guy
DC-3
Posts: 37
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Post by guy on Aug 18, 2008 10:32:47 GMT -5
Hi all,
I am sure there are people on this forum who know why the Connies (L049,1749,L1049,L1649) have those inclined or oblique frontwheels? What was the idea behind? Thanks in advance.
Happy landings to all.
Guy
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Post by mjahn on Aug 18, 2008 13:07:49 GMT -5
Terry Morgan, The Lockheed Constellation, p. 7
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guy
DC-3
Posts: 37
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Post by guy on Aug 18, 2008 13:59:52 GMT -5
Thanks for the precise answer.
Guy
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Post by johnhinson on Aug 18, 2008 23:39:42 GMT -5
All aircraft (and motor cars) have wheels set at an angle like that - it just looks more obvious on the Constellation. I suspect its design related more to balance, turning circles and retraction means. The purpose is not to save rubber but by setting the angle (it is called the "caster angle") the wheels will self-centre smoothly and correctly. Just because somebody has written something in a book, it doesn't necessarily make it fact!* Flight Simulator FDEs do, remarkably, have a setting for this - if you have an aircraft that has difficulty in straightening out (and seems to duck and dive a bit) on the yellow line after a turn, the aircraft.cfg setting almost certainly needs tweaking. John * - equally, you could argue that my saying this doesn't make it fact, but you can find more info at en.wikipedia.org/wiki/Caster_angle
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guy
DC-3
Posts: 37
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Post by guy on Aug 19, 2008 1:09:30 GMT -5
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Post by johnhinson on Aug 19, 2008 13:42:28 GMT -5
Fair point - I hadn't thought much about camber angle on aircraft, particularly on the nose wheel but of course the Constellation has two nose-wheels so this can be provided.
I don't think FS has a setting for this, or know what effect it might have on taxying performance.
John
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guy
DC-3
Posts: 37
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Post by guy on Aug 20, 2008 0:29:35 GMT -5
My initial question was not so much about FS ,but why the real Connie had that pronounced positive camber angle on the frontwheels. As you can see on this beautiful picture of the swiss Connie from Airliners.net below, in a sharp turn the outer front wheel is more or less in the air, so after all, it may well save rubber. www.airliners.net/open.file/1155495/L/Guy
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Post by johnhinson on Aug 20, 2008 3:08:19 GMT -5
My initial question was not so much about FS ,but why the real Connie had that pronounced positive camber angle on the frontwheels. As you can see on this beautiful picture of the swiss Connie from Airliners.net below, in a sharp turn the outer front wheel is more or less in the air, so after all, it may well save rubber. www.airliners.net/open.file/1155495/L/Guy With respect, that effect on the nose-wheel would be caused by the castor angle and the fact that the nosewheel is turned to nearly 90 degrees. You cannot judge the camber angle in that picture as the wheels are almost at right angles to the photographer. I would imagine that the forward thrust when taxying in a tight turn like that would soon ensure that wheel made contact with the ground. I do not think the "saving rubber" idea is at all valid. You would need to view the wheels end on to judge the camber angle. It is just my opinion, but I do not see any benefit in camber angle on wheels that close together - the benefit is gained when they are far apart, as on motor cars or perhaps in this example on the main undercarriage. John
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guy
DC-3
Posts: 37
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Post by guy on Aug 20, 2008 4:01:38 GMT -5
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Post by emfrat on Aug 20, 2008 4:15:04 GMT -5
From stuff that I learned way back when I was a motorcycle nut, I believe the steering geometry of the Connie is arranged to provide (a)straight-line stability at speed and (b) compensation for the heavy steering at low speed, caused by (a). If you want an erudite treatise on the subject, look here: en.wikipedia.org/wiki/Bicycle_and_motorcycle_geometryIn simple terms, the angle of the oleo leg combines with the relatively small wheel to produce a lot of trail, to give (a). The positive camber of each wheel also contributes to straight-line stability, because the left wheel is always trying to go left and the right one is trying to go right. However when the pilot steers the nose gear, the inside wheel increases its turning effect but the outside wheel becomes nearly vertical and has almost no turning effect. That gives (b). It is a sort of self-servo effect. I could well be wrong here, but it has always seemed logical to me. I don't know if the FS dynamics engine is clever enough to model those forces, and it really doesn't need to. Cheers MikeW
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guy
DC-3
Posts: 37
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Post by guy on Aug 20, 2008 6:17:13 GMT -5
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Post by capflyer on Aug 20, 2008 8:28:44 GMT -5
John, I don't think there should be any doubt about the Camber of the Connie's nose wheels. They are most definitely positively cambered and that's part of its "uniqueness".
However, I agree that it would be interesting to see traction tests to determine if it has any real change on the ability of the plane to make a sharp turn or save rubber, but my immediate guess would be that by angling the tires so that in sharp turns the inside tire is heavily cambered into the turn it would promote less scrubbing of the tire as the force on the tire would be more vertical than horizontal. It is working on the same principal as to why taking a motorcycle (or any 2-wheeled vehicle) and leaning it over improved cornering and traction. They are using this same principle on the Connie.
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Post by Tom/CalClassic on Aug 20, 2008 9:37:11 GMT -5
Hi John,
The wheels are indeed cambered and it is to reduce rubber scrubbing and ease the pressure on the tiller wheel.
Hope this helps,
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Post by johnhinson on Aug 20, 2008 10:00:11 GMT -5
John, I don't think there should be any doubt about the Camber of the Connie's nose wheels. They are most definitely positively cambered and that's part of its "uniqueness". Thanks - no doubt about that from the excellent photographs! John
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guy
DC-3
Posts: 37
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Post by guy on Aug 20, 2008 11:09:03 GMT -5
"However, I agree that it would be interesting to see traction tests to determine if it has any real change on the ability of the plane to make a sharp turn or save rubber, but my immediate guess would be that by angling the tires so that in sharp turns the inside tire is heavily cambered into the turn it would promote less scrubbing of the tire as the force on the tire would be more vertical than horizontal" You see that best on the picture I gave already above: www.airliners.net/photo/Breitling-Super-Constellation/Lockheed-C-121C-Super/0890853/L/What Mikew has said ( "when the pilot steers the nose gear, the inside wheel increases its turning effect but the outside wheel becomes nearly vertical and has almost no turning effect") seems true to me. In a sharp turn the outer frontwheel seems to leave te ground! www.airliners.net/open.file/1155495/L/As far as FS is concerned , I have seen now that the Abacus and also the FSDZign Connie model this behaviour rather well. The beautiful new L1649 by M.Jahn not (or not yet). Guy
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