Is This the Sort of Trailer Hitch He Hit? - 2013 Tesla Model S Long-Term Road Test
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2013 Tesla Model S: Is This the Sort of Trailer Hitch He Hit?

November 19, 2013

2013 Tesla Model S

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.

2013 Tesla Model S

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.

2013 Tesla Model S

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.

2013 Tesla Model S

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.

2013 Tesla Model S

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.

2013 Tesla Model S

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


Comments

  • kirkhilles_ kirkhilles_ Posts:

    I'd be interested to see some tests at how an average sedan/sports sedan would handle something like that. I don't know if it would cause a fire, but might cause a great deal of damage.

  • explorerx4 explorerx4 Posts:

    How about a 3 way like this? Hoping this works.

  • explorerx4 explorerx4 Posts:

    Didn't work. I see plenty of tow bars with a hitch ball on 3 of the 4 sides.

  • djwdjw djwdjw Posts:

    Tesla has apparently decided to roll-out an firmware update without any supplied documenation that a) raises the LOW ride height to begin with and b) disables LOW at highway speed on all cars (previously this was the default at highway speed, now STD is). You should verify the details independently, but it appears this change was made to all Model S cars with the air suspension option. Done over the air, without owner permission/consent (the change was not documented in any release notes). Changes in secret - they must feel a sense of entitlement and arrogance to make any changes they want to owner's cars at any time. TesNSA?

  • stovt001_ stovt001_ Posts:

    Amazing how gasoline powered cars burn to the ground due to damage or poor maintenance literally any day of the week, but an electric car does the same thing and everyone freaks out. Heck Ferrari 458s were burning down faster than they could build them when they were first released. The fact that it took a few minutes after he stopped (and after he drove for some time with the damage) just for the flames to appear is encouraging.

  • mercedesfan mercedesfan Posts:

    @stovt001, I completely agree about the overreaction, but electric cars are a unique case. I feel completely safe in my Model S because it is obvious Tesla did their job when it comes to isolating the battery pack. However, Li-ion batteries in general are

  • ebb2143 ebb2143 Posts:

    Maybe the driver was describing a hitch with substantial height adjustment, like this: http://b.cdnbrm.com/images/products/large/hitch_accessories/trimax_aluminum_adjustable_ball_mount_hitch2.jpg

  • quadricycle quadricycle Posts:

    @mercedesfan: Ever witness HF exposure? Mean stuff, that. Back on topic, I agree that chemical fires need to be looked at seriously, and that the Tesla battery isn't all that bad in this regard. Specifically that it ignites slowly (people have always mana

  • fordson1 fordson1 Posts:

    "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." None of the hitches you have shown would have been hit by the floor pan of a conventional car, for the simple reason that the floor pan of a car is not the lowest point of the underside of the car - any of these hitches would have been impacted by a front valence, radiator support, engine oil pan, crossmember or suspension parts. Go look at any number of your suspension walkaround photos you've done, Dan, and tell me why any of these hitches would have hit the passenger compartment floor rather than those components I named. Yes, I understand it's just speculation we're doing, because Tesla is not willing to talk about it...or about the drivetrain failures they are having.

  • adamb1 adamb1 Posts:

    There is also the possibility of a 3-ball hitch that you rotate to change the size of the ball. I see those frequently on trucks here in TN. They are generally substantial and their configuration would allow them to sit in the described fashion.

  • duck87 duck87 Posts:

    @kirkhilles: I can answer that- you can say goodbye either to your front bumper lip, the bumper itself, and/or the oil pan. I've never heard of an accident penetrating the floorpan, and you're probably more at risk of something coming through the firewall

  • hybris hybris Posts:

    http://www.etrailer.com/Ball-Mounts/Curt/C45001.html This is a much more realistic "3 pointed thing" as these are popular with small business drivers.------------------------------------- Tri-balls as I have seen do have a tendency to almost always land when dropped with a ball up so this is very possible, unless the burning Tesla driver's description is off at its just a regular drawbar and ball.--------------------------------------------------------- In either case the weight distribution drawbar is big enough as you said that they wouldn't fit under most cars gas or electric and if you hit one you will know you hit something bad.------------ I have doubts that hitting any of these in any other car would actually cause harm beyond floor pan damage let alone personal injury so maybe the guy is being more than a bit over zealous with the situation.

  • gslippy gslippy Posts:

    I love how the experts come out of the woodwork to tell us that Tesla should strengthen the bottom of the car - so reactive. No amount of 'armor' plating improvements under the S will prevent spearing by an object like that.

  • greenpony greenpony Posts:

    So the guy clearly drove over some substantial piece of road debris, yet people are talking about a design flaw with the car?

  • socal_eric socal_eric Posts:

    Tesla and the government should investigate the issue to see if there is a way to make the cars safer and reduce the chance of damage to the battery pack and other electronic that could lead to a fire, even if it is a rare event. With the electrification of many new models the research and design decisions may prove to make those types of vehicles safer. That said people and especially the media shouldn't jump on the bandwagon that there's necessarily a defect or problem with that car. Gasoline powered vehicle catch fire and while also extremely rare, there have been instances where road debris such as concrete rebar bouncing on the freeway has pierced the underbody and impaled/killed occupants.

  • bwake bwake Posts:

    @djwdjw Software companies do this all the time. Apple and Microsoft update your computer operating system automatically. You have to opt out to prevent it. Many applications software vendors do this too. As I understand it, Tesla Model S owners can cho

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