Tesla Semi Tractor Appears To Have “Electric Aero Ears”

Silver Tesla Semi cab, back view

FEB 28 2018 BY GEORGE BOWER 18

Elon Musk Tesla Semi reveal event

Tesla Semi reveal event

Or should we call them Tesla Semi “Wind wings.” Or how about “Gap Flaps”?

The Tesla Semi has very low drag. One way they keep drag low is to close the gap between the tractor and the trailer.

Figure 1

It appears that these aero panels move depending on the yaw angle of the trailer. It’s pretty clear if you watch the first 20 seconds of the YouTube Tesla Semi “Reveal” video:

.embed-container { position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; max-width: 100%; } .embed-container iframe, .embed-container object, .embed-container embed { position: absolute; top: 0; left: 0; width: 100%; height: 100%; }

There’s no mistaking it if you look at this screenshot:

Silver Tesla Semi

Figure 2

Also if you look at a shot of the tractor from the rear, sans trailer, you can see what appears to be actuators to move the panels:

Silver Tesla Semi

Figure 3

How much the “movable” part actually helps the aero characteristics is probably debatable. However, it seems obvious to us that they move out of the way to keep the tractor from hitting the side of the trailer when the trailer is cocked at a big angle.

Whatever the reason: pretty darn cool in our opinion.

You can also see the “flaps” in the recent video of the Tesla Semi driving on the highway:

.embed-container { position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; max-width: 100%; } .embed-container iframe, .embed-container object, .embed-container embed { position: absolute; top: 0; left: 0; width: 100%; height: 100%; }

Thanks to my research partner Keith Ritter for spotting this!

Categories: Tesla

Tags:

Leave a Reply

18 Comments on "Tesla Semi Tractor Appears To Have “Electric Aero Ears”"

newest oldest most voted
Doggydogworld

Moving panels gives zero aero benefit, since yaw angle is ~0 and speeds where aero matters (unless jack-knifing, ha).

As you note, the movement is for low speed turns. It’s the only way to close the aerodynamically horrible cab-to-trailer gap at highway speeds while still allowing low-speed turns without trailer impingement.

HVACman

Tesla designed the system for a very, very tight gap. It is not only the yaw angle, but also relative pitch that requires the gap-closing fairings to move out of the way. When the rig goes through a dip, the pitch angle of the tractor will suddenly change relative to the pitch angle of the trailer and possibly crash the top of the trailer front into the fairing. We haven’t seen any demonstration of how the fairings would handle the pitch, but it is likely the tractor 5th wheel has some tilt-position sensors that would pick up pitch changes dynamically just as it appears it has yaw-angle sensors.

Most conventional tractors with gap fairings edge them with about 3-4″ of flexible rubber that can handle incidental contact due to yaw or pitch. Also, most slope the top of fairing towards the cab so it has some build-in gap bias allowing for pitch variation.

AnonyMouse

Did Tesla actually design and make this system? I doubt it. I think a Tesla got another company called XStream Trucking to customize their off-the-self active cab-to-trailer aerodynamic system for the Tesla Semi. By 2016, XStream Trucking already had a prototype called the GapGorilla that won a first prize in a DOE competition. XStream Trucking patented its design, renamed its active-aero device as TruckWings, and publicly launched their product on November 10, 2017, less than a week before Tesla unveiled the Tesla Semi on November 16, 2017. Coincidence? I think not.

There are some key differences between TruckWings and the Tesla Semi’s active-aero flaps. One is that the TruckWings side flaps fold inwards, while Tesla Semi’s fold outwards. Another difference is that the TruckWings eliminates the cab-to-trailer gap between the top of the flaring and trailer, while the Tesla Semi has a large semi-circle shaped gap at its top flaring. The TruckWings top flaring folds downwards/inwards, while the Tesla Semis top flaring with its semi-circle gap is rigid and does not move at all.

https://m.youtube.com/watch?v=wL6FAnLy5hE

http://xstreamtrucking.com

AnonyMouse
AnonyMouse
AnonyMouse

TruckWings news article from the day before Tesla unveiled the Tesla Semi:

https://newatlas.com/truckwings-active-aero-fuel-saving/52198/

XStream press release launching TruckWings one week before Tesla unveiled the Tesla Semi:

https://www.businesswire.com/news/home/20171110005683/en/XStream-Introduces-Industry-First-Active-Aero-Device-Streamline-Trucks

HVACman

Great find, AM! I was poking around and didn’t see any active flap systems on any other trucks – even the Supertrucks that Freightliner, Navistar, and Volvo developed. I completely missed this system.

It looks like the Tesla version is a refined version of the Truckwings system, with each wing independently-controlled and out-swinging, as you noted. Possibly a licensing agreement between the two?

Thanks for the tip!

Pushmi-Pullyu

“…the TruckWings eliminates the cab-to-trailer gap between the top of the flaring and trailer, while the Tesla Semi has a large semi-circle shaped gap at its top flaring. The TruckWings top flaring folds downwards/inwards, while the Tesla Semis top flaring with its semi-circle gap is rigid and does not move at all.”

Yes, I too had noticed that Tesla’s gap-closing panels leave a gap at the top. I had hoped that there was a 3rd, horizontal moving panel to cover that gap, but apparently not.

Well, that’s a possible improvement that Tesla might make on the production vehicle. If so, then presumably that panel would swing inward rather than outward, because swinging out would mean swinging up, requiring even more vertical clearance than normal for a tractor-trailer rig. Vertical clearance is already a problem in many places, and Tesla wouldn’t want to see a swinging panel scraped off by a low overpass!

comment image

HVACman
The top curved gap-filler panel Tesla included fits closer than most other top-fillers on other trucks. About all that is open is the crescent-shaped arc. It is possible that between the very-close side fit they get with the active wings and the relatively-close fit at top, their aero studies found a negligible aero benefit in attempting to fully close the crescent-shaped opening as compared to the increased complexity of the mechanism (note how the Truckwing top filler is pieces that have to fold back into themselves). More likely: A fixed accessory insert attached to the top-front-end of the trailer with an arc matching the cab top gap filler panel arc would be simpler and more reliable. I think I’ve seen some trailers that already have something like that. This gets back to George’s basic point on the other trailer article. As all the other major truck manufacturers have found, 2/3 of the aerodynamics of a tractor-trailer combo is related to the trailer’s features, which takes some non-standard customization to fully-optimize. The reveal-trailer was a conventional trailer with just basic off-the-shelf aero accessories. To get to 0.36 Cd and a full 500-mile range, full trailer optimization is also required, paired with… Read more »
Pushmi-Pullyu
Quoting from the article: “Thanks to my research partner Keith Ritter for spotting this!” O_o It’s rather bemusing to see observations and facts which I stated in various comments to previous InsideEVs articles on the Tesla Semi Truck, reported as “news” with no mention of, or credit given to, my comments. I also reported some of this in InsideEVs Forum discussions, as you can see in these two posts from January 19: http://www.insideevsforum.com/community/index.php?threads/tesla-semi-has-been-revealed-pics-stats-and-prices.197/page-2#post-3670 http://www.insideevsforum.com/community/index.php?threads/tesla-semi-has-been-revealed-pics-stats-and-prices.197/page-2#post-3714 Not that I’m suggesting you and Keith couldn’t have come up with the same info independently, but it’s rather disappointing that my comments went unnoticed. 🙁 However, I thought the actuator arms were located on those things sticking out to the left and right of the upper portion of the rear of the cab. But perhaps you are correct; perhaps what I thought were combination hinges and actuator arms are just complex hinge mechanisms. * * * * * “Tesla designed the system for a very, very tight gap. It is not only the yaw angle, but also relative pitch that requires the gap-closing fairings to move out of the way. “We haven’t seen any demonstration of how the fairings would handle the pitch, but it… Read more »
Trolly

U r a d ou che

HVACman

PMPU –

First, kudus to your keen observation last November about the flaps and thanks for the heads-up that you had seen it first! It was a subtle feature. Neither George or I saw them or knew of their existence until just two days ago when I was reviewing thereveal videos for George, looking for details on the reveal-night trailer aerodynamic features. I saw the little wiggle and glint of the flaps moving. I mentioned it to George and he reviewed and confirmed what was happening and assembled a follow-up article on the trailer aerodynamics.

Unfortunately, neither George nor I had followed the forum thread on which you posted your finding, so did not realize you had already discovered and described this feature.

Just as Leibniz and Newton contemporaneously and independently discovered the secrets of calculus, so you and I independently-discovered the secrets of the Tesla wind wings. Guess that puts us both in good-company!

Pete Repete

It could just be that they’re able to swing out so you can get to the auxiliary lines, connections etc. and the movement of them has got nothing to do with aero and everything to do with practicality….

HVACman

yes, access too. Good point.

But the pivoting function is clearly for preventing trailer-to-cab contact. If you watch the reveal video, you can see the fairings pivot in as the semi swings one direction, then pivot out as it swings another. Both swings appropriate for the direction the trailer swinging

Bunny

For backing also, a lot of tight places you have to do 90 degree type back where the rear of the cab gets really close to the side of the box.

God/Bacardi

My two part question is why didn’t ICE Semi makers come up with this before and is there anything preventing ICE Semi makers from adding it now if its so great?

AnonyMouse

See my long winded comment above.

HVACman

Not long-winded – just complete. I for one appreciate a thorough and concise comment. Thanks again for the post.