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paulrod36(at)msn.com
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 Posted: Wed Aug 27, 2008 1:22 pm Post subject: Control Surface Flutter |
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<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]--> Here's one for our aeronautical engineers to ponder: While staring at my ailerons, wondering if they were going to flutter if ever I get this bird finished, a thought struck me.
Ailerons flutter because they are moving back and forth very fast.
They move back and forth very fast because they are light, and because they have no mass balancing them on the other side of the hinge.
It then struck me that, to add inertial mass doesn't necessarily mean putting a weight on an arm out front, or adding a flange so you can put weight in front of the hinge.
AHA! EUREKA! ZOUNDS! How about placing a mass, not necessarily equal to the weight of the aileron, on the pushrod itself? Mass is used to create inertia, and inertia doesn't care which way it's being made to reluctantly move. The aileron can't move very fast up and down if the pushrod doesn't want to move very fast backward and forward. There's no additional force needed to move the aileron, and if the weight is on the pushrod, it's inside, out of the airstream, where the wind (and supercritical observers)can't find it. I see a tubular lead weight on the pushrod, threaded, to snug up against the locknut at the bellcrank end of the pushrod.
Whaddayathink?
Paul Rodriguez
601XL/Corvair
[quote][b]
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Gig Giacona
Joined: 10 Jan 2006
Posts: 1416
Location: El Dorado Arkansas USA
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| Posted: Wed Aug 27, 2008 1:35 pm Post subject: Re: Control Surface Flutter |
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I'm not saying that would or wouldn't work. Mainly because it has been a LONG time since I took physics. But if it would work wouldn't weights attached to the cables do the same thing? And since the cable run inside the fuselage you wouldn't have to put the weight way out in the wing you could attach it to cable inside the fuselage.
[quote="paulrod36(at)msn.com"] Here's one for our aeronautical engineers to ponder: While staring at my ailerons, wondering if they were going to flutter if ever I get this bird finished, a thought struck me.
Ailerons flutter because they are moving back and forth very fast.
They move back and forth very fast because they are light, and because they have no mass balancing them on the other side of the hinge.
It then struck me that, to add inertial mass doesn't necessarily mean putting a weight on an arm out front, or adding a flange so you can put weight in front of the hinge.
AHA! EUREKA! ZOUNDS! How about placing a mass, not necessarily equal to the weight of the aileron, on the pushrod itself? Mass is used to create inertia, and inertia doesn't care which way it's being made to reluctantly move. The aileron can't move very fast up and down if the pushrod doesn't want to move very fast backward and forward. There's no additional force needed to move the aileron, and if the weight is on the pushrod, it's inside, out of the airstream, where the wind (and supercritical observers)can't find it. I see a tubular lead weight on the pushrod, threaded, to snug up against the locknut at the bellcrank end of the pushrod.
Whaddayathink?
Paul Rodriguez
601XL/Corvair
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_________________
W.R. "Gig" Giacona
601XL Under Construction
See my progress at www.peoamerica.net/N601WR |
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carlossa52(at)gmail.com
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| Posted: Wed Aug 27, 2008 1:54 pm Post subject: Control Surface Flutter |
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I don't think it would work. You need to increase the inertia of the part subject to flutter.
In other words, the ailerons mass needs to go up by rigidly attaching a weight to it.
Attaching the aileron to a brick wall won't help. Making it a brick wall will, but unfortunately, it will mess with your CG... 
do not archive, in case I am wrong.
Carlos
2008/8/27 <paulrod36(at)msn.com (paulrod36(at)msn.com)>
...
AHA! EUREKA! ZOUNDS! How about placing a mass, not necessarily equal to the weight of the aileron, on the pushrod itself? Mass is used to create inertia, and inertia doesn't care which way it's being made to reluctantly move.
....
[quote]
Whaddayathink?
Paul Rodriguez
601XL/Corvair
[b]
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Al Hays
Joined: 01 Oct 2007
Posts: 42
Location: Gore, VA
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| Posted: Wed Aug 27, 2008 2:53 pm Post subject: Control Surface Flutter |
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Without conjecturing on whether it would work regarding flutter, I
would be very concerned about that much added weight causing metal
fatigue in the pushrod tube, especially the threaded portion and rod
ends. Any added weight on the pushrod tubes would be bouncing up
and down putting bending forces on the tubes. JMHO. Thanks for
sharing the idea.
Al Hays
601XL/Corvair N5892H reserved
On Aug 27, 2008, at 5:35 PM, Gig Giacona wrote:
| Quote: |
I'm not saying that would or wouldn't work. Mainly because it has
been a LONG time since I took physics. But if it would work
wouldn't weights attached to the cables do the same thing? And
since the cable run inside the fuselage you wouldn't have to put
the weight way out in the wing you could attach it to cable inside
the fuselage.
[quote="paulrod36(at)msn.com"] Here's one for our aeronautical
engineers to ponder: While staring at my ailerons,
wondering if they were going to flutter if ever I get this bird
finished, a thought struck me.
Ailerons flutter because they are moving back and forth very fast.
They move back and forth very fast because they are light, and
because they have no mass balancing them on the other side of the
hinge.
It then struck me that, to add inertial mass doesn't necessarily
mean putting a weight on an arm out front, or adding a flange so
you can put weight in front of the hinge.
AHA! EUREKA! ZOUNDS! How about placing a mass, not necessarily
equal to the weight of the aileron, on the pushrod itself? Mass is
used to create inertia, and inertia doesn't care which way it's
being made to reluctantly move. The aileron can't move very fast
up and down if the pushrod doesn't want to move very fast backward
and forward. There's no additional force needed to move the
aileron, and if the weight is on the pushrod, it's inside, out of
the airstream, where the wind (and supercritical observers)can't
find it. I see a tubular lead weight on the pushrod, threaded, to
snug up against the locknut at the bellcrank end of the pushrod.
Whaddayathink?
Paul Rodriguez
601XL/Corvair
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rtdin
Joined: 16 Mar 2008
Posts: 46
Location: Florida panhandle
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| Posted: Wed Aug 27, 2008 8:11 pm Post subject: Control Surface Flutter |
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Interesting idea, Paul. I don't think that its ever been done. Sort of like a poor man's shimmy dampener. Take a walk through any aviation museum and look at what they were doing from the late 1930s on through to the present day. They are what's called "accepted practices." Very eye opening. A good first step would be to look at the articles that the late, great Tony Bingelis wrote over the years for EAA about balancing control surfaces. They are archived on the web site. Do a search for "Bingelis." Also see the Zenair Association Newsletters for early 1987 (they are available on CD for $40) and you will find drawings by CH for aileron mass balances. CH calls for less than 1.5 lbs of lead poured into a piece of streamlined tubing. That's about standard for planes of the size and speed of the 601.
I made mass balances for my project in 1967 or 68. It was a 1450 lb all metal with a 220 vne. The ailerons were practically identical in design to a 601. The designer called for 1.4 to 1.6 lb of lead on a 1/2" 4130 arm that passed under the rear spar and into the bottom if the wing tip. I still have the drawings.
A guy that I know lives about an hour away. He retired from USAF civil service as an Aerodynamicist. He looked over my drawings and gave me some good advice. I won't bore everybody with that.
Bob Dingley XL/Lyc Do not archive
**************
It's only a deal if it's where you want to go. Find your travel deal here.
(http://information.travel.aol.com/deals?ncid=aoltrv00050000000047) [quote][b]
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notsew_evets(at)frontiern
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| Posted: Wed Aug 27, 2008 9:03 pm Post subject: Control Surface Flutter |
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Please bore us. What was the advise????
SW
[quote] ---
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paulrod36(at)msn.com
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| Posted: Thu Aug 28, 2008 11:50 am Post subject: Control Surface Flutter |
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<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]--> Gig, I'd be very hesitant to put it on the cable because no matter how tight the cable was strung (in itself a possible danger) there would be (for lack of a better name) the "boing" effect, strumming on the cable. That might be even worse than flutter. I think it would be better to translate the up-and-down reciprocal motion to a captured, back-and-forth motion.
Al, the pushrod is only about 8 or 9 inches long between the ball ends, and I doubt there'd be enough moment arm, particularly at the end of the pushrod, to bend a 5/16" threaded steel rod. The weight ought not to have to be that heavy for its inertia to act upon the (potential) flutter.
Thanks, guys for your input. I believe all new ideas should be vigorously attacked. If they can be killed, they didn't deserve to live. If they survive peer attacks, they deserve to live. After over 25 yearsin the profession, I also came to believe in the Darwinian approach to industrial safety. (But that's another story......)
Paul Rodriguez
[quote] ---
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