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ProModeler Scorpion Power
Richardmid1

rrProfessor

Leeds, England

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Also I cant remember any gyro that does not have a rate mode .
CY SolidG. Awesome gyro!
.Tail servo is under less work and load when it's not correcting for ongoing mechanical trim error in addition to torque shift.
It is under the same load regardless of how it is set, there is always a constant load on the tail servo if the tail is stationary as it is constantly pushing against main rotor torque. It may have been different for very early HH gyros but not today's.

60% of the time, it works every time!

06-27-2016 07:51 AM
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Dr.Ben

rrMaster

Richmond, VA, USA

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As you wish. Do me a favor, though. If you are asked advice on tuning the tail on Futaba gyros, please don't suggest that mechanical trim does not matter. The gentleman that designed them has a different opinion.

Ben Minor

Team Synergy Team Futaba Team Kontronik USA
Progressive RC

06-27-2016 03:19 PM
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Richardmid1

rrProfessor

Leeds, England

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It may matter to performance but not the life of the servo.

60% of the time, it works every time!

06-27-2016 03:34 PM
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Four Stroker

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Atlanta

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This is a control loop design issue. If the guy who designed the loop says it matters, it matters. You could design a control loop that did not know or need to know where mechanical trim was. I am surprised that this is not the case.

06-27-2016 03:50 PM
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Dr.Ben

rrMaster

Richmond, VA, USA

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When Futaba released the GY520 gyro, the instructions stated to center the tail slider with 0 degrees of pitch in the tail blades. In testing problems immediately arose with inconsistent piro rate and even drifting issues, and the factory immediately instructed us to make sure we told customers to maintain established procedure to trim the tail first in rate mode. The reason for the inconsistent piros was not a rocket science concept either. When the tail is out of mechanical trim, the servo arm is immediately driven to varying degrees off center. Depending on the direction of the trim error, the resulting differential travel gives the gyro more to do as it crunches the numbers to maintain commanded yaw rate. I do concur with the point that the HH in a stable hover simply finds trim and hold the tail there and in doing so is under no greater load, but once you're flying around and doing aeros, and the system is fighting harder to maintain a consistent piro rate, then the tail servo is working harder as well. The gyro will drive the servo as hard and fast as it can to satify the control loop. The only thing the gyro knows is trying to maintain commanded yaw rate. If the tail is set up such that decrease performance is manifest, it's not because the tail and gyro are lazy. When whipping is observed, the gyro isn't keeping up, but it surely tries to, and that has to work a tail servo harder.

You can also noticeably change servo work level depending on how you balance mechanical and electronic gain. You can put a small wheel on the servo and run the electronic gain up really high. The tail will hold well (up to the point the arm is too small and travel is inadequate) but the servo also works pretty hard because the motor has to drive the geartrain further per unit of pushrod travel. If you go out a bit on the servo arm, you'll decrease electronic gain somewhat and have more mechanical gain, but then you get more pushrod travel per unit of motor and geartrain movement. We could debate the trade off of the mechananical advantage to the servo with a shorter arm versus a longer one and how that balances out against the motor being more active, but it the older days of coreless tail servos, I could surely heat one up quicker with high electronic gain and a short arm than with a longer arm and less electronic gain. Brushless servos forgive a lot of things, but good technique is comparatively timeless.

Ben Minor

Team Synergy Team Futaba Team Kontronik USA
Progressive RC

06-27-2016 06:14 PM
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Four Stroker

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Atlanta

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Mechanical differential sounds about right. Most heli's attempt to minimize the differential at the tail linkage. Trimming out in rate mode eliminates the differential at the servo wheel. Good practice.

06-27-2016 07:26 PM
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Jeff polisena

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westpalmbeachflorida usa

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Next

I stole it ,flew it and gave it back ;)

06-27-2016 07:44 PM
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Dr.Ben

rrMaster

Richmond, VA, USA

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I think we've murdered this horse, twice.

Team Synergy Team Futaba Team Kontronik USA
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06-27-2016 10:08 PM
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Richardmid1

rrProfessor

Leeds, England

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It may matter to performance but not the life of the servo.
It is down to the heli's tail design whether you have 0 pitch or some positive tail pitch when the slider is centered on the tail shaft. If the gyro manufacturers require the heli to be set with some tail pitch in rate mode but the heli manufacturers call for 0 pitch then you will never have a perfect tail setup.

60% of the time, it works every time!

06-28-2016 11:22 AM
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Four Stroker

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Atlanta

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The "designers" of model helicopters have never been aeronautical engineers. Mostly copy and paste or monkey see monkey do. But really it does not hurt anything to set the heli up in rate mode with servo arm and tail arm at neutral. Third times the charm.

EDIT: Well Dieter Schl├╝ter was an engineer.

06-28-2016 12:41 PM
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Dr.Ben

rrMaster

Richmond, VA, USA

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Ted Schnoonard I believe was too. And Taya san.

Ben

Team Synergy Team Futaba Team Kontronik USA
Progressive RC

06-28-2016 05:44 PM
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don s

Key Veteran

Chesapeake, VA

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And what headspeed should you be on when you set this mechanical rate dead horse stuff, b/c it changes with headspeed, and other things.

E820, Raptor G4N, X50F/E, E620, Forza 450, and some planks.

06-28-2016 07:46 PM
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Four Stroker

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Atlanta

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1) XCell - tail rotor on left. Pitch arm neutral at zero pitch.

2) Kalt - tail rotor on right. Pitch arm offset for hovering pitch at neutral.

3) Align - tail rotor on right. Standard pitch arm neutral at zero pitch.

4) Align - fancy multilink tail thing - Pitch arm offset in the OPPOSITE direction from Kalt ? I don't know what this is compensating for ?

Not much designer agreement ?

What happened to Taya ?

06-28-2016 08:28 PM
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Jeff polisena

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westpalmbeachflorida usa

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I've always went with models are designed to function at 1850 rpm so I figure if you can dial in at or close to then your good . Of course this is on nitro with motor tuning as well .I do same on electrics because that's how I learned when I started . After many years of building and setups I've learned tricks and tips plus an ear for getting a good safe setup ..

I find that the 'good enough ' 'going to crash anyways' mentality has been the norm and then leaves people wondering why the helicopter doesent fly rite .

Take info for what it's worth and do what you want with it. Info is not necessarily wrong but might help solve a problem .

I stole it ,flew it and gave it back ;)

06-28-2016 11:40 PM
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Dr.Ben

rrMaster

Richmond, VA, USA

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I think the last major heli design that Taya did was for TT - G4 series. Synergy squares the tail bellcrank with an average amount of pitch in the tail blades, not 0 degrees. Don, I trim the tail mechanically at the head speed at which I do most of my flying. My E5SS is pretty much single speed for lowish rpm 3D - 1525rpm. Jeff is surely correct. Equipment these days works ok with minimal effort. Most 750's I get a hand on for example have tails that hold pretty well, but it's amazing how much performance is left on the runway by not taking a bit of extra time to max out the tuning. This would apply to any brand of equipment, not just Futaba.

Ben Minor

Team Synergy Team Futaba Team Kontronik USA
Progressive RC

06-29-2016 12:09 AM
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Four Stroker

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Atlanta

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After some consideration, I think the CNC guy screwed up the Align multilink arm - the offset is in the wrong direction.

Most people didn't really appreciate the Concept 30. It was designed to fly like a then F3C ship. There was a time when I could do the entire FAI pattern (very simple back then) except for the rolling stall turn and of course the 180 auto. When it was "updated" to do 3D, it was an unstable pig.

Dr.Ben's analysis seems correct to me. Adjust the tail in rate mode for the rotor speed that you want it to fly best.

06-29-2016 01:15 AM
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coolice

Key Veteran

Northamptonshire, England

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Most people weren't around when the Concept 30 and a proper heli setup was needed. Most offering advice today rely more on the electronics to fix a poor setup than start with a good one in the first place. I've seen it many times.

With the tail neutral setup the old way was always to trim the tail in rate mode and it worked well. Then 3D came along and people switched to equal travel with zero centre, which worked reasonably well to.
Now it seems we've gone back to the old way on trimming against the torque in rate mode to get the best from the modern gyros and avoid over-shoots and bounces.
There are tricks to fix most mechanical design errors, the easy one is to flip the tail grips on some models to get the geometry better.

Ian

Ian Contessa
Team Robbe SchluterUK
Midland Helicopters

06-30-2016 08:24 AM
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Richardmid1

rrProfessor

Leeds, England

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I've always found zero tail pitch at neutral reduces over shoots and bounce back and gives more equal piro stop behaviour left and right. This is because in HH mode the servo will be offset in a hover to give some tail pitch against rotor torque, now as most helis have much more tail pitch available in that direction (against rotor torque) the servo has to travel equal or slightly more to stop a left rudder piro (usually the most sensitive and quickest stopping piro direction) and having the servo travel further adds delay and softens the stop. The opposite happens when stopping a right rudder piro so you get a sharper or more equal stop from right rudder piro. IF you set some tail pitch at servo neutral you have very little servo movement when stopping a left piro (very sensitive, high mechanical gain) but huge movement when trying to stop a right rudder piro resulting in a really soft stop and overshoot. So to summarise in most cases (airframes) setting zero pitch and servo neutral (90 degrees) means equal mechanical gain in both left and right rudder.

60% of the time, it works every time!

06-30-2016 08:42 AM
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icanfly

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ontario

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Doesn't gyro mounting for a nitro involve a piece of metal between two pieces of foam tape to act as a high frequency damper? Yes you have too much gyro tape under there. I have the sandwiched two thin pieces with metal between but I've also velcro strapped my ar7200bx on my nitro to secure it even better.

Where's the gyro mounted? In a place near or far from the main shaft, or the same distance from the main cog as the motor? It might be sitting on a harmonic hotspot on the chassis.

Too high gains in the gyro. Loose bearings somewhere, tt drive should be tightened up to the point of very slightly binding (no slop) and a dry lube used. Slop may be from the tube where it inserts to the beveled gears, nothing more. A thin piece of masking tape evenly placed around the tt ends may fix some of that, but not so much tape/shim the tube doesn't insert.

Mounting wise I discovered the further the gyro is mounted from the main cog the worse off the system will be resulting in hot overworked servos.

When I first had my nitro mounted with a gyro the servos heated up due to placing the gyro too far from the main cog and on a thin piece of aluminum bracket made to hold it, until I placed it right in front of the motor on a mounting plate (stock) did I realize placement and mounting method were very important.

In your bx there should be a section on tuning out vibes inherent with nitro models.

I thought I'd drop in because I experienced similar problems with my nitro model long ago and that this topic brings attention to monitoring a heli for signs of trouble on a regular basis.

And yes, get the 3s lipo with regulator going, 2s is just not keeping up with your high v demand rig, 4x hv servos plus gyro and rx/sat(s)? What else you got on there sucking power all at once? think about it.

06-30-2016 11:49 AM
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Richardmid1

rrProfessor

Leeds, England

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The BeastX and ar7200bx already have a heavy metal base so no need for additional weight for vibration damping.

60% of the time, it works every time!

06-30-2016 12:02 PM
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