Monday, October 12, 2015

Our First Afternoon at Hidden Valley

I'm definitely tired after my first day in Australia. Whoof, trans-pacific travel always takes it out of me. Just a minor status update on my last post - Lodz and ITS were both out at Hidden Valley today, although oddly, Stanford wasn't (although they're in Darwin somewhere). ITU is still MIA and RVCE still doesn't seem to have their car yet.

It was a busy day out at the track, and ScientificGems caught links to most of the minor incidents and issues, so I won't go on about most of them here. JU's wheel escaped to freedom before I got on site this afternoon, but they were back out and driving before the end of the day. UNSW also had a wheel issue near the end of the day - the aluminum center debonded from their carbon GHCraft wheel, stranding them out on the track at the end of the day until they could coax the damaged front wheel off the car and swap it out. No damage to eVe fortunately, and although they are down a wheel, several other teams are using the GHCraft wheels so UNSW shouldn't have any trouble finding spares if they need another.

Some thoughts on a few of the car, with pictures!

Challenger Class:

Michigan: Aurum looks even better up close than it does in pictures. It's FAST out on the track - they don't seem to have any qualms about the handling of the car. The steering packaging around the front leading-arm suspension is tight, but it all looks pretty clean. The inclusion of a steering damper is interesting, and fairly unique. It has dual CSIRO motors, one on each rear wheel, and the Gochermann array looks really good.

Aurum blasting down the front straight at warp speed. I'm shocked I managed to get it in frame.
Tight packaging around the steering rack.
Note the steering damper, and the padded space for a Semprius concentrator module.
There's a matching space at the back of the chassis.

MegaLux: The chassis and suspension of their car can only be characterized as "flawless craftsmanship". Everything is carbon - I overheard a team member telling an onlooker that there is less than 5kg of metal on the car (motor aside). Pitman arm/drag link steering is definitely a departure from traditional solar cars, but works well with the highly-offset driver. By the way, MegaLux is only using a single motor, on the wheel behind the driver - most teams seem to be using two. The wiring is so clean as to be nearly non-existent, and the car looked smooth out on the track. They weren't quite as ridiculously fast at Michigan around the track, but they were quite fast.

All that said, I'm not *super* impressed with the aerodynamics of the car. I guess we'll have to wait for the race start to see how it performs - and how well the rookie team's strategy is worked out.

Pitman arm and drag link: Once very common on passenger cars; typically only seen nowadays on lifted 4x4s.
Packages pretty well inside thin solar cars with offset drivers.
That dark stripe on the leading edge is an air intake at the stagnation point of the airfoil; it brings air into that very cleanly molded duct on the outside the the front wheel. There's a matching one on the left side of the car. Also note the small carbon bracket above the front suspension, is it part of their array stand?

Twente: I didn't see them at the track today, but they've unveiled a secret weapon that they claim will save them 30 minutes over the race. I confess to not exactly understanding what they are doing - could that post be summed up as "we built a better MPPT"?

Unfortunately, Tokai and Nuon weren't at the track today (at least not after I arrived there in the afternoon) and neither was Punch, so I didn't get to see them. Stanford has not shown up yet either, so I didn't get a look at any of the other top cars.

Cruiser Class:

Bochum: It's a real car. It has real doors that open at a touch, feel solid, and close smoothly. There was always a crowd around the car, and Bochum members were more than happy to let people take turns sitting in it. However, the solar array is old - it was definitely on their previous car in 2013, and maybe was originally on the 2011 car - which explains the 29.2% efficiency that some people were speculating about. The old array certainly won't help their performance...

So smooth, so shiny. They were letting everyone sit in the car, and there was quite a crowd! 
C7 Corvette headlights.

UNSW: Even though they're no longer the hottest looking Cruiser around, eVe still looks great. On the other hand, they have added over 100kg to the car since 2013 - mostly in finishing the interior nicely and reenforcing the doors for side impact protection. That extra weight isn't going to do them any favors; especially with only 4sqm of cells on the exterior of the car.

eVe ripping down the front straight...
...but maybe going a little too fast around some of the corners.
They damaged the front right wheel (but fortunately not the car itself).

Kogakuin: As with Michigan and MegaLux; I'm more impressed now that I have seen Owl in person - the fit and finish is exemplary, and there are a lot of aerodynamic details. This car has been engineered to win, and a lot of the Cruiser teams are eyeballing them.

I thought the link visible in the windshield was part of a swaybar setup, but it's actually a bellcrank-actuated steering mechanism, driven by an intermediate gearbox. 
The trailing edge of the fairings are cambered inward the higher they get, and the sharp fairing trailing edge is carried all the way to the aft edge of the car.
Deeply scooped out underside in the tunnel. Such aero, much wow.

Persian Gazelle: The car looked great out on the track. The inline seating has potential in general, but I believe that PG's specific implementation may not be that great - there's a lot of frontal area, and nasty compression zones between the driver fairing and the rear wheel fairings. I didn't really get a chance to see the inside.





Lodz: Their car is bigger in person than it appears in photos - some of the shapes and curves on the car make it appear much more diminutive than it really is.

Person for scale. See how the sides of the car are canted inward, but flare out at the top for the array.
Exposed rear suspension under the car?

Tires:

Look up at the photos of MegaLux and Michigan, comparing Michigan's Michelin tires to MegaLux's Bridgestone tires. The Bridgestones are basically slicks! I thought tires at WSC had to have tread? So I took a dive into the rules:

Prior to 2009, rules on tires were fairly lax. For example, reg B.6.1 from 2007 states: Tyres must be able to safely withstand the loads and forces imposed by the vehicle mass, speed capability and braking. Tyres must be suitably designed and rated and used in accordance with the manufacturer's recommendations.

However, the rules were changed in 2009. Regulation B.6.1 contained the same language as in 2007, but appended the following: Tyres must have a tread pattern across the section width that normally comes into contact with the road, at least 1.5 millimetres deep in a band that runs continuously around the circumference of the tyre, and must be free of any apparent defect. This eliminated several old standard tires in the solar car world (all slicks), and cemented the Michelin Radial X as the tire to have.

Although rearranged slightly, the exact same language was used in 2011 (B.10.1, B.10.2, B.10.3) and 2013 (2.51, 2.52, 2.53).

However, the tire regulations have in fact been changed for 2015. Reg 2.11.3 states: Tyres must have a tread depth of at least 1.5 mm, and be free of any apparent defect - eliminating language about location of the tread, effectively neutering this regulation. The new Ecopias have "show" tread wrapping the edges of the tire, but the contact patch is a slick. Sure seems convenient that the reg changed to allow Bridgestone's new tire, the same year Bridgestone is the title sponsor...

4 comments:

  1. One can't really argue with the event's title sponsor. But if (a) it rains towards the end of the race and (b) a car with Ecopias comes of the road as a result, that would be rather a bad look. Still, Bridgestone claims that the tires do actually grip well in the wet.

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  2. You mention eVe has 4 sqm cells on the outside; then they must not be using all GaAs because you can have only 3 sqm of those.

    If the cells on the Bochum car are indeed that old and have a lower efficiency, that will reduce their performance considerably. On the other hand, it doesn't make sense to do that on that wonderfully designed and built car for which no cost seems to be spared.

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    Replies
    1. Correct, they are using Silicon cells (like almost every other team). Teams are allowed up to 6sqm of silicon cells - but the styling features on eVe heavily restrict how many cells could be placed on the car.

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  3. Thorough and knowledgeable. As always. Many thanks, looking forward to your reports from the actual race.

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