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Old Dec 13, 2012, 10:35 AM
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California Condor's Avatar
CARMICHAEL, CALIFORNIA USA
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Here is one, the Pusher Pursuit. The rudders move only outward, held to the center with a spring (torsion) and pulled outward with a cord from the servo.
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Old Dec 13, 2012, 11:39 AM
UMs & parkflyers... for now.
davidterrell80's Avatar
United States, VA, Herndon
Joined Apr 2012
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On my Cartoon C-119 (a twin boom) I chose to drive one rudder and fixed the other in a neutral position. It flies quite well.
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Old Dec 13, 2012, 01:29 PM
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Southern Ontario, Canada
Joined Nov 2001
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Originally Posted by Sundancer View Post
There are lots of ways, look at Tomahawks build thread for his Plecan Falcon for one. However, the neatest and simplest solution I have seen you will find in detail on Page 8 of this publication: http://www.antiquemodeler.org/sam_ne...sets/dt162.pdf

It's definitely the one I would use.
Wish I had seen that one before I started working on the tail of my Falcon. Unfortunately with mine and this setup, it will work but not quite there as you still end up with different throws between the rudders. One rudder will have more throw than the other in one direction and in the opposite direction the other rudder will have more throw. The plane is still controllable but an issue to be aware of.

If you are planning on using the method George refered to for a large plane. I would recommend a better way to secure the pivit tubes than just glue.

Chris
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Old Dec 13, 2012, 01:52 PM
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Southern Ontario, Canada
Joined Nov 2001
604 Posts
I looked at that drawing a little closer. Twin rudders are a pain. I noticed that you have to use a Y setup on the pushrod to drive the elevator halves as the bellcrank is in the way if you wanted to use a simple bent wire to connect the two halves.

If your plane is big enough I recommend two small servos to drive the rudders separately.

Chris
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Old Dec 13, 2012, 09:26 PM
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United States, NJ, Browns Mills
Joined May 2005
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Sorry, but I don't have a picture to explain this.

I did a twin S400 HP Harrow, with all four (two on top and two on the bottom) rudders working. I did it with a pull-pull, using Spiderwire fishing line. I ran the line along the LE of the horizontal stabs, to small ply horns on the outsides of the rudders. From there, I ran the line under the HS, through a tube that ran through the fuse and back again. At the servo, I used EZ connectors and bits of bent music wire for fine-tuning the connection.

It really worked pretty well. I routinely did stall turns, spins, and so forth with the Harrow, without any problems. I finally sold the model last year, just to make room for something new.

CD
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Old Dec 13, 2012, 09:46 PM
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USA, Mt, Billings
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Quote:
Originally Posted by Sundancer View Post
There are lots of ways, look at Tomahawks build thread for his Plecan Falcon for one. However, the neatest and simplest solution I have seen you will find in detail on Page 8 of this publication: http://www.antiquemodeler.org/sam_ne...sets/dt162.pdf

It's definitely the one I would use.
Quote:
Originally Posted by giuseppi View Post
That's the most elegant way to do it that I've seen. The elevator hinges serving as push rod guides...ingenious.

g
Quote:
Originally Posted by Captain Dunsel View Post
Sorry, but I don't have a picture to explain this.

I did a twin S400 HP Harrow, with all four (two on top and two on the bottom) rudders working. I did it with a pull-pull, using Spiderwire fishing line. I ran the line along the LE of the horizontal stabs, to small ply horns on the outsides of the rudders. From there, I ran the line under the HS, through a tube that ran through the fuse and back again. At the servo, I used EZ connectors and bits of bent music wire for fine-tuning the connection.

It really worked pretty well. I routinely did stall turns, spins, and so forth with the Harrow, without any problems. I finally sold the model last year, just to make room for something new.

CD
I took a closer look at the illustrations this morning...this scheme works well (I'm sure) if the model is fairly small and you're using small diameter (very flexible) wire for the elevator hinge/rudder driver. A larger model with commensurately larger diameter wire for this job will not work, or at best will work poorly and only if you've got a whale of a servo.

Why? As the bell crank is deflected one way or the other the "eye" that the wire is attached to comes off-line from the hinge tube. This requires the wire to bend as it pushes into the hinge tube. If the wire is sufficiently limber this probably works pretty darn well, but since (and this is from memory based on square sections, please correct me if I'm off here) the stiffness of the material increases as a cube of the diameter then relatively small increases in wire gauge create very large increases in stiffness (resistance to that bending).

I'd thought of a similar scheme but not running it through the hinge wire. I'll have to experiment around a bit. That IS a neat sounding solution though!
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Old Dec 13, 2012, 09:48 PM
skumgummi dave
Gresham, OR.
Joined Mar 2004
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California Condor:

Are there plans available for the Pusher Pursuit? It's a cutie!

Dave-
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Old Dec 13, 2012, 09:58 PM
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USA, Mt, Billings
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Quote:
Originally Posted by Tomahawk View Post
I looked at that drawing a little closer. Twin rudders are a pain. I noticed that you have to use a Y setup on the pushrod to drive the elevator halves as the bellcrank is in the way if you wanted to use a simple bent wire to connect the two halves.

If your plane is big enough I recommend two small servos to drive the rudders separately.

Chris
There is NO question that dual rudders are a PITA! The project I'm on is a 60" span Ercoupe from Dare Designs. Being a Pat Tritle design it has a great deal of effort put into keeping it light light light. My concern is that Pat maybe went a bit too far this way, though, by driving the steering nose wheel with the elevator servo. That sounds like a recipe for disaster in a cross-wind takeoff, and we get to do PLENTY of that at our flying field.

The real Ercoupes didn't come with rudders (sold as a "spin-proof" plane), relying instead on ailerons and a fair bit o' dihedral turning duties. Many have been converted to working rudders which (I believe) are coupled to the ailerons and actuated with the steering wheel (no rudder pedals).

While the plane is fairly large I don't think I want to try to balance out two servos (or even one servo) back at the very tail of the plane where their weight has max leverage against whatever is employed to balance them out toward the front. My idea had been to install a fourth below the motor that drives the steerable nose wheel and the rudders. By installing it as far forward as reasonably possible I maximize what leverage it has against the weight of the rudder actuating mechanism(s). That's my thought anyway.

Quote:
Originally Posted by Captain Dunsel View Post
Sorry, but I don't have a picture to explain this.

I did a twin S400 HP Harrow, with all four (two on top and two on the bottom) rudders working. I did it with a pull-pull, using Spiderwire fishing line. I ran the line along the LE of the horizontal stabs, to small ply horns on the outsides of the rudders.
Sounds like it worked a treat, I'm just willing to try almost ANYTHING that keeps me from having to hang servo horns on the outside faces of the rudders. Purely an aesthetic decision on my part.
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Old Dec 13, 2012, 10:20 PM
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CARMICHAEL, CALIFORNIA USA
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Quote:
Originally Posted by foamdave View Post
California Condor:

Are there plans available for the Pusher Pursuit? It's a cutie!

Dave-
It was published in Air Trails. January 1943. It's an Old Timer because in those days the magazine came before the month of it's date.
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Old Dec 14, 2012, 06:13 PM
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Valencia, CA
Joined Oct 2002
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Originally Posted by planeman View Post
Here is an unusual one, the Jones S-125, a 20" span scale rubber model from Flying Aces magazine. The plans were cut up and placed on multiple pages of the magazine. I assembled them and copied and flipped the half top view with half a stabilizer to make a full top view and a complete stabilizer. I also added the photo.

Planeman
Beautiful assembly job on this plan! You would never know that it was pasted up from separate pages.

Pete G.
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Old Dec 14, 2012, 07:18 PM
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Napa, CA
Joined May 2007
624 Posts
Here's a Twin Lizzy rudder setup. The push-rod acts as the stab hinge. If I can find it, I have a good article on twin rudder setup.
By the way, this is someone else's fine craftsmanship, not mine!
Ok, found the article. I've used this: Works great on small stuff.
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Old Dec 14, 2012, 09:44 PM
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United States, NY, Ithaca
Joined Sep 2007
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Neat installation, but I'm surprised it works. The arc of the bellcrank would bend the wire every time you turned. Why wouldn't it bind in the hinges?

Jim
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Old Dec 14, 2012, 10:41 PM
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USA, TX, Friendswood
Joined Jul 2007
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Originally Posted by buzzard bait View Post
Neat installation, but I'm surprised it works. The arc of the bellcrank would bend the wire every time you turned. Why wouldn't it bind in the hinges?

Jim
It looks like there isn't enough deflection to cause any arcing or binding. I'd like to see some video of the completed model showing both surfaces being manipulated simultaneously. Maybe then it would be more convincing?

g
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Old Dec 15, 2012, 02:22 AM
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Toronto (Don Mills), Canada
Joined Dec 2002
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Looks to me like it would work quite well.
Because the wire is supported it could be quite thin, say 1/32", and still provide solid control.
Wire that thin can bend enough to prevent binding.

The weak link is the bellcrank, they are a potential source of slop in controls.
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Old Dec 15, 2012, 04:11 AM
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United Kingdom, England, Burnley
Joined Apr 2001
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To overcome any binding as the end of the pushrod in the bellcrank describes an arc whilst the rudder pushrods are captive on the elevator hinge line...
(as seen in picture 2)

...simply file the hole in the bellcrank - to make it a short slot that is the width of the pushrod... only a little - towards the tail - will do.

The slop will be minimal - and with both rudders working, the control will be effective.

Keven.
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