MAX Update No. 90: Why 'Real Old' Beats 'Old'

http://www.motherearthnews.com/green-transportation/100-mpg-why-real-old-beats-old.aspx

The secret to good mileage is streamlining and light weight. Okay, two secrets. Streamlining is essential at highway speeds, light weight is essential in city driving, and the two combined allow one to get satisfactory performance with a small engine. If you cut your car’s drag in half (via streamlining) and cut your car’s mass in half (via weight reduction) you can cut your horsepower in half without losing any performance. At present, MAX’s top speed is 90 mph, which is faster than I have any reason to drive, and that’s on 32 horsepower.

This is why my recent automotive designs look much like 50 year old road racing cars. Race cars have always focused on functionality, but after 1960, the function of race car bodies changed.

Before I leap into sports car racing history, I’d like to point out that streamlining hasn’t changed much in my lifetime.

090aLakestersHere are two “Lakester” class land speed record cars; both were record holders in their day. The rules require exposed wheels but the body shape is up to the builder. Note the visible similarity between these two cars; both have rounded fronts tapering to small sterns, though the upper car body was built in 1952 from a WWII fighter plane fuel tank, and the lower car body was built in 2004 from carbon fiber and polycarbonate. The shapes are slightly compromised by practical needs (the older car has a plexiglass bump on top so the driver can see out, the lower car has a scoop on top to let air in to the radiator) but they’re clearly built for the same purpose—going as fast as possible on a dry lakebed—and form follows function.

Compare those 50 years of lakesters with 10 years of road racers. You can’t tell by looking that a 1970 Le Mans car comes from the same sport as a 1960 Le Mans car—you can barely tell they come from the same planet.

Up to 1960, the limits of horsepower technology forced race car designers to focus on vehicle efficiency, in order to win races. The closest MAX look-alike is the Lola Mk1, a 75 horsepower two-seat sports racer with a great track record from 1958 to the early '60s, including a class win at the 1960 24 Hours of Le Mans.

Because the Lola Mk1 and its peers (such as the Lotus 11, which won the 1957 Le Mans Index of Performance with a 750 cc 59 horsepower engine...sniffing at 125 mph at the end of Le Mans’ 3.7 mile long Mulsanne straight) had so little power, they had to be light weight to accelerate quickly and well streamlined to go fast, and quick and fast won races.

The rules of the day required the Le Mans racers have suitable accommodations for driver and passenger, working headlights and tail lights, a spare tire, doors, space for an overnight case, and generally be practical, roadworthy sports cars. This wasn't hypothetical practicality; it was not terribly uncommon for race cars to drive to the races, even major races, because it saved a lot of gas compared to putting them on a trailer and pulling them with a truck. In 1960, that class-winning Lola Mk1 was driven from the factory in Huntingdon England to the Le Mans race course in...wait for it...Le Mans, France.*

And then horsepower hit the tipping point, with serious V8 power coming out of Detroit, and America discovered sports racing, with Group 7 and the CanAm Series. In 1965, Lola's top model was the T70, which came equipped with 400+ horsepower Chevys or Fords. With horsepower to spare, the corners suddenly mattered more than the straights. The goal of race car aerodynamics switched from streamlining to downforce, and increased drag was the cost of pushing the car firmly onto the track—instead of trying to cut -through- the air, the bodies were designed to wedge themselves -under- the air, and to use air pressure on top of the car to increase cornering and braking force by increasing the effective  "weight" on the tires.

The Lola T70 was known as the  "breadvan" when it was introduced, because its boxy rear end was such a departure from the streamlined racers of the past ("the past" = five years earlier). The T70 was faster on the straightaways that the Mk1, because it had four times the horsepower, and lots faster in the corners thanks to its downforce, but at a huge price in efficiency—the T70 Spyder had twice the aerodynamic drag of the Lola Mk1. With advances in horsepower from Stuttgart, the T70 was obsolete in a few years too, as the twelve cylinder turbocharged Porsche 917 entered the fray, peaking out at over 1500 horsepower in the early '70s. The 917 was the most powerful road racer ever made, and only the 1973 Oil Crisis (and its attendant 3 mpg rule in CanAm racing) ended its dominance.

I got to thinking about this at a recent car show. I was scouting the various solutions that car builders have come up with for getting in and out of covered cars (MAX’s next project is an enclosed cockpit) and came across this Porsche 917 replica.

090b917Stern 

The gullwing doors are slick, but the stern is definitely not slick. It’s a big blunt slab and there’s more than 15 square feet of it, and it’s the biggest reason this VW-bug-powered 917 gets 1/3 of MAX’s fuel economy.

090cVetteStern 

Despite the inefficiency of the breadvan rear end, it looks really racy and it’s been a styling inspiration for sports cars ever since. Here’s the 2013 Corvette Convertible for example—fast, powerful, 24 highway mpg.

 

 

 

090dMAXSternMAX (like pretty much all the road racing cars up to 1960) is rounded in front and tapers down in back, which reduces drag but does cause some lift. By the late ‘60s, all the serious Le Mans cars had doorstop noses and breadvan sterns, and generated negative lift (downforce) at the cost of drag. It is telling that the Lotus 11 that won the 1957 Index of Performance got 30 mpg and surpassed the 2011 CAFE standard for passenger cars—while racing at Le Mans for 24 hours at speeds up to 120 mph—and 15 years later, the fastest race cars in the world were going twice as fast at roughly 2 mpg.

Lift is not much of an issue at highway speeds, but drag sure is, and the energy issues of today beat 1973’s Fuel Crisis Lite by scads. And so MAX, and the rest of the cars on my drawing board, get their styling cues from racers of yesteryear. Extreme yesteryear.

*They didn't have the chunnel yet so there was a ferry involved.


Photos by Jack McCornack and GM Media 

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