So now that we had the chance to sleep once after the reveal of the amazing Tesla stainless steel Cybertruck, here are my thoughts about the economics of the mass manufacturing of stainless steel cars and its implications for the car industry.
I believe Tesla's design is even more advantageous than I initially thought - Tesla achieved a significant manufacturing break-through here - as described in more detail below.
Firstly, a bit of historic background. Somewhat ironically, carmakers have experimented with stainless steel designs as early as 1936, when Ford built six stainless steel sedans for the Ludlum Steel Co. to promote using their product.
This is how well they held up after almost 100 years:
But carmakers had many, many good economic reasons why they didn't make stainless steel cars in volume:
- Much more expensive tooling:
- Stainless steel is just too hard, and even the latest high-tech press-die alloys don't allow more than just a couple of ten thousand runs - i.e. amortization of these long lead time tooling items is incredibly high because dies that are durable enough to stamp hundreds of thousands of panels without wearing down are incredibly difficult to design and manufacture. I.e. the best, most important property of high precision stamping dies (durability) increases their cost and their lead time significantly.
- Stainless steel is not malleable enough and the press springs back hard which wears down other parts of the press as well IIRC. I believe @Krugerrand wrote about this a year ago or so? (@ReflexFunds might have mentioned it too.)
- Welding of stainless steel is rather difficult - there's contractors out there who do nothing but install and weld stainless steel as a specialty.
- Planned obsolescence: this was one of the major reasons given in a short article about stainless steel cars: they last too damn long and a major source of revenue for established carmakers is from maintenance of the fleet, much of which is out of warranty.
- Mass and efficiency disadvantages: stainless steel body panels are not structural, most of them are not load-bearing, so the extra weight and drop in fuel efficiency is significant.
And here comes Tesla and
turns all of these economic factors upside down with their first-principles stainless steel car design break-through:
- Much less expensive tooling and assembly:
- The folded-stainless-steel design requires no stamping.
- This also reduces tooling lead time significantly. Note how Tesla has announced to make it in 2021 already - basically 1.5 years from now. This is incredibly fast for a new product that changes basically everything about how cars are made, and future iterations will be even faster.
- Folded stainless steel doesn't have to be welded.
- Making durable cars is actually an advantage for an upstart carmaker like Tesla, whose average fleet age is less than 3 years - even if we ignore the whole benevolent 'save the planet' part of Tesla's mission.
- Vehicle mass and fuel/energy efficiency advantages: the "exoskeleton" design is load bearing, so the stainless steel has a triple role as a frame, skin and crash protection. The inherent weight disadvantages of stainless steel turn into weight advantages. That's I think a big part of how the Tesla Cybertruck will be able to reach 500 miles range - not just battery chemistry and pack manufacturing advances. Low mass also allows sports car properties ...
There's also a couple of unique advantages to stainless steel, which were mentioned here before, but which I believe are important to sum up to get a complete picture about the mass manufacturing economics:
- No paint required: No chemical bath to de-grease and clean the body before painting. No robots to spray several layers of paint. No ovens to dry the paint. No paint chemistry risk - which is still a source of expensive recalls even for much older carmakers.
- Corrosion resistance: corrosion of the car under-body, frame and chassis has been a bane of the automotive industry with expensive recalls, significant warranty risks and a longer design and testing cycle. Stainless steel is one of the most corrosion resistant materials, it is used all around in public transportation and construction with a ~100 years track record of the durability of the various stainless steel alloys.
- Stainless steel is significantly more fatigue resistant than the current material of choice of carmakers: aluminum. Stainless steel has 5-10 times the fatigue strength of aluminum, and within its (generous) plastic deformation constraints stainless steel has an infinite fatigue life:
I'm sure with time we will find some disadvantages of stainless steel - such as lower scratch resistance unless made really hard with chromium - but those are solvable IMHO and all the advantages are stacked up a mile high already...
The beauty of Tesla's design: I believe other carmakers will have
no choice but to embrace the stainless steel design.
On a final note, Elon disguised the true motivation for the Cybertruck masterfully, without warning the competition prematurely: what everyone thought to be a childhood dream and a personal folly of Elon (Blade Runner truck), was in fact dictated by the economics of this radically new stainless steel based vehicle mass manufacturing paradigm.