race action: World Solar Challenge and aero
 

Here's some footage, illustrating the challenges for extremely light aero structures under racecourse conditions
https://www.youtube.com/watch?v=Slxzf3duMMs

Now that's real eco-modding.

And relevant to this thread: ecomodder.com/forum/showthread.php/why-dont-cars-have-wings-partially-take-weight-39409.html

relevant
 

Yeah. It's tough to watch the crashes knowing the hardships all team members endure just to participate, all their work lost in a moment.
The importance of coefficients of adhesion and implications of compromising lateral acceleration g-forces which can be sustained at the road interface is really rammed home.
I tip my hat to all of them. They're the stuff that Tesla's made of. Literally!

LOL, I was just going to mention that this is evidence for why cars aren't airplanes.

Don't know why the embedded time skip isn't working, but skip to 11:48

http://www.youtube.com/watch?v=Slxzf3duMMs&t=11m48s

Playlist of the whole race:

https://www.youtube.com/playlist?lis...YGbl-wErl027uc

That's an interesting challenge.
I wonder if we could assemble a team ecomodder :D
There is quite some room for improvement to be seen on these vehicles and their driving strategies.

I would believe their aerodynamic theory is a bit in front of even Aerohead, or Julian. Most schools have compute power that dwarfs anything I see here. They definitely have a better manufacturing support system. But we're experienced. Hmmm.

We wonder if you could assemble a team ecomodder.

...and campaign the length of Oztralia.

The most I have seen is springing for an hour of wind tunnel time in Utah.

Piotrsko -- I've given it some thought.

https://ecomodder.com/forum/member-f...belly-tank.png

Just slap some panels on it.

We're experience eco-drivers and even making it all the way would place us better than many of them that do not finish.
I've also seen quite a few things there that are inducing way more drag than they need to.
Especialy the hard transitions on the catamaran designs are inducing quite some additional drag.

That design might be very areodynamicly optimize, but it lacks the optimisation to generate sufficient power.
There isn't realy any good place to mount the solar cells to it.

But we would likely have untill 2023 to come up with something as well as building it.

That was design to specific racing class rules. That's why it has four wheels.

One Ecomodder member did a CFD analysis (FWIW) of a feature that would fit it. A bellmouth diffuser.

https://ecomodder.com/forum/member-f...14-1-42-00.png

I haven't found the thread so I can't pass along his results, but it was similar to this one: a gravity racer in Barcelona. ecomodder.com/forum/showthread.php/making-more-efficient-aerodynamic-soapbox-gravity-race-car-32441.html
or this one:
ecomodder.com/forum/showthread.php/aero-teardrop-its-side-28652.html
This one is notable for Permalink #31
https://ecomodder.com/forum/showthread.php/gravity-racer-gallery-extreme-aerodynamics-1208.html
I'me seriously going to find a thread to repost the graphics from Permalink #31 (dates to 2008).

I think it's in the near future also. Mainly because CFD will be implemented with OpenVDB. It's already being rolled into Blender with its physics engine. Coding it is above my pay grade unfortunately. I used to work with programmers. I stand in awe.

Especially Ian Hubert and Dynamo Dream.

Speaking of rules, you could plaster the whole vehicle in PV cells and at least one side of the car will be getting optimal sunlight on them. But I do believe that these races also limit the number of solar cells that can be placed on the vehicle.

The car body could be a vacuum tube solar collector with a Stirling Engine. Now that's ecomoddin'.

Um, that's a bit like saying, "Why don't we develop an F1 team - there is quite some room for improvement to be seen on these vehicles and their driving strategies."

I know it's the web, but don't people even think of looking at what has actually been achieved before putting in their oars?

Dear me...

Those ultra-low rolling resistance tyres have very little lateral grip unfortunately, with a forward centre of pressure and large rear lift, in sudden changing crosswinds very high crosswind drag coefficient, 40 knot right wind and then 40 knot left wind. It is out of the hands of the driver.

Why not a vacuum tube solar collector that powers a steam engine? Wouldn't that be more efficient? Steam is actually a bad choice, refrigerant is the new steam. And the team would be putting all their food in the car to cook it because it gets so hot.

team
 

I'm not sure, but I thought it was limited to students only.
And other than crowd-funding $ 1,300,000 for the project, you've got out-of-pocket airfare for all team members, plus the free labor of thirty-six people as well. And multi-core processors and CAD-CAM-CFD software, plus shop facilities are provided free of charge ( if you ignore tuition ).

Surely all the solar challenges can't be only students?
You want ultra LRR tyres? Your team needs to be personally sponsored by a tyre company, who then charge you quite a lot for the tyres that only last 200 miles.

Unless ecomodder suddenly gets millions of funding, it isn't happening. Shell ecomarathon is slightly more realistic but still wildly optimistic

theory
 

I'm uncertain about any difference in theory. Having CFD to do the pick and shovel work is certainly an advantage ( that would cost us $ 400,000 ( US ), without data cloud models).
Scale-models are extremely expensive, cost as much as a full-scale vehicle, and can't be used for anything else, especially not for tooling.
California teams were transporting their cars all the way to North Carolina and back for full-scale wind tunnel testing at Aerodyne.
If you ignore $ 26,664 / year, for tuition, books, food, and housing, computer, software, and shop facilities are 'free.'

transition drag
 

The University of Michigan, 'NOVUM' solar race car project team used SIEMENS' CAD/CAM/CFD. This CFD incorporates smoothing protocols to reduce interference drag at component intersections ( minimum fillet radii ), so they have this covered.
Teams which have no access to wind tunnel validation would be locked into whatever CFD could do for them. Hopefully, all their CFD software includes the interference drag minimization code.

rules
 

The rule book changes every 4-years, so teams would be held to whatever limits/ boundaries, were defined in the applicable rule book specifications.

only students
 

The HONDA Dream solar race teams consisted of young engineers, at HONDA R&D. I think HOXAN did the same thing.
There may be different categories, like University, or Corporate.
There is the 'Cruiser-Class' which is a separate entity, with separate specifications, closer to 'actual' motor vehicles.
The North American Solar Challenge contestants have been provided tires gratis, getting free advertising for the tire-maker during the competition.
I believe, Bridgestone, Michelin, and Schwalbe all do this.
At Bonneville, you cannot 'own' a set of GOODYEAR racing tires. One can only 'lease' them, and must return them for destruction after the term of the lease, except for 'museum' display.

Didn't GM also participate in solar races before (reference, Who Killed the Electric Car?)

GM solar race participation
 

Absolutely! Their GM/AeroVironment Sunraycer of 1987 sorta, single-handedly redefined the solar race car.
Sunraycer was reported by Cal Tech to be the lowest drag land vehicle ever measured. Below Cd 0.1165.
I've heard as low as Cd 0.089 with wheel fairings. Cd 0.125 as-raced. And later, GM claimed Cd 0.147, but I think that this is a crosswind averaged Cd, based upon changing SAE protocols.
After 1987, GM provided Magna-Quench motor technology to teams, as well as access to their GM-owned Hughes Aerospace VSAERO, CFD software.
Many teams, including HONDA just copied Sunraycer for the 1990 race season.
Paul MacCready, of AeroVironment, calculated that with a modest ICE powerplant, Sunraycer would be good for 400-mpg, and their 'Impact' BEV, 100-mpg.
The 1991 GM Ultralite had the Impact aerodynamics, and did 100-mpg @ 50-mph.
GM's Oldsmobile AEROTECH long-tail set a closed-course land speed record, with AJ Foyt behind the wheel.
All of these cars, and other GM concepts have inspired my projects. :)

I think this is closer to our budget:

https://www.youtube.com/watch?v=1mF2bdmHCQY

our budget
 

' Like a soup made from the shadow of a crow that starved to death.' Abraham Lincoln:o

Autobahnschleicher -- Perhaps I'm the only one to take you seriously.

It would be fun to try and fail. How's about relocate to Bonneville Salt Flats? It's closer to you than Australia as far as I know. And members have been known to appear there. Bonnevile's a hoot. The first time I was there we met a guy who bought an old pickup truck and threw his motorcycle in the back and headed toward Bonneville knowing he needed a crew he didn't have. The guy he recruited has ridden his own Ducati there at 160 MPH and was on the salt flats in Bolivia last I heard.

So grassroots racing can happen.

It's all fun until you actually have to build something and put it in the field. Someone here could crunch some numbers. They seem to favor steam for external combustion.

A vacuum tube of the necessary capacity could be made from an acrylic tube 36" in diameter, slump molded in a [rented] infrared lamp bank and then inverted and placed on the back of an aero-Template tricycle (for cheaper tires*). aerohead knows how to fillet the wheel openings, see his Baby Template.

*witness that Max Balchowsky ran Buick station wagon tires on Old Yeller II against Ferraris and their ilk.

So I've been thinking about this. It's a North-South race during a solar day. Four wheels are a class requirement.

So.... An arcylic tube long enough to contain the allowance of solar panels in a linear area. IDK what the allotment is, maybe 3x21 feet? 2x25? Anyway, the long array tracks the sun morning to evening inside the tube. The four wheels are staggered and extremely cambered inside a single blister in front and back. Motorcycle tires with a variable pressure system.

https://upload.wikimedia.org/wikiped...berCar1960.jpg
https://ecomodder.com/forum/showthre...tml#post489465

Driver is supine in the diameter of the tube plus the visibility requirement. The solar cells operating in a partial vacuum would have a cooling jacket feeding a low-temperature Stirling engine to capture all the light the PV cells reject.

The tube could could have front and rear bogeys so it would look like a little log truck.

So it would be a delta, with smoll front wheels and bigger back wheels spread apart like a quasi-trike, with fins. Long wheel-base for fineness ratio and minimize the stagger in the front wheels. With the transparent tube in the middle it would look like an arrow. Smaller tube backbone frame and the solar array rolls across the top.

The driver is seated at the back slingshot style for control authority and there's four-wheel steering to insure it's never driving sideways, even a little bit.

What do you think, sirs?

I think a good starting point would be to read the race rules, read about the cars that have won the race over the last few decades, perhaps talk to some solar team members, maybe have a chat with someone who has done the aero for these cars, and perhaps read this book.

I have enough trouble trying to get people to talk with me about tiny houses. And who's rulebook, Solar Challenge or SCTA?

I'm not going to Australia, the women are too hot. And I hear there're spiders.

After we complete 24hrs of Lemons, we can discuss the much more expensive challenge of competing in a solar race.


At first glance I thought you were saying the women were spiders. Women shave their legs in Australia, right?

Pick a race then let's see if we can even agree as to what the design is (maniacal laughter sound track applied). Remember a camel is a horse designed by committee.

Can we even design a soapbox racer?

:)

Your search term is 'Gravity racer'. There have been some build threads.

My vote is for the Hyundai design

https://s1.cdn.autoevolution.com/ima...families_2.jpg
www.autoevolution.com/news/hyundai-soapbox-is-an-affordable-diy-project-for-family-and-friends-148664.html

My vote is a powerful electromagnet in the nose that pulls on the gate as it falls to get the slight advantage required to win every time.