Archive for the ‘four-wheel steering’ tag
Eugene A. Cernan poses with the LRV during the Apollo 17 mission. Photo courtesy NASA.
Research into contemporary electric vehicles is hardly a new effort; in 1969, GM and Boeing developed an electric vehicle with four-wheel drive, four-wheel steering, a rudimentary navigation system, airless tires and a theoretical range of 57 miles under the worst conditions imaginable. Though the Lunar Roving Vehicle (LRV) had a published top speed of just 8 MPH, utilized non-rechargeable silver-zinc potassium hydroxide batteries, and carried a price tag of $38 million, it gave mankind its first motorized journey on another world, and contributed automotive designs that are only now being put into production by manufacturers.
The LRV was born from a need uncovered in early Apollo moon landing missions. Humans can’t survive without life support systems in the lunar environment, and the “portable” units carried by astronauts greatly limited the distance they could travel on foot from the lunar module. To explore more ground, a vehicle would be needed to add mobility, and electric power seemed to be the most practical choice. NASA’s Marshall Space Flight Center submitted a request for proposals (RFP) on July 11, 1969, and three months later, Boeing was awarded the contract over rivals Grumman, Bendix and Chrysler. GM’s Defense Research Laboratories group was named as a subcontractor in the award, tasked with providing the LRV’s propulsion, suspension and tire systems, and the contract stipulated a finished product delivery deadline of April 1, 1971, giving Boeing and GM just 17 months to design, test and build the LRV.
Testing the LRV on planet earth, circa 1971. Photo courtesy GM Media Archives.
In addition to the obvious problems of designing a vehicle capable of traversing rough terrain in gravity that measured 1/6 that on earth and surviving temperatures as low as -118 degrees Fahrenheit, the LRV would need to fold to fit inside a compartment of the lunar module. Upon landing on the lunar surface, the LRV had to require as little effort as possible to turn into a working vehicle, as time spent constructing the buggy was time that could not be spent exploring the lunar surface. The product delivered by Boeing and GM met these criteria, although budget overruns meant the $19 million awarded by NASA carried a final price tag of $38 million.
LRV main components. Drawing courtesy NASA.
The LRV’s frame was constructed of aluminum alloy tubing with an aluminum floor, and each corner received a double wishbone and torsion bar suspension setup that gave 14 inches of ground clearance. Delco provided the electric motors used to power each wheel, as well as the two electric motors that provided front and rear-wheel steering. Each drive motor produced 0.25 horsepower at 10,000 RPM, and on paper the LRV was capable of a top speed of 8 MPH. As Eugene Cernan proved during the Apollo 17 mission, the LRV could be pushed quite a bit faster; with a recorded speed of 11.2 MPH, Cernan holds the title of the fastest man on the lunar surface.
James B. Irwin with the LRV during the Apollo 15 mission. Photo courtesy NASA.
Power for the electric motors (as well as the onboard navigation, communications and scientific equipment) came from a pair of 36-volt batteries that lacked any provision (or formulation) for recharging. Though the LRV’s theoretical range was approximately 57 miles, the operational limit for LRV usage was set by the astronaut’s portable life support equipment, and the farthest distance ever traveled from the lunar module was 4.7 miles. In the event of a catastrophic system failure on the LRV, such a reasonable distance could still be traversed on foot, and to further increase the margin of safety, each LRV mission began at the point farthest from the lunar module. It’s worth noting that no LRV ever failed, although a fender damaged during Apollo 16 nearly caused overheating due to the buildup of lunar dust. When a fender extension was damaged during Apollo 17, the astronauts repaired it with duct tape, clamps and maps of the lunar surface (which had proven too inaccurate to use for vehicular navigation).
The LRV was controlled by a T-handle joystick, which permitted operation by either astronaut using a single hand. Pressing forward provided acceleration, pulling backward provided braking (or, reverse if a lockout switch was pressed), and canting the stick left or right provided electric four-wheel steering. If a steering mechanism was damaged in the field, either system could be disabled allowing operation with the single remaining system (albeit with an increased turning radius). Thanks to the LRV’s unique airless tires, which consisted of zinc-coated steel mesh and titanium strips riveted in a chevron pattern, the LRV proved capable of climbing grades as steep as 25 degrees, even in the slippery lunar soil.
David R. Scott pilots the LRV during the Apollo 15 mission. Photo courtesy NASA.
Though accurate only to 100 meters, the LRV’s navigation system was quite remarkable for the time. Using a gyroscope to note the direction traveled and an odometer to capture the distance traveled, the information was recorded by computer and plotted into a route. This route could then be followed back to the lunar module, even if the vehicle was out of sight, giving astronauts additional peace of mind while traversing the lunar surface.
Four “space ready” LRVs were built, and an additional seven prototypes (of varying functionality) were constructed for development and testing. Three were deployed on Apollo missions (Apollo 15, 16 and 17, beginning on July 31, 1971), and when the program was canceled for budgetary reasons, the fourth was disassembled for spare parts. Though $38 million may seem like a steep price to pay for four vehicles, the LRVs met their design goals and much of the technology developed for the LRV is now being applied to earthbound transportation. Wheel-mounted electric motors are common in both electric and hybrid vehicles (though, in fairness, such a design was embraced by Ferdinand Porsche as far back as 1898), and electric steering has largely replaced hydraulic steering in production cars as manufacturers scramble for higher fuel economy numbers. Airless tires are rumored to be in development for passenger cars, and have already been released for all-terrain vehicles, and while active four-wheel steering is a trend that has seemingly come and gone, passive systems remain in use for a variety of vehicles.
The LRV in action during the Apollo 16 mission.
These technologies aside, the LRV remains a milestone vehicle in the history of transportation. No other wheeled vehicle has ever carried human beings across the surface of another planet, and the fact that it was jointly developed by two separate companies in a 17-month period makes it all the more remarkable. Like the Saturn V rocket that carried astronauts to the moon, both vehicles were developed during a time when our achievements were limited only by our imagination.
Dual overhead camshafts. Sixteen valves. A compression ratio of 10.3:1. Multi-point fuel injection. One hundred forty horsepower out of 1,975 cubic centimeters. And the 1999 Hyundai Elantra to this day remains invisible on our roads. Or, at least, most of them do. We’ll make an exception for Harry Bleiwise’s pushmepullyu four-wheel-steer airbagged Elantra, which, though it didn’t crabwalk home with any awards at our most recent cruise night, was nevertheless the most unique car in the show.
Double-enders, as Ray Scroggins termed them in Special Interest Autos in 1977, have been around for decades, and tend to come together to promote businesses, typically with some sort of lame slogan capitalizing on the cars’ curiosity. Harry, of nearby Manchester, Vermont, said he had his Hyundai built more out of whimsy than anything.
“I got the idea years ago when I saw a Chevy with two front ends and thought, ‘My God, that looks fun,’” he said.
So in about 2008 he took his 1999 Hyundai Elantra – a 29,000-mile car with no rust or damage whatsoever – to restorer and fabricator Dave Brooks, also of Manchester, and told Dave his plan. “He lasered this and lasered that, and now the car goes sideways and up and down,” Harry said.
Well, it did take a little more than just shooting the Elantra up with lasers, Dave said. Using another rust-free Elantra that one of Harry’s friends provided, Dave cut off both cars’ back halves and then mated their unibody structures to a cube that Dave fabricated out of 1/8-inch plate steel. “After that, it was just basic welding and bodywork,” Dave said. That is, if you don’t count all the goodies that Dave installed, including airbag suspension on all four corners, an onboard fire suppression system, a 120-volt converter, a smoke screen system, switch-activated four-wheel steering, and a skidplate under the back so Harry can drag the rear end and shoot sparks. Oh, and Dave also added mounts for “landing gear” that would descend from the central cube structure, lift the car’s four wheels off the ground, and spin it around, though Harry hasn’t elected to install that system just yet.
For all those modifications, Harry and Dave left much of the rest of the car alone, including the stock drivetrain (the back half is unpowered). “It runs fine,” Harry said. “Just a little slower now. But we still have a lot of fun with it.” All told, it took three winters for Dave to complete the modifications to Harry’s Elantra.
And as if the pushmepullyu Hyundai weren’t spectacle enough, Harry brought along his brand-new Ferrari 458 Spider and 1957 Chevrolet Bel Air. For future cruise nights, he’s considering bringing down his new Tesla or maybe a 2000 Gillig transit bus. “You gotta enjoy life every day because who knows when the curtain comes,” Harry said.
1990 Honda Prelude Si. Images courtesy of Honda Worldwide.
Honda’s second-generation Prelude coupe, launched in 1983, continued the automaker’s tradition of racking up praise for its performance-oriented products among the automotive press. Road & Track called it “a benchmark car that will send competitors back to the drawing boards,” then added the Prelude to its 1984 list of “12 Best Enthusiast Cars.” When it came time for the third generation of Prelude, Honda pulled out all the stops and debuted a car with an innovative feature that was soon to be all the rage among Japanese automakers: four-wheel steering.
The 1988 Honda Prelude Si 4WS was the first mass-production automobile from a major automaker to feature four-wheel steering. Furthermore, while rival automakers like Mazda, Nissan, and Mitsubishi were working on four-wheel steering systems of their own, each relied on solenoids and computers to change the angle of the rear wheels, based on sensors which read the steering angle of the front wheels. Honda’s system was strictly mechanical, which made it both elegant and complex at the same time, yet gave drivers precise control under a wide variety of driving conditions. To accomplish this, the Prelude 4WS utilized both front and rear steering boxes with a steering shaft running beneath the car and linking the two. The rear steering box used hypocycloid gear to accomplish the complex, steering wheel-driven positioning of the rear wheels, which were ultimately moved with conventional linkages.
Honda 4WS rear steering box.
Changing lanes at speed on the highway requires very little steering input, and in circumstances such as this Honda’s 4WS system turned the car’s rear wheels in the same direction as the front, but at a shallower angle. Dial in 140 degrees of steering input and the front wheels turn eight degrees while the rears turn 1.5 degrees. The net result was a quicker lane change, particularly helpful in avoidance maneuvers; in fact, that’s one of the ways that Honda engineers first pitched the system to management. Pushing the system’s handling benefits was likely to be a losing battle, but stressing its improvement in safety was sure to get the buy-in of senior Honda officials.
At greater steering angles, such as tight cornering, Honda found it beneficial to have the rear wheels assume a more neutral position. Honda’s 4WS system returned the rear wheels to zero degrees of steering input when the steering wheel was rotated 240 degrees (turning the front wheels by 15.6 degrees), giving maximum grip and delivering a traditional, balanced feel in tight corners.
The final scenario occurs at maximum steering angle, typically encountered only in low-speed turning or parking maneuvers. When the steering wheel was turned to lock (450 degrees), the rear wheels turned in the opposite direction of the fronts, up to 5.3 degrees, allowing the rear to swing out (or swing in, when reversing). This feature enabled a turning radius of just 33 feet, and gave the Prelude Si 4WS the ability to parallel park in very tight spaces unavailable to comparably sized cars.
Under certain circumstances, the 4WS did yield improvements to handling. Road & Track reported a slalom speed of 65.5 MPH from the 1988 Prelude Si 4WS, besting even the Chevrolet Corvette, which ran through the cones in 64.9 MPH. On paper, the 4WS system sounded as if it would take handling to a whole new level, but as owners soon found out, daily driving rarely involves a high-speed slalom course. Though handling was improved, it was not a night and day difference, and the increase in low-speed maneuverability proved to be of little benefit to the average American buyer, who rarely practiced the art of parallel parking.
The cost of the 4WS system was a deterrent, as well. Prelude Si models without the rear steering box sold for $16,645, while those with 4WS sold for an additional $1,300, pushing the sticker close to (or in some cases, above) the $18,000 mark. For a car with a younger buyer demographic, such sticker price increases need to come with more tangible benefits, like those offered by anti-lock brakes (oddly unavailable on Prelude Si 4WS models until the 1990 model year). Though the 4WS system proved to be reliable in normal operation, crash repairs and wheel alignments proved to be both more complex and more expensive than on front-steering-only counterparts, further putting off potential buyers.
In other areas, the 1988 Prelude Si was a clear improvement over its second-generation counterpart. The shape, though similar in appearance to the 1987 Prelude, was more aerodynamic, thanks in part to a lower hoodline (which also helped to increase frontal visibility). Narrower C-pillars helped with side visibility, yet Honda still managed to make the roof of the third generation Prelude stronger.
Up front, the Si’s engine was stronger as well. Though still just 2.0 liters in displacement, output grew from 110 horsepower and 114 pound-feet of torque on 1987 models to 135 horsepower and 127 pound-feet of torque on 1988 models. The gains came from a switch to a double overhead camshaft, 16-valve head, as well as a change from port to sequential fuel injection and the addition of a variable-length intake tract. Performance was inline with other imports of the day, with the run from 0-60 MPH taking somewhere around nine seconds, and the quarter-mile passing by in 17 seconds at a speed of 81 MPH.
While the third-generation Prelude models did much to advance Honda’s reputation for building economical, reliable and sporty cars, they proved less popular with buyers than earlier models. Given the car’s additional cost, it’s likely that Prelude Si 4WS models made up a mere fraction of Prelude sales, but an exact number isn’t known because Honda didn’t break out U.S. sales by individual model in the 1980s. Still, enough 4WS models were sold for Honda to continue the experiment, and a variation of four-wheel steering was available on Prelude models through the 1995 model year.
A tip of the hat to Brad Kosich for the suggestion.
The automobile was not an immediate success, as we all know. It was expensive, sure, but the poor quality of roads outside of metropolitan areas also prevented adoption of the horseless carriage by rural residents for more than a decade. Monroe Robert Grier had a solution to the latter problem – increase traction.
Born in Virginia in 1855, Grier farmed his whole adult life in and around St. Louis, Missouri. Farmers are, by nature, tinkerers, and by the turn of the century, Grier had a few patents to his name: one for a granary (293,574), one for a fan (449,025), and one for a gate (231,560). In 1905, he had one more idea he decided to patent – a four-wheel drive motor vehicle that also featured four-wheel steering and a primitive sort of portal axle. In the patent (834,008), he described it as a “utility hauling vehicle,” and its solid wheels, lack of suspension and simple frame construction suggest that it was to be used more as a cart for use around the farm rather than as a pleasure vehicle for passengers. Grier didn’t provide any specifications for the motor, only suggesting it be “of any suitable character.”
If you ignore for a moment the back-then-forth transmission of power to the front wheels, Grier still missed out on being the earliest American proponent of four-wheel drive by about a year. Grier applied for his patent in September 1905 and was granted it in October 1906, yet Californian Charles W. Van Winkle had Grier beat by 15 months with the issue of his patent (764,646) for a drivable, steerable front axle. Van Winkle then went on to build an actual four-wheel drive automobile in 1905. We’ve yet to find an earlier patent than Grier’s on four-wheel steering or portal axles, however.
We so far see no evidence that Grier ever built his vehicle. He assigned his patents, in half, to Albert Kunze, who apparently worked with inventors to capitalize on their patents. Kunze found success with Walter H. Cotton’s magnetic spark ignition patents, ultimately selling those to the Dayton Electrical Manufacturing Company in 1903, yet Grier’s patent doesn’t appear to have enticed any buyers.
Grier continued to farm until his early 80s and died in 1937.