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HomeAircraftHelicopterHelicopter Main Discussion › FF and Piro problem
04-24-2009 11:33 PM  9 years agoPost 1
stocky

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Taxachusetts

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TREX450SEV2
Futaba 401 Gyro & 9254 Tail Servo

I have a small problem with doing a piro in FF, not even Fast FF,
When I am in FF and give left rudder (nose left) to do a piro the tail hangs up for the 1st 45 degrees (like the wind is resisting against the tail vert fin) then it kind of seems to overcome this resistance and the rest of the piro is OK.

The heli piro's fast when in a stationary hover and seems locked in in all other respects.

I know the 401 is not constant rate but I am 100% that the heli should handle this better than it does.

Any ideas how I can make this better (lose the delay into the piro) ?

Thanks

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04-24-2009 11:41 PM  9 years agoPost 2
Mike Bilyk

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Tulsa, OK - USA

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buy a better gyro.

sell the 401.

AMA # 617778
Team MasterCard

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04-24-2009 11:58 PM  9 years agoPost 3
stocky

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Taxachusetts

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I know the 401 is not the best now but has been the standard for a long time.
I have seen people with 401's without this issue so I am reluctant to just blame the gyro off the bat.
If this was such a problem with the 401 I would have expected much more griping about it on RR etc.

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04-25-2009 12:08 AM  9 years agoPost 4
Yug

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UK. Herts

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Sounds like a binding problem in the control linkage.

Vegetable rights and Peace

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04-25-2009 12:11 AM  9 years agoPost 5
stocky

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Taxachusetts

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Thanks Yug.

I have a CF encased push rod so no push rod guides to bind and I just checked the linkage and no binding in the tail assembly and it is well lubed with tri-flow., any looser and it would be sloppy.

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04-25-2009 12:17 AM  9 years agoPost 6
Yug

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UK. Herts

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Interesting problem then. I use a 401 and 9650 on my 450 and it's bloody amazing; piros very consistent even doing high altitude rippers. The 9254 should be even better than the 9650 so I'm bound to thinking it may have something to do with your tail blade balance causing binding of the pitch fork. Whats your head speed ?

Vegetable rights and Peace

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04-25-2009 12:24 AM  9 years agoPost 7
stocky

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Taxachusetts

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Head Speed,

I knew someone would ask, it is so long ago since I set it up I cant remember, It flies OK (apart from this issue)so I didn't mess with it. I can't now even remember the pinion size or motor Kv to calculate it.
I have a tack so I will find out tomorrow.

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04-25-2009 12:27 AM  9 years agoPost 8
Yug

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UK. Herts

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Another tack - Is your heli noticably whippy in piro circles ?

Vegetable rights and Peace

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04-25-2009 12:50 AM  9 years agoPost 9
stocky

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Taxachusetts

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Hi Yug,

Either it is too dark now for the tach or my head speed is 5780 rpm
noticably whippy in piro circles
Whippy ???

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04-25-2009 01:01 AM  9 years agoPost 10
Yug

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UK. Herts

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5780 - ouch
Whippy - the piro rate is uneven in flight. Lats say you are flying in a horizontal straight line while piroing, with a consistent rudder input, the piro rate should be consistent. When the tail becomes whippy, it will fight against forward speed (ie, slow down as the tail moves towards the forward vector) snd suddenly whip round as the heli acquires a nose in forward attitude.

Vegetable rights and Peace

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04-25-2009 01:03 AM  9 years agoPost 11
stocky

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Taxachusetts

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YES YES, Exactly!!, you did a better job there of describing my issue.

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04-25-2009 01:04 AM  9 years agoPost 12
Al Miessner

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Virginia Beach, VA

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stocky
this sounds also like three possible solutions
1) the limits are not set correctly the servo should take it from end to end on the tail shaft right before it hits and binds.

2) if your servo horn is too long and causing too much strain.
should be around 12mm give or take not likely though you would have more tail issues than that

3) your delay is too high. set the delay to 0 because you are using the 9254? sure you don't mean 57 . your using a full sized tail servo on the 450?
and double check you have the DS selected for digital servo on the 401.
i flew the 401 a long time and never had that issue

someone already mentioned HS if that is too low it would cause a delay/ hang up all the way through almost 120 deg rotation in FF.

GrandRC Team Pilot/Team NINJA pilot Futaba 8FG (2X) Trex 700E DFC
Trex 450 Pro CGY750

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04-25-2009 01:41 AM  9 years agoPost 13
stocky

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Taxachusetts

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1) the limits are not set correctly the servo should take it from end to end on the tail shaft right before it hits and binds.
Yes, I have them set that way
2) if your servo horn is too long and causing too much strain.
should be around 12mm give or take not likely though you would have more tail issues than that
Just measured it, the ball is in the most inboard hole on the arm, and is 9mm from ball center to servo spline center
3) your delay is too high. set the delay to 0 because you are using the 9254? sure you don't mean 57 . your using a full sized tail servo on the 450?
and double check you have the DS selected for digital servo on the 401.
I got the servo part # totally wrong. It is an S9650 I just checked, The DS switch is set to on and the delay is at zero.

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04-25-2009 01:57 AM  9 years agoPost 14
VooDooX

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San Francisco Bay Area CA, US (San Mateo)

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check for loose belt or slipping grab the head and twist the tail if any play fix it could be the tail slipping till it got under enough load to catch mine did this a few times also make sure your expo isn't too high that could make it feel bad also

Velocity 50 "99.9999999999999% of an atom is empty space." also 01001000 01001001

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04-25-2009 02:14 AM  9 years agoPost 15
stocky

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Taxachusetts

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check for loose belt or slipping grab the head and twist the tail if any play fix it could be the tail slipping till it got under enough load to catch mine did this a few times also make sure your expo isn't too high that could make it feel bad also
OK, I can get the belt to slip if I hold the tail and crank the blades but I have to turn real hard, the belt tension seems OK, how hard I turn it is subjective and I don't know if what I consider turn hard is the same as what you would think.
I guess I will tighten the belt a bit more and see how it goes tomorrow.

Expo on the rudder is 4% (JR9303)Just enough to not induce rudder accidentally with collective.

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04-25-2009 02:28 AM  9 years agoPost 16
jphilli

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Atlanta, Ga.

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Sometimes temperature changes can cause gyros to act funny in regards to gain. Try increasing the gain until the tail hunts then back it off a few clicks. A low gyro gain can account for a whippy tail.

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04-25-2009 02:59 AM  9 years agoPost 17
stocky

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Taxachusetts

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Now there's a thing, my gain is set low at 47% more and I get wag.

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