RunRyder - Tail Rotor Torque Question

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Bergen R/C Helicopters > Tail Rotor Torque Question

jjones
Senior Heliman
Location: Pendleton, Oregon

For you gasser experts, I am having something weird happening to my tail rotor. I have it set up with the new ofset tail blade grips, 105mm v-blades, 700 mm mains, and a 502/9253 servo on the tail. I go into head holding and am trying to eliminate the rotation of my heli caused during aggressive climb-outs and descents.

I go into head holding and climb aggressively and it appears to not have quite enough tail compensation... I have mechanically adjusted the tail slider to allow for slightly more pitch that way, thus eliminating the climb-out problem, but them I have the same problem during descents. The tail will limit out trying to compensate and then spin slightly as it is out of tail compensation.

Any suggestions why I am needing so much tail, both in climb-outs and descents? Or is it something inherant to all gassers with lots of torque? I checked my rpms and they are fast enough, I know that can cause some weird torque and not enough tail speed.

Would a different gear ratio speed the tail up a bit? I believe my tail gears are 16 tooth... I start to do tumbles and the aggressive torque from the engine causes the tail to spin around during this manuever as well.

Just seems a bit sensative on the adjustments...

Josh Jones
Pendleton, Oregon

04-01-2003 Over year old.

HOMEPAGE

Chris Bergen
Key Veteran
Location: location

Good question to post.

You are correct, I believe, that your problem stems from the tail not turning fast enough. I am also running the V-Blades on the tail, but I'm using a 401 with 9252 servo.

The only time I can get the tail to break loose is when I let my rotor speed (main) get too low. Of course the tail speed is also then getting too low. I am running my head speed at 1700 or slightly higher.

Notice I am now running a 9252 servo on the tail. This is due to the 9253 servo giving up the ghost out in Las Vegas. I figured out it was the servo when I had no left turn in forward flight, and the tail was prone to breaking loose in hard maneuvres. (suggest you check servo)

Also, since this is a low torque servo, Insure that there is no binding whatsoever in your tail pitch change mechanism.

You didn't mention what the gain settings are for the gyro. Too low gain? Maybe?

Keep us up to date on how it works.

Chris Bergen

04-01-2003 Over year old.

Malorie
Elite Veteran
Location: Paw squared, MI

Are you running the belt drive or touque tube drive? I know the belt drive is a bit slow for aggressive 3D.

I agree with Chris, the 9253 is VERY VERY sensitive to ANY binding. I make sure that the tail linkages have ABSOLUTELY no binding or resistance. The tail on my gasser does kick a touch when I transition from posative to negative, but nothing extreme, maybe a few degrees. I'm using the 401/9253 combo.

I would also suggest using a short servo arm to effectively give the 9253 a bit more mechanical advantage.

Keep us posted,
Malorie

Life's a journey, NOT a destination.

04-01-2003 Over year old.

jjones
Senior Heliman
Location: Pendleton, Oregon

I am glad to here from two of the most experience bergen people out there and to here that your ideas on this are what I have experienced myself.

A bit farther back I was posting that the 9253 is VERY marginal for these. As long as it's smooth it has worked, but I am jumping to a more torque servo as well, not to mask a problem, but to provide insurance.

I have torque tube and have head holding at 40% or 45% and non-head holding at about the same. I have really been messing mechanically to get it as centered and true as possible to allow little torque both during accent and decent and finally got it very close. Little wag in either direction, but I fear I will not be able to eliminate it completely.

I do mechanically gave the servo a bit of a push, but decided that I would rather have it with more torque and loose a few hundredths of speed, of which I probably will never notice with a 9252...

I also speed the rotor up lower the pitch a bit to give less torque and more speed to the tail, it always helps.

thanks for the input... Question? what if the tail output shaft was a few millimeters longer to allow just a hair more throw of the slider? I have mechanically adjusted to get it almost perfect both in vertical ascents and descents, I'm just thinking an extra millimeter of throw in both directions would stop the final little bit of wag? perhaps not? Or is there some gear speeding up I can do?

thanks

Josh Jones

04-04-2003 Over year old.

HOMEPAGE

Malorie
Elite Veteran
Location: Paw squared, MI

jjones, if you can't get your gain higher than 40-45%, I would look at your gyro mounting some. I use the green goo tape on all my gyros. It sounds like your gain is too low and that very well could be causing the torque wag you're talking about. I have my 401 set to 80% without any signs of wagging in FFF and it is dead locked in in full backwards flight.

Keep us posted,
Malorie

Life's a journey, NOT a destination.

04-04-2003 Over year old.

steviewonder33
Senior Heliman
Location: London, England

Hi,

I dont know about the 502 but when I was using the 501 my gain values were very low aswell. I think it is just that perticular type of gyro. I put shorter tail blades on my model and was then able to up the gain value to about 55 - 60%.

Steve

04-04-2003 Over year old.

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jjones
Senior Heliman
Location: Pendleton, Oregon

I went and put an older 4131 servo on my tail today and it made all my tail problems I was having before disappear. Of course I got new problems, like a super slow servo hunting, but I can flip it both ways and piro very quickily. Both my ascents and descents have evened out a lot.

I think I will buy a 9252 with more torque and speed to boot. thanks for the input.

Josh Jones

04-05-2003 Over year old.

HOMEPAGE

1hander
Senior Heliman
Location: San Antonio, TX

voltage

i was having the same problem on my jetcopter, in hard climbout and decents, i put tail speed gears, 2 sets to be exact, it helped, but in the end it ended up being that the 9251 didnt have enouph guts to turn it. i went to 6 volts, which is not always right but, that fixed the problem,
as long as its not windy, then into the wind in a hover it wont turn, i was using 601/9251, by the way 9251's have been burning out, from the strain i guess, so what to do... im getting a bergen gasser, all i have is 601's/9251,
should i go to a 401/9252, i used this in my xcell gasser and it worked great. you know i dont understand why futaba cant step up and make a high speed servo with guts like 100oz/in torgue
i have some hitec digitals that i bought to try out 3 of them are metal gear digital, 127oz./in .08 at 6 volts, but i dont know if that will work with a 601 or just burn out.
thoughts please
rick

05-15-2003 Over year old.

HOMEPAGE

jjones
Senior Heliman
Location: Pendleton, Oregon

I seen those stats on the hitec servos as well and almost dropped my jaw. I don't think those are truly accurate numbers and for a cheaper digital servo??? I think the scales are tipped somewhere in their favor, or JR and Futaba would make a super fast, super torque servo and I'd use them on all my controls.

How about:

.08
120 oz torque
$25.00 each

JR? Futaba? Anybody?

Just my thoughts.

Josh Jones

05-21-2003 Over year old.

HOMEPAGE

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Bergen R/C Helicopters > Tail Rotor Torque Question

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