WHY DOESNT MY TAIL HOLD????

[noguy]

Hey I hope someone can help me out here. My mini Titan is my first heli with quality electronics. I am currently using a 401 with a analog servo on my tail. It performs excellent in every aspect but one. If I piro it is fast and when I let off BAM! It stops right there with no wag. Holds dead on except for.....

Well the problem is that in fast backwards flight it doesnt hold. It will start to lose position a little and then once it moves so far to the side it weather vains and spins the heli around. I can tell that the gyro is fighting it all the way but cannot overcome the wind drag of the fast reverse flight. I am only running 2600-2700rpm headspeed right now as I havent upgraded to CF main blades yet. Is the tail short on uhmph because it just isnt spining fast enough. Will it do better if I get my rpm's up???? What is wrong with my tail? please help.

Thank You, Noah

[BarracudaHockey]

Fast backwards is hard on a good setup, running a slow servo on the tail wont help matters.

[noguy]

What I am wondering though is what aspect of my setup is causing the lack of authority
My mechanical setup is spot on.
My servo specs are as follows:
Weight : 9.4g/0.36oz
Torque : 4.8V 1.3kg-cm / 17oz-in
Speed : 4.8V/0.09sec
Size(mm) : 24.5x11.5x22.5
Size(inch) : 0.98x0.45x0.90
Motor type : 3-Pole Ferrite
Gear type : Plastic
Ball Bearing: Single, Top

This servo is very fast so I am wondering if it is the lack of tourqe that is not allowing the tail blades to hold their pitch under extreme load cause a lack in thrust? Or is it just that the thing needs to be spinning faster?

I am thinking along these line because as the tail gets off to one side, I cannot even bring it back around with rudder input. Its like my tail has no guts.

Thanks again, Noah


Is ther a critical velocity in say sideways flight where the tail simply cannot make enough thrust to hold position?

[TT_Felix]

Let's try carbon rudder linkage rod . The stock steel wire act like a spring under loading . :?

[noguy]

What I am wondering though is what aspect of my setup is causing the lack of authority
My mechanical setup is spot on.
My servo specs are as follows:
Weight : 9.4g/0.36oz
Torque : 4.8V 1.3kg-cm / 17oz-in
Speed : 4.8V/0.09sec
Size(mm) : 24.5x11.5x22.5
Size(inch) : 0.98x0.45x0.90
Motor type : 3-Pole Ferrite
Gear type : Plastic
Ball Bearing: Single, Top

This servo is very fast so I am wondering if it is the lack of tourqe that is not allowing the tail blades to hold their pitch under extreme load cause a lack in thrust? Or is it just that the thing needs to be spinning faster?

I am thinking along these line because as the tail gets off to one side, I cannot even bring it back around with rudder input. Its like my tail has no guts.

Thanks again, Noah


Is there a critical velocity, say in sideways flight where the tail just doesnt have the thrust to hold to the side?

[Wheelhaus]

The problem sounds like it's due to one or all of three things...
One, servo speed.
A .09sec transit is very quick, but standard digital tail servos are down to .05sec. This is critical for hard flying since the servo needs to be able to react instantly.

Two, reaction time.
Analog servos react slower than digital servos because the internal computers run slower. Digitals can react quicker because the gyro can utilize a faster framerate to send information, kind of like comparing a 200mhz computer to a 1ghz computer. The 1ghz can simply process information quicker.

Three, tail authority.
This is most likely the problem, but don't discount the other two.
This has nothing to do with the first two, and nothign to do with which servo and gyro you use, but it does have everything to do with how much thrust the tail can generate. There's three things that affect this on the tail... RPM, pitch, and disk area. Increasing any one of these will increase the amount of power the tail can generate. The e620 comes with flexible plastic 85mm blades, try some 92mm or 95mm carbons. Being stiffer they will flex less, and being longer they will grab more air. Make sure the tail has full throw in both directions, and also try upping the headspeed (since it also determines tail rpm). Many tail problems can be resolved by simply running the drivetrain faster. I wish TT would offer different tail belt lengths and drive pulley sizes so we can fine tune the tail rpm seperately from the main rotor...

If you use longer blades, you will want to buy a longer tail fin or cut your own to keep the blades from touching the ground.

[noguy]

Wheelhaus,
Thanks tons for the great explanation. This is very helpful. Your the man.
:noteworthy
I have already moved to a little slower digital servo (the trusted s9650). And I have been playing with higher headspeeds now that I have some good main blades.

Thanks a ton, Noah

[murp]

Most likely the lack of torque from your servo and perhaps too low a gain setting on your gyro. The s9650 is pretty quick if run at 6.0 V (spec... 6.0V 62.5 oz-in. 0.11 sec/60° ) and has decent torque as well. It is a bit of a slouch at 4.8V though and you will probably have to use some delay to get a good response.

[noguy]

Yeah I am at 6v.... the tail i much better now...however my piro rate is much slower with this servo for some reason????? :dontknow

[LITHIUMSTATIC]

Is your subtrim for your rudder at 100%?

[murp]

Do you have your endpoints at their max? Your endpoints determine the piro rate. I usually start at 100% and increase from there until I get the piro rate I want. You can also use the endpoints to make sure you get the same maximum piro rate in both directions.

[noguy]

"TT_Felix Let's try carbon rudder linkage rod . The stock steel wire act like a spring under loading . :? "

Felix,, I missed that post somehow...Where do I get one? the teelone is not very rigid at all.


Lithium & murp, Yes my epa & subtrim are at default setting.

I remember now reading that the epa will control piro rate.... thanks for the reminder. It just seems a bit wierd that there was such a huge difference in the piro rate between the analog servo I had before and the 9650...

Thank you guys again, Noah

[LITHIUMSTATIC]

That is really odd...... I use a 401 & JR DS3400G with the stock linkage rod and mine piros crazy fast and the tail holds like a rock no matter what I do. I've heard of using the T-Rex450 linkage rod..... maybe try that and see if it helps.

[noguy]

My tail holds and performs great now with the 9650, best tail I have flown . The analog servo I had on at first would piro stupid-fast.
The 9650 (only changes were: raise travel-limit a couple points and selected digital servo) makes the heli piro at a much slower rate. It is still plenty fast just not stupid-fast(which is much faster).

[TT_Felix]

Carbon rubber linkage rod from Align should be good . I DIY the linkage rod with the stock Tail Support (PV0752) . As the carbon rod is so thick and it has no chance of bending .

[LITHIUMSTATIC]

Let me know if that helps..... If it does I'm with you on that mod.

[Bunter]

Carbon rubber linkage rod from Align should be good . I DIY the linkage rod with the stock Tail Support (PV0752) . As the carbon rod is so thick and it has no chance of bending .

Do you have a part number for the Align carbon rudder please, I can't seem to find it.

Cheers

Bill

[EricW]

I made my own carbon rod.
Very simple to make.
Just got a 2.5 mm carbon tube with a 1.3mm inner diameter from my LHS.
Cut a piece of the carbon tube the same length as the stock rod without the threaded ends (262 mm on mine).
Rolling it under a X-acto is the easiest way to cut it.
Cut the threaded ends + 10 mm extra from each end of the stock steel rod.
Then Epoxy the pieces of steel into the carbon rod.
This way you can use the standard links and have a very clean result and it works great sofar.

Eric

[Bunter]

I made my own carbon rod.
Very simple to make.
Just got a 2.5 mm carbon tube with a 1.3mm inner diameter from my LHS.
Cut a piece of the carbon tube the same length as the stock rod without the threaded ends (262 mm on mine).
Rolling it under a X-acto is the easiest way to cut it.
Cut the threaded ends + 10 mm extra from each end of the stock steel rod.
Then Epoxy the pieces of steel into the carbon rod.
This way you can use the standard links and have a very clean result and it works great sofar.

Eric

Thanks Eric, top tip, I've made a replacement as you described.

Cheers

Bill