canadagoose

My Feedback: (2)

Hi, i bought two new Hitec hs-81 servos for the plane that i'm building, these are rated at 36 oz/in torque. I was planning on using them to operate the ailerons, one for each, the ailerons measure 2.25" x 13.25". My question is will these be enough? or should i be going with bigger servos? The plane will weigh 5.5 lbs and probably cruise at about 60-65 mph. These are micro servos, they're quite small, here's a pic of one next to the aileron. Any thoughts, anyone with experience with these servos? Good or bad? Thanks in advance.

Terry

BobPhx

I would not put HS-81s on anything I was too concerned about. I use them in my park flyers and on the throttle on some other planes, they have a pretty wimpy gear train. I would suggest at least a standard-size servo of 50+ oz. Just my .02.
Bob

Fixed typo, should have said "concerned".
BB

XJet

You could replace the gear train with a metal one (effectively giving you an HS81MG) but doing that costs half as much as a brand new HS81MG anyway.

Go with something a little bigger and stronger -- ignoring the weight issue, a servo can never be too strong or too fast :-)

DBCherry

My Feedback: (4)

It would help to know what the plane is, but I don't think you'll have a problem with the 81's on a 5.5 lb plane. One on each aileron is much more powerful than a 46 oz single servo that used on many sport planes.

I wouldn't use one on the elevator though, it's a bit marginal for that purpose.
Dennis-

canadagoose

My Feedback: (2)

This plane is of my own design, i hooked one up and tried it out and it seems to have alot of torque so i hooked them both up, i'll try them out i know i wouldn't hesitate to have one standard servo operating both ailerons with pushrods and bellcranks. I hope the gear train will be suffiently strong in this application. They are hooked up with a mechanical advantage with the control horn being longer than the servo arm.

siclick33

I am flying a Staudacher aerobatic model with OS 52 four stroke. I have one Futaba 3101 on each elevator half. I am only an intermediate flyer but these little servos (similar to HS81) have coped with everything that I have thrown at them.

I don't know much about Hitec (I do have a couple of HS81s in a tiny little plane) but I think the power will be sufficient. How many people fly with a standard servo to drive both ailerons and think nothing of it? These servos are small, but you are using two of them. I can't comment on the quality or capability of the gear train but don't dismiss little servos just because they are little.

A Futaba 3102 is tiny but has more torque than a 148 or 3001 standard.

DBCherry

My Feedback: (4)

Canadagoose,
I LOVE that GEE BEE hybrid!!
Real nice job.
Dennis-

canadagoose

My Feedback: (2)

Thanks DBCherry, i'm just hoping it flys good too.

canadagoose

My Feedback: (2)

Here a shot of the setup, the distance from the hinge line to the hole the control rod goes through is about 2 1/2- 3 times longer than the servo horn. I still get 1/2" travel either way at the edge of the aileron. I think these little servos will work out ok, i can lift one side of the plane off the table by the trailing edge of the down deflected aileron and it doesn't budge even a little. Seems real solid. The weight savings over 2 standard servos will sure be nice on this size of plane.