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#12
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Corrie wrote:
"Rich S." wrote It may have something to do with the rebound spring. I think you're probably right. From what I can see of the pictures and drawings, it's probably sized to damp the natural frequency of the big spring, which is sized to damp the natural freq. of the small one. It might be possible to screw up the gear with differently-massed struts, wheels, brakes, tires, etc. so that the resulting natural freqs synch up, yielding undamped divergent feedback. (Remember the films of Galloping Gertie, the Tacoma Narrows bridge?) We had those kinds of problems in my Statics and Dynamics classes back in college. But they always made my head hurt. ;-) Rich, in the Emeraude plans, how specifically are the springs called out? Do they specify the stiffness (or the spring constant, may be the same thing), as well as the dimensions? (By way of contrast, the gear-retraction system of the CA-65 uses a garage-door spring , hardly a tight specification. But there's not likely to be much occillation, as the spring is just a mechanical assist while cranking up the gear. The gear in the Delta is a solid 1" round bar of 6150 spring steel. As I understand it, it gets a lot of spring from twisting the bar. The gear retraction is also spring assisted. Except John Dyke specified a Chevy hood spring. -- ----Because I can---- http://www.ernest.isa-geek.org/ ------------------------ |
#13
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"Corrie" wrote in message
om... It might be possible to screw up the gear with differently-massed struts, wheels, brakes, tires, etc. so that the resulting natural freqs synch up, yielding undamped divergent feedback. (Remember the films of Galloping Gertie, the Tacoma Narrows bridge?) We had those kinds of problems in my Statics and Dynamics classes back in college. But they always made my head hurt. ;-) Remember it? Heck I drive over it several times a week. It's still down there - under the new bridge. Rich, in the Emeraude plans, how specifically are the springs called out? Do they specify the stiffness (or the spring constant, may be the same thing), as well as the dimensions? On the plans, the coil springs are dimensioned by size and material, i.e. wire diameter, coil diameter, length & # of turns. The kicker is they call out 4130 steel as the material - entirely inappropriate for gear springs. Rich S. |
#14
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Have you ever looked at a Piper TriPacer (and other Piper models)? They use
bungee cords stretched over ears on what was originally an automotive shock (off an old Buick I think). The bungees provided "boing" and the shock smoothed the ground ride. Bruce A. Frank "B2431" wrote in message ... Can automotive shocks or McPhereson struts be used in landing gear struts? If so how would one determine which ones to use? Dan, U. S. Air Force, retired |
#15
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#16
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Don't forget the damping effect of the wings either. I don't think
designers bother much with damping on light aircraft. Too much weight and complexity for a function thats secondary in a flying machine. "B2431" wrote in message ... Can automotive shocks or McPhereson struts be used in landing gear struts? If so how would one determine which ones to use? Dan, U. S. Air Force, retired |
#17
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Ah So--velly good reasoning.
Jay wrote: Don't forget the damping effect of the wings either. I don't think designers bother much with damping on light aircraft. Too much weight and complexity for a function thats secondary in a flying machine. "B2431" wrote in message ... Can automotive shocks or McPhereson struts be used in landing gear struts? If so how would one determine which ones to use? Dan, U. S. Air Force, retired |
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