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Author Topic: Centrifugal Force Calculator  (Read 1246 times)

Offline CircuitFlyer

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Centrifugal Force Calculator
« on: March 25, 2020, 09:59:11 AM »
http://www.calctool.org/CALC/phys/newtonian/centrifugal. Just came across this.  Thought it may be useful to folks with a curious mind.  It has a variety of units to use. Plug in the radius (ft or m), the angular speed, lap time, (seconds per rev) and mass (oz, lbs or kg).  It spits out the acceleration (g, ft/sec^2, m/sec^2) and line pull (lbf, N).  Note: input linear speed or angular speed, not both.
Paul Emmerson
Spinning electrons in circles in Mississauga, Ontario, Canada
Low Cost DIY Control Line Timer - www.circuitflyer.com

Offline Dave Hull

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Re: Centrifugal Force Calculator
« Reply #1 on: March 28, 2020, 01:53:27 AM »
Paul,

Just to add a bit to your calculations--I read an article from an old 1960's model magazine that showed results of actual strain gage testing done while flying. I believe they were using Goodyear racers or something similar. They recorded values slightly higher than the straight centrifugal loads from level, unaccelerated (x-axis) flight. In a stunter, I might expect the aero loads to be even more of a contributor.

Dave

Offline Brett Buck

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Re: Centrifugal Force Calculator
« Reply #2 on: March 28, 2020, 09:16:09 AM »
Paul,

Just to add a bit to your calculations--I read an article from an old 1960's model magazine that showed results of actual strain gage testing done while flying. I believe they were using Goodyear racers or something similar. They recorded values slightly higher than the straight centrifugal loads from level, unaccelerated (x-axis) flight. In a stunter, I might expect the aero loads to be even more of a contributor.

   I would be interested in seeing that, but I would expect a pretty small number in the case of flying tangent. The line "sag" is, for sake of argument, 3 degrees, the component of the drag associated with the lines is maybe 1/2 lb, that's only .03 ish lbs out of maybe 10 lbs from the pure centrifugal force.

    I would expect the racing case to be have a  much larger component of "added" line tension, because I think the line drag is a much larger proportion of the total, maybe 50% as opposed to stunt which is maybe 10-20%.

     Brett

Offline Wolfgang Nieuwkamp

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Re: Centrifugal Force Calculator
« Reply #3 on: March 28, 2020, 03:09:25 PM »
The line drag has no influence on the centrifugal force. But the lines themselves certainly contribute to the centrifugal force, when measured at the handle.
Regards,
Wolfgang

Online Howard Rush

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Re: Centrifugal Force Calculator
« Reply #4 on: March 28, 2020, 03:23:17 PM »
I would expect the racing case to be have a  much larger component of "added" line tension...

It would for naughty racers.
The Jive Combat Team
Making combat and stunt great again

Offline Brett Buck

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Re: Centrifugal Force Calculator
« Reply #5 on: March 28, 2020, 06:26:30 PM »
The line drag has no influence on the centrifugal force.

   It doesn't? I thought the lines approached the airplane at an angle (say, 3 degrees, being generous), not square on.

     Brett

Offline Wolfgang Nieuwkamp

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Re: Centrifugal Force Calculator
« Reply #6 on: March 29, 2020, 10:05:07 AM »
Brett, you convinced me after making a principle drawing:


For clarity the line (red) sag is exaggerated.
Regards,
Wolfgang





Offline Serge_Krauss

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Re: Centrifugal Force Calculator
« Reply #7 on: March 29, 2020, 02:24:42 PM »
Centrifugal force and line tension are not the same. For a certain mass flying in a certain-radius circle at a certain speed, the centrifugal force is always the same. Aero forces change line tension.

Online Howard Rush

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Re: Centrifugal Force Calculator
« Reply #8 on: March 29, 2020, 05:05:30 PM »
Ainít no D line y, except for the tiny amount when youíre upwind or downwind.
The Jive Combat Team
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Online Howard Rush

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Re: Centrifugal Force Calculator
« Reply #9 on: March 29, 2020, 07:31:26 PM »
Now that I think about it, there would be a radial force on the line from the air blowing on it.  It wouldn't be drag, which is defined to be in the direction that the airstream is blowing on something, but a lift or side force component.  One could integrate that from the handle to the airplane.  I doubt if it would amount to much.  I could see what Dr. Hoerner has to say and calculate the net force. I guess, but I don't plan to. 
The Jive Combat Team
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Offline Serge_Krauss

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Re: Centrifugal Force Calculator
« Reply #10 on: March 29, 2020, 09:37:48 PM »
There are also aero forces from prop wash along the fuselage, from out-thrust, from any asymmetrical turbulence, from asymmetry of the fuselage ('lift'), from any yawing of the fuselage from the tangential, and from the outward canting of the nose to the relative wind when the fuselage axis is actually tangent to the circle.  For instance, when the fuselage axis is tangent to the flight circle, were it not from prop wash, the relative wind would be outward against the surface of the nose on the inside of the circle. That is, the nose is at an angle directed outside of the flight circle (tail would be the other way). FWIW...

Online Howard Rush

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Re: Centrifugal Force Calculator
« Reply #11 on: March 30, 2020, 01:57:43 AM »
There are also aero forces from prop wash along the fuselage, from out-thrust, from any asymmetrical turbulence, from asymmetry of the fuselage ('lift'), from any yawing of the fuselage from the tangential, and from the outward canting of the nose to the relative wind when the fuselage axis is actually tangent to the circle.  For instance, when the fuselage axis is tangent to the flight circle, were it not from prop wash, the relative wind would be outward against the surface of the nose on the inside of the circle. That is, the nose is at an angle directed outside of the flight circle (tail would be the other way). FWIW...

Yes, as you said above.  "Centrifugal force" is the mV2/R part.  I think Brett is generalizing the term to line tension felt at the handle.   

It is interesting to plot stuff like control deflection vs. non-rock-on-a-string force considering line bow from line drag and line elasticity.  I was working on that awhile back. I looked at the program tonight and couldn't figure what it did.  Such is dementia and poor documentation. 
The Jive Combat Team
Making combat and stunt great again

Offline Igor Burger

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Re: Centrifugal Force Calculator
« Reply #12 on: March 30, 2020, 02:44:26 AM »


 VD~

... just for info, wind (~1 m/s) is blowing TO the camera

Offline Wolfgang Nieuwkamp

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Re: Centrifugal Force Calculator
« Reply #13 on: March 30, 2020, 08:39:26 AM »
Howard,
the program just calculates F1 in my drawing.
Regards,
Wolfgang

Offline Brett Buck

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Re: Centrifugal Force Calculator
« Reply #14 on: March 30, 2020, 08:14:43 PM »
Yes, as you said above.  "Centrifugal force" is the mV2/R part.  I think Brett is generalizing the term to line tension felt at the handle.   

It is interesting to plot stuff like control deflection vs. non-rock-on-a-string force considering line bow from line drag and line elasticity.  I was working on that awhile back. I looked at the program tonight and couldn't figure what it did.  Such is dementia and poor documentation.

   Right. I was commenting on the centrifugal force VS what was measured by load cells on the lines, which was said to have a discrepancy.

    Brett

Offline Igor Burger

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Re: Centrifugal Force Calculator
« Reply #15 on: March 31, 2020, 03:37:32 AM »
So next time I must try really thick ropes as lines, they must improve line tension  VD~

BTW there are several other forces contributing to that measured force on handle and I think larger than those 3 degrees:
- lift force from rolled wing (tip weight)
- lift of yawed fuselge
- thrust of yawed prop

that is why I posted that video, line tension of indoors on 5m lines does not come from centrifugal force, it is only fraction of necessary line tension and even when model almost stops (angular speed) line tension is till enough for full controlling even overhead

Offline Brett Buck

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Re: Centrifugal Force Calculator
« Reply #16 on: March 31, 2020, 07:13:27 PM »
So next time I must try really thick ropes as lines, they must improve line tension 

  I did note that the difference is negligible. I care about this effect more than you do, because I try to trim out the other factors.

    Brett

Offline Brett Buck

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Re: Centrifugal Force Calculator
« Reply #17 on: March 31, 2020, 07:20:09 PM »
Brett, you convinced me after making a principle drawing:

   Generally correct, that was essentially what I was describing.

    I try to remove the other factors, those Igor describes, because while they give you more line tension, they also give significantly variable line tension (much larger variations than the drag component of the lines in a typical case), and are nearly impossible for most people to consistently deal with in terms of dynamics - like the "rotation about skewed axes" issue that demands some serious trickery to make happen without causing roll/yaw perturbations.

   Centrifugal force is plenty enough to do the maneuvers, "manufacturing" extra line tension above that is extremely difficult without creating other problems.

     Brett

Offline Igor Burger

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Re: Centrifugal Force Calculator
« Reply #18 on: April 01, 2020, 02:47:56 AM »
...  are nearly impossible for most people to consistently deal with in terms of dynamics - like the "rotation about skewed axes" issue that demands some serious trickery to make happen without causing roll/yaw perturbations.

Right, here is nice hint how to understand a thus deal with it  8)


Online Howard Rush

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Re: Centrifugal Force Calculator
« Reply #19 on: April 01, 2020, 03:09:05 PM »
Cool video.  The pitch axis of most stunt planes, by the way, is the intermediate axis. 
The Jive Combat Team
Making combat and stunt great again

Online Howard Rush

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Re: Centrifugal Force Calculator
« Reply #20 on: April 01, 2020, 03:14:34 PM »
So next time I must try really thick ropes as lines, they must improve line tension

I can give you a corollary.  Bob Carver, a physicist, would fly his Nelson .36-powered combat planes on .012" (.305mm) lines.  Sometimes the line tension would abruptly diminish to zero.
The Jive Combat Team
Making combat and stunt great again

Offline Serge_Krauss

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Re: Centrifugal Force Calculator
« Reply #21 on: July 07, 2021, 03:54:59 AM »
FWIW, since it this does not address the interesting point we mostly discussed...

I just re-viewed the original link and saw something that always troubles me, coming from people who should know better. Centrifugal force is not "fictitious." It is a real requirement of Newton's third law: for every action there is an equal and opposite reaction. Centrifugal force is the force you feel at the handle. It is one of a reaction pair of forces working on different objects that influence each other (pilot and plane). The pilot pulls on  the plane ( via the lines - or sub-atomic particles) with a centripetal force that accelerates the plane into a circular path. The plane pulls on the pilot with the required reaction force through the intermediary lines. The Centripetal force requires a reaction force applied oppositely and called centrifugal. A pilot attempting to use a 747 as a control liner would certainly not think a centrifugal force was "fictitious."

So,...to beat that "dead horse," centripetal and centrifugal forces are a reaction pair working on separate objects influencing each other. Fire away.
« Last Edit: July 07, 2021, 07:21:25 AM by Serge_Krauss »

Online Ken Culbertson

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Re: Centrifugal Force Calculator
« Reply #22 on: July 07, 2021, 10:54:56 AM »
Maybe this one explains why judges can't seem to agree on what properly flown maneuvers look like, well some anyway.



Ken
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If it is not broke, don't fix it.
USAF 1968-1974 TAC


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