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HomeScaleAircraftHelicopterScale Model RC Helicopters › tail servo.
04-18-2011 07:13 PM  7 years agoPost 1
munkey nuts

rrApprentice

wales uk

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ive got my vario huey, test flew it with a 9254 futaba tail servo but found it slow and sh*t really. is this common for a scale heli or do i need a servo with more torque.

i know there is a way to calculate the servo strength needed for the pitch etc, is there a way to calculate how much torque you need for the tail servo?

thanks for help

gareth

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04-18-2011 07:59 PM  7 years agoPost 2
coptercptn

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Mesa AZ. USA

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You shouldn't be having difficulty with that combination...I am running the same with no issues? Maybe move your links out and get some more authority? also I did notice a problem with mine early on and an increase in headspeed helped greatly...

Just a thought.

Home of the "Sea Cobra".....

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04-18-2011 08:32 PM  7 years agoPost 3
reddragon

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Brooklyn, N.Y.

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Something else is wrong somewhere. The S9254 Tail Servo is anything but slow. 0.06 sec/60° @ 4.8V

What gyro are you using? Is your set up bind free?

Wayne - Fly it like you stole it! You're in good hands with Runryder!

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04-18-2011 08:53 PM  7 years agoPost 4
BarracudaHockey

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Jacksonville FL

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Are you running a very low head speed and not getting enough tail authority?

Andy
AMA 77227
http://www.jaxrc.com

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04-18-2011 09:31 PM  7 years agoPost 5
PETER ROB

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Devon UK

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Tail authority
Gareth, just spent the last couple of weeks sorting out my huey tail
Forget all the calculators, and look at the basics
When I saw the control rod sticking out of the top of the tail in your build post I thought you may have problems
I have flexi drive and the golden rod (trade name)push rod for the tail pitch
My tail was was every where but where I wanted it, almost like I had too much authority
First thing I did was to put smaller blades on, similar to what you have fitted, still same problem
Chopper Jockey had a look and said that the control rod was pushing when it was working against torque, when the rod should pulling, this would stop any slack in the system
I changed the direction of the servo and gyro, this helped but did not cure the problem, also changed direction of the gearbox to get maximum travel against torque (my blades are on the opposite side to yours so you should not need to do this)
Looked at changing head speed but found I needed to stay between 1250-1280, any faster and the flexidrive started to wind up, any slower it made everything worse
Changed and repositioned the servo to a high torque one changed the gyro to a Futaba 401
Have a check on yours and see if any of my problems are similar to yours
Will take some photo's of my final solution, will post them tomorrow
Peter R

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04-19-2011 02:14 AM  7 years agoPost 6
Christopher J

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Kansas City, MO Californian lost in land of Oz

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I suggest checking for rod flex like Peter Rob mentioned, and also check for smoothness of operation. On my Huey build I used the Futaba 601 and servo that comes with it. I used the rod with the internal sheath and wire that came with the kit. I noticed that after I got the bends the way I wanted them and secured it in place it was smooth but a little "stiff" in movement until I lubricated it.

I'm inclined to believe your problem is the rod you're using.

Christopher J
same as I ever was
"Still all set & Flying the original"

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04-19-2011 03:55 PM  7 years agoPost 7
coptercptn

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Mesa AZ. USA

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Yes I can agree with the problems using the "Goldenrod".. You have to support it (hold it from flexing) about every 6" or so.. I made small mini bulkheads to hold mine and in one case filled the body with expanding foam... (But I wouldn't do that again..) If you can get in and watch the housing as you move the servo, just make sure it is not flexing..anywhere. Because if it is, without a load on it, all that movement will multiply when you are flying.

Home of the "Sea Cobra".....

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04-19-2011 04:47 PM  7 years agoPost 8
PETER ROB

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Devon UK

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push rod problems
Gareth, looks like you are not the only one experiencing similar problems, with flexing rods
On my Turbine Cobra I used the same "Golden Rod",, then put the rod and sleeve inside a length of thin wall brass tube, it only needed 3 secure fixings along it's length, never had a problem with it
My Huey is 30 years old, and the tail end is filled with foam, so I am not in a position to want to re-build the complete back end
Peter R

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04-19-2011 04:53 PM  7 years agoPost 9
coptercptn

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Mesa AZ. USA

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exactly what I did on my Cobra, Peter and have not had any problems ...but rebuilding with all that foam can be a challenge.. Don't ask me how I know

Home of the "Sea Cobra".....

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04-19-2011 05:03 PM  7 years agoPost 10
PETER ROB

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Devon UK

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direct push pull
Gareth ended with this combination
The servo is JR DS8425 at 11Kg, something that was laying around
The ball positions are dictated by the allowable space in the tail section
I did not notice any great changes in CofG, but I will be fitting a cockpit so that will compensate for any tail down syptoms there may be
I still have a small slot in the tail body section,which I have made a cover to hide, still to finish it when, I have finished all the other testing
Peter R

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04-19-2011 05:41 PM  7 years agoPost 11
coptercptn

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Mesa AZ. USA

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Very much the same thing I have on my Turbine CH-53.. except I used the Futaba BLS series servo. Rock solid.

Home of the "Sea Cobra".....

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04-19-2011 06:35 PM  7 years agoPost 12
munkey nuts

rrApprentice

wales uk

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thanks for the advice. i will try and move the ball link out a bit on the servo arm. is there a way to calculate how much torque you need for a tail servo?

gareth

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04-19-2011 06:38 PM  7 years agoPost 13
coptercptn

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Mesa AZ. USA

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you could use the fomula we used to use for horsepower when I worked @ Roush performance;
"A littles good, a lot is better, and too much is just about right"...

Home of the "Sea Cobra".....

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04-19-2011 06:53 PM  7 years agoPost 14
PETER ROB

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Devon UK

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Gareth,
it is not a calulation, that makes it work, it's getting the correct set up, there are too many variables for any one given formulea
Do a search for "moments about a force"
You can already find, what the output of the serv is, it comes in the servo box
thats my lot can not help you any more
Peter R

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04-19-2011 08:48 PM  7 years agoPost 15
munkey nuts

rrApprentice

wales uk

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i was always lead to believe that the servos for pitch should be 1.5 times the weight of the heli.
a 10kg helico-pter = 15kg of torque, i thought there may have been a guide for weight of heli or blade length. i can see what your saying peter, different headspeeds different size tail blades etc.

if a 9254 has been used on this setup before thats good enough for me.

thanks

gareth

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04-19-2011 09:24 PM  7 years agoPost 16
MattJen

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UK

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maybe just a further idea,
You may need to speed up your tail, I have found on both my scale machines and my Predator as the weight has increased so has the torque,but cannot run too a high a head speed due to size of blades and weight of them,and remain within in a safe calculated limit of the head.

As baracuda has said, you may need to look at the head speed you are running, if your tail is weak in authority and you cannot increase the head speed due to the limits of the flexi drive then your only option maybe is to speed up the tail using speed up gears or run larger wider tail blades.

There is always a way round it..
what can give you the confidence is there are people with the same setup running it well, but if you are using larger or different blades, or running a different head speed to theirs the result may vary.

On my predator wren i am using a 9254, which was fine for a 90 size engine, but as i added weight with the turbine I needed to by a set of speed up gears, to give the authority i needed..

it is just an idea matey maybe one worth trying if it is possible.

Good luck hope to see you at some fly inns

Matt

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04-19-2011 10:02 PM  7 years agoPost 17
coptercptn

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Mesa AZ. USA

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just so you know
i am flying that exact machine...Vario huey w/benzine mechanics converted to electric and 9254 on the tail with a 401 gyro. 9202 cyclics.. It flys great..

Home of the "Sea Cobra".....

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04-19-2011 10:38 PM  7 years agoPost 18
BarracudaHockey

rrMaster

Jacksonville FL

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If its the Benzin then thats the same gyro/servo I have in my Jet Ranger and it flys just dandy even at 1050 on the head

Andy
AMA 77227
http://www.jaxrc.com

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04-20-2011 04:32 AM  7 years agoPost 19
Christopher J

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Kansas City, MO Californian lost in land of Oz

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Same Huey for me as well (before trading it) 9202's on cyclic, 815mm mains rotating at 1150-1200 with plenty of tail.

Christopher J
same as I ever was
"Still all set & Flying the original"

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