Why The Tesla Cybertruck’s Body Has No Floor

Go to a junkyard. Take a look at any car in the lot. Save for the ones that are rusted out, you’ll note that they’ve all got floors. They’re an integral part of the unibody. Then look at a Tesla Cybertruck. It eschews a traditional floor entirely. The chassis has a big ol’ hole in the bottom.

It might seem ridiculous, but going floorless comes with some serious positives for manufacturing that could apply to EVs more broadly. Popular car teardown channel Munro Live takes us through the Cybertruck’s floorless (but not flawless) design, led by CEO and Tesla investor Sandy Munro.

The video focuses on dropping the Cybertruck’s battery pack, which is the key to this whole shebang. It’s not just the battery that’s coming out—it’s half the interior to boot!

Straight In, Straight Out

We touched on this aspect of the Cybertruck when we looked at Caresoft’s teardown last week.  Now, Munro and Associates have given us a better look at how the combined design of battery and floor completely changes the way the truck is built.

Traditionally, a unibody vehicle will have a floor and a roof, with pillars connecting the two. The pillars essentially form the frames upon which the doors are mounted. When building the vehicle, everything for the interior has to be effectively loaded in through the holes in the body. Automakers will install interior components like seats through the door holes, for example, and dashboards are often installed through the windscreen aperture before the glass goes in.

The Cybertruck does things in a more straightforward fashion. The body has no floor of its own. Instead, the battery is installed straight up into the body from underneath. Before installation, though, the battery is pre-loaded with a great deal of interior components. In the video, we see a thick foam underlay on the top of the battery, with the Cybertruck’s carpet laid on top. The front seats and center console are bolted on top of all that, the former installed on large cast aluminum brackets.

For comparison, here’s Munro’s look at the Rivian R1T, which uses a more conventional unibody-with-floor design:

This greatly simplifies interior installation for the Cybertruck. Pre-loading all these components on the battery can be done out in the open. This is much easier than installing these components inside the truck. The whole assembly is then pushed up into the truck in one smooth maneuver. It’s much easier than having workers or robots trying to twist and pivot seats into place through narrow door apertures.

Munro reckons it could save anywhere from $600,000 to $800,000  in assembly line costs, though doesn’t specify how he came to those exact numbers. “I don’t know why it is that we never thought about this before… loading the floor in at the same time as the seats and whatnot,” says Munro. He speculates it’s because of the sheer ubiquity of the unibody concept in the latter half of the 20th century. “We never really thought that hard about what could be done as opposed to what we were told to do,” he says.

While the benefits for manufacturing are obvious, one can also speculate as to the drawbacks of such a design. If the battery is acting as the floor, it needs a near-perfect seal to the rest of the chassis to avoid water ingress. This is more important for a floor than for doors, because water on the road splashes all over the underbody. Whether the seal between the two would survive the removal and insertion of the battery is also worth considering.

There’s also a question of structural rigidity. Leaving the floor open is akin to how convertibles lose rigidity by not having a roof. Obviously, bolting in a big stiff battery housing counteracts that somewhat, but it needs to be rigidly installed to do its job well. Effectively, the battery is kind of acting as a big structural brace to tighten up the chassis as a whole.

Overall, though, this could be a way for automakers to build EVs cheaper and quicker than before. It’s worth noting, though, that this same hack wouldn’t really work for ICE cars. They don’t have a big battery mounted under the body, so there’s nothing to act as a bolt-in floor. Of course, automakers could create large stamped floor panels for ICE cars and bolt them up into a chassis from underneath with the seats and carpet ready to go. In that case, though, the benefits are more tenuous versus just building a traditional unibody. This hack makes the most sense when you already have to sling a big battery under the body in the first place.

In Detail

The video gives us a full walkthrough on dropping the Cybertruck’s battery. This isn’t something you can do on your back in your driveway at home. You might be able to benchpress a small transmission, but the Cybertruck pack is simply a behemoth.

For dropping EV batteries, Munro has a new heavy-duty BendPak lifter. It’s a huge flat platform on a concertina jack that can be hydraulically raised and lowered to support a heavy battery as it’s dropped out of a car. It pairs nicely with the BendPak hoists in the Murno shop. Rated for 12,000 pounds, they’re more than strong enough to handle the heft of the 6,843-pound Cybertruck.

Andy Deloy, Munro’s Program Manager, explains where to find all the bolts for freeing the pack. There’s a row of fasteners along the rocker panels and the front lip of the battery, a few inside by the kick panels, and four more are accessed through the bed. It’s a lot of bolts, but it’s a perfectly reasonable amount given the weight and size of the battery.

Julian Aytes, lead engineer at Munro, then explains how the pack was made safe for removal. The main key is disconnecting the low-voltage supply, which de-energizes the battery contactors and cuts the HV supply to the battery’s external connectors. After checking the HV connectors are indeed showing zero volts, it’s safe to proceed. Fully removing the battery involves unhooking several additional connectors, including the blue low-voltage connectors that run to the electric seats. One also needs to consider the rigid aluminum lines that run vertically to the vehicle’s charge port, which are accessed through the bed area.

Examining the process involved in removing the battery, Munro speculates further on the benefits of the floorless design. Speaking on his experience in assembly line design, he believes the bottom-up load-in process could slash the number of assembly stations needed for the Cybertruck. “I think I can load it in one station and maybe run it down in a station after that,” says Munro, speaking on the battery and interior installation. “Two stations, versus maybe, twelve, fourteen, something like that.”

Basically, Munro is saying that the battery pack could be elevated and bolted into the Cybertruck in two assembly line stops at most. That’s with all the seating and carpeting attached, too. Deloy concurs with his assessment. “It’s a lot of time on the assembly line that it saves,” he says.

Munro points out that damage and mistakes in interior assembly are far less likely when it’s a single smooth operation. “It’s just straight up and down,” he says. “That’s maybe one of the reasons why they have 43 seconds per [assembly] station versus everybody else at 60 [seconds]” he explains.

It bears noting that this design isn’t unique to the Cybertruck. The Munro team notes the design is similar to Model Y. As in the Cybertruck, the seats, carpet, and center console all sit on the battery in much the same fashion.

It will be interesting to see if other automakers adopt similar designs in future EVs. It’s another example of Tesla doing things differently to cut costs at the manufacturing stage. Of course, other automakers are all busy implementing their own tricks to find their own edge in the marketplace. The battlefield of auto design has been ever thus.

Image credits: Munro Live via YouTube Screenshot