Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - Underfloor and Body design of Greenpower Car (similar to Electrathon)

stealth · 02-18-2016, 08:44 PM

Hello all, new here.
I'm currently designing a Greenpower car and would like to know which type of underfloor and ground clearance would be best for low drag. I don't know whether this is a good place to ask but since it's eco, electric and focused on aero, I'll try here.

Some information on a Greenpower car, it is essentially a extremely small single seater electric car and we enter into races with other student built cars. We have the same batteries and motor and therefore we have to design the most efficient car possibly to go as fast and far as possible in a hour race. Aerodynamics is the biggest factor which is why I want to get it right.
(http://www.greenpower.co.uk)

Fastest cars tend to go at 40mph + which all of my CFD testing is at. The racing is done on large tracks so only minimal steering angle is required.

We are given a set of rules and regulations that we have to comply with and the couple mains one are:

Minimum 500mm track, 4 wheels are required.
Maximum 2800mm length, 1200mm height and width
Only 14" - 20" bicycle wheels are allowed.
Must have a open cockpit opening of 350mm wide and 600mm long.
Ground clearance can't be any less than 30mm.
The bottom of the driver and batteries can't be higher than 100mm off the ground for roll safety.
Finally, it has to fit me (6ft) in the car.

If you are interested, you can have a look at this link which has many of Greenpower cars examples.
http://www.flickr.com/photos/querth/...h/21880485434/

Two most recent winners - See the difference in ground clearance and FA
http://www.facebook.com/GreenpowerRa...type=3&theater

With that out of the way, I have spent hundreds of hours designing a wide variety of bodies and testing it in a CFD software called Autodesk Flow Design. This doesn't however include any moving road simulation which is important for seeing what effect the ground clearance has on airflow underneath and behind the car. I was wondering if any of you guys would have any idea of what would be better in reality.

What would be better, 30mm of ground clearance which reduces the turbulence underneath the car but increases frontal area and makes it more difficult to taper the body at the rear without destroying the underflow,

or

95mm of ground clearance (maximum), which reduces frontal area which is relatively small already but have more turbulence underneath which can cause more drag and air spilling from underneath.

Would be interested to hear what your opinion is.

02-18-2016, 08:44 PM	#1 (permalink)
stealth EcoModding Lurker Join Date: Feb 2016 Location: Cornwall, UK Posts: 18 Stealth II - '16 Stealth Racing Stealth II 90 day: 2117.65 mpg (US) Thanks: 5 Thanked 11 Times in 7 Posts	Underfloor and Body design of Greenpower Car (similar to Electrathon) Hello all, new here. I'm currently designing a Greenpower car and would like to know which type of underfloor and ground clearance would be best for low drag. I don't know whether this is a good place to ask but since it's eco, electric and focused on aero, I'll try here. Some information on a Greenpower car, it is essentially a extremely small single seater electric car and we enter into races with other student built cars. We have the same batteries and motor and therefore we have to design the most efficient car possibly to go as fast and far as possible in a hour race. Aerodynamics is the biggest factor which is why I want to get it right. (http://www.greenpower.co.uk) Fastest cars tend to go at 40mph + which all of my CFD testing is at. The racing is done on large tracks so only minimal steering angle is required. We are given a set of rules and regulations that we have to comply with and the couple mains one are: Minimum 500mm track, 4 wheels are required. Maximum 2800mm length, 1200mm height and width Only 14" - 20" bicycle wheels are allowed. Must have a open cockpit opening of 350mm wide and 600mm long. Ground clearance can't be any less than 30mm. The bottom of the driver and batteries can't be higher than 100mm off the ground for roll safety. Finally, it has to fit me (6ft) in the car. If you are interested, you can have a look at this link which has many of Greenpower cars examples. http://www.flickr.com/photos/querth/...h/21880485434/ Two most recent winners - See the difference in ground clearance and FA http://www.facebook.com/GreenpowerRa...type=3&theater With that out of the way, I have spent hundreds of hours designing a wide variety of bodies and testing it in a CFD software called Autodesk Flow Design. This doesn't however include any moving road simulation which is important for seeing what effect the ground clearance has on airflow underneath and behind the car. I was wondering if any of you guys would have any idea of what would be better in reality. What would be better, 30mm of ground clearance which reduces the turbulence underneath the car but increases frontal area and makes it more difficult to taper the body at the rear without destroying the underflow, or 95mm of ground clearance (maximum), which reduces frontal area which is relatively small already but have more turbulence underneath which can cause more drag and air spilling from underneath. Would be interested to hear what your opinion is. Last edited by MetroMPG; 03-04-2016 at 01:31 PM.. Reason: (fixed links, added to title)