> "351CJ" <351CJ@msn.com> wrote in message
>> "Chris Zuhn" <firstname.lastname@example.org> wrote in message
>>> I have seen first hand what a shifting trailer load can do to cause sway.
>>> 65MPH, one-ton dually towing a two-axle 20 foot equipment trailer. The
>>> trailer load was a light-weight backhoe that was not secured at all with
>>> chains/straps. The backhoe worked its way toward the back of the trailer
>>> and as soon as the tongue started to lift, the rig started to sway. Rig
>>> got turned sideways in the 4 lane highway in about 10 seconds. Driver
>>> not have time to do anything. Luckily, no accident or injuries occured.
>>> The other drivers close by saw what was happening and got out of the way.
>>> The trailer and truck were probably close to the same weight.
>> What kind of idiot moves a backhoe that isn't secured at all with chains
>> or straps on a trailer on the highway? That guy is astonishingly stupid
>> and extremely unsafe.
> You're missing the point. The questions that we are pondering is "why?" I
> have searched all over the 'net and found no evidence that anybody ever
> studied it adequately to explain it.
> It doesn't matter how stupid people are who haul backhoes. What matters is
> that a formerly stable combination crashes itself with a different center of
> Do you have any input on that?
No mystery here. A trailer will tend to be stable when the
foward/leading end of the trailer is carrying a percentage of the weigh
on its hitch through proper CG (ie 10 to 15% of the trailers weight
being coupled to a stable tow vehicle) this forward mass stabilizes the
rest of the trailer to follow it (kind like follow the leader of sorts)
When CG shift to rear, the trailer becomes unstable because it is
heavier behind the axle CG than in front of it which makes it very
unstable plus this shift weight off of tow vehicle as well which gives
it even less control on the trailer behind it and with a sudden move or
maneuver, oscillation can set in because CG is behind axle in direction
of travel and the tall heavy condition influences its control over the
lighter front end as to masses (heavy rear light front) react against
each other across axle(s) center line and the heavier end will win an
since lighter end is guiding direction it can oscillate/whip tell you
loose control. The only way to recover from this before it is too late
is to apply trailer brakes as hard as possible and no vehicle brakes and
the force on trailer trying to brake itself and tow vehicle will restore
enough control (pendulum effect of sorts) to stop vehicle safely.