I got a Brio 2 meter plane which setup is better. The 2 servos in the stabs or single servo in the center of fuse using MK elevator bellcrank. Thanks.

I dont think that it is a matter of what is better, just what you prefer. Pick your poison

Thanks, I mean which setup is more user friendly or less worries. I heard that dual servos is little a bit harder to trim, due the fact that not two servos are alike. They may be the same model but doesnt have same speed.

I liked dual elevators and will use it again on my next plane.

I didn't notice a speed difference between the two elevator servos. Travel differences are actually easier to fix with dual elevator servos because you can use servo end point (aka travel) adjustment, whereas with a single servo you are limited to half or full turns on a bolt.

hi yepe, 1 servo faster than the other only occurs using "slave mode" other than that , its fine

I agree with Adam. I'm using two servos in my new pattern and I will do so with the next. The main reason I choosed this setup is for redundancy it provides: I know nowadays servos are very reliable, but other things can fail besides servo: screws, servo arms, etc. Once, my friend had an elevator servo arm broken very subtly, it was almost invisible by eye. Luckily, he had a dual servos setup! Ok, the servo arm were cut with a saw, so the original one should not exhibit this kind of failures. But the episode is enough to convince me to go with dual servos !

Furthermore, I think this setup is also better from an engineering point of view: the control linkages, besides being doubled, are much more SIMPLE. With Mk kato, certainly it is possible to end up with a perfect linkage with zero slop and so on (if CPLR uses it...), but it is definitely more complex: there are a total of 6 clevis and a carbon rod that could be point of failures (and source of wear). Also, one clevis is hidden into the fuselage, so you can't easily check if it is all ok. With two servos, the link is definitely much more simple with 2 clevis that can be checked on the fly.

So I definitely prefer two servo setup for its reliability and semplicity, even if there is a price: more weight, and in the tail. Not too much though, two futaba 9650 weigh 52 gr.

A side note: Don Szczur suggest this approach also, since it says that there are minor trim variations with temperature changes. He says that with a control rod setup he was used to put in several trim "beeps" during trimming pass at contests!

Watch your balance. My Brio was very tail heavy with a pair of 3421's!

From what I have heard from two friends who built Brios, they tend to come out a bit tailheavy. One guy did the dual servos in the stab and if memory serves correctly, he needed to add around 7 ounces in the nose. Now, that was using the stock rudder, which also makes a difference. Check out the other Brio thread where the rudder replacement with sheeted foam is discussed. Another consideration for your choice, just from a weight & balance standpoint, is whether you have the FG or all composite fuselage. From what I hear, the situation is worse with FG, much better with all composite. I don't have a Brio, so this is 2nd hand info, but I thought I would pass it along for you to validate before you are committed to a choice that *might* require you to add a bunch of unwanted weight in the nose.

i have used two futaba 9650 in my temptaion but on my new ZN line Twister i will go for the MK elevator bellcrank taht i will modify so that i can use pull pull on it then i got a wery nice and tight system that also are wery light!
i used a big futaba horn that i made the extra piece out off and glued \screwed it to the rest.
and i will use a normal dig. futaba servo ..but the heli servo that i have (same as CPLR) will still be to the heli!

Hi,

Both alternatives are well used ... I have tried many different set-ups, and they all worked ok ..

If you have a transmitter that can deal with the dual servo set-up, it is for sure a good method. Many of todays modern transmitters has a pre set program for dual elevators that can deal with the set-up and the adjustments. Some years ago, without this dedicated program, it was a bit different , and it could be hard to get it right ...

One of the most important advantages using one servo set-up, is the lower weight-moment ...
A way to understand this phenomen :

Let`s say i put 1kg of weight into each wing-tip of my pattern model ; the model would still balance in the roll axe, but what about the effect of the weight-moment , like stopping a point-roll , snap-roll or a spin ? Those manouvers`s would possibly continue a great way after i commanded it to stop ...

If i put some weight into the tail, the same thing would happen. The added weight has to be compensated somehow to get the CG right(directly or indirectly),then i have done the same thing as to the wing-tips ; increased the weight-moment that will make my model harder to accelerate/deaccelrate and stop into new positions, like snap-rolls , spins ... ..

The ideal thing for a model would then be to consentrate all the weight into the CG point, but since this would be impossible, it has to be some compromises ... The "one-servo-users" use this method to minimize this effect ...


Hmmm ... just a thought ...

Kjell Olav

I have used three different methods and all with good results. Pull/pull, MK bellcrank and the dual .070 c.fiber push rods with single servo's. I am seriously thinking about fourth method using dual servo's with the c. fiber pushrods on my next plane for two reasons.

1. Redundency, use the smaller digital serovs to keep weight down.
2. Keep the servo's near the center of gravity.

No long wire extentions. The c.f pushrods with a light ladder like constrution will weight about the same as two h.d. servo extentions. I will cross the pushrods going to the back to keep a near perfect straight line on the rods for smooth operation.

Wayne Galligan

Curious--

I see that you have a FMA servo on the rudder. Will the Futaba or another brand servo
arm fit on the FMA output spline?



Thanks
AW

I dont think there is an advantage to 2 servos, unless you need them mounted in the tail to balance, or unless you get a failure where the servo strips or fails in a neutral position. I have landed with 1 stripped elevator servo and the elevator luckily stuck near neutral. I dont know if you could land a plane with 1 servo stuck at or near full deflection. Granted you probably arent giong to land in 1 piece if a single servo fails in flight. That being said I have landed after one stab snapped off completely in flight and was flapping behind the plane, so I guess anything is possible.

Either way I would think single or dual servos on the CG is going to be a wash from a weight/functionality point of view, it just comes down to whatever you like.

The 2 servo setup basically will come out the same weight or slightly heavier than a single servo setup if you use 9650's (I checked before I made my decision for the DEPS, a 9151 is exactly the same weight as 2 9650's), but considering it takes 2 ball connectors and 2 rod ends to make up the 2 servo setup there is going to be minimal weight gain.

Either way using the DEPS system is going to give you clean, smooth and true elevator control. I really really like the DEPS a lot.

Just comes down to personal preference I think.[8D]

That servo was in there as a spare when my JR went out on me.
The Futaba control arm will fit the FMA. The FMA servo's had plenty of power but lack good centering.

Thanks for the feedback. I just wonder about these details.

AW

What's a good servo for the elevator servo set up (preferably futaba)? Are the 9650's up to it?

pmr,
for dual elevator setup I think 9650 is the best: small, light, digital, powerful. If you want to go analog, 9602 is the servo, but considering that price is the same and given digital advantages, why go analog

Also, some people use 9550, but are heavier.

Ps: if you wanted to know how uses them, Jason Shulman should be enough!

I decided to try making my own control horns out of G10 epoxy. Direct linkages, minimum parts count, no need for ball links because everything stays in line.
--Derek

Hi Derek,

my solution is almost the same, low cost parts, no play developed after 60+ hours flying time. I put the standard size servos into the stab, it is easy to mount in.