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Author Topic: New log flap drive crank idea  (Read 1003 times)

Online Mark wood

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New log flap drive crank idea
« on: October 26, 2021, 02:39:23 PM »
I've been working on a bunch of elements for new airplane design. It's been a slow process. As a total geek, I tend to deep dive in to elements. In my endeavors for the design I look at as many adaptations as possible. One of the observations I have is that stunt models seem to use much more flap deflection than is necessary and / or desirable. I performed multi configuration airfoil analysis and have begun some flight test videos with a tufted SV-11 wing which I'll post some results here. One of my 4/4 efforts is posted elsewhere on here. All of these tests and analysis support the premise. Igor Burger has developed his Logarithmic flap drive which is a proven step in this arena. From my analyses and testing, I think that even the 27 degrees of this flap system is a bit much and better performance can be had by a further reduction.

How to test this premise? Make a configurable flap drive. Have CAD. Have 3D printer. It can be done. I've spent a bunch of time working on this model, maybe a bit more than I should but it is addictive. I've also made several iterations along the way. The primary difference between what I have and Igor's is that I have turned the drive crank around and turned the flap horn into a "flap drive horn" which is connected independently to the flaps. With four turnbuckle connecting rods between the bellcrank the flaps independently and the elevator the entire system can be tweaked at one location accessed by a single hatch.


Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Online Mark wood

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Re: New log flap drive crank idea
« Reply #1 on: October 26, 2021, 06:03:50 PM »
I have found a collision with the pushrod to elevator linkage and need to make a revision. Again I posted  something a little early in the development stage. It's not a huge problem as I can move my intended connection over and get clearance

Oh well. At least I learned about making control joints in solid modeling.
 
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Offline Dennis Toth

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Re: New log flap drive crank idea
« Reply #2 on: November 09, 2021, 12:40:56 PM »
Mark,
What is the advantage to using this system over conventional flap drive? What problem are you having or did you have/notice with conventional hookups that you are working to overcome?

Best,     DennisT

Online Tim Wescott

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Re: New log flap drive crank idea
« Reply #3 on: November 09, 2021, 01:50:49 PM »
Mark,
What is the advantage to using this system over conventional flap drive? What problem are you having or did you have/notice with conventional hookups that you are working to overcome?

Best,     DennisT

Mark isn't pioneering the idea of a logarathmic drive -- he's building on the works of others.  Logarithmic flap drives have been in planes that have won the World's, so at worst they don't hurt.

The idea is that for straights and round maneuvers, you want a fairly high flap-elevator ratio.  At some point, the flap deflection just isn't help any more, so when the deflection is high you want to add a smaller increment of flap for each increment of elevator.  Basically, in the corners you want more turn, in the flats and rounds you want more lift.

The logarithmic flap drive provides this.
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Offline Dennis Toth

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Re: New log flap drive crank idea
« Reply #4 on: November 09, 2021, 02:40:27 PM »
Not to criticize development work just want to understand what it is trying to advance. So does this system reduces the amount of flap input to elevator as you apply more control? Or is it adding more flap as the amount of control is increased? And we can't do this with different mechanical ratio variations why? Does this allow a more rearward CG for tighter corners? What is it doing that is different from the basic Nobler flap/elevator setup? How much better is it?

Best,     DennisT

Online Mark wood

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Re: New log flap drive crank idea
« Reply #5 on: November 09, 2021, 03:02:28 PM »
Not to criticize development work just want to understand what it is trying to advance. So does this system reduces the amount of flap input to elevator as you apply more control? Or is it adding more flap as the amount of control is increased? And we can't do this with different mechanical ratio variations why? Does this allow a more rearward CG for tighter corners? What is it doing that is different from the basic Nobler flap/elevator setup? How much better is it?

Best,     DennisT

As Tim suggests I am not creating a new concept only building upon one. Actually, I am bringing three together. The first is the log crank, second readily modifiable ratios and third complete adjustability. Perhaps another one is easily achieved. I could send you one of these tomorrow.

The reason for making the flap ratio changeable is because of the other work I am doing with regards to increasing the flap size. A larger flap deflected less has the potential of doing the same job with less drag.  Igor's flap drive slows flap deflection down to about 27 degrees which is about where I am going to start. By changing out the second lever in the mechanism I can change the resulting drive ratio. A large flap deflected 18 degrees for instance wouldn't work correctly with the current ratios. Notice that the elevator to BC ratio doesn't necessarily change but can be done.

I have intent on changing the flap size and or hinge offset on the airplane. To do this the drive horns must also move and therefore the linkages need to be adjustable. The nice part is 100% of the trim adjustments will be accessible via a hatch most likely on the bottom as the connections change the sense of the motion.

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Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Offline Istvan Travnik

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Re: New log flap drive crank idea
« Reply #6 on: November 09, 2021, 05:33:42 PM »
Dear Mark,
In my album you can find some photos on my variable mechanism.
https://www.flickr.com/photos/171504164@N04/48094388683/in/photostream/
(Some 5-6 pictures about the mechanism)
My preferred measures: narrow wing with 30% flap at the core, 20% at the tip, concave flap, moving not more than 20°. Movement is linear, or slightly exponential.
Horizontal stab+elevator is round 1/4 area of the (complete) wing, elevator moving 45°, strongly exponential. (That means it is more than 2 times faster at the end, related to  the neutral position. )
I fly with this arrangement from the mid-eighties, only the material and outfit of mechanism altered.
The full album is connected to my "old" topic here:
https://stunthanger.com/smf/building-techniques/the-bluefoam-model-or-how-to-build-a-stunt-plane-without-a-bit-of-balsa/msg471991/#msg471991
Istvan

Offline Dennis Toth

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Re: New log flap drive crank idea
« Reply #7 on: November 09, 2021, 05:53:23 PM »
Istvan,
Interesting that you have the elevator moving exponentially faster at the high deflection end. I assume this is to give crisper corners, correct? Does it cause the round maneuvers to be harder to keep round? From what has been posted here in other threads as our ships go through round maneuvers we need to ease off at the top a bit since gravity is helping hold the flight path. This is usually a very small amount of control movement. With the conventional system the control surface movement slows as it gets more deflection because of the arch angle of the the bellcrank and control horns.

For you arrangement do you use a longer tail moment to smooth out the movement?

Best,     DennisT

Online Mark wood

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Re: New log flap drive crank idea
« Reply #8 on: November 09, 2021, 07:13:01 PM »
Dear Mark,
In my album you can find some photos on my variable mechanism.
https://www.flickr.com/photos/171504164@N04/48094388683/in/photostream/
(Some 5-6 pictures about the mechanism)
My preferred measures: narrow wing with 30% flap at the core, 20% at the tip, concave flap, moving not more than 20°. Movement is linear, or slightly exponential.
Horizontal stab+elevator is round 1/4 area of the (complete) wing, elevator moving 45°, strongly exponential. (That means it is more than 2 times faster at the end, related to  the neutral position. )
I fly with this arrangement from the mid-eighties, only the material and outfit of mechanism altered.
The full album is connected to my "old" topic here:
https://stunthanger.com/smf/building-techniques/the-bluefoam-model-or-how-to-build-a-stunt-plane-without-a-bit-of-balsa/msg471991/#msg471991
Istvan

Istvan

Thank you very much for that input. It sound like a point of confirmation to me on this path. I've done some work on the exponential mechanisms and I couldn't solve the equation properly for the elevator drive. What is desirable, in my mind, is that the slope around neutral should be less than that of a linear drive arrangement and increasing during deflection to reach a similar angle at around 30 degrees elevator then increasing from there. Seems like you might have something like that. I think I saw another variation of what you have here and I never sat down and worked out the equations for it, yet. I decided to work on the flap drive first and the flap proportions. I think that 30% flaps full span would not be unreasonable but maybe 35% tapering to 25% at the tips if there is any "tip stall" indications.
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Offline Istvan Travnik

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Re: New log flap drive crank idea
« Reply #9 on: November 10, 2021, 07:55:48 AM »
Dear Mark,
My "love story" with exponential elevator began that time, when I realized that I am too "wooden-handed" to fly without hunting, and without wobbling after the corners. Les McDonald in his article (in M.A.N.) advised "a bit of slop" in the elevator mechanism, against hunting. As a mechanic engineer I did not like this idea. (Chance of flutter, etc.)
My friends advised against wobbling closer distance of connection points of the handle. I found myself too slow-handed to fly sharp corners with this arrangement. But...
...That time advanced R/C transmitters appeared with so-called (analogue) "exponential knob", and I simply tried to model this function in the mechanics, and symmetrically.  It needs a luffing arm (made of slippery plastic, as nylon, Textolite (textile-bakelite), or now ZX-100 ), plus a polished hard steel standing pin. When this arm has several input- and output holes, plus maybe more positions for standing pin, the ratios and charecteristics are nearly limitlessly variable.
I never started to stand up the equation with many sin, tan, arcsin and arctan parameters, it looked more friendly to solve it on paper, with liner,  compasses, bevel and pocket calculator... :)


Offline Dennis Toth

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Re: New log flap drive crank idea
« Reply #10 on: November 10, 2021, 08:53:42 AM »
Interesting development to address the sensitivity around neutral. Some have addressed this with the slop in the horns as stated but I also agree that slop can lead to flutter and banging on the horn connection which could lead to failure. This was one of the things people talked about how older ships flew so stable vs. a new ship, that's where the slop idea came from.

More recently others have used the thick stab - thin elevator approach which gives a little dead zone around neutral elevator. How thick and thin is open for discussion.

Best,   DennisT

Online Ken Culbertson

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Re: New log flap drive crank idea
« Reply #11 on: November 10, 2021, 12:04:13 PM »
Interesting development to address the sensitivity around neutral. Some have addressed this with the slop in the horns as stated but I also agree that slop can lead to flutter and banging on the horn connection which could lead to failure. This was one of the things people talked about how older ships flew so stable vs. a new ship, that's where the slop idea came from.

More recently others have used the thick stab - thin elevator approach which gives a little dead zone around neutral elevator. How thick and thin is open for discussion.

Best,   DennisT
You gotta love this forum.  Ever since coming back in 2017 and flying the new stuff with no slop I have been having an issue with a drifting form of hunting.  Depending on the plane it could be either up or down.  Thinking about controls with a trimmed plane in level flight is going to result in some form of hunting.  Mine was the kind where the plane wanted to float or hug the ground.  Left unattended it would "tilt" the plane and be high on one side, low on the other like when you fail to account for the wind.  I had always flown with slop in the elevator which reverses the controls in that tiny space around neutral where the flaps would move before the elevator.  Subconsciously I had been "turning into the skid" to keep things level.  When I switched to logarythmic the small amount of slop was in the flaps meaning the elevator moved first.  When I realized what was going on it went away on the very next flight.  I only wish the conscious side would listen that fast!  Were it not for us talking about slop (in the controls that is) I probably would have tried to trim it out.

Why, if you are going to use slop to deaden the controls around neutral would you not put it at the flap horn instead of the elevator.  The whole idea is to not have the plane respond to that sudden onset of Parkinson's disease that seems to accompany nailing the first corner of the wingover not cause any control movement.  Why not both instead of just the elevator?

Ken
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Online Mark wood

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Re: New log flap drive crank idea
« Reply #12 on: November 10, 2021, 01:34:06 PM »
Dear Mark,
My "love story" with exponential elevator began that time, when I realized that I am too "wooden-handed" to fly without hunting, and without wobbling after the corners. Les McDonald in his article (in M.A.N.) advised "a bit of slop" in the elevator mechanism, against hunting. As a mechanic engineer I did not like this idea. (Chance of flutter, etc.)
My friends advised against wobbling closer distance of connection points of the handle. I found myself too slow-handed to fly sharp corners with this arrangement. But...
...That time advanced R/C transmitters appeared with so-called (analogue) "exponential knob", and I simply tried to model this function in the mechanics, and symmetrically.  It needs a luffing arm (made of slippery plastic, as nylon, Textolite (textile-bakelite), or now ZX-100 ), plus a polished hard steel standing pin. When this arm has several input- and output holes, plus maybe more positions for standing pin, the ratios and charecteristics are nearly limitlessly variable.
I never started to stand up the equation with many sin, tan, arcsin and arctan parameters, it looked more friendly to solve it on paper, with liner,  compasses, bevel and pocket calculator... :)

It's always an interesting exercise for me to work out the math involved. Number one because I am an ultra-nerd class geek and two because it gives me an understanding of the dependencies. I am becoming truly versed in Fusion these days and I will ultimately model your version. Some of the other exponential linkages are but they don't really do what we want which is to reduce the slope of the output around neutral. In order to reduce the meat servo induced hunting flattening the curve around neutral is what we desire then at some input point we want the output to catch up to original linear curve and get faster beyond that point.

Level flight wants a bit different control response than maneuvering which is where the log flap drive is desirable besides it's ability to limit max flap deflection. When the elevator flap deflection ratios are low the airplane can raise lower in altitude gently without the proposing induced by changing pitch.  The airplane pivoting to ascend and descend is more obvious to the outside observer with the score writing utensil than if it maintains it alignment and simply raises and lowers a few inches.

Now the magnitude of those displacements is a function of the response from the meat servo. A meat servo with a high proportional gain may cause great oscillatory motion in the flight path whether the airplane maintains its attitude or if it oscillates in pit pitch as well. This is where a an exponential control on the vehicle side can be beneficial. Slowing the response to the input from the meat servo at low deflections can help reduce the overshoot. By reducing the slope around neutral the high gain can be scaled back. In other realms of operation, such as looping maneuvers of the vehicle a higher gain is more desirable where turning rates are greater and corrections need to likewise be greater. The on the extreme end very high gain is desirable. That is what exponential control does and belongs between the input and the output to the flight controls.

By working out the math and plotting the results we can evaluate different systems to see if they can meet these conditions. So far, in my limit number of efforts, I haven't yet found a mechanical system that meets this exponential behavior in the above manor. I haven't yet done Istvan's version.
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Offline Istvan Travnik

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Re: New log flap drive crank idea
« Reply #13 on: November 10, 2021, 05:03:50 PM »
Dear Mark,
Here is a (little bit scandalous) hand-drawing of my model from 2000. This mechanism integrates Bellcrank & expo mechanism. The essential details translated to English from Hungarian. Dimensions in millimeters. Do not care with text, that is a question about math between input and output.
If you formulate it, you are a great man!
1. "KM és tántorgókar közötti csap" = junction pin between bellcrank and luffig arm
2. "Tántorgókar" = luffing arm
3. "Tolórúd-furat" = hole(s) for pushrod junction
4. "Álló csap" = standing (fixed) pin
5. "Kulissza" = precision slot for the standing pin in the luffing arm

Both the bellcrank and luffing arm made of ZX-100, however, Textolite & others can be used, too.
Istvan

Online Mark wood

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Re: New log flap drive crank idea
« Reply #14 on: November 11, 2021, 07:17:44 AM »
Dear Mark,
Here is a (little bit scandalous) hand-drawing of my model from 2000. This mechanism integrates Bellcrank & expo mechanism. The essential details translated to English from Hungarian. Dimensions in millimeters. Do not care with text, that is a question about math between input and output.
If you formulate it, you are a great man!
1. "KM és tántorgókar közötti csap" = junction pin between bellcrank and luffig arm
2. "Tántorgókar" = luffing arm
3. "Tolórúd-furat" = hole(s) for pushrod junction
4. "Álló csap" = standing (fixed) pin
5. "Kulissza" = precision slot for the standing pin in the luffing arm

Both the bellcrank and luffing arm made of ZX-100, however, Textolite & others can be used, too.
Istvan

Istvan, here's a question about this configuration. What is the biggest reason you are not using this unit? It looks fairly big in terms of integration. I worked out the math and this looks like it would indeed do a decent job of creating a good exponential output.

« Last Edit: November 11, 2021, 08:25:10 AM by Mark wood »
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Offline Istvan Travnik

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Re: New log flap drive crank idea
« Reply #15 on: November 11, 2021, 03:18:05 PM »
Dear Mark,
I fly RIGHT this  21 years old plane now, since my model made at 2012 is "ill" now. (Needs to be repared).
A little bit easier, and a little bit faster and better responsive than newer one.
However, the silencer is not so nicely hidden, beneath the engine...

Online Mark wood

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Re: New log flap drive crank idea
« Reply #16 on: November 11, 2021, 04:55:11 PM »
Dear Mark,
I fly RIGHT this  21 years old plane now, since my model made at 2012 is "ill" now. (Needs to be repared).
A little bit easier, and a little bit faster and better responsive than newer one.
However, the silencer is not so nicely hidden, beneath the engine...

It's unfortunate about the crash. If I were to make a comment on one item it would be the muffler inlet. It looks strange because it is large. The area of that inlet should be the same or slightly smaller than area of the passage around the muffle and the exit should be large by 1.5 times. I have spent some time working on my version of the IT Expo crank.

I present to you some photos.

Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Offline Istvan Travnik

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Re: New log flap drive crank idea
« Reply #17 on: November 11, 2021, 05:37:43 PM »
Wow!
This is beautiful & professional!
My one made of ZX-100 plastic, the rough plate was 8mm (slightly less than 1/3") thick.
I found the horizontal arms had to be ca. 2 times wider than your model,  for the sake of stiffness. 
This arrangement has only one drawback: since it is situated in the most hidden part of the ship, the variability is a little bit difficult. (And you cannot show to the comrades. :)  )
When the mechanism is under the (detachable) canopy, it is more attractive and variable...
Others: the muffler inlet of the other plane MUST be so large, since the whole muffler shall be push in thru that "mouth", when assembled, and shall be  pulled out thru, as well.
Think on Sophia Loren, or Julia Roberts... :)
« Last Edit: November 11, 2021, 05:57:57 PM by Istvan Travnik »

Online Mark wood

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Re: New log flap drive crank idea
« Reply #18 on: November 11, 2021, 06:28:59 PM »
Wow!
This is beautiful & professional!
My one made of ZX-100 plastic, the rough plate was 8mm (slightly less than 1/3") thick.
I found the horizontal arms had to be ca. 2 times wider than your model,  for the sake of stiffness. 
This arrangement has only one drawback: since it is situated in the most hidden part of the ship, the variability is a little bit difficult. (And you cannot show to the comrades. :)  )
When the mechanism is under the (detachable) canopy, it is more attractive and variable...
Others: the muffler inlet of the other plane MUST be so large, since the whole muffler shall be push in thru that "mouth", when assembled, and shall be  pulled out thru, as well.
Think on Sophia Loren, or Julia Roberts... :)

The fact that your crank work is visible in the canopy was not lost on me. I saw it and was instantly impressed. Why not show off your work? I figure the lever was going to need to be much wider which is a simple task of reversing the way the joint is done.
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Online Mark wood

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Re: New log flap drive crank idea
« Reply #19 on: November 11, 2021, 10:19:45 PM »
I liked the IT expo crank numbers enough that I printed one out to hold.
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Offline Istvan Travnik

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Re: New log flap drive crank idea
« Reply #20 on: November 12, 2021, 02:07:48 PM »
Dear Mark,
Wouldn't it be nice, if you "drill" another hole for the pushrod junction in the luffing arm, as close, as possible to the fixed pin (or in other words: to the end of the slot)?
That diagram could show more dramatic change of the input-output ratio...

Online Mark wood

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Re: New log flap drive crank idea
« Reply #21 on: November 12, 2021, 02:37:56 PM »
Dear Mark,
Wouldn't it be nice, if you "drill" another hole for the pushrod junction in the luffing arm, as close, as possible to the fixed pin (or in other words: to the end of the slot)?
That diagram could show more dramatic change of the input-output ratio...

Oh yeah. I did a number of iterations starting from what I could determine from the drawing. From that I played around with the pivot and the push rod dimensions. Too much curvature can lead to poor response at low angle and and excessive at higher angles. Intuitively, I think we want the two curve to intersect around 20-25 degrees bellcrank angle. That's just a bit before a typical square corner input is. My intent is to use this in combination with the log flap drive which does some "flattening" of it's own around center.

The struggle with this setup is getting the two conditions to converge, flattening the slope around neutral and crossing the "linear" curve at 20-25 degrees. Here are few condition analysis'.

First is an even ratio pivot length to bellcrank length 1:1 and PR located 1/2 between. This is how I interpret your drawing.

Next is when the pivot is very long and the PR actually goes backwards initially and never does converge with 45 degree bellcrank travel.. This could actually be a math thing and not physically capable of being made.

Finally a really good exponential curve but the trouble is that it doesn't catch up to the linear curve until 35 degrees or so which is beyond what we would be doing during flight.


Ultimately it isn't an easily modifiable system and is extremely sensitive on the ratios. Just a very minor change creates a big difference in the output. So, I settled on an iteration I felt was a good middle ground meeting the highest requirement and crossing the linear curve at 25 ish degrees for the one I would create a working prototype.

« Last Edit: November 12, 2021, 03:02:41 PM by Mark wood »
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Offline Istvan Travnik

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Re: New log flap drive crank idea
« Reply #22 on: November 12, 2021, 04:02:11 PM »
Wonderful curves!
Thanks a lot!
I think, almost nobody will try to make in real life this "extremist" and too hidden arrangement, but the other one, which one built into my 2012 model, can be built more simple, and freely variable.
...and some pilots, who feel himself a little bit "woodenhanded", like me, can find it useful, helpful, to fly better.
Since my 2012 model is broken now, I could make some photos, showing input and output junctions.
And, finally, I can design a more simple, conversion mechanism, which is additionally mountable, just for the elevator. (When I began, my very first step was that. )

Online Mark wood

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Re: New log flap drive crank idea
« Reply #23 on: November 12, 2021, 05:12:02 PM »
Wonderful curves!
Thanks a lot!
I think, almost nobody will try to make in real life this "extremist" and too hidden arrangement, but the other one, which one built into my 2012 model, can be built more simple, and freely variable.
...and some pilots, who feel himself a little bit "woodenhanded", like me, can find it useful, helpful, to fly better.
Since my 2012 model is broken now, I could make some photos, showing input and output junctions.
And, finally, I can design a more simple, conversion mechanism, which is additionally mountable, just for the elevator. (When I began, my very first step was that. )

Thanks for the photos Istvan. I had already made some assumptions on how your system was connected and I may have not understood the connectivity. The solution I evaluated looks more like a logarithmic function. I will return to that calculation and reevaluate it.


Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Offline Howard Rush

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Re: New log flap drive crank idea
« Reply #24 on: November 12, 2021, 07:15:53 PM »
Here's a discussion of similar mechanisms:  https://stunthanger.com/smf/stunt-design/interesting-bellcrank/
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Online Mark wood

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Re: New log flap drive crank idea
« Reply #25 on: November 13, 2021, 05:41:41 AM »
Here's a discussion of similar mechanisms:  https://stunthanger.com/smf/stunt-design/interesting-bellcrank/

That's a very interesting discussion. Thanks for sharing Howard.
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Offline Istvan Travnik

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Re: New log flap drive crank idea
« Reply #26 on: November 13, 2021, 09:42:47 AM »
Dear All,
I have read this long discussion from beginning of 2012. Sometimes I was laughing loudly. That time I haven't read that, I do not know, why.
But I remember well, how many times we discussed with Jan Skrabálek in the '90s, on that theme "expo, or logarithmic", at the "Józef Gábris Memorial" contests, in Bratislava. I knew which is better for me, (expo), I worked it out, and reconciled to that fact, I will never be so talented as Jan, or some years later, Igor. 
My Hungarian comrades -not being mechanical engineer, or too innovative minded- always observed nothing else, what is more succesful in the world. And then copied, or bought that. So I walk my way technically alone, at least from1982.
But, when somebody is interested, I do not hide nothing.
Istvan 


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