How Lotus is going to build lightweight electric sports cars

An average EV will last longer than 8 years. Early fears of battery longevity proved to be unfounded.

There's a big wikipedia article on the various vehicle frame technologies thru the ages.

https://en.wikipedia.org/wiki/Vehicle_frame

So my commuter car is a cheapie Yaris ICE not EV. Its lead acid battery lives on a shelf attached to the frame, kind like a body on frame by analogy, except instead of bolting a car body to the frame they're bolting a battery shelf to the frame. If they ripped out the battery shelf and embedded a shelf directly into the front quarter panel of the body, then theoretically the car would be a little lighter. Its probably not worth it for a small lightweight lead acid battery. Giant EV battery, on the other hand 5% lighter might be a lot of weight...

Maybe a more intuitive way to understand the difference between a unibody type design and a body on frame design, is to look at old pickup trucks and you can rip the pickup bed off the frame and the truck works fine because the wheels and brakes and all the parts attach to a frame, so a bed-less pickup truck is just a pickup truck without a bed. Now if you rip off the back of a unibody car the entire back of the car would literally disappear because there is no frame, the frame is the body. Like the suspension parts attach to the body. There is no separate body and frame, there's just "the back of the car".

So one way to build a EV is to convert an existing chassis by bolting big battery pack "boxes" onto the frame. There exists a frame of a car and you bolted boxes of batteries to it as an addon. But a lighter way, which takes a lot more engineering, is building the battery "boxes" into the frame itself; there is no separate battery box there's a compartment in the frame that holds the batteries. You can't replace the battery "box" or the frame separately because they are not separate they are the same piece of metal. Much more engineering, much lighter.

I would imagine you can replace the batteries just as easily in a unibody EV as a body-on-frame EV. But you can't replace the rusted out battery box on a unibody EV because there is no separate battery box, its engineered into the frame.

The biggest disadvantage of unibody designs is everything is embedded in everything else so in a body on frame car a minor fender bender you remove and replace part of the body. But with a unibody the whole suspension and drive train gotta go too. To replace EV battery in a body on frame design you simply remove the battery from the frame. In a unibody system there might be a lot more labor hours maybe you gotta remove all the wheels and doors and seats to yank out a substantial chunk of the middle of the car.

There are many motorcycles with the motor as a structural component. It does not mean you throw away the bike instead of repairing or replacing the motor.

Ideally the whole car collapses simultaneously.

So a Zoe is 1570kg and has a tiny engine and 50kw battery :) not sure it's comparable with something that's has 4 motors, 2000hp and a 70kw battery :) The battery alone on the evija is 680kg and probably very different just to be able to get the amp up enough to power the massive engines and spike output when needed.

You want a low center of gravity but also weight in the center of the 4 wheels of car, that's why most sports cars nowadays are 'mid-engine'. Weight in the center helps in turns since the car wants to rotate around itself.

> The article mentions a lower height

There’s also an emotional component in the difference in perception of driving at 250 Km/h on a BMW 750 or in a Lotus where your seat is hugging the road under you.

My understanding is that the skateboard would have to be too thick to fit within the shorter wheelbase, substantially raising the occupants, etc. I think this also plays into the chassis design since they say they can build the "chest" design as part of the chassis. I think the skateboard requires more of a traditional body on frame. This is sort of a guess though, but slightly based off of the explanation of how they designed the chassis of the C7 Corvette to be light and more rigid.

Edit: thanks for the additional link

and at a time nobody even did care for aerodynamics of a cars underbelly [its ventro-basal anatomy, so to speak] Chapman aimed to optimize on a level known only from constructing air-planes. shark-skin'ish foils, if not mistaken, they too were among the first testing on racing cars

I don’t understand why you’d buy an automatic miata, let alone an electric one. Is there even a market for this?

Have you forgotten the original Tesla Roadster? The Miata occupies a very specific niche (there are other sports cars, but none with the same balance of affordability and performance and availability as the Mazda Miata), but there are quite a few EV sports cars. They're just not remotely humanly affordable.

A lot of people want electric Miatas. I think the main reasons they aren't being made is that Mazda would have to invest a lot of R&D into designing it and they're a relatively small car company that can't do everything and they're probably not convinced that they can make an EV that feels like a Miata.

The main issue is batteries. They could either make a light EV without much range, or make a long-range EV that's quite heavy. Placement's an issue too. If they put the batteries in back under the trunk, they'll have too much weight in the rear causing it to spin out on corners. If they put it under the middle of the car like in most modern EVs, it'll make the car taller and look very un-Miata like. Best case is probably to put most of the battery in the front where the engine was, but I suppose that might be a safety issue (it could be crushed in a collision).

I think an electric Miata will happen eventually, but probably not until Mazda can buy cells that are in the 250-300 watt hours per kg range.

(Personally I would love to see an EV Miata with a manual transmission, but that's probably not going to happen.)

That's in line with the Lotus philosophy of light weight. A lighter battery doesn't need as much superstructure (the rest of the car) and doesn't need as much raw power to accelerate itself around.

Perhaps thermal management could be somewhat opened up to the driver with short "sprints" possible, to add some more driver involvement to the experience.

There must be a balance. The lighter the car, the more acceleration you get per watt.

I’d be very happy with a light weight EV Miata that went 0 to 100km/h in under or around 4 seconds. Not Model S Plaid or high end 911 fast, but still by far the fastest production Miata.

It depends on the batteries. It's true that larger packs generally draw less current per cell; whether you can get away with a small pack depends on whether the cells are designed to handle high discharge rates without damage.

Tesla's approach seems to be to optimize their cells for energy density rather than power density. They can do that because the packs they use are huge. On the other hand you have relatively small batteries that go in hybrids that are optimized for power density.

If 28 kWh is enough for an entire Formula E race, I think 33.2 kWh in a Lotus would work out okay.

Why can't you brake aggressively with regenerative braking?

That's a No True Scotsman when EV enthusiasts don't count as auto enthusiasts.

Think of hypothetical scenario where EVs were the norm first. I don't think EV people would consider switching to ICE as increasing fun: much more complex, louder, hotter engine with worse torque that needs extra hardware and operations to avoid slowing you down.

The noise and gear shifting is only associated with power/speed/fun because that's how cars used to work.

He was wrong IMO. Teslas are just meh in styling. They look OK, certainly better than the clown-car EVs that preceeded them (and are still produced by some manufacturers), but they don't stand out compared to the styling and interior quality of Mercedes, BMW, to say nothing of exotics like Lotus.

Eh. Car people tend to be more generational than tech or computer people. My generation certainly has its own amusing peculiarities as we replaced our muffler exhaust tips with clothes dryer vents.

We're not going to get mass market EVs due to range anxiety and thats not going away until the boomers go away, just kinda how it is.

If you're going to look only at the power-to-weight of the engine itself and ignore everything else needed to make a car, I look forward to the superior hydraulic engined-cars!