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Old Aug 15, 2014, 10:24 AM
nurseguy
United States, FL, Largo
Joined May 2013
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Advantages/disadvantages of duel elevator control horns

What are the advantages/disadvantages of having two control horns and control rods on the elevator?
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Old Aug 15, 2014, 10:57 AM
B for Bruce
BMatthews's Avatar
The 'Wack, BC, Canada
Joined Oct 2002
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There's no advantage at all. The only time I would use a split pushrod and dual horns is if I had to due to the hinge lines being swept or dihedral/anhedral in the stabilizer or some other design feature that requires separate elevators.

It is simply much easier to construct the elevators with a joiner of some sort and use a single pushrod. And that way you're sure that both will return to neutral consistently and that there won't be any difference in the throw from side to side.
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Old Aug 15, 2014, 12:25 PM
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Canada
Joined Nov 2000
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Some do this for the purpose of turning the separately operated elevator halves into Elevons.
Yesss, it works well .....albeit more so on quicker than slow flyer models

Other than that? Perhaps to use smaller individual servos or to deal with a non linear hinge line.
Often the 'bigger is better' notion takes precedence / complicates things.
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Old Aug 16, 2014, 05:58 AM
nurseguy
United States, FL, Largo
Joined May 2013
42 Posts
Thanks Guys, I sort of felt the same way, but I thought I was missing something. I have been building for many years (more than I like to admit to) and never saw this before until I bought this Tower Kaos 40. It shows two pushrods connected to one servo. Makes no sense to me so I will connect the two elevator halves together and use one push rod.
Thanks again.
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Old Aug 16, 2014, 09:51 AM
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eflightray's Avatar
South Wales U.K.
Joined Mar 2003
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I wonder how many people building a model have fixed the two elevator halves together before installation, then had to chop a piece out of the fuselage for the joining rod to attach the elevator.

Me for one, but only the once. Twin push rods can have an advantage.

No joining rod that gets in the way, no flexing between the two sides if the joining rod is not a very heavy gauge.
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Old Aug 16, 2014, 10:05 AM
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Joined Mar 2007
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Two systems means twice the likelihood of failure, I suppose.... if using two servos.

Buuut, a failure is less likely to be catastrophic.

A split pushrod? ... no problems, afaics. I've used 'em to good effect. Wouldn't be my first choice, though.
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Old Aug 16, 2014, 07:03 PM
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Moab, Utah, USA
Joined Apr 2003
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I think you will find that duel elevators are a very bad idea. When the elevators are fighting each other it makes it extremely difficult to control the airplane. However, dual elevators are a whole different ball game.

Larry
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Old Aug 16, 2014, 07:43 PM
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United States, MD, Elkton
Joined Oct 2011
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If you're building scale airplanes, it's necessary to hide the linkages as much as possible, so over the years it's become a habit with me.

I use heavy wire for the connector, and since the horn is connected in the middle, any "deformation" is likely equal, not that I'd give it a second thought..

We used to fly 84" wingspans with a single servo in the middle, and pushrods and bellcranks to the ailerons.. Plenty adequate.

Now, with pilots demanding 1.20's on .40 size airplanes, they use 4 servos on ailerons, and two or three on the elevator.
According to what / how you fly, a single servo on connected elevator halves is fine.
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Old Aug 16, 2014, 08:21 PM
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AA5BY's Avatar
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One disadvantage was discovered recently. My transmitter glitched for whatever reason and threw the elevators full throw in opposite directions. A plane doesn't control well in that configuration and I'm just now nearing completion of repairs, which included a complete front end rebuild.

No logical reason for it happening. The glitch remained in the model memory until going to the wing setup, un-mating the gear ch and then re-mating it back.

P.S. I've changed the elevator mating to Aux 3 and moved the engine choke to the gear ch in hopes of it not happening again. The manual outlines that the gear ch can be used and that when doing so, it disconnects the gear ch from the gear switch. Something went wrong but I guess the more advanced technology becomes, the greater the scope of possible glitches.
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Old Aug 16, 2014, 10:26 PM
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Joined Dec 2009
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now that you guys have explaned all the disadvantages!

for one, an elevator joining rod, will flex under hard deflexion, as in 3d style!

with a single servo, split rod, you do not get that!

with a duel servo, duel control rods, if you loose one servo,( I have) you can still fly the plane, handles a lil funny but flyable!

I personally have never seen a duel servo set up, go in opposite directions! not saying it can't happen, just saying!

in my opinion, the cut line is around a .60 size aircraft, anything under that is not needed!

unless you have a high powered 60 size plane with over size flying surfaces, then I would go with duel elevator servo's, and of course anything larger!
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Old Aug 17, 2014, 10:51 AM
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United States, IA, Rockwell
Joined Jul 2011
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The modern F3A guys are using dual pushrods with great success. Here is a link to a dual pushrod set up. Looks like a good system to me and I believe the F3A guys are all about reliability and precision.

http://www.centralhobbies.com/instru.../depsinst.html

Ken
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Old Aug 17, 2014, 11:09 AM
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Quote:
Originally Posted by whiskykid View Post
now that you guys have explaned all the disadvantages!

for one, an elevator joining rod, will flex under hard deflexion, as in 3d style!

with a single servo, split rod, you do not get that!

with a duel servo, duel control rods, if you loose one servo,( I have) you can still fly the plane, handles a lil funny but flyable!

I personally have never seen a duel servo set up, go in opposite directions! not saying it can't happen, just saying!

in my opinion, the cut line is around a .60 size aircraft, anything under that is not needed!

unless you have a high powered 60 size plane with over size flying surfaces, then I would go with duel elevator servo's, and of course anything larger!
First time for me to ever see it happen. In fact, it is my first time ever to experience a computer radio logic glitch that stayed in memory to be observable and confirmable.
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Old Aug 17, 2014, 09:22 PM
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The Netherlands, OV, Almelo
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Show me the photographs of the test of your pattern ship

Central linking of the Taurus.

The pushrod is fixed in the fuselage at the servo position. the servo is mechanically disconnected.

Unloaded, symmetrical position indicated by the wooden sticks. photograph 2

Photograph 4 (and 1), loaded with 2191 grams (4.8 pounds!) at the trailing edge of the elevator halves.

Of course this is an absurt situation but ..................... position still symmetrical and so it will be symmetrical in ALL less loaded positions.

I nowhere read the quality of the elevator halves!!!!! Very important the deformation, even little!, depends on the material of the elevator halves! See photograph 4 the yellow ovals, yes of course there is 'some' deformation when loaded with 4.8 pound at the trailing edges. 50 times overloaded?


Central linking
Profit, the tail feathers don't look like a christmas tree!! Lowest drag of all solutions. Cheap (Dutch)

Taurus Flyer
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Old Aug 17, 2014, 09:47 PM
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scoobiemario's Avatar
United States, VA, Williamsburg
Joined Jan 2011
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Once control horn broke on elevator half on my 47. Thankfully I had two servos/two pushrods setup. Still landed safely.
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Old Aug 17, 2014, 11:39 PM
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The Netherlands, OV, Almelo
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Quote:
Originally Posted by scoobiemario View Post
Once control horn broke on elevator half on my 47. Thankfully I had two servos/two pushrods setup. Still landed safely.
Show me the photographs the way you tested the setup!
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