2013 Tesla Model S: Is This the Sort of Trailer Hitch He Hit?
November 19, 2013
We've all heard about the most recent Tesla fire, the one that happened in Tennessee over a week ago. The driver reportedly remains a Tesla fan after hitting a "rusty three-prong trailer hitch" that was "sticking up with the ball up in the air."
As he tells it, he couldn't miss the object, which subsequently passed under the car and made hard contact. "I felt a firm "thud" as the hitch struck the bottom of the car, and it felt as though it even lifted the car up in the air."
But I haven't yet found a photograph of the actual "rusty three-prong trailer hitch" in question.
We do a lot of towing tests here at Edmunds, so we have a collection of hitch equipment in our garage. I went downstairs and inspected what we had to see if any of it made sense.
The "three-prong" description immediately brought to mind a load-equalizing hitch, a very common hitch setup that nearly all travel trailers are towed with because they tend to be quite nose heavy. The 3-foot spring bars are like wheelbarrow handles that hold up the back of the truck and distribute excess nose weight back onto the trailer axles.
But it's very unlikely the spring bars were attached like this in this scenario. They're only in place if a trailer is in the act of being towed, and no one has said anything about a trailer crash preceding the Tesla incident.
When the spring bars are absent, the hitch head indeed has a 3-prong appearance. Folks often leave this part plugged into their truck even when they're not towing. And it's easy to imagine someone forgetting to insert the secondary retaining pin and have the main pin vibrate loose and fall out.
Tesla or not, it'd be a formidable chunk of debris for any car to hit no matter how it wound up on the road. These things are pure steel. And that 2-inch shaft, the part that plugs into the hitch receptacle, is solid, not hollow. Each one of these weighs about 50 pounds, a figure that came from our own scale in preparation for our most recent towing test.
Here's the smaller of the two we own sitting ball up, as described in the driver's account. Imagine a Tesla Model S arriving on the scene left-to-right at 70 mph, the speed the Tennessee car was travelling at impact.
Like ours, that car had air suspension, so at that speed it would have been running along in Low mode with 5.2 inches of ground clearance under the battery box. My water bottle is 8-inches high. The hitch head is quite a bit taller. The math doesn't work out well.
These hitches are bottom-heavy where the absent spring bars are meant to plug in. It wants to sit this way. If hit from the left, the initial impact could tip it up like this and present a 2-inch square solid steel spear to the underside of the car.
Even if it wasn't oriented in this position, it's clear an equalizer hitch like this would do major damage to any car that ran over it. And this could easily explain why he thinks his Tesla got lifted off the ground. Why the quarter-inch battery box sheathing got torn open.
So why is he still a Tesla fan? For one, the fire didn't really get going for five minutes. After the impact he got two levels of warnings, the first of which he ignored in an attempt to make it home. He heeded the second, pulled over, got out and began to collect his things. Then the first smoke appeared underneath. At this point he says he walked about 100 yards away. Flames didn't appear at the front of the car (ahead of the battery) for another two minutes.
But he also says this: "I am thankful to God that I was totally uninjured in any way from this impact. Had I not been in a Tesla, that object could have punched through the floor and caused me serious harm."
From this I take it the size of the object he hit, the thud and the lifting off the ground made a real impression on him. It's another clue that makes me think my equalizer hitch theory is plausible. Any of the above objects could easily cause "serious harm" if hit by a standard car. After all, the sheetmetal under our heels is not much thicker than a half-dozen sheets of paper. We might not have feet left if we ran over one of these.
To his point about the impact itself, the Tesla Model S's underfloor battery box represents a 4-inch thick barrier that prevents objects like this from piercing the cabin. That's no bad thing from a direct-injury point of view. He's probably right.
Am I overestimating the size of the hitch? Could it be a regular one like this? You be the judge. For my part, I don't see any "three prong" resemblance. And the above 2-inch receiver with 2-inch ball isn't quite 5 inches tall. It's quite possible one of these could pass cleanly underneath and make zero contact.
But this is all speculation. Tesla has not responded to my request to interview the driver or share these pictures with him to see if they are similar to the thing he hit. I'm hoping we'll know for sure someday, and that goes for the similar incident in Kent, Washington, too.
Dan Edmunds, Director of Vehicle Testing @ 11,923 miles