and nicer

I understand what you are going for, but having the links on an angle, to get the phasing correct, will allow you to lower your head.








Im using a beastX and a devo1002rx

"... but having the links on an angle, to get the phasing correct, will allow you to lower your head."

You are right. My words were short... I meant if I could use parallel rods, I could replace the rods with shorter ones (almost zero visible metal lenght)
AND replace the shaft with a shorter one, for example with a DFC shaft.

(If I'd shorten the shaft now, the follower would hit the rods)

Original MD500 head + a nice model head with parallel rods (and mechanically engineered phasing setting below the swash!)

The answer is: V-bar. I have 3 of them installed in other helis...
Just need to tear the 3GX out and swap it with any of my Vbars...

I deserve a facepalm.



This is the screen I was overlooking for almost a year. Technically, I can set the phasing with the "Rotate" button into any degree...



Anyway, I hope it was interesting for all of you

salve. vorrei settare la mia radio (devo 8s con firmware aggiornato) in modo da poter utilizzare l'Helicommand 3d (robbe).
potete aiutarmi?
grazie

Hello. I would set my radio (I 8s with updated firmware) so you can use the Helicommand 3d (robbe).

can you help?

thanks