Back in 2019, Rivian lit up the automotive internet with Tank Turn, demonstrated by the 2022 Rivian R1T in a viral YouTube video. Since then, though, the company has announced the feature is delayed and won’t be ready at launch. There are several reasons why, which R1T chief engineer Charles Sanderson walked us through.
Tank Turn takes advantage of the R1T pickup and the R1S SUV’s quad-motor platform to make the vehicle to spin like a top; to do so, the motors and wheels on one side of the vehicle rotate forward and the wheels and motors on the other side rotate backward at the same time. It’s a devilishly simple idea that’s proven much harder to program than you’d expect, and the core concern is safety. Getting the truck to Tank Turn safely and consistently is not a small challenge.
The biggest issue is the number of variables involved. What you see in the video was a best-case scenario, and the Rivian team was lucky enough to capture a good turn on the first try.
First, unless conditions are perfect, it’s possible each wheel will have a different amount of grip than the others and require more or less power to break traction. While the truck’s computer can read the road surface via suspension inputs as you’re driving, there’s no good way for it to know exactly what the surface under each tire is like when you come to a stop. If any wheel is getting too much or too little power during a Tank Turn, it can cause the vehicle to spin off in a random direction instead of rotating in one place. Power delivery has to be programmed very carefully to respond to changing grip before and during a Tank Turn. You can see this issue crop up right at the beginning of the video.
Next, because the truck’s wheelbase isn’t square (that is, because there’s more distance between the front and rear axles than there is between the wheels on either side of each axle), it won’t always rotate around the exact center of the vehicle, especially if the surface isn’t consistent. If the point of rotation is off center, it can cause the vehicle to spin off in any direction instead of rotating in one place. A safeguard needs to be programmed to recognize this situation and either correct it or end the Tank Turn.
Then there’s the matter of gravity. In order to execute a Tank Turn, all four wheels have to break traction. Once that happens, the truck is at the mercy of physics. If the surface is inclined in any direction, the truck will slide that direction as it spins. A safeguard needs to be programmed that can recognize this and shut it down before the truck spins into a tree, a ditch, or worse.
Finally, there’s the matter of speed. During testing, Rivian discovered the amount of power needed to get all four wheels spinning results in a lot of wheel speed, which ends up making the truck spin around very fast. From inside the truck, it’s a hell of a ride, so much so there’s concern it’ll scare drivers who aren’t ready for it, which could result in a loss of control if the driver panics. Speed, of course, also exacerbates all the above issues.
Put it all together, and Tank Turn is really only easy to do in the middle of a big, flat, slippery field. Making it work anywhere else is a big challenge. The places a Tank Turn would actually be useful off-road are never level, wide-open spaces. The amount of programming and testing needed to make Tank Turn work safely and predictably is far too great for Rivian to develop it purely as a gimmick, so the engineers are dedicated to making it actually useful.
Right now, though, the majority of Rivian’s engineering resources are dedicated to getting the R1T, R1S, and Amazon van out the door as smoothly as possible. After that, they’ll have the R2 and R3 models to work on. Although the team hasn’t forgotten about Tank Turn, a complicated off-road tool that most buyers will only ever use once to show off to their friends and family just isn’t a top priority. Sanderson couldn’t give us an updated timeline, but he knows full well how cool Tank Turn is and how plenty of people on his team are eager to perfect it.
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