Discussion: The two demons of the X Prize

[virtualeric]

1. Mass

2. Wind resistance

Two rules we must obey...and yet we long to forget.

Yes they are obvious. And yes every X Prize team has built their car obsessing over them and gambling that their innovations make up for their compromises in weight and aero. But come June and July, team after team in this X Prize will be relentlessly vanquished by these two demons of auto design. The third killer will be judging a team's platform to decide if it is fiscally viable and has been designed to incorporate future compliance and comfort. But make no mistake -- mass and wind are the twin guillotines in this gauntlet of efficiency.

IMHO the X Prize contender that reduces the penalty of mass and air the most is going to win. I don't see any other way to win, let alone make it to 100mpge, which is still an uncertainty for many -- if not all -- of these teams despite their claims.

The X Prize teams have deployed the most efficient drive systems they could get their hands on. They did and continue to do all they can before June to reduce mass and increase aero, efficiency and handling. But only those who will have surrendered to gravity and air, from the first day of their creation to the last, will emerge from the knockout rounds.

I have come to believe that a chosen drive system in the X Prize matters less than weight and aerodynamics. It sounds like a team Edison2 question, but it is a question worth asking: does the 95% efficiency of an electric motor make up for added battery/chassis/parts weight and counteract the demons of gravity and air more than a fuel based motor?

If so, then IMHO only the lightest, most aerodynamic electric car will win. If not, then we are realistically and rhetorically -- as I found myself recently -- back at the top of this post, punished in our dream of non-CO2 efficiency by the relentless demons of mass and wind...how we long to forget.

Still, after this summer there will be two separate arcs in automotive history: the arc before X Prize, and the arc beyond.

[mtrivich]

Actually, I'd call #1 mass. This affects acceleration, start, stop, cornering.
Gravity is a secondary effect, on hills. I doubt that the X-prize has many hills.

Mike
2h #670

[virtualeric]

Originally Posted by mtrivich

Actually, I'd call #1 mass.

That makes more sense. Thanks.

[NeilBlanchard]

Yes, and designing is *always* compromise. Years ago, I had a job as an assistant mechanic, and we had a couple of sayings:

"Don't cry -- modify!"

"Don't force it -- use a bigger hammer!"

[PatQ562]

No argument that mass and air resistance are the forces to overcome. But there's just as much to gain in what PROVIDES the thrust. Even among electric drivetrains, real world wall-to-wheels efficiency could range from 50% (a really stinko old-tech PbA with lossy charger and series motor) to maybe 80% (a really optimized state-of-the-art design). In a given vehicle, such a difference could move the mpge from 62 to 100.

ICE fans rightly point out how much chemical energy a few gallons of fuel carries. My biggest complaint about hyper-efficient gas cars is the "lawnmower engine" you get after downsizing. The world needs a fuel-cell system powering a nice smooth electric motor, that runs on convenient liquids rather than hydrogen.

Pat Q