Reinventing the Wheel

Driving the Screw: A twist on a classic

In 1899, Jacob Morath filed a patent for a tractor that had, in place of wheels, a pair of sharp augers that would plough the field while propelling the vehicle over it.

These augers rotated in opposite directions—a stabilizing technique used across the so-called archimedes screw vehicles of which the Morath device was the first, but also now common across aviation. Since the two screws are counter-revolving, they compensate for any side-to-side motion, particularly since they’re so much longer than they are wide. Such a device could drive in a straight line across reasonably stable terrain, tearing up the earth as it did. But steering presented a problem, which Morath solved by also having wheels (which would raise as the screws lowered and vice versa). Eight years later, before Morath’s patent was expired, competitor Peevey solved this problem by raising or lowering one screw, thus changing the amount of contact it has with the ground. The raised screw would mostly slip, so the vehicle would move in the direction of the lowered screw—a feature we’ll later see in some wheel assemblies.

Screw vehicles did not meet success in agriculture: Morath’s design seems never to have been built, and later variations couldn’t compete with the new technology of tank treads. However, in the 1920s, the Armstead Snow Motor showed that there was a market for screw drives (this time, beefy barrels) to hook to your existing car or tractor so that it could whiz along the top of deep snow.

During the second world war, ice-obsessed spy/mad scientist Geoffrey Pyke pushed the British to adopt screws over treads for snow warfare (the same way he pushed them to adopt aircraft carriers made of frozen paper mache), unsuccessfully. Again, tank treads won out.

Finally, in the 1960s, screw vehicles found their (very small) niche: the water. A large hollow barrel with a screw along the outside will function semi-acceptably on snow, dirt, and mud while also acting as a floating propeller, so these machines are truly all-terrain—at least in theory. In practice, it typically makes more sense to use a vehicle suited for your particular environment, rather than a single vehicle that works poorly everywhere—unless, like the intended users of the ZIL, you are a lost cosmonaut.

Tri-Star Pictures, the segue to the Segway

In the late 1960s, some engineers at Boeing tried using the wheels-within-wheels concept for an all-terrain vehicle—by reducing the central wheel to an abstraction. The tri-star wheel arrangement gives you three wheels in a triangle, linked together in such a way that the group of wheels may turn freely while each wheel is driven by a shared power source.

On solid ground, you drive on two wheels; if you hit a pothole deep enough to trap an ordinary vehicle, instead, the whole assembly will flip over and you’ll drive on barely noticing a bump.

Unlike the screw drive, whose relationship with the ground is tenuous at best and who wastes a huge amount of energy in slippage, each wheel in the tri-star configuration is potentially quite ordinary. And if you want it, you can have the nice thick contact patch you’d expect from car tires: a car retrofitted with these can still drive at highway speeds.

However, you need three times the number of wheels and tires, along with a bunch of extra hardware for the framework and power transfer, and then you also can’t turn very well because your front wheels are twice as long.

Not even the military was encountering massive potholes often enough to make these tradeoffs worthwhile: the full extent of their interest in this technology seems to have been sticking one on a prototype howitzer in the 70s.

Instead, tri-star wheels went to the movies, as the most interesting visual element of the Landmaster, the armored amphibious tank that’s the only memorable part of the 1977 nuclear-winter flop Damnation Alley.

(The Landmaster is so memorable that it appears in lots of other things and has inspired an unrelated electric tractor that has taken its name but lacks the signature wheel system. The movie, on the other hand, ruined the reputation of an otherwise well-liked short story already damaged by a weak novelization.)

Today, tri-stars are mostly used for stair-climbing wheelchairs (notably those by Dean Kamen, who was best known for these before he became much better known for the Segway). NASA, for its part, prefers to solve the same problems with its spidery rocker-bogie suspension, which keeps the body of the vehicle steady better and requires fewer moving parts, while simultaneously looking deeply upsetting.

Our list so far has been skirting the outlines of a few massive gaps: new wheels like the ones we have been discussing, but so successful and omnipresent that we do not consider them exotic. A couple you might be familiar with:

• The caster wheel only dates to the middle of the eighteenth century, and wasn’t used outside of furniture manufacturing until the middle of the nineteenth; the conceptual innovation that it represents is similar to technical wheels.
• The tank tread came up at the same time as the archimedes screw drive, and out-competed it along with its cousins, the pedrail and dreadnought wheels.

In many ways, the wheel itself is “new”: the myth of the wheel as the most monumental invention is itself an invention of the 20th century, when road infrastructure was massively expanded to support those new wheeled inventions—cars and bicycles. Only with nicely-paved and well-maintained modern asphalt roads going everywhere you want to go does it become obviously better to take a vehicle with wheels rather than riding an animal or walking.

In fact, there is a pattern, which we can see in the history of the wheel itself and in its many variations: The wheel spends centuries or millennia after its invention in toy, low-load operations. It remained limited until design refinements coincide with changes to infrastructure to suddenly make it widespread.

The era of tri-star-configured linear screw wheelsets is at hand after the squid people invade, I’m sure.

--

Thanks to John for sharing his piece. Be sure to check out his website.

Find this one an interesting read? Share it with a pal!

Develop your analytical side: Check out our sponsor Scrimba, which mixes video lessons with interactive code windows—and makes it feel downright approachable. Sign up here for a 20% discount.