Measuring forces:
Thread Starter
Joined: May 2004
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From: The center of the earths surface
Forces:
Quote: What forces, precession of what?
Presumably you've already looked through a standard engineering mechanics textbook for the basic formula e?
Gengis Mate! I am just a mere airframe position er, and am not up to speed with the intricacies of the science, hence my question which I think very basic and fundamental, mind you if I had any brains I would not be shifting aluminum and bundles of meat around the various destinations.
So as per the Q, if you can refer me to such that I can learn for myself, or tell me.
Now what I have is TWO rotating masses, each to cancel out the forces applied to the other, I am looking at having a computer program to manage this hopefully linear resultant!
Yes it is an "interesting" project.
But one thing with NZ mate, although its right up the dark end of nothing, and behind the rest of the world, the likes of dear old Bert and co, are still very much to the fore! we do a lot with #8 wire mate! due solely to our location, mind you next week I will be In Aus! then Fiji, then Solies, then NZ, then Aus?
But just think of what Bert could have achieved with a system such as PP! or kiwi biker!
Excuse my tongue in check belligerence mate, but I posted the Q because I did not know where else to go after Google! and I am not a academic.
Chr's
H/Snort
Presumably you've already looked through a standard engineering mechanics textbook for the basic formula e?
Gengis Mate! I am just a mere airframe position er, and am not up to speed with the intricacies of the science, hence my question which I think very basic and fundamental, mind you if I had any brains I would not be shifting aluminum and bundles of meat around the various destinations.
So as per the Q, if you can refer me to such that I can learn for myself, or tell me.
Now what I have is TWO rotating masses, each to cancel out the forces applied to the other, I am looking at having a computer program to manage this hopefully linear resultant!
Yes it is an "interesting" project.
But one thing with NZ mate, although its right up the dark end of nothing, and behind the rest of the world, the likes of dear old Bert and co, are still very much to the fore! we do a lot with #8 wire mate! due solely to our location, mind you next week I will be In Aus! then Fiji, then Solies, then NZ, then Aus?
But just think of what Bert could have achieved with a system such as PP! or kiwi biker!
Excuse my tongue in check belligerence mate, but I posted the Q because I did not know where else to go after Google! and I am not a academic.
Chr's
H/Snort
Joined: Jul 2007
Posts: 1,158
Likes: 62
From: 51.50N 1W (ish)
Still insufficient information.
However, given that precession can be considered as rotating a force applied to a rotating mass by precisely 90 degrees, then simple geometry would indicate that to cancel out a force using only two rotating masses, the two would need to have parallel axes of rotation and opposite sign.
But you will need to explain much more clearly what you are trying to achieve, and if this would negate your patent application, then find a clever engineer to do the hard work, and get him to sign a contract assigning design rights.
However, given that precession can be considered as rotating a force applied to a rotating mass by precisely 90 degrees, then simple geometry would indicate that to cancel out a force using only two rotating masses, the two would need to have parallel axes of rotation and opposite sign.
But you will need to explain much more clearly what you are trying to achieve, and if this would negate your patent application, then find a clever engineer to do the hard work, and get him to sign a contract assigning design rights.
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Joined: Feb 2000
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From: UK
As fitter2 says, you don't really tell us what the problem is. But, precession/gyroscope maths is generally labelled under "dynamics" in engineering teaching. This is reckoned to be a pretty good book on the subject I believe (all the ones on my bookshelf - which are in an office about 600 miles away at the moment, are out of print, but if you can find a copy the one by Hibbeler, same title, was pretty good.)
From memory, it's a case of defining rotational inertia as a vector, then if you multiply that vector by the input rotation vector, you get a resultant output torque vector? Or something like that.
If you are trying to balance two gyroscopes, presumably it's a case of making the right hand side of the two equations the same, then playing around with the left hand terms to keep that true.
I always hated vector algebra! Give me scalars and angles every time!
G
From memory, it's a case of defining rotational inertia as a vector, then if you multiply that vector by the input rotation vector, you get a resultant output torque vector? Or something like that.
If you are trying to balance two gyroscopes, presumably it's a case of making the right hand side of the two equations the same, then playing around with the left hand terms to keep that true.
I always hated vector algebra! Give me scalars and angles every time!
G
Thread Starter
Joined: May 2004
Posts: 290
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From: The center of the earths surface
Measuring forces:
Gengis & Fitter2:
Thank you, now I know where to go to do some reading!
As you can appreciate, I am deliberately being a tad coy! on the exactness.
Its new is all I will say, I jolly well think it will work, I guess if it doesn't, then it will probably kill me!
But before that I have to somehow test my theories! somehow?
Time and money & work are the two biggest killers with anything new and self funded.
Chr's
H/Snort.
Thank you, now I know where to go to do some reading!
As you can appreciate, I am deliberately being a tad coy! on the exactness.
Its new is all I will say, I jolly well think it will work, I guess if it doesn't, then it will probably kill me!
But before that I have to somehow test my theories! somehow?
Time and money & work are the two biggest killers with anything new and self funded.
Chr's
H/Snort.
Joined: Jul 2007
Posts: 1,158
Likes: 62
From: 51.50N 1W (ish)
Time and money & work are the two biggest killers with anything new and self funded.
(apologies to Monty Python)
Joined: Oct 2003
Posts: 1,300
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From: Canberra Australia
Precession
The thread begs a question.
It would be of some significant interest to have someone calculate the approximate precessional force produced by 4 engines of a typical airliner at cruise in a rate one turn: and maybe for the engine of an F-16 pulling 9g. Side loads on the spool bearings need to be contained and do the FBW computers make compensatory allowances during manoeuvres?
The thread begs a question.
It would be of some significant interest to have someone calculate the approximate precessional force produced by 4 engines of a typical airliner at cruise in a rate one turn: and maybe for the engine of an F-16 pulling 9g. Side loads on the spool bearings need to be contained and do the FBW computers make compensatory allowances during manoeuvres?
Joined: Nov 1999
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From: East side of OZ
G'day Milt,
I reckon it'd be more interesting to calculate the loads during the takeoff rotate when the engines are at or close to max rpm and the aircraft pitches up to 20deg in fairly short order.
Regards,
BH.
I reckon it'd be more interesting to calculate the loads during the takeoff rotate when the engines are at or close to max rpm and the aircraft pitches up to 20deg in fairly short order.
Regards,
BH.
Joined: Oct 2003
Posts: 1,300
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From: Canberra Australia
BH
Care to make a few guesses for your V2 case?
Some of the precessional forces from a high RPM turbojet must be considerable particularly by those with fans. Cannot recall feeling those forces seperately identified from all the other forces acting on a manoeuvering aircraft. Natural stability will tend to dampen out the unwanted effects to some extent.
Care to make a few guesses for your V2 case?
Some of the precessional forces from a high RPM turbojet must be considerable particularly by those with fans. Cannot recall feeling those forces seperately identified from all the other forces acting on a manoeuvering aircraft. Natural stability will tend to dampen out the unwanted effects to some extent.
Last edited by Milt; 21st July 2009 at 07:44. Reason: spelling
Joined: Jun 2009
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From: Oxford, England
Could some one tell me please how too, or indeed if there is a formula to determine/measure the forces of precession?
No excuses - if you're smart enough to dream up the application and the questions, then you are smart enough to do this yourself
Chris
Joined: Mar 2006
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From: Just south of the Keevil gap.
HNR,
As other posters have suggested, a Google search should turn up some answers. You could start with Sperrys rules of precession.
Also try here
I wonder if you are thinking of something along the lines of Alex (Sandy) Kidds machine. 3 coupled gyros (I think) and it convinced Prof. Eric Laithwaite that when powered up, it "lost" weight.
Still some way to go before we get to the spindizzy .....
As other posters have suggested, a Google search should turn up some answers. You could start with Sperrys rules of precession.
Also try here
I wonder if you are thinking of something along the lines of Alex (Sandy) Kidds machine. 3 coupled gyros (I think) and it convinced Prof. Eric Laithwaite that when powered up, it "lost" weight.
Still some way to go before we get to the spindizzy .....
