Can 2 9gr servos replace a large servo ?

[solentlife]

In Building section - I am running a thread on my build of the 54" 60 glow engine size biplane.

The Skymaster has ailerons on bottom wing .... each being approx. 2" wide and 21" span ......

Design is for single standard servo of the 80's .... driving aileron torque rods.

So the question is .... can 2 normal 9gr servos such as Towerpro SG90's replace this ... by having each aileron direct to it's own wing mounted servo ?

[Richard]

The standard sized Futaba S148 is rated for 3kg, the 9g tower pro is about 1.8kg. So in theory it should be strong enough.

Of course the most force applied on the ailerons will be at speed, as long as they dont strip they may feel sluggish. You could go for a midi servo such as the Ripmax SD200, Hitec HS81/82 or HS-322 HD.

[solentlife]

(02-09-2011 23:04)Richard Wrote:  The standard sized Futaba S148 is rated for 3kg, the 9g tower pro is about 1.8kg. So in theory it should be strong enough.

Of course the most force applied on the ailerons will be at speed, as long as they dont strip they may feel sluggish. You could go for a midi servo such as the Ripmax SD200, Hitec HS81/82 or HS-322 HD.

My servos used in 1980's for this model are beside me now ...

JR standard : 2 x NES-L501, 1 x NES-101, 2 x NES-3001 mini servos

I have spare from Heli use (new) :

3 x Corona CS-929MG metal gears, 2 x Towerpro SG90 plastic gears.

To be honest - I'm financially embarrassed at moment after an extended cruise on the boat and not working. Seeing about using what I have.

[Richard]

Having thought a bit more, if its one servo per wing the up/down ailerons will balance the force applied to the servo. The only force applied will be to over come the air flow, I don't think gears will strip it just may become sluggish at speed.

Fit the Corona servos all round expect for one wing which will have the tower pro, sorted

[solentlife]

Decisions .... Decisions .... I have wing jigged at moment to fit as designed the torque rods ...

My 9grs are small enough to sit in wing without problem .....

Now this is silly - BUT .. is there any reason I cannot fit torque rods for single central servo ... but still fit separate servos ? Reason I ask is that to fit torque rods later would be surgery job ... in event that I change to them.