Re: [A/S] Sway

["John P Sargeant" <john.sargeant@xxxxxxxxxxxx>]

> What do you do when the
> a/s sways? Is there something we could have done?".

 I don't think that the group has addressed the question that is primary
here namely- is there something we could have done when a trailer goes into
a sway.
Seems to me that when  that happens the first inclination is to try to
regain control by slowing down.
 When your trailer starts swaying it seems like you are out of control, but
yet we all know that all trailers sway slightly as they  travel down the
road. If you look at a semi with a trailer going down the road, the trailer
is swaying slightly and moving slightly from side to side. That pendulum
effect only causes problems when the side to side motion gets so pronounced
that the weight of the pendulum bob(trailer) overcomes the fulcum (hitch
point) of the pendulum. If you slow down suddenly, that effect has to be
more pronounced. You are forcing the rear to front forces to shorten the
pendulum, which of course they can't do because it's solid. So where do the
forces then go? It seems to this grade 12 physics student, that they have to
go sideways, (especially if the trailer is not dead centre on the tow
vehicle and facing exactly straight ahead)  thereby increasing the force and
speed the pendulum bob ( trailer) moves to the side. If this force becomes
great enough (increased deceleration) it overcomes the speed and direction
of the tow vehicle and then it looses direction, friction forces holding it
on the road are overcome, and it starts to slide, hits the curb or shoulder
and the whole investment becomes  inverted.

It seems to me  that  when gross swaying occurs that the following steps
should be taken
    1. Don't panic
    2. Don't slam on the brakes
    3. Ride it out without changing direction quickly (like you do on an icy
road surface)
    4. Don't look where you might end up but look where you need to be and
make all efforts to regain your position. If you look into the oncoming lane
when you are trying to regain control, you will probably end up there. If
you concentrate on where you should be going, you likely will end up there.
    5. Last resort, slam the accelerator to the floor to increase speed of
the fulcum, steer in the direction you want to go and then use your trailer
brake.

The next time you are in a vacant parking lot, practise the slam, steer,
trailer brake sequence. It's what the airline pilots do to gain habit in
place of  forethought.

So that's the Tinhut theory of overcoming sway. I have touched the
acclerator rather than the brake when wind-washed by a semi and it seems to
work with my Reese / on sway bar lash-up.

OK physics majors and engineers, what do you think.

http://csep10.phys.utk.edu/astr161/lect/history/newton3laws.html   (That's a
web site with Newton's Three Laws of Motion on it for reference purposes)