Automotive shocks in aircraft

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.


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