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.

Hmmmmm...Â* I'd say either don't let your wife pull the trailer or else
have HER hook it up to the car. :-D

On 3/17/2019 2:12 AM, wrote:
"...how many of you have had a trailer break away from
the tow vehicle and what was the cause?"

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

As I recall the first of her efforts was on the I-10 somewhere between Quartzite and Phoenix. The vehicle was an 18-passenger Ford van with the interior modified into a family camper of sorts. It had a step bumper to which the 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 our problems with sailplane trailers relate to their length and the resulting very high rotational moment of inertia about their axel. The loads on the hitch as the vehicle’s back wheels fall into a dip or go over a bump 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 decelerated together. There was no significant damage, except to the bumper, the mounting 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’t 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 (washboard) dirt road. Just after turning onto the pavement the trailer departed from the tow vehicle, maneuvered off to the right side of the road, probably following the crown of the road, and pulled to a stop alongside her. In this case the ball on the tow vehicle was attached to a proper heavy-duty tow 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… only it wasn’t. In fact, the safety clip was nowhere to be found. I had hooked up the trailer at home hours before and I’m sure I put the safety pin in properly, but I am also certain a properly installed safety clip cannot possibly fall out. So there. Anyway, the safety chains were attached to rings on each sides of the tow bar so they departed with the tow bar. One of the other crews leaving the airport that morning stopped to help my wife hook the rig back together. They had a spare safety clip in their vehicle. Again, I didn’t hear about it until after I landed.

My wife’s third attempt was by far her best. She’s driving a Suburban at 60 mph in the right lane of a busy four-lane undivided highway between Joshua Tree and Twentynine Palms. In this case the cause of the separation was, as Charlie so aptly put it, “a worn imperial ball in a metric hitch�. I like that wording. It almost seems to absolve me of any responsibility for the subsequent events, despite the fact that I’m 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’t work. They aren’t 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, threaded 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 land at a nearby airport.

--
Dan, 5J

Any clunking noise from the ball/hitch combination is a warning that should not be ignored.
Good on you for accepting responsibility.

On Sunday, March 17, 2019 at 8:53:46 AM UTC-7, Dan Marotta wrote:
Hmmmmm...Â* I'd say either don't let your wife pull the trailer or else
have HER hook it up to the car. :-D

On 3/17/2019 2:12 AM, mskoe.... il.com wrote:
"...how many of you have had a trailer break away from
the tow vehicle and what was the cause?"

SNIPPED
The trailer turned to the left, probably driven off by the last of the two hooks to break, threaded 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 land at a nearby airport.


Whew.

Fran's got more miles/hours in front of a glider trailer than most readers of RAS have in their logbooks. She knows how to hook'em up, but expects the PIC to do a preflight of all the equipment. Rightly so.

I can think of two other self-launching trailers.....but I am not familiar enough to know the specific causes. I would lay the first flyer on the repetitive event of Lots of Miles and Wear on the attachment ball. Henry Combs' custom trailer launched over an embankment on the downhill slope through Red Rock Canyon on a return leg. No one injured but N301Q. Both the glider and trailer were back in service after appropriate care. Mike might know about safety chains on that one. The tow car had logged around 300,000 crew miles.

And a Region 12 contest around 1988 or so, Trip Mellinger's trailer speared across northbound traffic and attacked a gas station wall in Mojave. That was probably a very early Komet trailer, attached by someone other than the pilot and left the airfield with an impromptu indentured crew. (All my suppositions.... )

I know there is a Charlie Spratt tale of a trailer that spent a long set of hours waiting in a grassy median for the bleary-eyed crew to make the next gas stop. Then they got to backtrack to find said detached-loiterer . . . ..

So.
It happens. More often than we would like. Preflight before you pull out the drive. One more walk around. Those two minutes save a lot of heartache. And the pre-spring maintenance underview also saves a lot of angst and expense.

Best to all,
Cindy

On Friday, March 22, 2019 at 12:59:16 AM UTC-7, CindyB wrote:
On Sunday, March 17, 2019 at 8:53:46 AM UTC-7, Dan Marotta wrote:
Hmmmmm...Â* I'd say either don't let your wife pull the trailer or else
have HER hook it up to the car. :-D

On 3/17/2019 2:12 AM, mskoe.... il.com wrote:
"...how many of you have had a trailer break away from
the tow vehicle and what was the cause?"

SNIPPED
The trailer turned to the left, probably driven off by the last of the two hooks to break, threaded 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 land at a nearby airport.


Whew.

Fran's got more miles/hours in front of a glider trailer than most readers of RAS have in their logbooks. She knows how to hook'em up, but expects the PIC to do a preflight of all the equipment. Rightly so.

I can think of two other self-launching trailers.....but I am not familiar enough to know the specific causes. I would lay the first flyer on the repetitive event of Lots of Miles and Wear on the attachment ball. Henry Combs' custom trailer launched over an embankment on the downhill slope through Red Rock Canyon on a return leg. No one injured but N301Q. Both the glider and trailer were back in service after appropriate care. Mike might know about safety chains on that one. The tow car had logged around 300,000 crew miles.

And a Region 12 contest around 1988 or so, Trip Mellinger's trailer speared across northbound traffic and attacked a gas station wall in Mojave. That was probably a very early Komet trailer, attached by someone other than the pilot and left the airfield with an impromptu indentured crew. (All my suppositions.... )

I know there is a Charlie Spratt tale of a trailer that spent a long set of hours waiting in a grassy median for the bleary-eyed crew to make the next gas stop. Then they got to backtrack to find said detached-loiterer . . .. .

So.
It happens. More often than we would like. Preflight before you pull out the drive. One more walk around. Those two minutes save a lot of heartache. And the pre-spring maintenance underview also saves a lot of angst and expense.

Best to all,
Cindy

Cindy brings up a salient point. the pilot owner/driver should always be the person to close and secure and hook up or at the minimum do a through check. I picked up a glider from the shop having had a bit of work done. the shop owner had put the glider in tailer and closed up trailer. I was in a hurry and did not check everything. When I got to the first gas station I saw the back door of the Minden Fab trailer was no longer on the trailer.