Cobra Trailer Emergency Brake Experience

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.

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Dan, 5J