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Author Topic: Bellcrank tilt  (Read 29656 times)

Offline Wolfgang Nieuwkamp

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Bellcrank tilt
« on: November 16, 2014, 05:34:06 AM »
Why donīt we tilt the bell crank to get equal flap movement?
The flap horn has to be modified somewhat, but the opening in the top sheeting can be made smaller. See drawing example.

Regards,

Wolfgang

Offline Phil Krankowski

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Re: Bellcrank tilt
« Reply #1 on: November 16, 2014, 06:13:11 AM »
It will make building the bellcrank mountings more difficult due to the angles.  Of course there should be no problem building a simple jig to solve this problem.  It has been described and done before.  Similar results can be obtained using offset bends in the push rods.   Now...which has a lower required force "cost".

In fact the idea is roughed out in the "building a better profile" article under controls

http://pampacl.org/resources/articles.html

Phil

Offline Tim Wescott

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Re: Bellcrank tilt
« Reply #2 on: November 16, 2014, 12:53:02 PM »
Some people do.  Howard Rush has a comprehensive spreadsheet that analyzes control movements given the control system geometry.
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Offline Wolfgang Nieuwkamp

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Re: Bellcrank tilt
« Reply #3 on: November 16, 2014, 01:38:56 PM »
Tim, I could not find the spreadsheet. Can you give me a link?

Thanks,

Wolfgang

Offline Tim Wescott

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Re: Bellcrank tilt
« Reply #4 on: November 16, 2014, 01:48:33 PM »
Tim, I could not find the spreadsheet. Can you give me a link?

I'm not sure it's up on the web anywhere.  I have a year-old copy that I'll send you if you send me an email (my email address is in the members area).  Send an email to Howard, too -- he may have the latest.
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Offline Howard Rush

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Re: Bellcrank tilt
« Reply #5 on: November 16, 2014, 03:00:28 PM »
It's a three-dimensional problem.  I sent you the spreadsheet and accompanying cartoons with definitions.
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Offline Serge_Krauss

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Re: Bellcrank tilt
« Reply #6 on: November 16, 2014, 05:30:56 PM »
I have a similar (I think) spreadsheet I got from Larry Cunningham. As Howard says, the problem is 3-D. The horizontal motion and angles of the bellcrank arm/control rod enter in, and some of these motions apparently make flap movement more symmetrical for standard bellcranks. My spreadsheet says that you can get pretty symmetrical output from asymmetry in the bellcrank operation. In essence, you can get equal handle up vs. down movement for an equal chosen flap deflection, with fractional-degree asymmetries at smaller deflections. There are some results posted and probably accessible via the search functions.

I found that by using a bit less tilt of the flap horn than is necessary for it to be perpendicular to the control rod at neutral, you can get pretty good results with a standard bellcrank that is flat at flap-hinge level. The graph below shows for one of my models the amount of asymmetry in bellcrank deflection (delta alpha) graphed vs chosen symmetrical flap deflections (betas) for a variety of flap horn tilts at neutral (Beta sub zeros). Where each curve crosses the horizontal axis, there is equal bellcrank deflection for equal flap deflection of the value given at that intersection. The red curve is for the control rod being perpendicular to the flap horn at neutral and is obviously not the best choice. You can see though that picking a reasonable maximum flap deflection (past which asymmetry increases fast), you will get a fraction of a degree asymmetry for my flat bell-crank configuration. It does not appear that tilting the bellcrank is really necessary.

SK

Offline Howard Rush

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Re: Bellcrank tilt
« Reply #7 on: November 16, 2014, 06:24:07 PM »
Once again, I suggest that the bellcrank angle is irrelevant.  The important relationships are between differential control line displacement and elevator and flaps.

I'm currently trying to figure out how to implement Igor's flap mechanism at the bellcrank.  I hope I can get it to come out right with the bellcrank in the X-Y plane, because adding another rotation to that mess is difficult. 
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Offline Serge_Krauss

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Re: Bellcrank tilt
« Reply #8 on: November 16, 2014, 11:14:03 PM »
Once again, I suggest that the bellcrank angle is irrelevant.  The important relationships are between differential control line displacement and elevator and flaps.

I'm currently trying to figure out how to implement Igor's flap mechanism at the bellcrank.  I hope I can get it to come out right with the bellcrank in the X-Y plane, because adding another rotation to that mess is difficult. 

Assuming that my spreadsheet works as well as Howard's (it hasn't produced any inconsistencies), I agree. I ran quite a few trials, and that is what I found.

Offline Howard Rush

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Re: Bellcrank tilt
« Reply #9 on: November 17, 2014, 12:40:26 AM »
Oh, I was suggesting the angle that the bellcrank moves about its pivot when you pull a leadout, relative to control deflection, is irrelevant.  More poor communicating on my part.  I haven't tried many bellcrank tilt angles--I've tilted bellcranks based on considerations like avoiding obstacles and having straight pushrods--but as Serge said (I think) it was always pretty easy to fiddle with other parameters and get the response linear.  My favorite parameter with which to fiddle is the bellcrank output arm angle (DeltaBellcrankPushrodArm0 in the program). 

One trick you can use to see if you have a linear response is to plot elevator angle vs. leadout movement, as on Chart 1 of the program, and have Excel add a 2nd-order polynomial "trendline", as Excel calls it, to the plot.  Then fiddle with inputs like bellcrank output angle and flap control horn tilt to make the x2 multiplier small.
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Offline Chris Wilson

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Re: Bellcrank tilt
« Reply #10 on: November 17, 2014, 02:22:34 AM »
I have seen the interior twin lead-out arms of the bell crank system that were solidly attached to a driven mounting pivot and the single output arm that was exterior and above the wing section.
In essence the the push-rod at neutral was parallel to the thrust-line and always entirely outside of the wing.

It would seem to be the best method in theory, and quite adjustable for crank output ratios using a slotted arm.
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Offline Howard Rush

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Re: Bellcrank tilt
« Reply #11 on: November 17, 2014, 03:04:25 AM »
I have seen the interior twin lead-out arms of the bell crank system that were solidly attached to a driven mounting pivot and the single output arm that was exterior and above the wing section.
In essence the the push-rod at neutral was parallel to the thrust-line and always entirely outside of the wing.

It would seem to be the best method in theory, and quite adjustable for crank output ratios using a slotted arm.

I think you'd need a more sophisticated analysis than mine to see if this is a good idea.  When I figured this stuff, I assumed straight, perfectly stiff pushrods with ball links on the ends.   I also neglected structural, weight, and friction considerations. 
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Offline Wolfgang Nieuwkamp

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Re: Bellcrank tilt
« Reply #12 on: November 17, 2014, 06:19:02 AM »
Quote
I have seen the interior twin lead-out arms of the bell crank system that were solidly attached to a driven mounting pivot and the single output arm that was exterior and above the wing section.
In essence the the push-rod at neutral was parallel to the thrust-line and always entirely outside of the wing.

It would seem to be the best method in theory, and quite adjustable for crank output ratios using a slotted arm.
Quote

If you rotate the outside pivot, the kinematics are comparable with a tilted bell crank.

The tilted bell crank still has the advantage of making a small opening for the push-rod possible, so I will continue to use it ;)

Offline Tim Wescott

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Re: Bellcrank tilt
« Reply #13 on: November 17, 2014, 08:37:15 AM »
One trick you can use to see if you have a linear response is to plot elevator angle vs. leadout movement, as on Chart 1 of the program, and have Excel add a 2nd-order polynomial "trendline", as Excel calls it, to the plot.  Then fiddle with inputs like bellcrank output angle and flap control horn tilt to make the x2 multiplier small.

So, a curve like this one? 
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Offline Serge_Krauss

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Re: Bellcrank tilt
« Reply #14 on: November 17, 2014, 09:33:16 AM »
Once again, I suggest that the bellcrank angle is irrelevant.  The important relationships are between differential control line displacement and elevator and flaps.

I was thinking that with a symmetrical bellcrank, the control line/handle movements would depend on the bellcrank's angular displacement, if skewed for line rake. Are you looking at different length control arms on the bellcrank ('differential control line displacement') and/or arm angles asymmetries, as varied by line rake? I was operating at a more elementary level, considering the bellcrank arms to be prpendicular to the mean line direction.

You were correct in what I was implying.


Offline Wolfgang Nieuwkamp

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Re: Bellcrank tilt
« Reply #15 on: November 17, 2014, 09:46:16 AM »
For the bell crank angle I assumed +/- 45 degrees from neutral. The bell crank tilt in my drawing is 11 degrees. Am I mixing up things?

Offline Howard Rush

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Re: Bellcrank tilt
« Reply #16 on: November 17, 2014, 12:51:53 PM »
For the bell crank angle I assumed +/- 45 degrees from neutral. The bell crank tilt in my drawing is 11 degrees. Am I mixing up things?

No.  I was being careless with definitions. 
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Offline Howard Rush

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Re: Bellcrank tilt
« Reply #17 on: November 17, 2014, 01:00:19 PM »
So, a curve like this one? 

Looks hard to fly.

On the other hand, if you can design a mechanism that will move balance tabs relative to flaps with that curve, I'm interested.
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Offline Tim Wescott

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Re: Bellcrank tilt
« Reply #18 on: November 17, 2014, 01:02:49 PM »
Looks hard to fly.

On the other hand, if you can design a mechanism that will move balance tabs relative to flaps with that curve, I'm interested.

No, I meant does it look straight enough -- it has a zero x2 coefficient.

Put an angle sensor on your bellcrank and I can make the TUT make a curve like that.
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Offline Howard Rush

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Re: Bellcrank tilt
« Reply #19 on: November 17, 2014, 02:31:17 PM »
No, I meant does it look straight enough -- it has a zero x2 coefficient.

You rascal.

Put an angle sensor on your bellcrank and I can make the TUT make a curve like that.

That would be putting active controls in the pitch axis, a crime that carries a stiff prison sentence followed by having to register as a control line offender.  You'd have to wear a GPS anklet that would notify the AMA if you got within 1000 feet of a control line circle.  
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Offline Tim Wescott

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Re: Bellcrank tilt
« Reply #20 on: November 17, 2014, 04:20:58 PM »
That would be putting active controls in the pitch axis, a crime that carries a stiff prison sentence followed by having to register as a control line offender.  You'd have to wear a GPS anklet that would notify the AMA if you got within 1000 feet of a control line circle.  

I don't think it's against the rulz, especially if the function is memoryless.

For that matter, I don't think stability augmentation is against the rules either -- and the TUT has the physical plant to do that; it only wants for smarts.
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Chris Wilson

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Re: Bellcrank tilt
« Reply #21 on: November 17, 2014, 04:32:19 PM »
The tilted bell crank still has the advantage of making a small opening for the push-rod possible, so I will continue to use it ;)

Nope, having the bell crank pivot as a drive shaft will be the smallest possible opening ever as you do not need to factor in pushrod angularity since it becomes entirely external.
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Online Brett Buck

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Re: Bellcrank tilt
« Reply #22 on: November 17, 2014, 10:20:47 PM »
I don't think it's against the rulz, especially if the function is memoryless.

For that matter, I don't think stability augmentation is against the rules either -- and the TUT has the physical plant to do that; it only wants for smarts.

   The way it is now, despite some impassioned arguments against it, NOTHING is against the rules as far as autopilots or stability augmentation. No one could be bothered to put in a proposal, so anything goes  - until 2017.

     Brett

Offline Howard Rush

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Re: Bellcrank tilt
« Reply #23 on: November 17, 2014, 10:40:57 PM »
Nope, having the bell crank pivot as a drive shaft will be the smallest possible opening ever as you do not need to factor in pushrod angularity since it becomes entirely external.

I confess that I didn't notice until now just what you were describing.  That's very interesting.  Ed Bryzs of Detroit had some combat models with one of the bellcrank input arms above the wing and the other below, a similar idea.  I don't remember where his pushrod attached. 
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Offline Chris Wilson

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Re: Bellcrank tilt
« Reply #24 on: November 18, 2014, 02:55:22 AM »
Hi Howard, I first saw the idea of internal input arms and external out arms on a Russian stunter and refined on one of Aussie Brian Hamptons models where the external output arm is double sided and slotted.

So both full length pushrods were initially driven from the output arm and not sequentially from crank, then flap horn and on to the elevator horn. Independently adjustable and mechanically the most correct for consistent input/output ratios.
http://stunthanger.com/smf/index.php?topic=17589.15;wap2
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You have enemies? Good. That means you've stood up for something, sometime in your life.
 Nothing in life is so exhilarating as to be shot at without result.  It's not enough that we do our best; sometimes we have to do what's required

Offline Paul Smith

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Re: Bellcrank tilt
« Reply #25 on: November 18, 2014, 02:19:44 PM »
I confess that I didn't notice until now just what you were describing.  That's very interesting.  Ed Bryzs of Detroit had some combat models with one of the bellcrank input arms above the wing and the other below, a similar idea.  I don't remember where his pushrod attached. 

A very effective pullpull system.
Paul Smith

Offline Tim Wescott

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Re: Bellcrank tilt
« Reply #26 on: November 18, 2014, 03:42:36 PM »
   The way it is now, despite some impassioned arguments against it, NOTHING is against the rules as far as autopilots or stability augmentation. No one could be bothered to put in a proposal, so anything goes  - until 2017.

Part of me is appalled by the very notion, but I comfort myself by thinking that as long as it remains a system that follows pilot commands from the wires with stability augmentation, and not some magic autopilot, that it won't be worth more than a few points improvement at your level.
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Offline Chris Wilson

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Re: Bellcrank tilt
« Reply #27 on: November 18, 2014, 08:14:06 PM »
I have always thought that rules were inclusive and a set of permissions - not the other way around.
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Online Brett Buck

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Re: Bellcrank tilt
« Reply #28 on: November 19, 2014, 09:46:22 AM »
I have always thought that rules were inclusive and a set of permissions - not the other way around.

    Everything is allowed unless it is specifically excluded or contradicted. No rules banning auto-pilots = you can have all the autopilots you want. 

    Brett

Offline Igor Burger

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Re: Bellcrank tilt
« Reply #29 on: November 22, 2014, 08:03:49 AM »

I'm currently trying to figure out how to implement Igor's flap mechanism at the bellcrank.  

something like that? :- ))

(yes yes, little bit nicer, cleaner, newer ... this was 30 years old :-P ... also thread rod is not the best solution, but what to expect from young guy? :-P )

Offline Howard Rush

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Re: Bellcrank tilt
« Reply #30 on: November 22, 2014, 11:52:23 AM »
Any new idea I get, Igor had it first. 

He attracts all the girls, too.
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Offline Tim Wescott

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Re: Bellcrank tilt
« Reply #31 on: November 22, 2014, 12:00:46 PM »
Everything is allowed unless it is specifically excluded or contradicted. No rules banning auto-pilots = you can have all the autopilots you want.

The rules say that the wires control the plane, so a fully autonomous autopilot that ignores the bellcrank position would be ruled out.

But any amount of stability augmentation appears to be, at this moment, legal.

Perhaps someone should build a tail-firster with zero stability margin?  I canardly wait!
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Offline Phil Krankowski

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Re: Bellcrank tilt
« Reply #32 on: November 22, 2014, 12:45:39 PM »
The rules say that the wires control the plane, so a fully autonomous autopilot that ignores the bellcrank position would be ruled out.

But any amount of stability augmentation appears to be, at this moment, legal.

Perhaps someone should build a tail-firster with zero stability margin?  I canardly wait!

but what about a servo control in the handle  VD~

(maybe a bit ridiculous, but maybe not so far fetched)

Phil

Offline Chris Wilson

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Re: Bellcrank tilt
« Reply #33 on: November 22, 2014, 05:37:10 PM »
    Everything is allowed unless it is specifically excluded or contradicted. No rules banning auto-pilots = you can have all the autopilots you want. 

    Brett
Ok, so if you allow auto pilots because they are not banned what name do you put down under registered competitor on your entry form - Microsoft, NASA?

The MAAA rules give -
"Definition: Control line flight is flight during which the model aeroplane is
aerodynamically manoeuvred by control surfaces in altitude or attitude, by the pilot on
the ground, by means of one or more inextensible wires or cables directly connected to
the aero model. "
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Online Brett Buck

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Re: Bellcrank tilt
« Reply #34 on: November 22, 2014, 07:09:05 PM »
Ok, so if you allow auto pilots because they are not banned what name do you put down under registered competitor on your entry form - Microsoft, NASA?

The MAAA rules give -
"Definition: Control line flight is flight during which the model aeroplane is
aerodynamically manoeuvred by control surfaces in altitude or attitude, by the pilot on
the ground, by means of one or more inextensible wires or cables directly connected to
the aero model. "

    Which also fails to exclude autopilots. In all proposed cases, the lines still go to a bellcrank, and you hold the handle and make it do things. The bellcrank, instead of being connected to pushrods, etc, is connected to a potentiometer, resolver, or position sensor of some sort. The output of that goes to a mysterious control box, then to some servos, then to the control surfaces. Nothing in the paragraph above is violated.

     Bear in mind, I am not trying to promote autopilots or other trickery. Howard Rush and I (among the several that can see the potential and at least some of how to implement such a solution) have both suggested that someone add a rule that somehow prevents an autopilot. Howard want only mechanical connections, I would hope to figure out some way to word it that would permit "simple" systems (after proposing the mechanical corrections rule for FAI many years ago, like 15 or so years ago). Plenty of other people were thinking along the same lines. But there *were* no proposals to that effect, so here we are.

    I don't think it is an emergency. Going from where we are now, to a *competitive* system, still seems to be several years or more away. But I would like to avoid the situation where it was legal, then "banned" after someone had already gone to the effort of building it. Like was done with ARFs and ARCs, note the impassioned wailing and rending of garments over that.

    Brett

 

Online Brett Buck

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Re: Bellcrank tilt
« Reply #35 on: November 22, 2014, 07:14:44 PM »
The rules say that the wires control the plane, so a fully autonomous autopilot that ignores the bellcrank position would be ruled out.

  You wouldn't ignore the bellcrank position, you would use it to initiate the maneuvers, or initiate perfect 87 degree corners, at pilot command. Like the "Roll Button" on an RC plane. Perfectly legal.

   I am one the fence about stability augmentation, actually. I would only ban that if there was no other way to also ban autopilots. Howard pointed out the extreme difficulty of banning one and keeping the other, just like same argument in the 2000 time frame, and the second round of the same argument when Kim Doherty and Pat Pat Mackenzie showed theirs to be workable on '09.

     Brett

   

Offline Chris Wilson

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Re: Bellcrank tilt
« Reply #36 on: November 22, 2014, 07:26:15 PM »
Hi Brett,
             to my mind you are adding something that simply is not there.
I suppose we agree to disagree on this one.

Cheers mate.
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 Nothing in life is so exhilarating as to be shot at without result.  It's not enough that we do our best; sometimes we have to do what's required

Offline Tim Wescott

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Re: Bellcrank tilt
« Reply #37 on: November 22, 2014, 08:46:28 PM »
to my mind you are adding something that simply is not there.
I suppose we agree to disagree on this one.

I think Brett is correct that the rules leave a loophole open for an autopilot where the role of the pilot in the center of the circle is just to say "go".  It's not a big loophole, and it's one that may not get by everyone, but their one way or another there would be much wailing and gnashing of teeth if someone seriously tried it.

I also think he's correct about it being possible some day.  It's well within the grasp of someone with a Master's degree in the right sorts of mathematics or engineering.  All that's missing right now is a reliable way for the controller to know where the plane is, and some serious effort on the designer's part.  I've designed sensor fusion products for customers that use sensors that are easily available, teeny, and good enough to do that job if integrated with a GPS receiver.  As long as you flew the whole shebang flown far enough away from cliffs, metal buildings, or other objects that might cause multipath interference to the GPS, you could just screw a speed pole into the center of the circle, connect the line to it with an appropriate swivel, let the plane go and watch it do a pattern.

I'm pretty sure, in fact, that if you took one of my TUT circuit boards and added some sort of a ground proximity sensor that you could do away with the GPS receiver.
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Online Brett Buck

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Re: Bellcrank tilt
« Reply #38 on: November 23, 2014, 12:33:54 AM »
Hi Brett,
             to my mind you are adding something that simply is not there.
I suppose we agree to disagree on this one.

   Perhaps - I don't see how I am adding anything.  For example, it doesn't say that mechanical controls are permitted, either. If you think the rules specify the entire range of legal alternatives, you can't have a bellcrank. 

    Forget this topic, the notion that "everything is banned unless mentioned in the rules" is definitely not correct and the rules certainly aren't written that way in any other case. At least in the US, the law works (or is supposed to work) the same way - you can to anything you want as long as there is no law against it.

   I am not upset about it, but interpreting it the way you suggest can't work.

    Brett

Offline Igor Burger

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Re: Bellcrank tilt
« Reply #39 on: November 23, 2014, 02:08:03 AM »

    Forget this topic, the notion that "everything is banned unless mentioned in the rules" is definitely not correct and the rules certainly aren't written that way in any other case. At least in the US, the law works (or is supposed to work) the same way - you can to anything you want as long as there is no law against it.



Yes. However I do not know AMA rules and I am not lawyer, but our rules have also parts telling that C/L model has fixed wing and it is controlled by lines and does not say that R/C helicopter is banned, and anyway, you cannot come and compete with R/C helicoper in F2B :- ))) ... So yes we have parts telling that allowed is only "something" and nothing else. Simply we have definition of event and tdefinition exclude alll beside allowed, without specificaly banning all other. That definition of c/l is especially about system of control, so I think any autopilots ARE banned also without specific wording, unfortunately it could be only my interpretation.

I think if rules say model is controlled by pilot, then my understanding is that it cannot be controlled by clockwork. The problem is, (as we saw in past and as we see also in this thread) that someone consider the clock work for whole pattern rule breaking, but not single figure executed by lines (because it WAS controlled by pilot - he started it), or someone yes but not the single turn (corner) ... or corner done by pilot, but improved to exactly 90 degrees by some other trick, or simply some active stabilization unit. Who can say what is still ok and what is not? Whwre is the border? That was reason why I always commented that all such devices should be banned. Simple bacause:

1/ we cannot clearly say what is allowed and what is already rule breaking

2/ we cannot INSPECT all tricky devices especialy if implemented as program running in black box if they are breaking rules or not IF we would be able to say where is border.

But that all is not only about bellcrank and elevator. None can today imagine what everything could be done as we did not try yet. I have on desk several working tricks which I developed and they improve flying, but I told myself I will not be the first using such things. May be someone remembers my pictures with servos and PCBs sticked on model. There are many thing from stabilization, automatic trimming, compensation of tubulence, side wind, tip weight adjusting ...... if we do not want model full of electronic, we will need ban all of that sooner or later, and the only clean way is to allow only direct (means without any timing functions and power steering) mechanic controll system. It is inspectable and does not allow clockworks.

Yes I heard I am trying to stop spinning of world, but simply I think that is the only way.

 

Online Dave_Trible

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Re: Bellcrank tilt
« Reply #40 on: November 23, 2014, 10:37:05 AM »
I agree our sport would be better served to keep all electronics out of the flight control system and if no one else does I'll propose that myself next cycle.  Of course what opened that door to begin with was the advent of electric power in stunt and the electronics to control the power unit.  It became an issue to say you could use the electronics for one thing but not another.  Said new rules would have to be done in a way to carve out the minimum nessessary for electric power operation.  (Oh well says I). To my thinking that would also mean the autonomous features described by Igor above need to be ruled out.  We need wording to the effect that all flight control is by direct human manipulation of mechanical control hardware.

Dave

My apologies to  Wolfgang for railroading your thread... Things evolve.

« Last Edit: November 23, 2014, 10:57:30 AM by Dave_Trible »
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Offline Wolfgang Nieuwkamp

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Re: Bellcrank tilt
« Reply #41 on: November 23, 2014, 11:00:52 AM »
Maybe we need an addition to the rules like

"The above mentioned control surfaces shall be mechanically connected to the inextensible wires."

Offline Chris Wilson

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Re: Bellcrank tilt
« Reply #42 on: November 25, 2014, 05:34:39 PM »
  Perhaps - I don't see how I am adding anything.  For example, it doesn't say that mechanical controls are permitted, either. If you think the rules specify the entire range of legal alternatives, you can't have a bellcrank. 
You are adding an autopilot of which there is no mention. Sure the written rules make no mention all permissions but what about peer group acceptance, tradition and precedence?
Do you really want to argue the line of no bell crank when it has been accepted for so long?
  
 Forget this topic, the notion that "everything is banned unless mentioned in the rules" is definitely not correct and the rules certainly aren't written that way in any other case. At least in the US, the law works (or is supposed to work) the same way - you can to anything you want as long as there is no law against it.
The notion was not the "banning everything unless mentioned" but more that "you need permission to do anything."
Permissions can range from verbal pilot acceptance on the day to FAI regulations printed in triplicate, and as Igor rightly says - RC choppers are not denied but they are not accepted either, so what conclusion can you draw from that?

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Online Brett Buck

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Re: Bellcrank tilt
« Reply #43 on: November 25, 2014, 05:58:46 PM »
You are adding an autopilot of which there is no mention. Sure the written rules make no mention all permissions but what about peer group acceptance, tradition and precedence?
Do you really want to argue the line of no bell crank when it has been accepted for so long?
   The notion was not the "banning everything unless mentioned" but more that "you need permission to do anything."
Permissions can range from verbal pilot acceptance on the day to FAI regulations printed in triplicate, and as Igor rightly says - RC choppers are not denied but they are not accepted either, so what conclusion can you draw from that?

  Well, I was talking about what the rules actually say, not what you might get away with or would meet with general approval. In fact, you *don't* need permission to do anything - if it does not violate a written rule, it is legal. The example of a bellcrank was an illustration of the fallacy of this notion.

 In fact, I think you *can* fly a helicopter or autotgyro, too, as long as it is controlled by the lines. I don't think the AMA rules say anything about fixed-wing aircraft (although I don't have it in front of me to check).  It can't be RC, that *is* a rule.

  Don't get me wrong - I don't think there should be autopilots, or RC helicopters, either. I am pointing out that if someone had one, the existing rules wouldn't stop it.

   Brett

Offline Steve Helmick

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Re: Bellcrank tilt
« Reply #44 on: November 25, 2014, 06:17:12 PM »
I thought it was pretty clear that F1 events are free flight, F2 events are controline, and F3 events are Radio Controlled. F2 is especially unique in that in FAI all controline events require two (or more) lines, AFAIK. At least, I am not aware of any that allow monoline.

But back to the bellcrank tilt...I think it is a good idea, but also causes a bit of a problem with the inboard leadout clearance for the wing mounted landing gear socket. Since I'm intending to stay with piped IC power, the wing mounted LG solves at least one problem (pipe clearance but also removeability without also removing the pipe), and gives better landings from my experience.  D>K Steve
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Offline EddyR

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Re: Bellcrank tilt
« Reply #45 on: November 26, 2014, 12:16:27 PM »
One thing no one has considered is the effect with having one leadout above the vertical CG and one below it.. If we used a .5" tilt that would put one bellcrank arm 1" above the other. If the vertical CG is on the bellcrank center the the front are is pulling from below the CG and the back are is pulling from above the vertical CG. I know we fly from the wing tip but it might be worth considering if you were going to use it. ~^. In the real world of super duper stunt models the vertical CG is seldom on the bellcrank center line.  n~
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Offline Chris Wilson

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Re: Bellcrank tilt
« Reply #46 on: November 26, 2014, 07:22:28 PM »
Would not the FAI Sporting Code (Section 4C) that the AMA rules point to stop automatic pilots with "a model aircraft shall not be equipped with any device that allows it to be flown automatically to a selected location."

And "Automatic flight path control and/or automatic maneuvering are not permitted."

This deserves a separate thread.
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Online Dave_Trible

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Re: Bellcrank tilt
« Reply #47 on: November 26, 2014, 07:42:14 PM »
Would not the FAI Sporting Code (Section 4C) that the AMA rules point to stop automatic pilots with "a model aircraft shall not be equipped with any device that allows it to be flown automatically to a selected location."

And "Automatic flight path control and/or automatic maneuvering are not permitted."

This deserves a separate thread.
Chris there isn't really much relation between the FAI Sporting Code and AMA/Pampa stunt rules.  FAI rules already permit a few things AMA doesn't (like an R/C type fuel shut off device until this new cycle for 2015).  What is used here is almost entirely AMA rules, other than our own FAI Team Trials.  Yes this needs its own thread.  That should wander over to the rules section.

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Offline Chris Wilson

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Re: Bellcrank tilt
« Reply #48 on: November 26, 2014, 07:59:38 PM »
The relation that I am seeing is under the AMA 2014 World entry blank and gives (a direct copy and paste) -
 
"Rules in Effect
Rules of the Finals contest shall be in accordance with the current
FAI Sporting Code,
except
where superseded by the Team Selection Committee, the Event Director, the Team Selection Jury, or
as noted in the Contest
Information.
Contestants are urged to read the FAI Sporting Code"

Anyway I will stop there as I am out of my depth with this one.
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Re: Bellcrank tilt
« Reply #49 on: November 26, 2014, 08:40:54 PM »
I'm standing to be corrected but I'm pretty sure this part is in reference to how AMA wants the U.S. FAI Team Selection program to be handled and not so much normal AMA contests here in the US.  In standard form we 'write our own rules' for domestic contest flying.

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Online Brett Buck

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Re: Bellcrank tilt
« Reply #50 on: November 26, 2014, 11:00:06 PM »
The relation that I am seeing is under the AMA 2014 World entry blank and gives (a direct copy and paste) -
 
"Rules in Effect
Rules of the Finals contest shall be in accordance with the current
FAI Sporting Code,
except
where superseded by the Team Selection Committee, the Event Director, the Team Selection Jury, or
as noted in the Contest
Information.
Contestants are urged to read the FAI Sporting Code"

Anyway I will stop there as I am out of my depth with this one.

That is what is used for the Team Trials. That effects maybe 15 people here every two years. Otherwise we use the AMA rules. The AMA rules do not refer back to the FAI Sporting code. 

   The FAI rules were originally a copy of the AMA rules. For the most part they are very close, and many times changes are made to keep them the same - not merely for commonality, but because if a change is well-thought out, it will be useful for either set of participants.
  
    Brett

Offline Jonathan Chivers

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Re: Bellcrank tilt
« Reply #51 on: January 03, 2015, 07:33:42 AM »
So what was the conclusion over the benefit (or other wise) of tilting the bell crank?

Jonathan

Offline Howard Rush

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Re: Bellcrank tilt
« Reply #52 on: January 03, 2015, 11:08:38 AM »
So what was the conclusion over the benefit (or other wise) of tilting the bell crank?

I tilt the bellcrank as needed for structural or clearance issues, then fiddle with other parameters to get the requisite control response.  It's pretty easy to get the response you want from whatever tilt angle you pick.  My conclusion is that you gotta do a 3D analysis to see what the control response is, meanwhile knowing what to look for.   
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Offline Jonathan Chivers

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Re: Bellcrank tilt
« Reply #53 on: January 03, 2015, 02:41:22 PM »
Thanks Howard, I will experiment.

For those that like the design phase, I can recommend two cheap CAD products, DevFus and DevWing. Each product walks you through the design parameters of a wing or fuselage and let us see in 3D the impact of your design choices. When you have finished they can export to a CAD package for final tweaking or straght to DXF for feeding into a laser cutter. And you can try for free, but with the print and export functions disabled.

Jonathan


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