Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - CarBEN Model -- 1/24th scale model and 3D computer model for EV

NeilBlanchard · 10-01-2010, 10:14 PM

The CarBEN is just 5'- 4" inches wide. If I narrow it to 4'-4" wide I could not fit two seats side by side. And how can I fit a ~55kWh battery in with any less frontal area? The frontal area of the battery is 40" x 5.5" and there is no way to fit 768 cells in "inline" with any other part of the car; let alone with the best Cg possible.

Removing the middle foot reduces the interior volume by a huge amount: that is the tallest and longest portion. The widest interior dimension is about 4'-6" and the narrowest is ~2'-8" -- those drop to 3'-6" and 1'-8", which probably turn it into a 3 seat car. No thanks.

Even if you don't lower it a proportional amount (which you would have to, since a 5'-6" tall by 4'-4" wide vehicle looks a lot like the Tango!), you would lose 1/3 of the battery bay, dropping the capacity to ~37kWh.

The weight saving in the chassis would be minimal since the "perimeter" only would drop from 21'-8" to 19'-8".

The frontal area is just ~25 sq ft as it is. And if the Cd is between 0.11 and 0.14 (WAG) then the CdA is between 2.75 sq ft and 3.5 sq ft. Even saving 6 sq ft of area only drops that range to 2 - 2.66 sq ft.; as savings of a whopping 108 sq in or 12" x 9". That's a lot of sacrifice for a small result.

If I put in side doors, then the weight is probably increased and the strength in crashes is decreased. The shape of the CarBEN is based on the aerodynamic shape combined with a practical and usable space. I did not design it around the rear entry, though it does allow for the weight savings and greater crash protection.

Show me any other car under 14' long that holds five people and has aerodynamics as good as the CarBEN design. The Illuminati Seven holds 4 people, and "hides" the frontal area of the 52kWh battery in the middle of the passenger compartment -- but it is 21' long and weighs 3150 pounds.

How *specifically* would you design a better electric car, that has the general "specs" that CarBEN does?

Dave Cloud's Dolphin has a smaller frontal area (close to the 19 sq ft that Matt is asking for?) and maybe even better Cd, and while it might be made to fit four people, they would not be nearly as comfortable, and then fitting in an 11 cubic foot battery pack would be a trick. It has just the two side doors, and no hatch (so no access to storage).

It is not just the quantity of the frontal area, but also the layout of the frontal area. CarBEN is close to a square, so it encloses the just about the most volume possible for that frontal area. Take a foot away from the height, and make the width 1'-2" wider (6'-6" total) to keep the same area, and the seats must be reclined to fit people in, and then the length must be increased to still fit them. And the "perimeter is" now slightly greater, along with the added length, means more weight. How the seating is set up determines the comfort and you are still left with the question of where to put the 11 cu ft of battery.

Drop the height another foot and the width needs to be 8'-4" to get the same area...

10-01-2010, 10:14 PM	#181 (permalink)
NeilBlanchard Master EcoModder Join Date: May 2008 Location: Maynard, MA Eaarth Posts: 7,908 Mica Blue - '05 Scion xA RS 2.0 Team Toyota 90 day: 42.48 mpg (US) Forest - '15 Nissan Leaf S Team Nissan 90 day: 156.46 mpg (US) Number 7 - '15 VW e-Golf SEL TEAM VW AUDI Group 90 day: 155.81 mpg (US) Thanks: 3,475 Thanked 2,952 Times in 1,845 Posts	The CarBEN is just 5'- 4" inches wide. If I narrow it to 4'-4" wide I could not fit two seats side by side. And how can I fit a ~55kWh battery in with any less frontal area? The frontal area of the battery is 40" x 5.5" and there is no way to fit 768 cells in "inline" with any other part of the car; let alone with the best Cg possible. Removing the middle foot reduces the interior volume by a huge amount: that is the tallest and longest portion. The widest interior dimension is about 4'-6" and the narrowest is ~2'-8" -- those drop to 3'-6" and 1'-8", which probably turn it into a 3 seat car. No thanks. Even if you don't lower it a proportional amount (which you would have to, since a 5'-6" tall by 4'-4" wide vehicle looks a lot like the Tango!), you would lose 1/3 of the battery bay, dropping the capacity to ~37kWh. The weight saving in the chassis would be minimal since the "perimeter" only would drop from 21'-8" to 19'-8". The frontal area is just ~25 sq ft as it is. And if the Cd is between 0.11 and 0.14 (WAG) then the CdA is between 2.75 sq ft and 3.5 sq ft. Even saving 6 sq ft of area only drops that range to 2 - 2.66 sq ft.; as savings of a whopping 108 sq in or 12" x 9". That's a lot of sacrifice for a small result. If I put in side doors, then the weight is probably increased and the strength in crashes is decreased. The shape of the CarBEN is based on the aerodynamic shape combined with a practical and usable space. I did not design it around the rear entry, though it does allow for the weight savings and greater crash protection. Show me any other car under 14' long that holds five people and has aerodynamics as good as the CarBEN design. The Illuminati Seven holds 4 people, and "hides" the frontal area of the 52kWh battery in the middle of the passenger compartment -- but it is 21' long and weighs 3150 pounds. How specifically would you design a better electric car, that has the general "specs" that CarBEN does? Dave Cloud's Dolphin has a smaller frontal area (close to the 19 sq ft that Matt is asking for?) and maybe even better Cd, and while it might be made to fit four people, they would not be nearly as comfortable, and then fitting in an 11 cubic foot battery pack would be a trick. It has just the two side doors, and no hatch (so no access to storage). It is not just the quantity of the frontal area, but also the layout of the frontal area. CarBEN is close to a square, so it encloses the just about the most volume possible for that frontal area. Take a foot away from the height, and make the width 1'-2" wider (6'-6" total) to keep the same area, and the seats must be reclined to fit people in, and then the length must be increased to still fit them. And the "perimeter is" now slightly greater, along with the added length, means more weight. How the seating is set up determines the comfort and you are still left with the question of where to put the 11 cu ft of battery. Drop the height another foot and the width needs to be 8'-4" to get the same area... __________________ Sincerely, Neil http://neilblanchard.blogspot.com/ Last edited by NeilBlanchard; 10-01-2010 at 10:51 PM..