how do u select the rudder servo for a Heli?
I'm searching one for my 250size heli..looking forward help regarding it..thank you..

it should be a fast servo preferably digital and with metal gears and with fast response time , rest all depends on your pocket 

oh! one more thing it should be compaitable with your Gyro too.

Hi

Futaba 9257 is a good choice for 250 and 450 size heli.

pls dont pick up a 9257 for a 250 size heli.. its too large and will not suffice the requirements... 9257 is a 24gms servo and is good for a 500 or a 450 size heli..
for a 250 go for any hi speed 9gms servo.. especially with the trex 250 having tail wag issues i recommend that you go for a hyperion or a JR servo and yes pls upgrade to the trex 250se tail that has chinese weights inbuilt in it if possible

Dont think metal gears are recommended for rudder servos, they usually come with plastic/nylon gears.

not necessarily... i have stripped quite a few of rudder servos in a crash and now I am using Metal gear 9257 servos on my rave and protos... its little bit expensive but saves me the hassle of ordering gears and changing them 

Ok, wont metal gears reduce the speed of servo?

not at all... its the same..

Ok, thanks

All the Align 20 series servos used for rudder (DS420, DS520 and DS620) have metal gears.

My experience is only with the Align DS420 servos that come in the combo version, they seem to work well.  You may still have or not have tail issues on the 250 due to geometry/build/quality issues, and in one case I had to get the a new tail slider set ("super" version) to fix wag issues for someone.  But it is clear that the Align DS420 is all you need.

unfortunately i could never get rid of the wag with my ds420's... shifted to hyperion ds11gcb on one and on another heli i have the jr ds290g... very satisfied with the performance now (have gone fbl on one with the min v)

[Admin Note] Changed "ds250" to "ds420" above.

I see the Hyperion is much faster, so it would have an impact.  The JR seems similar in specs with the DS420.

i have a servo which i bought for my hk450..can i use it?

Go ahead and use it. Repeating what I mentioned in earlier PMs, the more torque your servo has, the better it will work with less than perfect tail mechanics. And the HK clone 250 will likely need it because of the slop and lack of chinese weights. At your stage of learning, it doesn't demand much from the servo, so use what you have.

+1 to rajesh... however for tail servo i would look at more speed rather than torque

thanks alot guys..

Sujju as a general recommendation, I agree with you. If one were to buy a good tail servo speed and adequate torque should be looked for. Servos that have high speed and large torque are costly. You have to compromise on one if you are looking to save costs. Looks like he hasn't mentioned it in this thread, but he is using a HK gyro on a HK 250 heli. A good servo is a waste here.

For a person learning to hover, the speed will not make much difference. I have seen people using standard servos with .17 to .20 speed and they work fine for hovering. Torque would still be necessary to overcome the notchy of sticky behaviour of less than perfect tail assemblies. Tails without chinese weights also demands higher torque.

Once you start flying around, especially backwards the speed becomes more important. The higher speed will let you run with higher gains and the gyro control loop stabilize faster.

BTW, which HK servo are you using ?  And please do post your experience once you start flying the heli

yeah I forgot to mention..its my HK250GT kit..wanna a try a cheap or moderate setup..

Again... which particular HK (tail) servo ?

I have this one

www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=10976

thinking to get this one

www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=4697