Cobra Trailer Emergency Brake Experience

Holy crap that not at all funny. Glad to hear no one was hurt. Mix of
imperial and metric never a good thing IMHO



At 08:12 17 March 2019, wrote:
"...how many of you have had a trailer break away from=20
the tow vehicle and what was the cause?"=20

My wife has thrown sailplane trailers 3 times (thrown as in had them
comple=
tely separate from the vehicle while in motion).

As I recall the first of her efforts was on the I-10 somewhere between
Quar=
tzite and Phoenix. The vehicle was an 18-passenger Ford van with the
interi=
or modified into a family camper of sorts. It had a step bumper to
which
th=
e trailer ball was mounted. Unfortunately, the chains were also clipped
to
=
the bumper. The bumper was rated for a 5000 lb. trailer. I think a lot of
o=
ur problems with sailplane trailers relate to their length and the
resultin=
g very high rotational moment of inertia about their axel. The loads on
the=
hitch as the vehicle=E2=80=99s back wheels fall into a dip or go over
a
bu=
mp at high speed must be astronomical. At the very least, they
exceeded
the=
expectations of this particular bumper manufacturer. The bumper fell
off.
=
Responding to the resulting commotion my wife gradually applied her
brakes=
.. The trailer caught up with the tow vehicle and the hitch, with the
bumper=
still attached, nosed under the back of the van. The two vehicles
deceler=
ated together. There was no significant damage, except to the bumper,
the
m=
ounting brackets of which showed clear evidence of fatigue. Good
Samaritans=
helped park the trailer and bumper off to the side of the freeway,
sending=
my wife on her way to get me. I didn=E2=80=99t hear about it until
after
I=
landed when she showed up without the trailer. It was a long
weekend.

Her second try was after leaving the gliderport, which is on a bumpy
(washb=
oard) dirt road. Just after turning onto the pavement the trailer
departed
=
from the tow vehicle, maneuvered off to the right side of the road,
probabl=
y following the crown of the road, and pulled to a stop alongside her. In
t=
his case the ball on the tow vehicle was attached to a proper heavy-
duty
to=
w bar in a square receptacle welded to heavy bars which in turn were
bolted=
to the frame of the vehicle. The tow bar slides into the square
receptacle=
and is held in place by a lateral pin which in turn is held in place by
a
=
safety clip=E2=80=A6 only it wasn=E2=80=99t. In fact, the safety
clip was
n=
owhere to be found. I had hooked up the trailer at home hours before
and I=
=E2=80=99m sure I put the safety pin in properly, but I am also
certain a
p=
roperly installed safety clip cannot possibly fall out. So there. Anyway,
t=
he safety chains were attached to rings on each sides of the tow bar so
the=
y departed with the tow bar. One of the other crews leaving the airport
tha=
t morning stopped to help my wife hook the rig back together. They
had a
sp=
are safety clip in their vehicle. Again, I didn=E2=80=99t hear about it
unt=
il after I landed.

My wife=E2=80=99s third attempt was by far her best.
She=E2=80=99s driving
=
a Suburban at 60 mph in the right lane of a busy four-lane undivided
highwa=
y between Joshua Tree and Twentynine Palms. In this case the cause of
the
s=
eparation was, as Charlie so aptly put it, =E2=80=9Ca worn imperial
ball
in=
a metric hitch=E2=80=9D. I like that wording. It almost seems to
absolve
m=
e of any responsibility for the subsequent events, despite the fact that
I=
=E2=80=99m a mechanical engineer and the hitch had been banging
up and
down=
on the ball for years. The safety chains had fairly beefy cast iron
hooks,=
such as are often found on safety chains. Those don=E2=80=99t
work. They
a=
ren=E2=80=99t able to withstand a sudden, forceful jerk. The trailer
turned=
to the left, probably driven off by the last of the two hooks to break,
th=
readed it way across the other 3 lanes of traffic and wandered out into
the=
desert. This time I did hear about it. I turned around and came back
to
la=
nd at a nearby airport.