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Offline Motorman

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« on: December 25, 2021, 10:51:51 PM »
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« Last Edit: January 16, 2022, 10:11:03 PM by Motorman »

Offline Ken Culbertson

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Re: Thrust line Vectoring
« Reply #1 on: December 25, 2021, 11:52:05 PM »
Has anyone tried linking the elevator control system to the motor so that the thrust line goes up and down with control input? Do you think this could eliminate the need for flaps?


Motorman 8)
I considered that with the advent of electric but that is "thrust vectoring" and is specifically forbidden in the new rules.  Probably because I thought of using it! HB~>

Ken
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Offline Mark wood

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Re: Thrust line Vectoring
« Reply #2 on: December 26, 2021, 08:20:15 AM »
Has anyone tried linking the elevator control system to the motor so that the thrust line goes up and down with control input? Do you think this could eliminate the need for flaps?


Motorman 8)

Thrust vectoring would be interesting but I wouldn't think the result is what you'd want. I don't think it should be specifically outlawed but then who am I? The reason for flaps isn't as clear as they create more lift to be able to make corners. That can be done easily by reducing wing loading or increasing velocity. Combat wings can easily fly the PA sequence but the lack of the their presence in the winners circle indicates there is more to it than shear lift. So lift isn't the primary reason. It is actually, IMO, for presentation. A flapped model will track with the fuselage more tangential to the flight path than a non flapped model. At the exit a flapped model will have less pitch attitude to relieve than a non flapped model and appear to bobble less thereby presenting better.

Using thrust vectoring increases the pitch rate more than it increases lift. This is used for fighter aircraft to gain a better firing solution. In my ARMY days we were pitted helicopter v jet in ACM exercises and could win a large majority of encounters PROVIDED we weren't waxed by an A-A missile launched via early detection of us. The reason we could win these is that we could swing to aim our guns and missiles to keep the opponent within firing solution longer. Since the focus on thrust vectoring began and increased shortly after, I assume that the lessons learned from those exercises are what prompted it.

Watch the cobra maneuver, the jet continues along a fairly straight flight path but the nose is pitched well past 90 degrees. That's what using thrust vectoring would do. This kind of result would not work well in front of judges looking for ballerina like gracefulness in PA. Now if there were paradigm a shift in the concept and follow in to a realm of the RC 3D world  opening a more freestyle approach then thrust vectoring would be an asset. As it is the rule forbidding thrust vectoring isn't really necessary as it's behavior would self eliminate.
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
“Physics is like sex: sure, it may give some practical results, but that’s not why we do it.” – Richard P. Feynman

Offline Trostle

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Re: Thrust line Vectoring
« Reply #3 on: December 26, 2021, 10:50:19 AM »
... that is "thrust vectoring" and is specifically forbidden in the new rules.

Ken

Where is it in the rules that "thrust vectoring" is specifically forbidden in the rules?

Keith

Online Brett Buck

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Re: Thrust line Vectoring
« Reply #4 on: December 26, 2021, 11:05:39 AM »
Where is it in the rules that "thrust vectoring" is specifically forbidden in the rules?

Keith

  News to me, too.

    Brett

Offline Dan McEntee

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Re: Thrust line Vectoring
« Reply #5 on: December 26, 2021, 11:31:07 AM »
   I would hate to have to work out that kind of linkage. I imagine that it would take a lot of leverage to move the motor with the gyro effect a prop at speed would generate. Not to mention the resulting "looseness" of that type of joint. The thrust line position is critical, and trying to get it to return exactly to it's "zero" point would be really difficult. The weight of everything required would be enough to turn me off to any potential advantages of thrust vectoring. If it were too be tried, I think the actual range of motion would need to be quite small, but that wouldn't make it any easier to execute reliably in my opinion.
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Offline Mark wood

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Re: Thrust line Vectoring
« Reply #6 on: December 26, 2021, 12:07:02 PM »
My bad, I assumed it to be true. I haven't personally looked at the rules for thrust vectoring. Hinging the propeller would eliminate the precession troubles.

Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
“Physics is like sex: sure, it may give some practical results, but that’s not why we do it.” – Richard P. Feynman

Online Fred Underwood

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Re: Thrust line Vectoring
« Reply #7 on: December 26, 2021, 12:16:28 PM »
Maybe part of the confusion, a comment from another thread, but not the actual rule.


Re: Data logging accelerometer
« Reply #31 on: December 21, 2021, 01:53:31 PM »
Quote
Quote from: Ken Culbertson on December 21, 2021, 11:49:33 AM
This is beyond cool.  It would have wild bill rolling over in his grave.  Fly by wire.  If done without the aid of radio it is probably legal.  It might even be legal to eliminate the bellcrank entirely and have the signal come directly from the handle as long as it was done w/o the aid of radio.  So after designing the ultimate arm mounted Joy Stick we reference further and find there is only a 1 line requirement and although there is a requirement to have the center of the circle marked, I can find no requirement to have the pilot stand in it!.   So we *could* have a 5' center post that we borrowed from the speed guys tether the plane while we sit back and fly from our lawn chairs.  And that is just the beginning...  How long before we become just a VR app? LL~

It is not a servo -- it used to be a servo.  It's a servo that's been gutted of all its gears, and the electronics replaced with a sensor transmitter.  It's just a convenient position sensor mounted to a shaft, in a box with room for electronics, all packaged in a way that matches the vernacular of connecting stuff up mechanically inside a toy airplane.

Quote from: Ken Culbertson on December 21, 2021, 11:49:33 AM
I would support a rule change to block this sort of thing from ever happening, but it won't.  It is building season and the mind wanders.
 
Ken

Too late -- that rule got accepted this rules change cycle.  Brett Buck started it but ended up just throwing it to the community.  I completed it and filed it.

No moving flight controls by any means other than mechanically.

No thrust vectoring.

Thrust control via motor speed or pitch changes is allowed, but only if it does not change direction of thrust.
Fred
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Offline Ken Culbertson

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Re: Thrust line Vectoring
« Reply #8 on: December 26, 2021, 12:25:30 PM »
Maybe part of the confusion, a comment from another thread, but not the actual rule.


Change #10 Approved

2.7.4 Items intended to vector the propulsion thrust or apply maneuvering torque or force
(including but not limited to engine gimbals, cyclic propellor pitch control, thrust vectoring
vanes or direct lift control) shall be considered "aerodynamic control surfaces". Any such
aerodynamic control surfaces shall be actuated entirely manually and only respond to control line
movement through mechanical linkages as in paragraph 2.7.1 above.

Ken
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If it is not broke you are not trying hard enough.
USAF 1968-1974 TAC

Offline Mark wood

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Re: Thrust line Vectoring
« Reply #9 on: December 26, 2021, 12:33:43 PM »
Change #10 Approved

2.7.4 Items intended to vector the propulsion thrust or apply maneuvering torque or force
(including but not limited to engine gimbals, cyclic propellor pitch control, thrust vectoring
vanes or direct lift control) shall be considered "aerodynamic control surfaces". Any such
aerodynamic control surfaces shall be actuated entirely manually and only respond to control line
movement through mechanical linkages as in paragraph 2.7.1 above.

Ken

That isn't a prohibition of thrust vectoring but a prohibition of using an automated system which would control thrust vectoring. A gimbal would have to be operated by a connection to the handle controls. Before anyone decides to go down this path, send me a PM and phone number.

Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
“Physics is like sex: sure, it may give some practical results, but that’s not why we do it.” – Richard P. Feynman

Online Brett Buck

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Re: Thrust line Vectoring
« Reply #10 on: December 26, 2021, 12:51:05 PM »
Change #10 Approved

2.7.4 Items intended to vector the propulsion thrust or apply maneuvering torque or force
(including but not limited to engine gimbals, cyclic propellor pitch control, thrust vectoring
vanes or direct lift control) shall be considered "aerodynamic control surfaces". Any such
aerodynamic control surfaces shall be actuated entirely manually and only respond to control line
movement through mechanical linkages as in paragraph 2.7.1 above.

   You just have to do it mechanically, rather than with a servo (feedback or otherwise).

     Brett

Offline Tim Wescott

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Re: Thrust line Vectoring
« Reply #11 on: December 26, 2021, 03:29:16 PM »
I considered that with the advent of electric but that is "thrust vectoring" and is specifically forbidden in the new rules.  Probably because I thought of using it! HB~>

Ken

Oh god, I'm a purveyor of misinformation.

That's thrust vectoring using electronics.  If you want to do thrust vectoring with mechanical linkages, knock yourself out.  Let us know how it goes.

CLA21-10 is the relevant proposal; it was approved and should make it into the next rule book.  The section in question reads:

Quote
2.7.4 Items intended to vector the propulsion thrust or apply maneuvering torque or force
(including but not limited to engine gimbals, cyclic propellor pitch control, thrust vectoring
vanes or direct lift control) shall be considered "aerodynamic control surfaces". Any such
aerodynamic control surfaces shall be actuated entirely manually and only respond to control line
movement through mechanical linkages as in paragraph 2.7.1 above.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Tim Wescott

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Re: Thrust line Vectoring
« Reply #12 on: December 26, 2021, 03:46:15 PM »
... As it is the rule forbidding thrust vectoring isn't really necessary as it's behavior would self eliminate.

Well, true.  But the rule against electronic thrust vectoring was written specifically to allow mechanical thrust vectoring.  I think it's been tried before?  @BrettBuck?

The motivation for that section of the rule was to prevent someone from putting three or four fans on a stunt ship (ala quadcopter) and using them for pitch and roll control, then trying to claim that they're not aerodynamic because they're propellers you see, not wings.

If you're clever about how you define a "mechanical linkage" there's nothing to prevent you from building a mechanical analog computer and using that for thrust vectoring.  Should be interesting, especially if you use friction wheels to implement integration and get some castor oil on the mechanism.  The rule is ambiguous about driving an air compressor and using fluidics for computation -- if anyone wants to go there I'll help with modifcations to the rules to clearly allow it.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Mark wood

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Re: Thrust line Vectoring
« Reply #13 on: December 26, 2021, 06:17:19 PM »


The motivation for that section of the rule was to prevent someone from putting three or four fans on a stunt ship (ala quadcopter) and using them for pitch and roll control, then trying to claim that they're not aerodynamic because they're propellers you see, not wings.



But under the rules as written that would be allowed with the provision they would be mechanically operated. I think the idea that any claim propellers are not aerodynamic would fail the most basic of test. Again the concept would pretty much self eliminate. Quad copter style back flips would fall under the Arnold Schwarzenegger bull in a china shop style points arena.  Entertaining for sure but definitely not graceful.
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
“Physics is like sex: sure, it may give some practical results, but that’s not why we do it.” – Richard P. Feynman

Offline Howard Rush

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Re: Thrust line Vectoring
« Reply #14 on: December 26, 2021, 06:20:34 PM »
I wonder what direction one would vector the thruat.
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