Andy Ross <[EMAIL PROTECTED]> wrote:
> David Megginson wrote:
>> Paul Surgeon writes:
>> > I don't know about everyone else's experience but I haven't found
>> > one aircraft in FG that wants to sit still on the ground even with
>> > the engine off.
> An ideal mechanism would keep track of how much force each wheel
> "could" apply in the ground plane, and then calculate the right amount
> to apply to keep the aircraft from moving. This basically comes down
> to solving a bunch of simultaneous equations for each FDM iteration.
> It's a big mess; I'd be really scared of making this work.
I'm not shure if it would be really that difficult - although I don't
know precisely what's already there.
As mentioned previously some sort of ground FDM would be a really nice
thing. If it was plugged into SimGear then people designing racing card
simulations (once discussed on this list) could profit from it.
Simulating friction on the ground should be quite easy as long as you
know some parameters: You have to know about position as well as
horizontal and vertical forces of _each_ wheel. Probably this is
already there for a C172 (as mentioned above, I don't know), the rest
is sort of practical mechanical numeric almost every student in
engineering should learn in the first or second year.
Look, it's quite easy to calculate how a tyre will move when you put a
force onto it. I suppose it would be useful if you have a tyre object
that you hand a force vector over. Because of the tyre being elastic it
will move a bit to the side as long as the vector contains a component
that crosses the longitudinal axis of the aircraft. The tyre object
contains an easy calculation which results in a sideway position shift
(and a counterforce). When you know this position shift you don't have
to deal with forces any more as long as the aircraft sits on the
ground. When the vertical forces onto the tyre decrease then the
sideway shift will increase because the tyre slips over the ground. If
the tyre gets into snow slush then the force vector returned by the
tyre object will not only contain a sideway component but also a
longitudinal one.
O.k., I'n not the one to tell Andy, Dave, Jon, Curt and all the others
to be too stupid to understand the simplicity ;-) So please would
someone explain to me the missing parts in my idea ? Did I overlook
something, do I miss some relevant information ?
Thanks,
Martin.
--
Unix _IS_ user friendly - it's just selective about who its friends are !
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