DarZeelon

Jim,


As Barry, being a chopper pilot knows too well, just saying 'torque' isn't enough...
The axis around which the torque is applied must be stated, or implied, or this word is of no value.

If a gyroscope spins around the 'X' axis, when torque is applied around the 'Y' axis, it will induce the gyro's spin axis to move toward the 'Z' axis.


This is the basis of cyclic control in any helicopter's main rotor.


And I agree the explanation in Wikipedia is rather minimalistic and vague... This is why it can be edited by the reader...
I edited a few values, but I am not enough of a physicist to edit this value.

Kmot

My Feedback: (24)

Thanks for the info Dave. She looks good with that oil burner up front!

Sport_Pilot

What is vague about it?
It even gives a few equations which would give the torque if you knew the period of spin, which unfortunately is unknown due to the fact that we correct for it. I am sure there are some sites with more detail and more equations. Perhaps you could post one.

DarZeelon

Hugh,


Here's a couple:


http://www.gyroscopes.org/behaviour.asp

http://cybercom.net/~copters/aero/gyro.html

http://helicopterflight.net/gyroscopic%20P.htm

http://www.metacafe.co.il/watch/6164...ecession_cool/


....Well, a bit more than a couple...

Sport_Pilot

Dar,
Those are good links, but they have less information than the simple equations in Wikipedia.

DarZeelon

Hugh,


Although I did study physics to quite a high level, I prefer to explain thing in words that a layman would understand.

The equation in the Wiki link is quite comprehensive, but people who are not scientifically orientated, will only become disorientated from trying to comprehend it...

I am sure Barry will concur about the use of the gyroscopic precession effect and how it is used to allow the pilot to control his helicopter.

...Or more importantly for this thread; how a propeller with a large amount of inertia can adversely alter the course of a model, in a maneuver, due to its gyroscopic precession.

Sport_Pilot

Yes but if you redo the equation to solve for torque, then it is fairly large. That is the torque required to overcome precession. Wonder about the torque from torque induced precession? Nevermind, I don't have time to go over a more comprehinsive site right now. Gotta work.

MinnFlyer

My Feedback: (4)

True, Graupner props are not made for 3-D

But then, most airplanes aren't made for 3-D

But if you fly REAL airplanes, Graupner's are the best!

RVM

PFFFT!!!

DarZeelon

Yeah, Mike.


Look at this great Hartzell... Oops! Graupner prop!

wcmorrison

My Feedback: (2)

You are flying a gyrscope with that big prop.

Cheers,

Chip

downunder

My mistake there Dar...it's a 10.5x8 and I don't know how come I typed 11.5 because as far as I know this was the only size Taipan made with that blade shape. The angle I've taken the photo gives almost a plan view of the blade shapes and sizes as a comparison. Second from bottom is a normal Taipan 11x5 while the rest are the deep cuff types.

As for the rest of the discussion, here's a link to a modeller's page on precession (with formulas). http://www.supercoolprops.com/articl...gyroscopic.php

I mentioned earlier that it's dependent on where the mass of the blades is concentrated and by sheer good timing there happens to be a discussion on this over at [link=http://www.clstunt.com/htdocs/dc/dcboard.php?az=show_topic&forum=103&topic_id=274445&mesg_id=274445&page=]SSW[/link] with a way to determine this for any prop. The text in the diagram is a bit hard to read but is understandable.

Of course another way to do it would be to get a similar prop, cut it in half across the hub and see where the blade balances.

DarZeelon

Thanks, Brian.

I was under the impression it was a misprint...


Cheers.

Sport_Pilot

Yes that is why a proper equation uses "moment of inertia" not just the mass. That doesn't seem to be properly accounted for in the Supercool version. Because a props mass is closer to the center VS the heavy outer rim of a gyroscope I suspect the Supercool formula exagerates the force by a considerable amount. While the effect is stronger than someone had posted earlier, I don't think it is nearly that strong. The site referanced in SSW is spot on to use the radius of gyration instead of the total radius to figure out the moment of inertia.