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HomeAircraftHelicopterBeginners Corner › Controlling tail rotor
08-09-2009 06:08 AM  8 years agoPost 1
dipling

rrNovice

Valley Village, CA USA

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I have a problem controlling the tail on my mini titan e325.
For test purposes I have taken the gyro out, with rudder stick in neutral position my tail rotor blades are straight (0 pitch) and I can control the pitch both way to full extend, but when I try to hover I can't make it turn clockwise even when the rudder stick is all the way to the right. The heli turns counter clockwis.
Can somebody tell me please what is wrong?
Thanks

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08-09-2009 07:20 AM  8 years agoPost 2
Aaron1100us

rrApprentice

Cedar Rapids, Iowa

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Are your blades spinning the right direction? Do they change pitch in the right direction? I'd hook up your gyro in rate mode and set neutral pitch at about 7 degrees.

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08-09-2009 08:45 AM  8 years agoPost 3
dipling

rrNovice

Valley Village, CA USA

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Yes it rotates in correct direction, the belt tension is fine.
I noticed this sympton when I had the gyro on, so I took it out to analyze the problem. I can see that the pitch is at maximum but it still tends to turn CCW, but I release the throttle stick ank keep the rudder command at max for CW it does spin 1 or 1.5 turns clockwise.
I will try tomorrow to follow your advice and see what happens.
Thanks

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08-09-2009 08:59 AM  8 years agoPost 4
twistedrcpilot

rrNovice

Houston, Tx - USA

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Revo adjustment backwards on your radio?

Also, rudder should never be zero.

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08-09-2009 03:28 PM  8 years agoPost 5
BrunoBL

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Pomerode, SC, Brazil -26.71, -49.17

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If you do in fact have full-right rudder and still the heli yaws left, then maybe your headspeed is too low, not giving full tail rotor authority?


...Bruno.
Spectra G on Avgas 100LL, Jewel generator
T-Rex450SE V2
DX7

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08-09-2009 06:49 PM  8 years agoPost 6
dipling

rrNovice

Valley Village, CA USA

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I notice the opposite effect. At low speed (low enough to stay on the ground) I can controll the tail. It takes less command for CCW, but 100% of commmand for CW. It is at higher speed that CW control is not effective. It was fine before I changed the main rotor shaft. Everything was put together according to manual.
I also tested the rudder control by taking the main rotor blades off. With main blades off the rudder cntrol is fine in both directions without showing any preference for either direction starting at low and going to full speed.

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08-09-2009 06:54 PM  8 years agoPost 7
BrunoBL

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Pomerode, SC, Brazil -26.71, -49.17

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I notice the opposite effect. At low speed (low enough to stay on the ground) I can controll the tail.
This is because as you are still on the ground and not much lift is requested from the main rotor, torque is still low and more easily overcome. When you get in the air, torque is much higher and you need good tail rotor authority. One possible reason of not having this authority is low (but enough to fly) headspeed. Have you tached your rotor yet?

Also, your tail rotor/servo mechanical setup may be off.


...Bruno.
Spectra G on Avgas 100LL, Jewel generator
T-Rex450SE V2
DX7

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08-10-2009 06:14 PM  8 years agoPost 8
dipling

rrNovice

Valley Village, CA USA

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Tail servo is fine, this the first thing I checked and I get a full swing both way (up to mechanical stop in both direction).
Yesterday I took the main shaf out and rechecking all the links I also like to balance the blades (I just weigh it) when I get a balancer.
I haven't measured the RPM, I don't have a tach.
I will post some more results, when i put everything back together.
Thanks

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08-11-2009 02:58 AM  8 years agoPost 9
fenderstrat

rrProfessor

Aston,Pa

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start from scratch and verify EVERYTHING dont just assume

tail blades on properly,dont laugh people have done this

tail blades spinning in proper direction,the forward blade spins up into the main rotor

verify there is only 1 twist in the belt/belt tension,teeth on both pulleys/pulleys are not slipping

servo is working in the proper direction,right rudder moves servo arm forward

I dont see how this is headspeed related,on either of my MT's even when spooling up you should be able to control the tail
It is at higher speed that CW control is not effective. It was fine before I changed the main rotor shaft. Everything was put together
if you are loosing tail authority as the headspped gets higher something is slipping,or mechanically out of adjustment,you said yourself it was fine till you changed the mainshaft,something is not the same

did you have a crash?check the pin that holds the tail drive gear on the tail drive shaft

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08-11-2009 05:04 PM  8 years agoPost 10
BrunoBL

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Pomerode, SC, Brazil -26.71, -49.17

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I dont see how this is headspeed related,on either of my MT's even when spooling up you should be able to control the tail
Low HS is indeed quite possible (not saying it is indeed his problem).

EDIT - Fixed the above paragraph, got garbled up somehow. The edit didn't change the meaning.

As I have already said, when you are on the ground spooling up, the main rotor is not yet generating a lot of torque, because at low pitch it is not yet generating a lot of lift. Even you are already at or near take-off RPM, torque is ultimately still low because lift is still very small (most of heli's weight is on the ground). When you add collective and the rotor's lift is increased to the point of lifting the heli, THEN torque goes up significantly, even if RPM is the exact same as just before lifting off.

In the scenario I described in my other reply, a low head speed (thus low tail rotor RPM) could potentially result in a situation where you need high main blade pitch just to keep hovering, and high tail rotor pitch just to keep from yawing left, with little margin for additional right rudder authority.

I hope it is clearer now.


...Bruno.
Spectra G on Avgas 100LL, Jewel generator
T-Rex450SE V2
DX7

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08-11-2009 11:03 PM  8 years agoPost 11
fenderstrat

rrProfessor

Aston,Pa

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you took my statement out of full context,as right after, I quoted the original poster who has said the problem gets worse at higher headspeed.so if more headspeed is not helping,headspeed is most likely not the problem.

if you are up at a hover and have almost no tail authority in one direction,its most likely something mechanical

now headspeed could be right but his pitch curve is wrong,but again,that is a mechanical/radio thing

but he said all was well till he changed the mainshaft,which once again leads to mechanics

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08-11-2009 11:16 PM  8 years agoPost 12
Kentoby

rrApprentice

Seattle area

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Same thing happende to me on my 450...
Move the tail blade assembly more outboard on the shaft so you get more pitch. Keep in mind, the heli will rotate much more easily in the opposite direction that the main blades rotate but the tail requires more pitch to yaw the heli in the same direction that the main blades rotate in. Again slide the assembly outward on the tail shaft a bit and this will do the trick (assuming the servo is moving the pitch control enough).

KT

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08-12-2009 01:16 AM  8 years agoPost 13
BrunoBL

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Pomerode, SC, Brazil -26.71, -49.17

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fenderstrat,
you took my statement out of full context,as right after, I quoted the original poster who has said the problem gets worse at higher headspeed
At the risk of turning this into an uninteresting dispute, I will try again, and in the process show you why I did not take your statement out of full context.

My reply was in response to this:
I dont see how this is headspeed related,on either of my MT's even when spooling up you should be able to control the tail
The above is self-contained, not in need of context. But, even in the context of the OP's saying that the problem occurs "at higher speed", what RPM do you suppose he meant? It was "higher", but was it high enough to rule out a low RPM situation? Who is to know, not even the OP knows his RPM yet, he didn't tach the heli. Additionally, your heli spooling up on the ground cannot be used as reference or as an example for another heli in hover, as torque is entirely different in both situations. *That* was what I replied to.

Not enough tail rotor authority may have many origins, one of them being low RPM. Having tail rotor control on the ground but not enough authority in the air is consistent with low RPM for the reasons I have already said on this thread.

Of course, low RPM is only one of many possible causes, I wouldn't be surprised if his problem is caused by something else. All I am saying is that this is a possibility.

Note that I closed my other reply (the one you responded to) with "could" and "potentially". By no means I presumed to know what the problem was, I have no crystal ball. I offered the low RPM scenario as a possibility.

Yet again, I hope to have cleared it up.


...Bruno.
Spectra G on Avgas 100LL, Jewel generator
T-Rex450SE V2
DX7

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08-12-2009 02:15 AM  8 years agoPost 14
fenderstrat

rrProfessor

Aston,Pa

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I understand exactly what you are explaining but consider this.the original poster said the tail did NOT have this problem before he changed the main shaft.so if the headspeed was not the issue before(i.e.tail was holding) why would it be an issue now.

we are not talking about lack of authority,we are talking about almost no tail control at all in one direction,two different things.something is most likely not functioning properly mechanically

at one point I had one of my MT's set up for max flight time,an 11T pinion and tame throttle curve,but the tail still held in both directions,not as crisp as with the 13t and 90% throttle curve,but it held like a rock in a hover

we can go back and forth and speculate all we want,could it be headspeed possibly yes,I am not saying its not possible but is it likely?I would check mechanical before i spent time trying different headspeeds,thats all i am saying.regardless,we need more info from the OP.why was the shaft changed...crash?he hasn't answered any of my questions so without any more info,we are just going in circles

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08-12-2009 02:39 AM  8 years agoPost 15
BrunoBL

rrKey Veteran

Pomerode, SC, Brazil -26.71, -49.17

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without any more info,we are just going in circles
I am getting dizzy already!
More info from the OP is of course needed. He doesn't seem to have a tach, but if he flies with other people maybe he can borrow one and put the RPM issue behind.
set up for max flight time,an 11T pinion and tame throttle curve,but the tail still held in both directions,not as crisp as with the 13t and 90% throttle curve,but it held like a rock in a hover
Now THAT'S an example. Your hovering heli vs the OP's hovering heli. Point taken. I still need his head speed, though...

When I mentioned RPM in my other replies, I meant some abnormally low head speed, not just a low-ish one, so I wasn't talking about trying different RPMs, but just checking once, to see if it's within reasonable range for his heli. Just a quick check would be enough to confirm or move on to other ideas.

Whatever his problem is, I do hope he gets it sorted soon. It is no fun to stumble on problems when wanting to fly.


...Bruno.
Spectra G on Avgas 100LL, Jewel generator
T-Rex450SE V2
DX7

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08-12-2009 02:43 AM  8 years agoPost 16
fenderstrat

rrProfessor

Aston,Pa

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alright DIPLING,we are waiting,info man we need info. this will drive me nuts too,I like to find out what the fix was.even if it is headspeed i'll trade being wrong for knowing what the fix was

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08-12-2009 03:03 AM  8 years agoPost 17
BrunoBL

rrKey Veteran

Pomerode, SC, Brazil -26.71, -49.17

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...Bruno.
Spectra G on Avgas 100LL, Jewel generator
T-Rex450SE V2
DX7

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08-12-2009 01:19 PM  8 years agoPost 18
kangarooster

rrApprentice

Orlando Fl-USA

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I think it is too much pitch causing drag and low headspeed.
Recheck the head setup.

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08-14-2009 06:28 AM  8 years agoPost 19
dipling

rrNovice

Valley Village, CA USA

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Thanks for all these informative posts. As I reported I am waiting for my balancer to arrive and I ordered also a second kit so I can compare.
I sill don't undrstand why RPM number is so important for this particular problem.
Isn't it so that the higher the RPM the more tail rotor pich is needed to counteract? So if my max tail pitch can't stop the heli from spinning at low RPM than it wouldn't stop it at higher.
Thanks

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08-14-2009 07:29 AM  8 years agoPost 20
dipling

rrNovice

Valley Village, CA USA

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I just measured the RPM: rotor rpm approximatetly 3000 RPM when the throttle stick is 3/4 up.
Next I want measure the ratio (or calculate) of main/tail RPM and see if it stays constant when I change the speed (belt/gear problem).

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