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The article should be called "How Lotus is going to build electric sports cars" - as there's absolutely no detail given on how they're going to make them more l

by mft_ 5y ago

The article should be called "How Lotus is going to build electric sports cars" - as there's absolutely no detail given on how they're going to make them more lightweight than current concepts? The options discussed are batteries under the floor vs. mid-rear batteries behind the driver in a two-seater... but these still require lots of cells, and in the absence of other innovation, still therefore presumably carry a major weight penalty vs. ICE, as with all current EVs? The direct comment from Lotus comes closest to providing some details ("...significant weight savings have been achieved throughout... for example, by utilizing the vehicle structure as the battery enclosure, having an integrated EDU, eliminating subframes and optimizing the multi-link suspension components.") - but this is essentially fairly standard vehicle engineering, and doesn't innovate around the weight of the battery at all. (I'm not being contrary here - FWIW I own both a Lotus and an EV - but this just seems like weak journalism from a PR release.)

giantg2 5y ago
Agree. The thing you sort of hint at but don't specifically call out is that using the chest configuration gives it a shorter wheelbase, which means less chassis, body, etc weight than the skateboard design. It's still going to weigh a lot, but it will be less than many other EVs (of similar battery/ motor size).
- mannykannot 5y ago
  It is not clear to me how putting the batteries behind the riders rather than under them makes for a shorter wheelbase. The article mentions a lower height, which presumably reduces aerodynamic drag, all else being equal. Maybe it is a matter of getting a good compromise between wheelbase, drag and center of gravity height? Update - more on that here: https://arstechnica.com/cars/2021/09/heres-how-lotus-is-going-to-build-lightweight-electric-sports-cars/?comments=1&post=40256412 https://arstechnica.com/cars/2021/09/heres-how-lotus-is-goin...
  - poniko 5y ago
    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.
    - hinkley 5y ago
      Smaller moment of inertia at the same weight.
  - rbanffy 5y ago
    > 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.
  - giantg2 5y ago
    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
tromp 5y ago
"utilizing the vehicle structure as the battery enclosure" is more commonly described (by Tesla at least) as a structural battery, i.e. utilizing the battery enclosure as an integral part of the chassis.
- niblettc 5y ago
  This is what scares me about electric cars. This type of design seems more likely to mean disposable cars. This is the automotive equivalent of a glued in non serviceable battery in a phone. From an environmental standpoint this seems like a step backwards. It can be cost effective to replace entire damaged engines and transmissions even in older vehicles. People are keeping cars for longer, currently the average is over 8 years.
  - varjag 5y ago
    An average EV will last longer than 8 years. Early fears of battery longevity proved to be unfounded.
  - VLM 5y ago
    There's a big wikipedia article on the various vehicle frame technologies thru the ages. https://en.wikipedia.org/wiki/Vehicle_frame 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.
poniko 5y ago
It might be lightweight compared to the Teslas of the world, Evija is only a smidge over 1600kg .. heavy compared to the Elises but light compared to the other ev-players .. who knows, I'm going to buy one anyhow :). Want to order the Emira but Sweden is quickly going down the path of taxing the hell out of all new ICE cars.
- speedgoose 5y ago
  1600kg is not very lightweight in the EV world. It's 100kg more than an old Nissan Leaf or Renault Zoé, which are very common in Europe. The old first gen BMW i3 weighs 1200kg. For sure it's not the same performances but weight didn't seem to be the main focus for this Lotus.
  - poniko 5y ago
    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.
    - speedgoose 5y ago
      An old Lotus Elise was all about the weight, not power. They didn't follow this concept with the Evija, with so much power requiring a huge and heavy battery pack.
      - poniko 5y ago
        Agree, owned an Lotus Elise, truly amazing driving car but bad at everything else. Creating an electric car at 900kg is just not possible today even with just 250hk. With all new regulatory requirements like all cars need autobreak and other active safety features I'm not sure a new Elise would be possible, I think that's why the new Emira focus on beings a good all around sports car instead of weight.
Andrew_nenakhov 5y ago
Lotus has a history of producing extremely lightweight sport cars, see Lotus Seven [1], famously featured in the opening sequence of "The Prisoner" TV series. [1]: https://en.m.wikipedia.org/wiki/Lotus_Seven https://en.m.wikipedia.org/wiki/Lotus_Seven
- Torwald 5y ago
  Yes, the founder of Lotus, Colin Chapmann, had this egineering philosophy regarding racing cars: "Every part's weight is something I have to carry. If a part doesn't even exist, it doesn't have any weight." (Paraphrased by me.) The biography "Colin Chapman The man and his cars" by Jerry Crombac is the got to read for this topic. BTW., Crombac is a legend in sports journalism in his own right.
  - artiszt 5y ago
    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
- fragmede 5y ago
  Don't forget their involvement with the original Tesla Roadster. Lotus was Teslas original contract manufacturer for their cars, back in the day, and helped out Tesla with some engineering and design resources. https://www.tesla.com/blog/lotus-position https://www.tesla.com/blog/lotus-position
- technothrasher 5y ago
  > famously featured in the opening sequence of "The Prisoner" TV series. Not just featuring in the opening sequence, but indeed symbolic of the entire show. A quirky, agile stand-out from the crowd that represents freedom and individuality, yet in the end is still imprisoned to follow the same roads as everybody else.
  - deleted 5y ago
toss1 5y ago
Agree that this article really didn't deliver on its headline, as we're still in the dark about how the measures mentioned will lead to lightweighting (not that they won't do it, just the article doesn't deliver). The first thing that concerns me about this layout is that it looks like the "Chest Layout" with the batteries mid-mounted in that tall trapezoidal shape will significantly raise the center of mass. I've found that this almost inevitably results in worse handling performance, unless offset. Of course, if this somehow achieves far lighter overall weight than a "Skateboard" layout, it could still be a winning design (but we don't know that yet).
usrusr 5y ago
Perhaps battery sized for a reasonably long joyride and nothing more? I'd say that's how you'd build a lightweight electric sports car.
- ArchStanton 5y ago
  That makes sense. I keep wondering why we haven't seen an EV Miata, but you'd probably end up with a small, 4000lb car. Lacking significant battery improvements, I'm thinking the electric F150 is going to be the game changer in all this.
  - rowing 5y ago
    I don’t understand why you’d buy an automatic miata, let alone an electric one. Is there even a market for this?
    - ArchStanton 5y ago
      Fine. We'll design a control system for EVs where you can feel that a fake clutch actually does something. We can supply speakers and a simulated tach to give the full sports car experience. Really my own guess is that the manual trans will continue on the way out due to emissions law if nothing else (and lack of interest). Modern cars have little visceral interest in any case, probably better to buy a hemicuda with a stick or a Cobra kit.
    - rbanffy 5y ago
      I’d buy a small electric sports car because of the high acceleration. I drove manual transmissions all my life and, while it’s fun in a race course, it’s far less entertaining in traffic.
      - elihu 5y ago
        Gas-powered cars are annoying to drive in traffic because the engine has a minimum RPM. EVs don't have that, so in stop-and-go traffic you'd be able to just leave it in 2nd gear the whole time and never touch the clutch.
nabilhat 5y ago
At least it's not "How Lotus is going to build electric sports cars lightweight"? Seriously though, it's a little disappointing to see 66.4 kWh for a minimal two-seater that's supposed to represent the Lotus philosophy. Any 2-seater that passes for Lotus can easily expect 4 miles / 6.5 km per kWh in normal driving. That's a lotta range to be lugging around. It would be nice to see a track focused version with half the battery capacity. Take advantage of the reduced pack volume and shorten the wheelbase for additional weight loss, now the weight can be on par with an ICE Lotus. RWD with CoG behind centerline and tighter polar moment than an Elise on top of EV torque sounds like an absolute handful; call it a Evropa and have some fun at the local autocross!
- zrm 5y ago
  The problem is you need the extra capacity on the track because you use it more there. In normal driving you accelerate to highway speeds and then coast, or you're in city traffic and benefit from regenerative braking. On a track, you brake late on purpose because it's faster, but to stop that fast you have to rely more on traditional braking and can't recover the energy. Then you immediately want to accelerate back to high speeds again. If you put a small battery in an electric track car, it would be flat in ten minutes.
  - nabilhat 5y ago
    If 28 kWh is enough for an entire Formula E race, I think 33.2 kWh in a Lotus would work out okay.
    - ggreer 5y ago
      28kWh isn’t enough for a Formula E race. They swapped cars in the middle of the race back when they used those smaller batteries. They now use 54 kWh batteries[1], though power output is limited to less than a Tesla Model 3. Next year they’re supposed to increase power output to 350kW, which is comparable to a Model 3 Performance. Of course Formula E cars are much lighter, so acceleration and handling are far better than the Tesla sedan. 1. https://en.wikipedia.org/wiki/Spark_SRT05e https://en.wikipedia.org/wiki/Spark_SRT05e

by mft_ 5y ago

giantg2 5y ago

Agree. The thing you sort of hint at but don't specifically call out is that using the chest configuration gives it a shorter wheelbase, which means less chassis, body, etc weight than the skateboard design. It's still going to weigh a lot, but it will be less than many other EVs (of similar battery/ motor size).

mannykannot 5y ago
It is not clear to me how putting the batteries behind the riders rather than under them makes for a shorter wheelbase. The article mentions a lower height, which presumably reduces aerodynamic drag, all else being equal. Maybe it is a matter of getting a good compromise between wheelbase, drag and center of gravity height? Update - more on that here: https://arstechnica.com/cars/2021/09/heres-how-lotus-is-going-to-build-lightweight-electric-sports-cars/?comments=1&post=40256412 https://arstechnica.com/cars/2021/09/heres-how-lotus-is-goin...
- poniko 5y ago
  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.
  - hinkley 5y ago
    Smaller moment of inertia at the same weight.
- rbanffy 5y ago
  > 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.
- giantg2 5y ago
  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

tromp 5y ago

"utilizing the vehicle structure as the battery enclosure" is more commonly described (by Tesla at least) as a structural battery, i.e. utilizing the battery enclosure as an integral part of the chassis.

niblettc 5y ago
This is what scares me about electric cars. This type of design seems more likely to mean disposable cars. This is the automotive equivalent of a glued in non serviceable battery in a phone. From an environmental standpoint this seems like a step backwards. It can be cost effective to replace entire damaged engines and transmissions even in older vehicles. People are keeping cars for longer, currently the average is over 8 years.
- varjag 5y ago
  An average EV will last longer than 8 years. Early fears of battery longevity proved to be unfounded.
- VLM 5y ago
  There's a big wikipedia article on the various vehicle frame technologies thru the ages. https://en.wikipedia.org/wiki/Vehicle_frame 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.

poniko 5y ago

It might be lightweight compared to the Teslas of the world, Evija is only a smidge over 1600kg .. heavy compared to the Elises but light compared to the other ev-players .. who knows, I'm going to buy one anyhow :). Want to order the Emira but Sweden is quickly going down the path of taxing the hell out of all new ICE cars.

speedgoose 5y ago
1600kg is not very lightweight in the EV world. It's 100kg more than an old Nissan Leaf or Renault Zoé, which are very common in Europe. The old first gen BMW i3 weighs 1200kg. For sure it's not the same performances but weight didn't seem to be the main focus for this Lotus.
- poniko 5y ago
  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.
  - speedgoose 5y ago
    An old Lotus Elise was all about the weight, not power. They didn't follow this concept with the Evija, with so much power requiring a huge and heavy battery pack.
    - poniko 5y ago
      Agree, owned an Lotus Elise, truly amazing driving car but bad at everything else. Creating an electric car at 900kg is just not possible today even with just 250hk. With all new regulatory requirements like all cars need autobreak and other active safety features I'm not sure a new Elise would be possible, I think that's why the new Emira focus on beings a good all around sports car instead of weight.

Andrew_nenakhov 5y ago

Lotus has a history of producing extremely lightweight sport cars, see Lotus Seven [1], famously featured in the opening sequence of "The Prisoner" TV series. [1]: https://en.m.wikipedia.org/wiki/Lotus_Seven https://en.m.wikipedia.org/wiki/Lotus_Seven

Torwald 5y ago
Yes, the founder of Lotus, Colin Chapmann, had this egineering philosophy regarding racing cars: "Every part's weight is something I have to carry. If a part doesn't even exist, it doesn't have any weight." (Paraphrased by me.) The biography "Colin Chapman The man and his cars" by Jerry Crombac is the got to read for this topic. BTW., Crombac is a legend in sports journalism in his own right.
- artiszt 5y ago
  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
fragmede 5y ago
Don't forget their involvement with the original Tesla Roadster. Lotus was Teslas original contract manufacturer for their cars, back in the day, and helped out Tesla with some engineering and design resources. https://www.tesla.com/blog/lotus-position https://www.tesla.com/blog/lotus-position
technothrasher 5y ago
> famously featured in the opening sequence of "The Prisoner" TV series. Not just featuring in the opening sequence, but indeed symbolic of the entire show. A quirky, agile stand-out from the crowd that represents freedom and individuality, yet in the end is still imprisoned to follow the same roads as everybody else.
- deleted 5y ago

toss1 5y ago

Agree that this article really didn't deliver on its headline, as we're still in the dark about how the measures mentioned will lead to lightweighting (not that they won't do it, just the article doesn't deliver). The first thing that concerns me about this layout is that it looks like the "Chest Layout" with the batteries mid-mounted in that tall trapezoidal shape will significantly raise the center of mass. I've found that this almost inevitably results in worse handling performance, unless offset. Of course, if this somehow achieves far lighter overall weight than a "Skateboard" layout, it could still be a winning design (but we don't know that yet).

usrusr 5y ago

Perhaps battery sized for a reasonably long joyride and nothing more? I'd say that's how you'd build a lightweight electric sports car.

ArchStanton 5y ago
That makes sense. I keep wondering why we haven't seen an EV Miata, but you'd probably end up with a small, 4000lb car. Lacking significant battery improvements, I'm thinking the electric F150 is going to be the game changer in all this.
- rowing 5y ago
  I don’t understand why you’d buy an automatic miata, let alone an electric one. Is there even a market for this?
  - ArchStanton 5y ago
    Fine. We'll design a control system for EVs where you can feel that a fake clutch actually does something. We can supply speakers and a simulated tach to give the full sports car experience. Really my own guess is that the manual trans will continue on the way out due to emissions law if nothing else (and lack of interest). Modern cars have little visceral interest in any case, probably better to buy a hemicuda with a stick or a Cobra kit.
  - rbanffy 5y ago
    I’d buy a small electric sports car because of the high acceleration. I drove manual transmissions all my life and, while it’s fun in a race course, it’s far less entertaining in traffic.
    - elihu 5y ago
      Gas-powered cars are annoying to drive in traffic because the engine has a minimum RPM. EVs don't have that, so in stop-and-go traffic you'd be able to just leave it in 2nd gear the whole time and never touch the clutch.

nabilhat 5y ago

At least it's not "How Lotus is going to build electric sports cars lightweight"? Seriously though, it's a little disappointing to see 66.4 kWh for a minimal two-seater that's supposed to represent the Lotus philosophy. Any 2-seater that passes for Lotus can easily expect 4 miles / 6.5 km per kWh in normal driving. That's a lotta range to be lugging around. It would be nice to see a track focused version with half the battery capacity. Take advantage of the reduced pack volume and shorten the wheelbase for additional weight loss, now the weight can be on par with an ICE Lotus. RWD with CoG behind centerline and tighter polar moment than an Elise on top of EV torque sounds like an absolute handful; call it a Evropa and have some fun at the local autocross!

zrm 5y ago
The problem is you need the extra capacity on the track because you use it more there. In normal driving you accelerate to highway speeds and then coast, or you're in city traffic and benefit from regenerative braking. On a track, you brake late on purpose because it's faster, but to stop that fast you have to rely more on traditional braking and can't recover the energy. Then you immediately want to accelerate back to high speeds again. If you put a small battery in an electric track car, it would be flat in ten minutes.
- nabilhat 5y ago
  If 28 kWh is enough for an entire Formula E race, I think 33.2 kWh in a Lotus would work out okay.
  - ggreer 5y ago
    28kWh isn’t enough for a Formula E race. They swapped cars in the middle of the race back when they used those smaller batteries. They now use 54 kWh batteries[1], though power output is limited to less than a Tesla Model 3. Next year they’re supposed to increase power output to 350kW, which is comparable to a Model 3 Performance. Of course Formula E cars are much lighter, so acceleration and handling are far better than the Tesla sedan. 1. https://en.wikipedia.org/wiki/Spark_SRT05e https://en.wikipedia.org/wiki/Spark_SRT05e