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HomeAircraftHelicopterRobbe Cuatro - Millennium - Nova - Dyna-X › Roll servo holder moves / Nova Cuatro
12-03-2015 09:08 AM  32 months agoPost 1
Yeager

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Lisbon, Portugal

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Gents,

Could somebody please confirm, if while inputting pitch(elevator) command ONLY on the transmitter, not only does the pitch(elevator) servo move as commanded and expected, but this command also makes the aileron/roll servo holder move - ever so slightly. It's really very little movement on the roll servo holder, but it does move a bit.

I've noted this, while setting up the phasing of the multi blade rotor head, as it's impossible to get "no movement" of the main rotor blade while inputting elevator command (blade over the tail boom) - as long as the roll servo holder moves.

The Nova Cuatro has the three cyclic servo system only, not the four servo system as on the Futura SE/SS.

Thanks for you time.

Robbe Nova Cuatro Gas/Nitro, Futura Nova Nitro, Futura SS Nitro, Vario Scale S300C/1002/21 Gas.

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12-03-2015 04:28 PM  32 months agoPost 2
dela

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Stillwater Oklahoma

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I haven't done the math, but I would be amazed if there weren't a little movement. It is a 3 degree of freedom, coupled, closed loop, 3-dimensional linkage system.

It might be possible to make ALL servo arms and bellcrank arms the same length, put everything at appropriate angles, and get rid of the motion.

I would never go to that much trouble.

Ron D.

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12-03-2015 11:02 PM  32 months agoPost 3
Sparkhead

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Melbourne Australia

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I think that due to the way the system 88 is designed to use the second servo as the pivot piont you are going to get some interaction due to the slop in the system. Out of interest have you set the servo horn balls up at 180Ëš to each other or at 90Ëš to the pushrods?


Mick.

Robbe & Futaba.

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12-04-2015 02:00 AM  32 months agoPost 4
Yeager

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Lisbon, Portugal

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Yeah, I'm also not sure that it's possible at all to have zero movement of that roll servo holder, due to the interaction from the swash plate. I've just not paid particular attention to this fact until now, while setting up the phasing for the multi blade head. Anyways, it's very little interaction, and likely the 3 axis gyro system will deal with it.

@ Mick.,

I'm not quite sure what you mean with you question about the servo horn balls. I've attached photo of my servo setup, with pwr.on and all sticks at mid point (0 deg. on collective pitch on my setup).

Robbe Nova Cuatro Gas/Nitro, Futura Nova Nitro, Futura SS Nitro, Vario Scale S300C/1002/21 Gas.

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12-04-2015 07:12 AM  32 months agoPost 5
Sparkhead

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Melbourne Australia

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On your top view photo if you draw a line from the servo horn screw through to the pushrod ball you will see that that imaginary line doesn't form a right angle to the pushrod.

After going to all of the trouble of levelling the swash, levelling the bell cranks and making everything symetrical then the servo horn throws it all out the window.

Not sure if it will be an issue with the new gyros but there was definitely an interaction problem with the flybar setup.

I'll try and find some photos of what I mean.


Mick.

Robbe & Futaba.

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12-04-2015 07:32 AM  32 months agoPost 6
Sparkhead

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Melbourne Australia

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Here's a photo of one of mine. Hopefully someone else will chime in as I vaguely remember having a roll issue when I pulled up into a loop so maybe only one of the servo horns needs the fix.


Mick.

Robbe & Futaba.

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12-04-2015 07:36 AM  32 months agoPost 7
Yeager

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Lisbon, Portugal

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Sparkhead,

I think I see what you're saying. However, if I do understand you correctly, then The Cuatro was never designed to have that servo horn and the pushrods at a perfect 90 deg. angle.

I've actually now narrowed the "issue" down a bit further, and found that the actual interaction (between the pushrods) resulted in a slight decrease in cyclic pitch (same for up and down, as the swash driver have been precisely aligned for the multi blade head).

I figured out, that I could use the Transmitter program mix, "ELE+-PIT." and make the small adjustment needed to basically eliminate the interaction and archive zero movement of the cyclic pitch during elevator stick input. So, yeah a small electronic manipulation of the system, is just what I have to accept, unless somebody can figure out, where I mechanically have failed to setup the System 88 correctly..

Thanks a lot for the inputs.

Robbe Nova Cuatro Gas/Nitro, Futura Nova Nitro, Futura SS Nitro, Vario Scale S300C/1002/21 Gas.

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12-04-2015 07:55 AM  32 months agoPost 8
Yeager

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Lisbon, Portugal

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Sparkhead,

Comparing your top view photo of the servos with my photo, I see that your pushrod from the collective pitch servo horn to the elevator servo ball (on the servo horn) is straight at 90 deg. and mine is not... Is that the issue that you're addressing?

Robbe Nova Cuatro Gas/Nitro, Futura Nova Nitro, Futura SS Nitro, Vario Scale S300C/1002/21 Gas.

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12-04-2015 11:05 AM  31 months agoPost 9
Sparkhead

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Melbourne Australia

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No it's not the pushrod your showing, it's the 4 pushrods on the rocking servos. The System 88 setup is the same on all of the later models and they all came with the servo horn doublers that you are using. Someone years ago refined the system slightly to get rid of the interaction problems and the fix was what you see on my heli of sorts.

Probably worth a bit of research on this forum as this is where I saw it but never implemented correctly. I moved onto different brands of helis and never really revisited my setup.

From memory what you will find with an original stock flybarred setup is that when you do a roll the elevator is introduced and the heli will pitch up at the end of the roll. Then if you do the fix as I have you get the rolling off to one side in a loop. So the fix only needs to be done on one of the servos but I'm not sure which one.


Mick.

Robbe & Futaba.

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12-04-2015 12:23 PM  31 months agoPost 10
Sparkhead

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Melbourne Australia

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If you go to page 22 of this Robbe section you will start to see the info on the interaction. Here is a good thread with some pictures etc.
https://rc.runryder.com/t216884p2/
You can see a photo of the drill jig as well.


Mick.

Robbe & Futaba.

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12-05-2015 02:25 AM  31 months agoPost 11
Yeager

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Lisbon, Portugal

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Ok, very cool, thanks a lot for the lead. I will head back on the pages and see what this brings me.

I have to remark, that with the ever so slight ELE-)PIT program mixing in the Tx, I can barely makeout any actual movement on the servo holders, and likewise with blade grips. Obviously the collective pitch servo are moving to compensate for the interaction.

Robbe Nova Cuatro Gas/Nitro, Futura Nova Nitro, Futura SS Nitro, Vario Scale S300C/1002/21 Gas.

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12-06-2015 08:47 PM  31 months agoPost 12
HeliAdict

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Texas

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From ramsters gallery

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12-07-2015 03:10 AM  31 months agoPost 13
Yeager

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Lisbon, Portugal

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Sparkhead and HeliAdict,

Thanks a lot for your replies. I've had a look "back into the past", and noticed, as Sparkhead said, that there was a lot of discussions going on back in around 2004 in this regard.
I've only just noticed this "interaction" now (2015), because of setting up the phasing for multi bladed heads I'm installing. I did not notice this small interaction when I first started flying the System 88 Cuatro's back in 2011, as those were with original fly bar heads and I was not performing flight maneuvers that would have disclosed the "interaction".

Having read some of the topics from back around 2004, and seen the mechanical solutions, I've decided that the mechanical fix is not going to be my route, despite otherwise always trying to setup my helis as mechanically perfect as possible. It would be to much of an amendment to the original design (though obviously not being perfect), and I've concluded (at this point) that the gain from that perfect mechanical amendment vs. the small electronic mixing, is not worth the effort.

What I'm not quite able to comprehend, just yet (or ever), is how the 3 axis gyro systems (say CGY750) and the minor Tx program mix will handle this "interaction" design flaw. Time will tell - when the machines gets flying. I'll do my best to report back - but unlikely to happen until mid 2017.

Once again to both of you for pointing me in the right direction, back to 2004.

Cheers,
Claus

Robbe Nova Cuatro Gas/Nitro, Futura Nova Nitro, Futura SS Nitro, Vario Scale S300C/1002/21 Gas.

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12-07-2015 09:17 AM  31 months agoPost 14
Sparkhead

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Melbourne Australia

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I fly a 2 blade FBL setup with a set of Milli 2 mechanics with both my BK117 and Royal and it flies fine for me but I don't do any 3D with either heli.

Good luck with the multi blade, I was looking forward to hearing how it went as I'm still toying with putting one on the BK117. There's a pretty good chance I'll get it done before you if you can't get it done before mid 2017. Or did you mean mid 2016?


Mick.

Robbe & Futaba.

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12-07-2015 02:35 PM  31 months agoPost 15
Yeager

rrApprentice

Lisbon, Portugal

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Mick.,

Sorry, but unfortunately while I'm residing in Hong Kong, I'm not planning on any flying of the helis - hence 2017 is correct at this point in time. Anyways, it's always nice to have something like that to look forward too..

Thanks for your replies, and please update on your BK117 progress!

Cheers,
Claus

Robbe Nova Cuatro Gas/Nitro, Futura Nova Nitro, Futura SS Nitro, Vario Scale S300C/1002/21 Gas.

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12-07-2015 09:59 PM  31 months agoPost 16
Sparkhead

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Melbourne Australia

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Where did you get that and do they have any more????


Mick.

Robbe & Futaba.

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12-08-2015 02:10 AM  31 months agoPost 17
Yeager

rrApprentice

Lisbon, Portugal

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The original Robbe four blade rotor head, I found just 2 weeks ago by doing either an ebay or google search (can't remember) for Robbe S2914, and it came up with ebay Italy. It was shear luck, that some Italian train collector shop had come across it, for all I can tell.
I have to say that I've been ridgedly and systematically searching the internet for the original Robbe heads, and was equally lucky to find the S2913 from a Swedish distributor six months ago, who only had that last one piece in stock.

I would be surprised if there from time to time, would not be one of these up for sale on ebay, though even more likely on the German ebay.de, as I've noted that a search on ebay.com, does not always include ebay.de items, which the seller has listed for sale in Germany only. I will let you know if I come across any, while doing my regular searches for Robbe spare parts!

Now, I've already installed a Vario 4 blade rotor head on one Cuatro ( though not yet test flown ). Vario Germany custom drilled the extra main shaft hole required, free of charge. Also the Vario head is bolted onto the main shaft in two places (the Robbe ones are only, like the flybare setup, bolted on in one place), so that's an added safety feature I like about the Vario. The Vario swash driver is also recommended, as opposed to the hard to find Robbe S2802 swash driver. Again the Vario swash driver has two individual screws, fastening to the main shaft, as opposed to one on the S2802.
As for the pod and boom Cuatro, the Vario head fits right in with linkages etc. Just as a reminder watch out for the Vario rotor head option of having one OR two rotor blade bolts mounting the blades. I chose the one bolt mount, just for blade commonality and availability.

There's spare parts available for the Vario setup, and basically nothing for the Robbe setup.

However, there is just something about originals, and that's my reason for taking on the Robbe accessories whenever possible.

Robbe Nova Cuatro Gas/Nitro, Futura Nova Nitro, Futura SS Nitro, Vario Scale S300C/1002/21 Gas.

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12-19-2015 04:25 PM  31 months agoPost 18
Ramster

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NJ

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A few years back I worked on a solution to sys-88's swashplate interaction. The new design involved eliminating the original swashplate anti-rotation bracket and placing a minimum of two new anti-rotation limiting brackets across two of the swash's 45deg opposing arms. This I believed would have helped separate the cyclic inputs. But when Robbe's heli division died, messing with Robbe helis felt somewhat necrophilic (-: so I stopped.I may have the details of this design saved somewhere.

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12-21-2015 05:22 AM  31 months agoPost 19
Sparkhead

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Melbourne Australia

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Mick.

Robbe & Futaba.

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12-28-2015 04:16 AM  31 months agoPost 20
Yeager

rrApprentice

Lisbon, Portugal

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Hi Ramster,

I've decided to not pursue the 100% mechanical interaction free setup, and go with a small electronic mixing instead (on the collective pitch). I'm going to be flying them with multi heads and 3 axis gyro, so I'm not sure I'll notice anything, after all.

Many thanks for offering to find the "old" design, but I should not be needing it this time.

Robbe Nova Cuatro Gas/Nitro, Futura Nova Nitro, Futura SS Nitro, Vario Scale S300C/1002/21 Gas.

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