The Tesla Model Y and Casting Cars: The Return of the Alien Dreadnought

I bet you wouldn't expect to see a Tesla Model Y at the Museum of Very Large Cast Objects, were that ever to exist.  Sure, you'd find that 49-feet tall bronze Buddha there that was cast in 751, and presently sits in Nara, Japan's Great Buddha Hall (where its head fell off during an earthquake in 855). And probably the 20-ft tall Dhammazedi Bell that was cast in 1484 of silver, gold, copper and tin, and now rests on a river bottom with the ship that was stealing it, somewhere near the junction of the Bago and Yangon Rivers in Myanmar. And then there's the biggest casting of them all, a 358-ton steel part for a German forging press, cast in 2015 by Sheffield Forgemasters International in England. It isn't as interesting as the Buddha and the bell, but it's certainly gigantic and seems to have stayed out of trouble. But the Model Y? Why?

By comparison, the biggest castings in the car business have been small potatoes—engine blocks and such. However, there was a golden age of artistry, if not immensity, in automotive casting during the 1920's and '30's. Google engine images of the Alfa-Romeo 8C 2300's or the supercharged Miller 91's Straight 8s, and I guarantee they'll permanently change you.

In the last several years, castings have been finding their way into chassis, a notable one being the current Acura NSX's with its six large aluminum 'nodes' that are home to the suspension's multiple pick-up points. Honda worked with a company called Alotech Inc. to develop its novel manufacturing process, called ablation casting, wherein a sand mold containing the hot, being-cast part, is strategically eroded by high-pressure water jets. By targeting the cooling, the aluminum's mechanical properties are tweaked to match the ductility and energy absorption of the surrounding parts it'll be bonded to, so it's suitable for use in crash zones. Appropriately, they won Casting of the Year Award in 2015 from the American Foundry Society. There's an award for everything.

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More recent examples include the even bigger castings hidden in the C8 Chevrolet Corvette, a car that's percentage of them has jumped from 8 percent to 18 percent since the C7 Corvette. Corvette Chief Engineer, Tadge Juechter, calls them 'enormous,' and the rear suspension's pair are real showstoppers, stretching vertically all the way to the tops of the spring-shock units. Unlike the NSX's ablative casting, the Corvette's are formed by high-pressure die casting allowing for very thin and intricate stiffening webs, and at a higher-speed production rate, too. If I owned a C8, I'd consider removing the bodywork and driving it around as a naked chassis. Frankly, its beautifully-webbed castings are prettier than the car.

And now we have the automotive king of casting, thanks to—no surprise—to Elon Musk.

When Sandy Munro—car-disassembler extraordinaire—famously autopsied a Tesla Model 3, he found plenty to like about the car's electronics. And details about its platform that made his eyes wince. It was unnecessarily complicated, heavy, and expensive to manufacture.

This must have been frustrating news for Musk, who originally envisioned its assembly line as an 'Alien Dreadnought', a high-speed, insanely efficient, car-making firehose that would disrupt the industry. The machine that makes the machine, remember? One wonders if the simple, folded-stainless steel fabrication of the Cybertruck was some sort of emotional reflex to both Munro's Model 3 critique and the headaches with the Dreadnought dead-end. But apparently, that dream wasn't dead quite yet.

During the middle of Model 3's production hell, Musk approached his engineers with a Die-Cast toy model car. I don't mean one of the complicated ones (AutoArt's or Tecnomodel's are amazingly detailed—and expensive) but the cheap, simple ones with a die cast bottom and top you screw together.

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"Why can't you build a car like this?" he said (or something to that effect). It turns out that there isn't a machine big enough for that, so they contracted to have one constructed, capable of casting about 40-percent of the platform's length. For its production debut in the Model Y, this monstrosity stretches completely across the car's rear, and is comprised of two, bolt-together halves that perch the rear suspensions and drivetrain.

The Tesla team's biggest challenge—learned from Model S and X castings—was that heat-treating such a large part would be impractical due to warpage. So, working with the materials group Tesla shares with SpaceX, the team created an alloy, similar in strength and elongation to heat-treated, 300-series T6 aluminum that doesn't need heat-treating. It's Dreadnought-quick to produce, too—within 10 milliseconds, about 88 pounds of the molten alloy gets injected; two minutes later, the result emerges. This final, two-part unit eliminates 80 parts and about 700 joints.

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Why at the rear and not the front? Frontal crash structures take years to develop, making the rear a simpler starting point. (A collapsible structure between the rear bumper and the casting gets sacrificed in a moderate impact; It can be unbolted and replaced afterward). But eventually, the two halves will be replaced by a single, really giant casting that'll include a cast, collapsible crush structure as well.

And maybe someday the whole platform? Like a 100 percent scale, cast Model Y?

That would definitely earn it a prime spot in the Museum of Very Large Cast Objects.