Automotive shocks in aircraft

Corky Scott wrote:

On Tue, 15 Jul 2003 07:44:26 -0700, "Rich S."
wrote:

"Corky Scott" wrote in
message ...

You can fabricate a set of landing gear
using springs only (it'd be a bit boingy). . .

Corky.........

Is this just a gut feeling or a pronouncement? )

The Emeraude has springs only (main and rebound) and isn't the least bit
boingy.

Rich S.

It was an attempt at a humerous way of saying continual undamped
motion. :-) Undamped springs can lead to uncommanded oscillations.
You see this all the time with cars that have worn out shocks. In the
worst cases, you see them come to a stop or drive over a bump and just
keep on bouncing up and down.

This is most often the result of undamped (shocks with little or no
oil in them anymore) coil spring suspensions. Leaf spring suspensions
actually have some damping built into the several leafs and the action
between them when the suspension gets deflected so they will damp down
motion a lot quicker than a coil spring.

Bungee cords also have a certain amount of damping effect so you don't
often see that type of landing gear with shocks too.

I'm guessing that the undamped wittman springs and leaf springs work
because the landing gear has very little unsprung weight compared to
automobile suspensions, and also because the suspensions are
relatively short and fairly stiff.

I'm betting that if you were to somehow attach shocks to your
Emeraude, you'd notice a smoother ride across grassy strips. Don't
know if it's worth the weight/drag penalty though.

Corky Scott

The tires, which are typically inflated such as to provide "cushioning
and floatation" and which look underinflated when compared to modern
automobile tires, also provide a great deal of damping. They also
provide a modest amount of drag when taxiing on pavement as well as low
footprint pressure footprint pressure for operation from grass. If you
overinflate the tires so that the mains do not have their normal 25% to
30% deflection, they are decidedly "boingy"; although this is in the
range of a couple of inches, rather than of visibly bouncing the aircraft.

Peter