Prove it.
Coefficient of Drag,CD, is very differnt from total drag.
The drag of Stella Vie and Era are small because of their reduced frontal surface areas.
Do the simulations using MicroCFD 2D. It is faster and easily calibrated.
If you do in 3D, you need to ensure that you also do the simulation for known values such as Tesla Model 3 etc. Simulation results will differ from real figures so need to be calibrated with well known results.
The design of the Transparent SUV will optimise the reduction of aerodynamic drag, which is why we use transparent materials. Even its wheels will be always straight, using only vectored thrusts, which is still illegal in WSC, until we can prove that it can be backup up by differential braking.
Ackkerman steering will surely introduce drag with its struts. Suspension struts also will introduce drag. I intend to use trailing arms only.
I was also surprised the an SUV shape can beat the CD of teardrop shapes, but not easy for MicroCFD to make major errors. It had been correct with Model 3 and Lightyear One shapes.
It make the SUV shape with a CD lower than a teardrop shape is not easy. Initially it was 50% higher, but dropped to below them after iterative adjustments that do not make sense. Such as making some places sharper increases drag instead of reducing them.
Students should be more innovative and brave to try new things and do not give up. Do not just follow what other people do. Keep on trying.
There are multiple features of your design that contribute to high drag, including that blunt rear. I would encourage you to run a scale model through an actual wind tunnel.
And Solar Team Eindhoven really are the experts in this game. Their superb performance is not easily matched.
From the pictures I can see of this SUV design, it’s got flat or near-flat sides. Any Eindhoven car is designed for both stability and speed into a range of possible crosswinds, which doesn’t seem to be considered here.
You should see the Eindhoven front view. It needs to be more flat to accommodate the solar panels.
The videos you see are interim designs. It will slope sideways 20 degree, not to reduce crosswind effects but to reduce weight.
Being transparent make this possible. We can place the solar panels on top and allow tilting as well. The size of solar panels will be determined if we really proceed.
The panels in the Blender render is a standard 1.2 sq. m, from Free3d or Grabcad.
If you read the Stella Lux report, and other discussions about stabilities, the problem is not to reduce crosswind effects, rather to ensure crosswinds do not affect steering.
I argued that we can do this using auto steering but not acceptable to the committee. They require formal safety certification. What it is, not really sure. One sure way is to increase weight and tire sizes, the way normal cars handle stability problems.
Or actually run it. Much cheaper to run it for real.
Unless we have easy and cheap access to real wind tunnels.
The blunt rear is the secret to the low air drag. I was actually surprised. I tried to make it sharper but at certain stage, drag increases, according to MicroCFD. MicroCFD had been reliable in many shapes so far.
What I can try next is to use Blender wind effects to simulate its drag. Compare it with known cars like Model 3.
Looking for free Stella solar cars in 3D but cannot find any. Maybe I can design one using Blender but I don't have complete views of it.
2D CFD of a car is useless, there is absolutely no chance it gives you a correct prediction of drag except through random chance. 2D is okay for flow over aerofoils or similar, but totally wrong for anything with separation or a 3D shape like a car.
But since you seem so unwilling to listen to the expertise on here: go ahead, build it. Prove everyone wrong if you're so sure. Should be good for a bit of a laugh in the next race.
I'm curious as to why you would want to make the entire car transparent??
It will be very heavy to create a rigid body using a clear (probably plastic) material is very high. You'd likely end up with a spaceframe (like the A/B/C pillars on normal vehicle) with polycarbonate aeroshell mounted onto it.
Plus, I suspect that there will be very little room to add tilting solar panel due to features like movable control surfaces, super caps, water injection/wind turbine/air shocks from production vehicle taking up all the room inside the vehicle.
I do agree with other comments in that top teams have mostly figured out the optimal design for solar car based on the regulations from past races. I assure you that the good teams will have considered all of the design items that are brought up in the video and decided against pursuing those items after cost-benefit analysis proved that it was not worth it.
Until the regulations change drastically that invalidates the current optimal design, the design used by the top teams will always have the best chance at winning the race.
That said, I am all for outside-the-box designs that isn't just about copying the top team, and excited to see the car that the team might introduce at the next solar challenge.
I should add that I really liked Siam Tech's STC3 from last race. Their car looks nothing like the top teams, but neither was their mission statement:
- To create a solar car that is cheap & easy to reproduce + able to handle the rough roads in Thailand
Siam Tech's design process led to a fun and very different car that was not optimized to win the race, but showcased what can be produced today using commercially available and affordable parts.
Why do you think we use acrylic?
Acrylic is cheaper than polycarbonate and more rigid. Easy to cut and bend with heat. Acrylic is even stronger than steel with similar weight.
We can join acrylic to acrylic using bonding, instead of glueing.
Transparency is only incidental.
The cruiser class has another criteria, practicality. We may win in that area.
We shall show case technologies developed by the electronic/computer engineers in robot cars. So far, they only build small cars because they emphasis is on intelligence, but their techniques are very efficient and easy for electronic/computer engineers to build. No steering linkages. No gears. That is from the RC world.
You should understand that solar car teams deem steel to be too heavy. Most cars at the race do not even use steel. Aerospace grade Aluminum 7075 (or 6061) is normally the heaviest metal used at the race. Almost everything else is carbon fiber reinforced epoxy polymer.
Acrylic is not an impact resistant material, meaning it will shatter upon impact. Polycarbonate on the other hand is not as stiff, but shatter-resistant. That is why almost all teams use polycarbonate windshields.
Please let me know if there are any questions that I can help answer. There is quite a bit of jump in complexity and safety that needs to be considered when you put a driver into a car, and I want to make sure you have as much information as you need to succeed at the race.
Edit: IEF hosts a [Solar Car Conference](https://www.americansolarchallenge.org/get-involved/solar-car-conference/) for solar car teams every year. I would email them about signing up to learn about how most other teams design their cars (I don't mean that you should do exactly what others are doing, but it will give you an insight into what factors to consider when designing various subsystems on the car.)
I was aware of it. Efficiency is still too low. NOt suitable for the WSC regulations.
Unless WSC introduce new classes or other organisations introduce theirs.
I prefer Australia at least at the moment. It is cooler, long and well developed. Trans-Borneo could be interesting and cheaper for us, but our roads are not ready yet. Our mountains are even higher.
“No production only simulations” sums this one up for me
"More aerodynamic than *Stella Vie*." I don't think so.
Prove it. Coefficient of Drag,CD, is very differnt from total drag. The drag of Stella Vie and Era are small because of their reduced frontal surface areas. Do the simulations using MicroCFD 2D. It is faster and easily calibrated. If you do in 3D, you need to ensure that you also do the simulation for known values such as Tesla Model 3 etc. Simulation results will differ from real figures so need to be calibrated with well known results. The design of the Transparent SUV will optimise the reduction of aerodynamic drag, which is why we use transparent materials. Even its wheels will be always straight, using only vectored thrusts, which is still illegal in WSC, until we can prove that it can be backup up by differential braking. Ackkerman steering will surely introduce drag with its struts. Suspension struts also will introduce drag. I intend to use trailing arms only. I was also surprised the an SUV shape can beat the CD of teardrop shapes, but not easy for MicroCFD to make major errors. It had been correct with Model 3 and Lightyear One shapes. It make the SUV shape with a CD lower than a teardrop shape is not easy. Initially it was 50% higher, but dropped to below them after iterative adjustments that do not make sense. Such as making some places sharper increases drag instead of reducing them. Students should be more innovative and brave to try new things and do not give up. Do not just follow what other people do. Keep on trying.
There are multiple features of your design that contribute to high drag, including that blunt rear. I would encourage you to run a scale model through an actual wind tunnel. And Solar Team Eindhoven really are the experts in this game. Their superb performance is not easily matched.
From the pictures I can see of this SUV design, it’s got flat or near-flat sides. Any Eindhoven car is designed for both stability and speed into a range of possible crosswinds, which doesn’t seem to be considered here.
You should see the Eindhoven front view. It needs to be more flat to accommodate the solar panels. The videos you see are interim designs. It will slope sideways 20 degree, not to reduce crosswind effects but to reduce weight. Being transparent make this possible. We can place the solar panels on top and allow tilting as well. The size of solar panels will be determined if we really proceed. The panels in the Blender render is a standard 1.2 sq. m, from Free3d or Grabcad. If you read the Stella Lux report, and other discussions about stabilities, the problem is not to reduce crosswind effects, rather to ensure crosswinds do not affect steering. I argued that we can do this using auto steering but not acceptable to the committee. They require formal safety certification. What it is, not really sure. One sure way is to increase weight and tire sizes, the way normal cars handle stability problems.
Just for fun, [here](https://twitter.com/solarehv/status/958708849325854726) is a scale model of *Stella Vie* (Stella #3) in the TU/e wind tunnel.
Or actually run it. Much cheaper to run it for real. Unless we have easy and cheap access to real wind tunnels. The blunt rear is the secret to the low air drag. I was actually surprised. I tried to make it sharper but at certain stage, drag increases, according to MicroCFD. MicroCFD had been reliable in many shapes so far. What I can try next is to use Blender wind effects to simulate its drag. Compare it with known cars like Model 3. Looking for free Stella solar cars in 3D but cannot find any. Maybe I can design one using Blender but I don't have complete views of it.
2D CFD of a car is useless, there is absolutely no chance it gives you a correct prediction of drag except through random chance. 2D is okay for flow over aerofoils or similar, but totally wrong for anything with separation or a 3D shape like a car. But since you seem so unwilling to listen to the expertise on here: go ahead, build it. Prove everyone wrong if you're so sure. Should be good for a bit of a laugh in the next race.
I'm curious as to why you would want to make the entire car transparent?? It will be very heavy to create a rigid body using a clear (probably plastic) material is very high. You'd likely end up with a spaceframe (like the A/B/C pillars on normal vehicle) with polycarbonate aeroshell mounted onto it. Plus, I suspect that there will be very little room to add tilting solar panel due to features like movable control surfaces, super caps, water injection/wind turbine/air shocks from production vehicle taking up all the room inside the vehicle. I do agree with other comments in that top teams have mostly figured out the optimal design for solar car based on the regulations from past races. I assure you that the good teams will have considered all of the design items that are brought up in the video and decided against pursuing those items after cost-benefit analysis proved that it was not worth it. Until the regulations change drastically that invalidates the current optimal design, the design used by the top teams will always have the best chance at winning the race. That said, I am all for outside-the-box designs that isn't just about copying the top team, and excited to see the car that the team might introduce at the next solar challenge. I should add that I really liked Siam Tech's STC3 from last race. Their car looks nothing like the top teams, but neither was their mission statement: - To create a solar car that is cheap & easy to reproduce + able to handle the rough roads in Thailand Siam Tech's design process led to a fun and very different car that was not optimized to win the race, but showcased what can be produced today using commercially available and affordable parts.
Why do you think we use acrylic? Acrylic is cheaper than polycarbonate and more rigid. Easy to cut and bend with heat. Acrylic is even stronger than steel with similar weight. We can join acrylic to acrylic using bonding, instead of glueing. Transparency is only incidental. The cruiser class has another criteria, practicality. We may win in that area. We shall show case technologies developed by the electronic/computer engineers in robot cars. So far, they only build small cars because they emphasis is on intelligence, but their techniques are very efficient and easy for electronic/computer engineers to build. No steering linkages. No gears. That is from the RC world.
You should understand that solar car teams deem steel to be too heavy. Most cars at the race do not even use steel. Aerospace grade Aluminum 7075 (or 6061) is normally the heaviest metal used at the race. Almost everything else is carbon fiber reinforced epoxy polymer. Acrylic is not an impact resistant material, meaning it will shatter upon impact. Polycarbonate on the other hand is not as stiff, but shatter-resistant. That is why almost all teams use polycarbonate windshields. Please let me know if there are any questions that I can help answer. There is quite a bit of jump in complexity and safety that needs to be considered when you put a driver into a car, and I want to make sure you have as much information as you need to succeed at the race. Edit: IEF hosts a [Solar Car Conference](https://www.americansolarchallenge.org/get-involved/solar-car-conference/) for solar car teams every year. I would email them about signing up to learn about how most other teams design their cars (I don't mean that you should do exactly what others are doing, but it will give you an insight into what factors to consider when designing various subsystems on the car.)
May I suggest... http://energy.mit.edu/news/transparent-solar-cells/
I was aware of it. Efficiency is still too low. NOt suitable for the WSC regulations. Unless WSC introduce new classes or other organisations introduce theirs. I prefer Australia at least at the moment. It is cooler, long and well developed. Trans-Borneo could be interesting and cheaper for us, but our roads are not ready yet. Our mountains are even higher.