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

stealth · 02-25-2016, 07:55 PM

I used corroflute, which is a very light plastic material and used Polyproplene hot glue to fasten the panels together on the inside and a strip of electrical tape.

The bezels are for reducing the frontal area as much as possible as corroflute is a flat sheet material and can't be formed into compound curves and therefore I used three sections on the side as shown below. By the way all of the wheels are cambered 10 degrees inward.

Aerodynamically, yes it was a better body with much better rear aero as it tapers to a point. However other factors such as increased in car weight, and dying batteries meant that it performed about the same as the first version.

Aerohead - Thanks for the ideas, there's a lot of restrictions in the rules that prevents some of the ideas you're mentioning, I will try to rattle through them, a lot of them I have tried to implement into my design.

The 2D side profile of my best body so far is similar to a streamline shape as you can see below, just stretched out. It's slight cambered towards the front to minimise the squashing of the airflow at front of the car.

This has a 95mm ground clearance at the middle and towards the front and increases up to 150-170mm at the backm, so similar increase to what you're saying. I'm not sure I was clear before but the 100mm ground clear only applies to the batteries base height and the driver's bottom. Everything else can be much higher so there is some flexibility there.

The top surface does keep increasing in height until the canopy, same as you suggested. Also the head fairing is as faired as much as possible.

The roll bar has to be exposed because there is a line is drawn from the front roll bar to the rear, there must be 50mm of clearance between the line and my helmet. Also recently, they banned any fairing for the top 150mm of the rollbar, the other teams weren't very happy at all about that.

The plan is both the front and rear track to be at the minimum of 500mm plus all wheels have a 8-10 degrees negative camber to reduce the frontal area even more. The frontal area is about 0.225m^2 or less, about 10 times smaller than an average car.

I did some flow simulations on the three designs I posted on here, I did them on the more accurate Solidworks software and it gave me some surprising results. The 3 wheeler even though it has completely tapered rear end, the amount of surface area made it a lot worse, about 40% higher drag force than the second design. So I would agree with you with that completely enclosed wheels are the way to go.

Also if you're interested to know, the third design (the catamaran design with the side flanges cut off) I posted in permalink #9 has about 15% more drag force than the second design. The channel underneath and the side flanges is definitely helping out reducing the drag.

02-25-2016, 07:55 PM	#18 (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	I used corroflute, which is a very light plastic material and used Polyproplene hot glue to fasten the panels together on the inside and a strip of electrical tape. The bezels are for reducing the frontal area as much as possible as corroflute is a flat sheet material and can't be formed into compound curves and therefore I used three sections on the side as shown below. By the way all of the wheels are cambered 10 degrees inward. Aerodynamically, yes it was a better body with much better rear aero as it tapers to a point. However other factors such as increased in car weight, and dying batteries meant that it performed about the same as the first version. Aerohead - Thanks for the ideas, there's a lot of restrictions in the rules that prevents some of the ideas you're mentioning, I will try to rattle through them, a lot of them I have tried to implement into my design. The 2D side profile of my best body so far is similar to a streamline shape as you can see below, just stretched out. It's slight cambered towards the front to minimise the squashing of the airflow at front of the car. This has a 95mm ground clearance at the middle and towards the front and increases up to 150-170mm at the backm, so similar increase to what you're saying. I'm not sure I was clear before but the 100mm ground clear only applies to the batteries base height and the driver's bottom. Everything else can be much higher so there is some flexibility there. The top surface does keep increasing in height until the canopy, same as you suggested. Also the head fairing is as faired as much as possible. The roll bar has to be exposed because there is a line is drawn from the front roll bar to the rear, there must be 50mm of clearance between the line and my helmet. Also recently, they banned any fairing for the top 150mm of the rollbar, the other teams weren't very happy at all about that. The plan is both the front and rear track to be at the minimum of 500mm plus all wheels have a 8-10 degrees negative camber to reduce the frontal area even more. The frontal area is about 0.225m^2 or less, about 10 times smaller than an average car. I did some flow simulations on the three designs I posted on here, I did them on the more accurate Solidworks software and it gave me some surprising results. The 3 wheeler even though it has completely tapered rear end, the amount of surface area made it a lot worse, about 40% higher drag force than the second design. So I would agree with you with that completely enclosed wheels are the way to go. Also if you're interested to know, the third design (the catamaran design with the side flanges cut off) I posted in permalink #9 has about 15% more drag force than the second design. The channel underneath and the side flanges is definitely helping out reducing the drag.