align 3 bladed heads

[Tim@Align]

Originally Posted by rando

I asked Alan about it via facebook but so far no response.

If you want a response I would message Colin Bell on FB. He also has a 3 bladed setup.

[Atomic Skull]

Originally Posted by eBlade

Bought it, installed it on my T-Rex 700 stretch and here's my first hand report. The little "dog bone" pitch links are just too short. I can get only 18.5 degrees pitch one way but a whopping 48.5 degrees against the torque. This is simply unacceptable!

When I piro nose left, the tail will stop on a dime, but a piro to the right will bounce back about 10 degrees every time, regardless of tail blade size or head speed. Apparently 18.5 degrees is not enough to crisply stop even a medium speed pirouette.

If anyone has a different experience, please let me know. Right now, I will probably just go back to the stock 2 blade setup. Meanwhile, I hope Align will address this obvious design flaw!

Knowing Align they'll wait until all of the old flawed stock clears and then sell you a fix. With that in mind I came up with a fix of my own.



Details here:

https://www.helifreak.com/showthread...75#post7054275

[ticedoff8]

I looked at "AtomicSkull"'s solution for this odd asymmetrical L/R throw on the Align 3-bladed tail rotor.
And, it works.
It definitely results in equal L/R travel with 0-degree pitch when the pitch-slider is at the middle of its travel.
I tried it on mine using the parts recommended in his thread.

However, here is a thought:
This tail rotor system was designed for the 3GX and GPro.
This is important.
Why?
The GPro / 3GX do not want you to set the tail blades to 0-degree when then servo arm is set to 90°.
This is done on other FBL gyros (VBar, Beast, Skookum, iKON, Brain), but not the GPro or 3GX.

With the GPro / 3GX, when the servo arm is at 90°, you are supposed to fly the helicopter with the tail gyro set to "Rate Mode" and adjust the length of the tail rotor control rod's links to achieve a stable hover with the rudder stick centered.
Basically, cancel out the torque of the head while hovering.
This will result in the tail rotor blades being at 10° (or so) of pitch when the servo arm is at 90°
Then, set the TR gyro to "Heading Hold" mode and fly

I have not confirmed this, but my gut tells me that if I converted back to the original Align dog-bones, and then setup the tail as recommended in the GPro / 3GX style, I would end up with "equal" L/R travel.

As in:
If the hovering tail blade angle is around 10°, the R-max would be 48° (10° + 38° travel) and the L-max would be 28° (10° - 38° travel).

If you set this up using the FBL recommended method of setting the servo arm to 90° and then set the blade angle to 0°, I think that is where the problem is.

But, AtomicSkull's solution seems to make the Align 3-bladed TR work with those FBL systems that need the blades at 0°

[Atomic Skull]

Originally Posted by ticedoff8

I looked at "AtomicSkull"'s solution for this odd asymmetrical L/R throw on the Align 3-bladed tail rotor.
And, it works.
It definitely results in equal L/R travel with 0-degree pitch when the pitch-slider is at the middle of its travel.
I tried it on mine using the parts recommended in his thread.

However, here is a thought:
This tail rotor system was designed for the 3GX and GPro.
This is important.
Why?
The GPro / 3GX do not want you to set the tail blades to 0-degree when then servo arm is set to 90°.
This is done on other FBL gyros (VBar, Beast, Skookum, iKON, Brain), but not the GPro or 3GX.

With the GPro / 3GX, when the servo arm is at 90°, you are supposed to fly the helicopter with the tail gyro set to "Rate Mode" and adjust the length of the tail rotor control rod's links to achieve a stable hover with the rudder stick centered.
Basically, cancel out the torque of the head while hovering.
This will result in the tail rotor blades being at 10° (or so) of pitch when the servo arm is at 90°
Then, set the TR gyro to "Heading Hold" mode and fly

I have not confirmed this, but my gut tells me that if I converted back to the original Align dog-bones, and then setup the tail as recommended in the GPro / 3GX style, I would end up with "equal" L/R travel.

As in:
If the hovering tail blade angle is around 10°, the R-max would be 48° (10° + 38° travel) and the L-max would be 28° (10° - 38° travel).

If you set this up using the FBL recommended method of setting the servo arm to 90° and then set the blade angle to 0°, I think that is where the problem is.

But, AtomicSkull's solution seems to make the Align 3-bladed TR work with those FBL systems that need the blades at 0°

It shouldn't be 0 degrees at center, how do you have your tail set up like in the top image or the bottom one? The top is the correct way to set up the Align double jointed slider. When set this way with the two blade tail you get 8 degrees at neutral. Watch how the tail control arm moves and you'll see why this actually makes sense. The easiest way to get it right is to make the second joint of the control arm parallel with the tail sideplate.



EDIT: It's also buried in the back of the manual.



The neutral point with the new dogbone links should not be significantly different because the distance from the control point on the slider bearing (where the control arm connects) to the ends of the links is almost identical. I think it's about 0.5mm difference which probably puts the neutral pitch at around 6 degrees which is just about right for a no drift rate mode hover with a three bladed tail.

[ticedoff8]

The top picture is correct.
And, the description in the manual is correct

The 10mm is the starting point.
The final setting is made during the test flight with the gyro in Rate Mode and adjusting the length of the TR control rod to achieve a stable hover with no rudder input on the transmitter

[Atomic Skull]

Originally Posted by ticedoff8

The top picture is correct.
And, the description in the manual is correct

The 10mm is the starting point.
The final setting is made during the test flight with the gyro in Rate Mode and adjusting the length of the TR control rod to achieve a stable hover with no rudder input on the transmitter

You should not be getting zero degrees at neutral with the new links. I can't understand how this is possible because the distance from the control point on the slider where the arm mechanics is attached to the endpoint of the plastic control link is exactly the same. The amount of pitch at neutral and the overall pitch range of the tail should match the 2 bladed tail with the replacement links.

[RC/DC_5000]

But the most accurate way to get it right is to hover the helicopter in rate mode and adjust the linkage rod until the helicopter holds a heading on its own mechanical advantage. No electronic input from the gyro. That is true neutral.

The diagrams only get you close so you can hover and adjust only a few times. There is no absolute way that a measurement alone with actually hold true neutral in flight. Slight variations in motor power, RPM, weight bias/COG will require more or less tail thrust to counter torque and hold neutral.

If you're hovering at 1000 rpm and I'm hovering at 1700 rpm. Your tail slider will need more tail pitch to counter torque and hold a heading because the tail prop is generating less thrust from RPM. If you're using a two bladed tail and I'm using a three bladed tail, the pitch for neutral will be different because the thrust is different. The tail slider pitch is not universal.

[Atomic Skull]

Originally Posted by RC/DC_5000

But the most accurate way to get it right is to hover the helicopter in rate mode and adjust the linkage rod until the helicopter holds a heading on its own mechanical advantage. No electronic input from the gyro. That is true neutral.

The diagrams only get you close so you can hover and adjust only a few times. There is no absolute way that a measurement alone with actually hold true neutral in flight. Slight variations in motor power, RPM, weight bias/COG will require more or less tail thrust to counter torque and hold neutral.

If you're hovering at 1000 rpm and I'm hovering at 1700 rpm. Your tail slider will need more tail pitch to counter torque and hold a heading because the tail prop is generating less thrust from RPM. If you're using a two bladed tail and I'm using a three bladed tail, the pitch for neutral will be different because the thrust is different. The tail slider pitch is not universal.

Some FBL gyros e.g. Skookum want you to just set it to zero degrees and then set the neutral point electronically. Naturally these work better with helis that already have symmetrical tail mechanics with no built in pitch offset e.g. Gaui helis. But even on machines that do have a built in pitch offset (which is most of them) it will degrade performance with the Skookum if you don't set it to zero degrees pitch because that's what the software expects.

For that matter, all FBL gyros I've seen electronically set the proper neutral point electronically during the trim flight regardless of the mechanical center.

Many FBL gyros don't even have a rate mode anymore for example on the Vbar Neo rate mode has been removed.

[ticedoff8]

There is a lot of old posts about this.
When we made the transition from flybar equipped heli with only a tail rotor gyro to 3-axis gyros for FBL, the question was always was "do I still setup the tail the same way?"

I stopped doing it the old way, because I got lazy.

But, I think the old way yields a better mechanical setup.
I truly think the engineers at Align believe in the purity of the mechanics.
And, the GPro / 3GX are designed as stability augmentation systems for their airframes that have their roots in the flybar world.

On the bench, when the servo arm is set to 90° and the the TR blade angle is at 0°, it is easy to setup.
In flight, this setup will cause the servo to rotate quite a bit off the 90° point to maintain a stable hover (no pirouetting drift).
Think of that new servo arm angle and tail blade angle as being the "true center".
All tail rotor blade angles should be measured +/- from that new "true center".
But, the servo arm is already 10° or 12° rotated off mechanical center (90°).
That means that further rotation in that direction results in less "maximum" blade angle measured from the new "true center" as rotating in the other direction.

EG: Lets say you setup your tail such that at 90° servo arm, the tail blades are 0°.
At +/-30° servo arm angle (60° "lock to lock" servo travel), you have +/- 25° tail blade pitch
In flight, the heli hovers with +5° blade pitch and the gyro adds this as normal compensation.
The +5° is working against torque in a hover (upright or inverted)
In this setup, there is only an additional +20° pitch and a whopping -30° of pitch from "true center".

Now, set up the same tail using the "old school" method.
On the bench, you set the servo arm to 90° and you set the tail blades to +5°.
Then you set the +/-30° servo arm limits to +30° / -20
Now fly it and adjust to give it a stable hover.
You end up with an equal +25° / -25° of tail blade pitch.

This is the same "problem" that people have "solved" on Align's 2-bladed tail rotors by cutting the tail rotor control rod.
To get the 0° blade pitch, we would cut 5mm out of the CF rod.

I don't think Align made a mistake in the design.
The dog-bones are "correct" according to their design philosophy

But, I like the Associated Servo Spacers because I am lazy

And, I don't think most helis need the extra TR blade pitch anyway.
Once the angle of attack exceeds a certain limit, the blade stalls and you end up with a tail-blowout.

[RC/DC_5000]

I agree... Almost all of the gyros can work well without true neutral anyway. IKON, Vortex,CGY750, VBar, GPro, 3GX can still be set in rate mode for a true neutral mechanical hover though. I find without setting it.... that repeated tail leading loops... will not track as straight. The loop will continue to open up as you go. The gyro does not know what straight is. It only knows what's changed.

Its this logic. When the gyro does absolutely nothing.... the helicopter is going straight.

I don't doubt the new gyros are good enough to not need it. Technology is a daily miracle. The Neo has two different sets of multi axis sensors. Basically the new gyros are more accurate.

[Atomic Skull]

Originally Posted by ticedoff8

I don't think Align made a mistake in the design.
The dog-bones are "correct" according to their design philosophy

Yeah actually they did or else the pitch link endpoints would match the standard two blade tail which they do not. If you accept that they did not make a mistake with the three blade tail then you must also accept that the two blade tail is inherently flawed in it's geometry. (and also note that a three blade tail needs LESS pitch at hover not more)

So one is flawed and the other isn't, they cannot both be correct.

[Atomic Skull]

Originally Posted by RC/DC_5000

I agree... Almost all of the gyros can work well without true neutral anyway. IKON, Vortex,CGY750, VBar, GPro, 3GX can still be set in rate mode for a true neutral mechanical hover though. I find without setting it.... that repeated tail leading loops... will not track as straight. The loop will continue to open up as you go. The gyro does not know what straight is. It only knows what's changed.

There is no "true" neutral on a helicopter anyway, in forward and reverse flight the amount of tail trust needed changes. Also bear in mind that any tail precomp you add in the setup will figure into the adjustments you need to make for a rate mode hover which will throw off the tail mechanics.

You're better off forgetting about the "neutral" point and instead worrying about symmetry of resolution and mechanical gain in the tail mechanics which are two things that actually will have an impact on the performance of the tail control loop. Gaui has the right idea here get rid the the pitch offset and just make the mechanics symmetrical to begin with.

[vojta]

TOP 3+3 Speed



****. Align Speed Fuselage - the canopy does not fit on a TOP model
*.... Align Canopy Mounting Bolts
***.. Heli Option Quick Change Canopy Mount
***** Quick UK magnetic canopy mounting set
****. Align 800E PRO Landing Skid fluorescent
****. Align 3-blade rotor, ø 1.56m, 1900 RPM
****. Align 3-blade tail head
****. Align brushless motor Dominator 850MX (490KV) 5.1 kW (peaks 11 kW)
****. Align slanted main gear and pinion 112:12
****. Castle EDGE HV 160 Brushless ESC with Telemetry Link Spektrum XBUS
***** Spektrum AR7210BX Rx w/BeastX flybarless system w/SAFE technology
***** Spektrum telemetry TM1000 [Rx, ESC, GPS]

[Atomic Skull]

If you replace the radial bearings in the three blade tail with e.g. Avid or some other non stock bearings you should also replace the stock 8x10x0.3 shims with 8x10x0.2 ones or else the grips may lock up due to tolerance differences. The Align bearings seem to have a slightly narrower width than most other 6x10x3 bearings and that combined with the very tight tolerance can cause the grips to lock up when the screws are tightened up.

I replaced the radial bearings in mine with Avid ones and with 8x10x0.2 shims the grips are perfect with zero play. (Avid carries these shims so you can order them with the bearings)

[Solmanbandit]

Originally Posted by vojta

TOP 3+3 Speed

Just out of curious, why the speed fuselage with a 3 bladed head and tail? 3 bladed setups are not good for speed.

[vojta]

Maybe, it has been stated several times in other threads, that Align's Speed Fuselage is not optimized for speed flying at all. Personally, I prefer improvement of visibility due to the tail part of Speed Fuselage. As for 3-bladed head & tail, I've been just curious about its flight performance, and about its improved(?) gyro effect

[Solmanbandit]

Yea I don't follow the speed stuff. I have seen the 3 bladed head a few years ago and it was pretty cool.