Concept Design - thoughts?
Discussion
What made you decide on a spaceframe?
How much do you expect it to weigh?
Tell us a bit more about the electric motors and their power source. Electric-only capability and range? What speed range do they operate in?
What's the combustion engine's output, and have you decided on a gearbox?
I'm surprised that the front brakes seem considerably more serious than the rears, despite the mid-rear engine layout and them presumably being assisted by energy recovery.
Looks interesting
How much do you expect it to weigh?
Tell us a bit more about the electric motors and their power source. Electric-only capability and range? What speed range do they operate in?
What's the combustion engine's output, and have you decided on a gearbox?
I'm surprised that the front brakes seem considerably more serious than the rears, despite the mid-rear engine layout and them presumably being assisted by energy recovery.
Looks interesting
Hi McSam,
Steel spaceframe is cheap, relatively easy to fabricate, quite light and very strong. Not as light and stiff as a carbon tub, but less than 1/3 of the cost. It can also be done in-house.
Weight-wise, we'd be looking at under 1100kgs wet.
Electric motor would be an oil-cooled 3-phase item powered by 50 100Ah 3.2v li-ion batteries. The electric powertrain would give a max pulsed discharge of 155 kW or just over 200bhp. Max continuous would be about 17kw/h or 23bhp. So conservatively, that would be sufficient for well over an hour of city driving (daytime) or an extra-urban range of 100 miles(ish) with regenerative braking
The Audi TFSI 5-cylinder can be tuned with modest modification to over 600bhp, but that's not great for fuel economy and will destroy the transmission quite quickly. We'd aim to keep it at about 450bhp running through a slightly uprated DSG transmission. This would keep the cost of components down.
That would give a max combined power of 650bhp for long enough to do a fast lap of most racetracks.
Other option is Volvo/Ford modular engine, 5-cylinder turbo, though this isn't quite as tough as the Audi unit. Both are very compact for their power output.
Front brakes are probably over-specced at the moment, while the rears are just placeholders. However the rear bias would be reduced by the distribution of batteries. Additionally, most electric motors don;t like to be subjected to massive regeneration forces, so for enthusiastic braking, you'd want a decent brakes at the front to do the hard work before the electric regen could come in - otherwise you'd need a much bigger and heavier motor.
Steel spaceframe is cheap, relatively easy to fabricate, quite light and very strong. Not as light and stiff as a carbon tub, but less than 1/3 of the cost. It can also be done in-house.
Weight-wise, we'd be looking at under 1100kgs wet.
Electric motor would be an oil-cooled 3-phase item powered by 50 100Ah 3.2v li-ion batteries. The electric powertrain would give a max pulsed discharge of 155 kW or just over 200bhp. Max continuous would be about 17kw/h or 23bhp. So conservatively, that would be sufficient for well over an hour of city driving (daytime) or an extra-urban range of 100 miles(ish) with regenerative braking
The Audi TFSI 5-cylinder can be tuned with modest modification to over 600bhp, but that's not great for fuel economy and will destroy the transmission quite quickly. We'd aim to keep it at about 450bhp running through a slightly uprated DSG transmission. This would keep the cost of components down.
That would give a max combined power of 650bhp for long enough to do a fast lap of most racetracks.
Other option is Volvo/Ford modular engine, 5-cylinder turbo, though this isn't quite as tough as the Audi unit. Both are very compact for their power output.
Front brakes are probably over-specced at the moment, while the rears are just placeholders. However the rear bias would be reduced by the distribution of batteries. Additionally, most electric motors don;t like to be subjected to massive regeneration forces, so for enthusiastic braking, you'd want a decent brakes at the front to do the hard work before the electric regen could come in - otherwise you'd need a much bigger and heavier motor.
tommyjj said:
... though the hinges haven't been worked out yet.
Don't underestimate the development costs of this sort of detail.Lotus tried to develop a gullwing roof section for the hardtop on the S2 Elise, and were ultimately forced to abandon it because they couldn't get it to seal properly.
Apart from the hinges, you've got to make the the door stiff enough to make the seals work (which means the weight and cost will probably rise), and arrange gas struts strong enough to hold that big door open, without getting in the way or looking amateurish when the door is closed.
..and I have to agree, that door opening looks awfully restricted by the spaceframe, even compared to the high sill on an Elise.
MintSprint said:
Sort of a cubist interpretation of a cross between an AC 3000ME and a Pelland/Kudos, with maybe a bit of Lancia Stratos thrown in.
Never seen a Pelland/Kudos before - pretty little thing, and I see what you mean about the AC3000There's probably a bit of 288 GTO in there too, since there's one on the office wall
I'd be impressed if you can keep the weight of that to 1100kg, surely you've got an awful lot of drivetrain weight?
I quite like the styling and the concept but it'd need to have a naturally aspirated or supecharged engine for it to be of any interest to me; could you squeeze a longitudinal V6 in? I'm guessing it'd be well beyond anything I could justify spending anyway though.
I quite like the styling and the concept but it'd need to have a naturally aspirated or supecharged engine for it to be of any interest to me; could you squeeze a longitudinal V6 in? I'm guessing it'd be well beyond anything I could justify spending anyway though.
Edited by kambites on Saturday 13th December 11:42
Thanks for the extra detail.
The brakes make a little more sense now, and I didn't realise the batteries were yet to be added. How big's the battery pack/converter/charging apparatus, and what does it all weigh? What will the weight distribution be with it in place, and where's the fuel tank? Interested to see how everything's laid out.
16kWh is an impressive capacity for this type of application - almost as much as an i3!
I wonder how well a supercapacitor would work if you went in a motorsports direction and wanted to maximise regeneration at the cost of having enough storage for electric-only use..
With that new image, I'm afraid I have to agree about the ingress/egress issue. Even assuming the roof cutout can make it in, I don't think it would be a natural movement to go "up and out" as you suggest - firstly the door is still quite low, and it doesn't solve the huge and irregular step over the spaceframe. A wider sill would be preferable to such a high structure, so if you can get the strength you need that way, I think it'd work much better and you could also revert to a normal door.
Not sure how you'd achieve this with the current spaceframe, though. How much does the frame itself weigh? I too am trying to work backwards to 1100kg, which seems impressively light.
The brakes make a little more sense now, and I didn't realise the batteries were yet to be added. How big's the battery pack/converter/charging apparatus, and what does it all weigh? What will the weight distribution be with it in place, and where's the fuel tank? Interested to see how everything's laid out.
16kWh is an impressive capacity for this type of application - almost as much as an i3!
I wonder how well a supercapacitor would work if you went in a motorsports direction and wanted to maximise regeneration at the cost of having enough storage for electric-only use..
With that new image, I'm afraid I have to agree about the ingress/egress issue. Even assuming the roof cutout can make it in, I don't think it would be a natural movement to go "up and out" as you suggest - firstly the door is still quite low, and it doesn't solve the huge and irregular step over the spaceframe. A wider sill would be preferable to such a high structure, so if you can get the strength you need that way, I think it'd work much better and you could also revert to a normal door.
Not sure how you'd achieve this with the current spaceframe, though. How much does the frame itself weigh? I too am trying to work backwards to 1100kg, which seems impressively light.
Absolutely no chance on the mass target if you want any kind of "road car" levels of NVH.
Your electric powertrain will have a piece price alone of around £35k in low volumes.
50 100Ah 3.2v li-ion batteries, all in series is only 160Vdc. Fail. (you're going to need around 400 for 200bhp) So either will need more smaller capacity cells in series, or a massive DC-DC, and then you'll find your system current might become limiting.
No way will an oil cooled AC motor deliver 200bhp for more than a couple of minutes.
You battery pack will be heavy, bulky, and fitting into a small "curvy" car will be a nightmare of packaging and cooling / crash constraints (not for nothing do Tesla/BMW/Nissan design the car around the battery and not vise versa!)
As mentioned, build a mock up of the cabin ergonomics, even if you do it in mdf etc. No way in CAD can you really estimate how difficult entry/engress and general usability of the car will be. What percentile person are you designing for etc?
You need to take a long hard look at type approval (low volume) requirements, for things like sight lines, lighting, cabin safety etc etc.
What does this car bring to the party that others don't? And what are your price point & volume aspirations?
Your electric powertrain will have a piece price alone of around £35k in low volumes.
50 100Ah 3.2v li-ion batteries, all in series is only 160Vdc. Fail. (you're going to need around 400 for 200bhp) So either will need more smaller capacity cells in series, or a massive DC-DC, and then you'll find your system current might become limiting.
No way will an oil cooled AC motor deliver 200bhp for more than a couple of minutes.
You battery pack will be heavy, bulky, and fitting into a small "curvy" car will be a nightmare of packaging and cooling / crash constraints (not for nothing do Tesla/BMW/Nissan design the car around the battery and not vise versa!)
As mentioned, build a mock up of the cabin ergonomics, even if you do it in mdf etc. No way in CAD can you really estimate how difficult entry/engress and general usability of the car will be. What percentile person are you designing for etc?
You need to take a long hard look at type approval (low volume) requirements, for things like sight lines, lighting, cabin safety etc etc.
What does this car bring to the party that others don't? And what are your price point & volume aspirations?
Edited by anonymous-user on Saturday 13th December 13:52
Lotus may not be selling a huge number of cars these days but trying to go head-to-head with them would IMO be suicidal.
You'd be better off doing that design as a body only conversion of Elise. Avoids all of the design, engineering, interior, homologation issues. You might even be able to sell in North America if you keep the complete crash structure.
You'd be better off doing that design as a body only conversion of Elise. Avoids all of the design, engineering, interior, homologation issues. You might even be able to sell in North America if you keep the complete crash structure.
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