All electric motors, you might well think, are endearingly simple, sausage-shaped, cylindrical, and similar in efficiency and weight.
They have few moving parts and are much smaller than the combustion engines they are busy replacing in the world’s cars. Official figures say they also make great use of energy, producing efficiency figures that are heading towards 90%. That sounds great, given that the latest and greatest gasoline and diesel engines are well above 40%.
The truth is less simple. Most current electric vehicles use sausage-shaped radial flow motor technology. But in recent years, a different design has emerged, developed by the British, called Yasa. Yasa is an axial-flow electric motor in a disc-shaped design that is more efficient and much lighter.
The design of the Yasa engine is segmenting and yokeless armor. has already begun to bring large reductions in size and weight to electric vehicles. Although they are not yet the conventional ones. But that’s coming.
In essence, a Yasa engine abandons about 25 kg of iron in a sausage engine the size of Tesla. Which is replacing it with a much more compact mechanism frame that weighs about 3 kg. Tim Woolmer says, a dozen years ago, its efficiency continues to improve at the rate of 25% per year.
Woolmer says the Yasa principle was “a known technology”. He dug it up for his doctoral thesis in 2008 and built a 27bhp, 88lb-ft prototype that weighed a then-promising 20kg.
The project is possible by the emergence of new materials, he says. His research showed that the principle would work and he found a way to cope with internally generated heat. which was previously an unclear obstacle. It seemed promising enough that Woolmer would persist with the research after his Ph.D. had been awarded.
In 2012, it struck a historic deal with Jaguar Land Rover and Williams Advanced Engineering. It is for its engines to power the promising Jaguar C-X75 hybrid supercar. That looked like a rival to the Ferrari LaFerrari and McLaren P1.
By then, the power of the proposed Yasa engine had jumped to 214bhp and its torque tripled to 266lb-ft, while its weight had increased by just a measly 4kg.
The ultra-low-volume Koenigsegg Regera hybrid hypercar was the first to use a Yasa engine in production in 2015. But the technology made a much more important debut in 2020. It has a key component of the homologated Ferrari SF90 Stradale plug-in hybrid hypercar.
That engine was designed in 2017 to fit between the ultra-low-mount gasoline engine and transmission. It weighs a remarkable 12kg while producing 207lb-ft. No wonder it was a time when Yasa had the technology to meet Ferrari requirements.
Including Ferrari’s work, Yasa has “four or five” supercar programs. This program runs and produces several different versions of its axial flow engines at a factory near Oxford with an annual capacity of 100,000.
It announced that Yasa Motors would power many of its future electric vehicles. It starts with the Mercedes-AMG EV range from 2025. Added that its Berlin factory will dedicate to building Yasa powertrains, with production in the millions.
Meanwhile, the progress of Yasa’s design is fast. Woolmer says the company already has “a very good portfolio of 130 patents” and, if anything, the number is accelerating.
Woolmer shows how axial flow outputs are progressing, even beyond Ferrari. The Woolmer reveals that an AMG engine designed last year and programmed for an EV of the future produces no less than 590 lb-ft of torque and 480bhp of power. It has reached 98% efficiency. It can generate a g-force rotor speed more than three times that of the SF90 Stradale unit. And yet it weighs only 24kg, only 20% more than that original pre-prototype.
Despite the clear advantages of axial flow (“it has benefits that do not extract from a radial machine”). The rest of the automotive industry continues to spend billions on radial flow.
Part of their problem is that apart from the partners Mercedes is willing to share with, they don’t have access to axial flow patents. But Woolmer also attributes it to the herd mentality. “They follow each other,” he says. “It’s rare to see a big OEM come out on a limb.”
All this makes the rapid acquisition of Yasa by Mercedes seem very decisive. Woolmer is not specific, but it is clear that the enthusiasm comes from the head of Mercedes, Ola Källenius. The acquisition of British technology by a German owner brings a severe reminder of the fate of the lithium-ion battery. It’s designed at Oxford University but produced (and monetized) in Japan.
Woolmer understands the allusion. He says Yasa had reached a crossroads in her development: “We had to think carefully. The choice was to remain independent and alone, as we were doing, which was a big risk. It requires and involved huge amounts of capital, or goes with Mercedes. We remember the principle we had used to form the company: there are no electric cars. Let’s do some technology to make them visible and attractive. We decided to listen to what Mercedes was saying.
“They were convincing. And they had announced the decision to switch to all-electric from 2030. They told us they saw our technology as strategic. AMG’s entry point seemed suitable for what we were trying to achieve. They had the industrial power and the desire to manufacture our engines in the millions. They would want to protect our status as a fast-moving R&D hub, a kind of speedboat to their supertanker.”
Woolmer believes that the company’s technology provides a strategic advantage for Mercedes. But by 2040 it might be extended further. Axial flow technology needs commodity, he says, but not yet.
As for Yasa’s impressive technical progress, Woolmer says he has reached his fourth generation and can see the fifth on the horizon.
At every opportunity, he emphasizes the core benefits of axial flow machine changes. it brings “weight down, size down, costs down, and efficiency up. These things only deliver their potential when future cars make the best use of their advantages.
AMG electric vehicles and later standard Mercedes models will use Yasa’s rapid progress in two stages, he explains. The first is illustrated in a “beautiful” new drive unit. It has already been designed for an AMG. It incorporates a 1000bhp engine, inverter, and epicycle gearbox. Gearbox, in a single concentric torque-vectoring unit on the rear axle. The likely effect of this unit on the vehicle’s packing freedom could be enormous.
Beyond that, Woolmer says, there’s a realistic promise of engines on the wheels. It is a live technology for which details remain super-secret. it’s possible that the sixth-generation Yasa could create special engines. Engines that are light, compact, and powerful enough to fit inside a car’s steering wheel, in unity with its hub.
“Imagine,” says Woolmer, with even more of his usual help of passion, “a wheel with 400bhp at 500bhp and its conventional braking system as a backup.
“We all love things that are small and light, but it’s when they start to change the architecture of the vehicles that they get really interesting…”
What follows ‘peak battery’?
Yasa boss “Tim Woolmer” believes that improving the efficiency of electric vehicles, a major property of his company’s unique axial flow electric motors. It will drive car design and production in the coming years, once the current era of “maximum battery” has passed.
“Look at the premium sector today,” he says. “The cars headed to have batteries above 100kWh to deliver ranges between 250 and 350 miles. That’s because customers need peace of mind about how to make the switch to electric vehicles. As aerodynamics improve and weight decreases, we’ll see these long ranges maintenance for a while, but with smaller batteries.”
Charging infrastructure improvement ranges could more decrease. It allows for a further reduction in battery size and cost to ensure the new generation of owners can afford the cars.
When range anxiety disappears and there is no cheaper ICE option, manufacturers’ concern will be focused on the cost of purchasing and construction. “That becomes a big efficiency issue,” Woolmer says.
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