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Need help!! Bi-plane ailerons

Old 04-11-2011, 03:06 AM
  #1  
Don Sims
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Default Need help!! Bi-plane ailerons

A new member sent me this.... can you give him a hand??


I'm making my first foamie bi-plane. I'm trying to hook up the ailerons. I have 2 on top, & 2 on the bottom. What do you use to connect them? How do I connect the pushrods for the ailerons to 1 servo? If you could send me pics. that would be great. I thank you very much for your help.

Tim
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Old 04-11-2011, 04:13 AM
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FlyingMonkey
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The Eflite foam ultimate bipe had a great set up. The servo was in the lower wing, and had a push rod from each side of the servo. These connected to the inside portion of the lower ailerons.

Out in the middle of the ailerons, was a tab that stuck straight back, with a hole in it. With a z bend in each end, there was a control rod fitted from the lower aileron, to the upper. This way one servo could control 4 ailerons.

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Old 04-11-2011, 05:24 AM
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tobydogs
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thats the way I'd do it,good description FM!

if the servo is inside the fuse then control arms are hidden in the Te , but a very easy solution is to mount the servo like this....a landing gear is a must obviously.
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Old 04-11-2011, 05:38 AM
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Wildflyer
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I set up a Pitts biplane with 4 ailerons, and used exactly what FlyingMonkey described. I used about 3/32 aluminum tubing flattened and drilled for connector, on one end and scratched up with sand paper and glued into trailing edge of ailerons, on the other end, make 4, works great. I let the tubes stick out about 1/4"
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Old 04-13-2011, 01:48 AM
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TimMarkham
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Hi FM,
Do you have any close up pics. for me? I need some sort of diagram. I thank you very much.

Tim
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Old 04-13-2011, 03:12 AM
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Old 04-13-2011, 03:19 AM
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Old 04-13-2011, 03:20 AM
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Old 04-13-2011, 03:32 AM
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My early "Possum Holler Bipe" foamy had a setup just about like that but with the servo in the middle of the upper wing. The later revisions only used upper ailerons.

My "Bipe 33" uses 2 aileron servos, but the tie rods are the same. Ive never had any problems that werent directly caused by pilot error. Reckon I need to be a better pilot!

Possum
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Old 04-13-2011, 09:44 AM
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JetPlaneFlyer
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Originally Posted by stuart View Post
thats the way I'd do it,good description FM!

if the servo is inside the fuse then control arms are hidden in the Te , but a very easy solution is to mount the servo like this....a landing gear is a must obviously.
Actually that's not a great way to do it. With the linkages 'splayed' out at an angle like that and using a straight servo arm you will get considerable differential movement on the ailerons. it's not so bad if the servo is on top of the wing because that way the differential will be 'the right way' (i.e. up-going aileron moved further than down-going one) but with the servo on the bottom you will get inverse differential that will potentially cause all sorts of handling problems.
What you should always look for on any pushrod is, with the control centred, an angle of 90Deg between the pushrod and servo arm. Also at the other end of the pushrod you should look for 90 Deg between pushrod and a line drawn between control surface hinge line and the hole in the control arm.
You should only deviate from the 90Deg rule if you are intentionally designing in differential movement.
The arrangement in the photo could be fixed by using a circular servo arm and mounting the pushrods in a more forward facing hole such that you achieved the desired 90deg between pushrod, hole in arm, and servo output shaft.

Steve
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Old 04-14-2011, 07:31 PM
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flypaper 2
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Also the pushrod between the ails should have the hinge point at the centre of the trailing edge where it comes to a point.. If not, as in using a horn mounted at the bottom of the upper ail and the top of the lower ail. will make one ail move further than the other at full deflexion.

Gord.
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Old 04-14-2011, 08:46 PM
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JetPlaneFlyer
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Originally Posted by flypaper 2 View Post
Also the pushrod between the ails should have the hinge point at the centre of the trailing edge where it comes to a point.. If not, as in using a horn mounted at the bottom of the upper ail and the top of the lower ail. will make one ail move further than the other at full deflexion.

Gord.
Thats true, in the ideal world that's how it should be done, like the Eflite ultimate earlier in this thread..
In practice you can 'get away with it' ok if you connect as near as flush with the surface of the aileron and as far back as practical, as FlyingMonkey did it on his yellow biplane.

Steve
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Old 04-14-2011, 11:20 PM
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Wildflyer
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Default My answer to Biplane aileron hookup

To clarify my previous post,

I did not like the appearance of the control horns mounted on the top and bottom of the ailerons, even though that is what was shown on the plans. Plus I did not want a differential movement in the secondary ailerons.

So I stopped work on the Pitts until I came up with this idea, it is aluminum tubes flattened on the end and roughened on the rest, drilled and epoxied into the aileron, almost to the hinge line. I made a little jig out of hardwood to center the drill bit on the thin edge of the ailerons, sorry I didn't keep it. It was just an 1/8' hole in a piece of wood with 2 strips glued on, centered on the hole, and spaced so the edge was a snug fit.

I get equal movement, and I don't think it looks too bad.

I think these pictures will it explain better, I am not a great writer
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Old 04-15-2011, 12:47 AM
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flypaper 2
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Great job. Looks a lot cleaner too.
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Old 04-15-2011, 12:54 AM
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JetPlaneFlyer
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Wildflyer,

That linkage is ideal from a linkage geometry point of view. The problem i had with doing it that way is that my ailerons were built up balsa construction and the tube would have cut in two the strip of balsa that forms the trailing edge, which would have severely weakened the aileron in the exact place which sees most stress.

So i made up a flush mounted linkage.. While theoretically less than 100% perfect there is in practice no discernible differential aileron movement.

Steve
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Old 04-15-2011, 01:41 AM
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quorneng
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Of course you don't have to use a push rod between the ailerons on a biplane, Sopwith didn't!
My foamy Pup used a single closed loop wire connecting all four ailerons just like the original.
These pictures show the cable running from the servo out under the lower wing.
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Up from the trailing edge of the lower aileron to the upper.
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Across the top wing.
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Repeated for the other side and eventually back to the servo in the fuselage.
Tricky to set up correctly (just like the real thing!) but very light.
And it worked.
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Old 04-15-2011, 05:32 AM
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Wildflyer
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Jetplaneflyer,

That's great Steve, each plane deserves it's own solution.
I guess you might have filled in a small space, but I'm truly glad you got it hooked up. This was just my solution on my little Pitts,
I have several biplane kits, but I don't know how I will hook up the next one.
There are many ways to do it, some better than others. The main thing is to make sure the linkage works good, and does not come loose or bind, and has very little slop in the setup. I may do my Sopwith Pup as quorneng described.
I have seen some hookups from beginners you would not believe, pushrod epoxied to servo and control horn was a real good one.
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Old 04-21-2011, 08:19 AM
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solentlife
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Originally Posted by flypaper 2 View Post
Also the pushrod between the ails should have the hinge point at the centre of the trailing edge where it comes to a point.. If not, as in using a horn mounted at the bottom of the upper ail and the top of the lower ail. will make one ail move further than the other at full deflexion.

Gord.
As long as distance from hinge line is same for both top and bottom ailerons - its fine.

For the wing with widely splayed servo to aileron rods ... I would have modified to use cable .... ie servo arm fore-aft ... cable and outer eiether side at 90 then a nice curve round to face the aileron horn exact in line. The cable outer can be buried nicely into the wing.
OR
The traditional torque tube method where aileron is fitted to a torque tube rod along hinge line ... other end via tube in static part of wing to exact in line with servo ... exiting vertically to have rods connected ...



Despite some comments you hear - done correctly it works very well.
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Old 04-21-2011, 03:20 PM
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JetPlaneFlyer
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Originally Posted by solentlife View Post
As long as distance from hinge line is same for both top and bottom ailerons - its fine..
it's not quite that simple.. What you are really looking for is an angle of 90 deg (or very close) between the pushrod and an imaginary line drawn between the clevis pin and the hinge... on both top and bottom wings.

just having the same distance between clevis pin and hinge isnt good enough. As example of this see attached diagram (this is what was actually recommended in one instruction manual I had) for a linkage that wouldnt work at all, but which has equal hinge line to pin distances:
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Old 04-22-2011, 08:50 AM
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If sides of a parallelogram are equal to the opposite side ( by definition they must be ), with a pivot at each point of intersection, no matter what you do, the sides will stay parallel, it can not get out of parallel.

If the hinge line to hinge line distance is the same as the center to center distance for the connecting link, and the hinge line to the connecting link distance is equal top and bottom. Then the ailerons will move the same.

Try it with 4 sticks of wood, just keep opposing sides equal.

( I lived next door to a geometry teacher when I was in high school, I didn't dare not understand geometry or I was toast. )
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Old 04-23-2011, 03:30 PM
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Originally Posted by Wildflyer View Post
If the hinge line to hinge line distance is the same as the center to center distance for the connecting link, and the hinge line to the connecting link distance is equal top and bottom. Then the ailerons will move the same.
That's almost true.. the key issue there being that the hinge to hinge and pushrod lengths need to be equal (which Solentlife didn't state)

However even with hinge to hinge and pushrod lengths being the same it's possible to come up with an arrangement that wont work.. see attached. The problem with the arrangement I've sketched is that although movement of both ailerons would be equal it would be a lottery if they moved in the same or opposite directions!
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Old 04-23-2011, 03:34 PM
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On my Waco biplane the control rod goes from trailing edge to trailing edge.
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Old 04-23-2011, 04:17 PM
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Originally Posted by JetPlaneFlyer View Post
That's almost true.. the key issue there being that the hinge to hinge and pushrod lengths need to be equal (which Solentlife didn't state)

However even with hinge to hinge and pushrod lengths being the same it's possible to come up with an arrangement that wont work.. see attached. The problem with the arrangement I've sketched is that although movement of both ailerons would be equal it would be a lottery if they moved in the same or opposite directions!
Forgive me for puttiing it bluntly - the diagram you show with pushrod through slot and based on close to hinge line is daft ! Anyone who made such is asking for trouble.

For servo to control surface - you want connection to be in-line with hinge as best as possible. For interconnecting rods between surfaces such as biplane ailerons ... best is actually as far from hinge line as possible so as to 'firm-up' the connection and reduce flutter.
In practical terms that's the connector in T/E of the aileron.
Given the geometry exercise that some have brought into this ... then reference has to be made to where in the depth of the wing to aileron face is the hinge. If it's centred - that is half way between top and bottom surface and T/E is similar - then it makes no difference and if distance from hinge line is same on both ailerons - movement will be identical. The time it will MINUTELY differ is when the hinge line is NOT centred ... ie a top hinge by tape or similar.

Back to practicalities ........... rod between T/E's is the oft seen solution and works.

I'm soon to be owner again of one of the best display bipes ever in UK ... the Skymaster. My original back in 80's had single low wing ailerons .... well this one I'm getting - same Mk 1, when I make her up - she will have dual ailerons ... ie top and bottom wing. How will I interconnect ? Rod on T/E's ... How will I actuate by servo ? Most likely by single servo and torque tubes in bottom wing.
Power ? Instead of the 60 IC I used in previous ... I shall go for a 15cc Petrol job ... ( I know this is Wattflyer .... but just illustrating that a big model can have such arrangement ).
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Old 04-23-2011, 04:52 PM
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Originally Posted by solentlife View Post
Forgive me for puttiing it bluntly - the diagram you show with pushrod through slot and based on close to hinge line is daft ! Anyone who made such is asking for trouble.
I totally agree, it's stupid and nobody in their right mind would do it that way.. but i was just trying to illustrate a point.

i think we all agree TE to TE is best

Steve
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