Cars

Weird Engines

You’ve probably noticed I’ve been on an automotive kick lately. Don’t worry, I don’t think I’m in any danger of becoming a babbling gear-head. Firstly, I don’t have the patience or mechanical skill to actually put an engine together without blowing myself up and setting the neighborhood on fire. Secondly, where I live, working on cars isn’t a cheap hobby, and the fact that I’m considering going to grad school means all my pennies are spoken for.

I’m interested in engines the same way a little boy would be. They’re big, loud, powerful, complicated, and mechanical. I could probably come up with fancy reasons for being curious about engines, but the fact is, I just like them. But I like them in kind of a shallow way. The more intricate details of engines still confuse me. There’s a reason I call myself Hobo Sullivan: in pretty much all the areas I talk about, I’m like a hobo being dragged into an art gallery. I can say “That painting looks like shit” or “That’s a really pretty painting,” but if you start trying to teach me about composition or Postmodernism, my eyes’ll glaze over and I’ll start asking when I get my bowl of soup.

Which is a really long-winded way of saying that this post isn’t intended for engine experts. If you’re into engines, you probably know every single thing on this list. This is a post for people who are casually interested like me. This is me emerging from the Google Caves with a handful of funny-shaped crystals and saying “Look at this cool stuff I found!” This list has nothing to do with with deciding on the best engine or anything fancy like that. This is a list of the engines I’ve found in my bizarre curiosity that made me say “That’s kinda cool…”

The Boxer-6

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(Image from CarThrottle.com)

The boxer-6 isn’t all that weird, since it’s still in common use. That’s partly because you’ll find it in sports cars like the Porsche 911, and in some of Subaru’s current cars and SUVs. When I first started learning about weird engines, I thought the boxer-6 was just a V6 where the V got all flattened out. Engines like that do exist, but they’re not called boxer-6s. The difference is, in a boxer-6, pairs of pistons opposite each other move in and out simultaneously. Unlike in a lot of V-engines, each piston’s connecting rod has its own bearing on the crankshaft. What does any of this matter? Well, it’s unusual, for one. For two, the peculiarities of engine dynamics (which I don’t pretend to understand) make the boxer-6 a very smooth-running, well-balanced, low-vibration engine. Also, the fact that its cylinders aren’t crammed cheek-to-cheek in a V means that even fairly high-power boxer-6s can be air-cooled (though some are still water-cooled).

But you guys know me by now. You know I always go to extremes if given the chance. I’m not going to be satisfied with a six-cylinder engine, no matter how nice.

The H-16

brm_h16_engine

(From Wikipedia.)

We’ve made quite a leap. While you could go out right now and buy a car with a boxer-6 in it, the only way you could have an H-16 engine is time travel, or by being an insane millionaire and having one built for you.

The engine above is British Racing Motors’ H16 engine. There are plenty of weird, esoteric terms used in automotive circles, but the weird letters that show up in engine names are perfectly sensible (mostly). My car is powered by an I4 engine, which means it’s an inline-four: four cylinders in a straight line. A V6 has six cylinders in two banks of three, with the pistons angled so that their connecting rods form a V-shape, with the crankshaft at the tip of the V. You’d refer to the boxer-6 above as an F6, for flat-6.

What, then, is an H16 engine? Well, it’s horrifying, is what it is:

h-engine

(Again, from Wikipedia.)

An H-16 is two flat-8s stacked on top of each other, each with its own crankshaft. The crankshafts are connected at the end by gears. Like I said, I don’t know engines, but that seems like a bad idea.

For some applications, it’s actually not. H-engines are mechanically pretty well-balanced, for one. For two, they’re a bit more compact than, say, a V-engine with the same number of cylinders, which made them popular for high-power airplanes.

But car enthusiasts will know that the H16 I showed at the top of the section didn’t come from an airplane. It came from British Racing Motors’ ill-fated P83 Formula 1 car, which has a peculiar, and if you ask me, slightly unpleasant sound.

BRM’s H16 was plagued with problems. For one thing, having two sets of cylinder heads on opposite sides meant it needed two radiators and a split fuel system. It also needed dual camshafts (which are the mechanical clockwork-type devices that tell a cylinder’s valves when to open the intake valves and let in fuel, and when to open the exhaust valves to let out burned fuel). It needed dual camshafts for each cylinder head. That’s bad enough in a V-engine, where you have two cylinder heads, but the H16 had four. For another, it was more complicated and fuel-hungry than even its competitor, the mighty V16. Unsurprisingly, the engine wasn’t a success, partly because a lot of them just blew up during races. Apparently, British Racing Motors’ troubles at the time, and their obsession with complicated engines, earned them the nickname “British Racing Misery.”

Still, it’s a weird, interesting engine, and somebody had some serious gonads to say “You know what? A V16 is just too damn simple.”

The Napier Deltic

napier_deltic_animation

(From Wikipedia, again.)

You remember that scene in the first Back to the Future where Dr. Brown is talking about inventing the Flux Capacitor? “I slipped, hit my head on the edge of the sink, and when I woke up, I drew this.” I’ve gotta figure a bonk on the head inspired the Napier Deltic. For those who don’t know much about engines, let me explain why the picture above shows one of the weirder engines ever invented.

Opposed pistons. In a common piston engine, the air-fuel mixture burns, and the pressure from the hot gas pushes a piston down, which applies torque to the crankshaft, which drives whatever machine the engine is running. There’s just a cylinder head holding the hot gas in. In an opposed-piston engine, though, there isn’t a cylinder head, but rather, two pistons in a headbutt configuration in every cylinder. The fuel-air mixture enters the space between the two heads and burns there, pushing the two pistons apart, driving two crankshafts.
The delta design. As you can see, the Deltic isn’t even as simple as a regular opposed-piston engine. That picture shows three cylinders, containing six pistons, driving three crankshafts. It’s weird, but it’s got a certain geometric appeal to it. It was also, apparently, a lot more compact and powerful than similar engines of the time, which made it attractive for British torpedo boats and locomotives.
It was a two-stroke. If you don’t know, two-stroke engines are usually what you find powering small power tools like weed-whackers and chainsaws.The engines of most modern cars are four-stroke. The differences are subtle. In a four-stroke engine (which most gasoline engines are), the piston has to go up or down a total of four times to complete a full cycle: It moves down to suck in in air and fuel, moves up to compress the air and fuel before ignition, is pushed down by the burning air and fuel, and finally rises up to push out the exhaust. In a two-stroke engine, the intake and exhaust steps happen at the same time: often, the piston pushes down on a fuel-air mixture in the crankcase, and the pressure pushes the mixture into the engine, which pushes the exhaust out. The major advantage of a two-stroke engine is that it doesn’t need mechanically-operated intake and exhaust valves, since the piston controls intake and exhaust. This saves weight and complexity, which is vital when your engine is powering, say, an airplane, or a boat, or a chainsaw that needs to be light enough to hold up for long periods, without getting tired and dropping it on their foot.

The Deltic was fairly successful, since it packaged eighteen or more cylinders (two pistons each) into a smaller package than was possible with other designs of the same cylinder number. It was a lot lighter than comparable engines, too.

Why aren’t there more Deltic-type engines around? Well, a little research suggests that’s mostly because Napier was bought out after World War 2, and switched to making things like turbine engines and turbochargers, the former of which were rapidly filling a lot of the niches the Deltic once occupied. I suspect the peculiarity of the delta design also played a part, since my first reaction to it was “there’s no way that was a success.” I was wrong about that, but I bet the Deltic scared off more than a few mechanics.

The W12

napier_lion_ii

(Still Wikipedia.)

We’re not done with Napier yet. Above, you see the Napier Lion.

Although it’s not entirely accurate, you wouldn’t be far off if you described a V8 engine as two I4 engines driving the same crankshaft. The Napier Lion is a broad-arrow W12, which is what you’d get if you took a V8 and jammed another I4 down the V (sounds like a weird fetish fantasy…)

You’ve probably heard of W engines before, even if you’re not into cars. A W16 is the powerplant behind the Bugatti Veyron, which is famous for two things: holding the Guinness record for fastest street-legal car, and being a rare example of a supercar that isn’t absolutely horrible to look at. (I mean, it’s still not great, if you ask me. It looks like ergonomic furniture. But look at a Lamborghini Aventador and tell me the Veyron isn’t better-looking, if only because it’s not as…pointy.) But the W16 in the Veyron is a different type: it has two banks with eight cylinders each, and those cylinders are jammed just about as close as you can get them. Each of the banks is essentially a VR8: a V8 with a very narrow V. Since it only has one crankshaft, W isn’t exactly a good letter to use, but as a double-vee, I guess I get it. (I’m tempted to call the Napier Lion a Ш12, but Sh-12 isn’t exactly catchy.)

What the hell are you getting at, I hear you ask. I get that question a lot. The reason I bring up the Napier Lion is that it demonstrates, better than the Veyron’s W16, that you can take a pretty ordinary set of cylinders (banks of I4s) and turn them into bizarre, high-power variants. It was weird aircraft engines like the Lion that got me interested in weird engines to begin with. Unsurprisingly, someone took a pair of W12 Lions and put them in a car, breaking a land-speed record and becoming the first to break the 350 mph barrier. And trust me, it’s not the last time we’re going to see weird engines dropped in cars.

The Radial

radial_engine_timing-small

(Wikipedia.)

For some reason, I think that looking at that animation while you had a really bad fever (or after eating funny mushrooms) would be really scary. But there’s not that much scary about it. It’s just a radial-5 engine, which proves that, there are more interesting ways to arrange pistons than lines and Vs.

I really like radial engines. There’s something pleasing about that five-fold symmetry. It’s like a starfish made of explosions. It also offers some serious advantages if you’re looking for an engine to stick in a propeller-driven airplane: compact and powerful, but with pistons still far enough apart that you can air-cool them, which eliminates the radiator, which is a notoriously brittle piece of hardware. And you don’t want brittle stuff on, say, a fighter plane.

For symmetry and smoothness, nearly all four-stroke radial engines have odd numbers of cylinders. A two-cylinder radial is just a two-cylinder boxer. I’ve seen videos of three-cylinder radials, but I like pentagons better than triangles, so I won’t bother with those. Plus, talking about five-cylinder radials gives me an excuse to show you a video of a Toyota being powered by an airplane engine. And this whole section has pretty much been an elaborate segue to talk about the Plymouth Air Radial Truck:

016-1939-plymouth-radial-airplane-truck-gary-corns

(From Motor Trend.)

Because, sometimes, you wake up in the morning and think “You don’t see enough nine-cylinder hot rods out there.” That is a 300 horsepower Jacobs 9-cylinder radial airplane motor from the 50s. There are plenty of things about hot rods that I don’t like (they’re always alarmingly low to the ground, for one, which bothers me for some reason), I will never deny that hot rodders are insanely creative in all the right ways. My proof? Look at that picture again.

Naturally, the radial engine lost a lot of its popularity when turboprop and turbojet engines became reliable and affordable for airplanes. It didn’t help that, eventually, engines like the I4 and F4 became refined enough and powerful enough to do the same job as a radial without needing the specialized radial construction.

But there was a period when the radial was king of the air. Within that period was a really wild period when planes needed more power than an ordinary radial could give them. Trouble is, if you want to make a radial engine with more than 11 cylinders, you have to make it really wide so that those cylinders can stick out to be air-cooled. And if you do that, then you’ve just stuck what amounts to a dinner plate on the front of your airplane, which is no good for aerodynamics. Engine manufacturers solved this with multi-bank radial engines.

The Wasp Major

biggest_rotary_cutaway

(Bet you can’t guess the source.)

That is a cutaway of the Pratt and Whitney Wasp Major, which is a beast of a machine. It has 28 cylinders (four banks of seven cylinders) and a built-in supercharger. It has a displacement of 71 liters (compare that to the Bugatti Veyron or Dodge Viper, two high-power cars, both of which displace all of 8 liters.) It produced up to 3,500 horsepower in its original form, and over 4,000 once they added turbochargers. It also sounds pretty fucking awesome. If I was a millionaire and wanted to build a hot rod, I think this is the engine I’d put in it. Either this, or our next weird engine…

The Zvezda M503

3630728158_62398cce2a

(From Flickr, this time.)

I live in North Carolina. We’re one of the home states of NASCAR, which might be the ultimate in redneck racing. I went to a monster truck show last weekend, at which one of the events was lawnmower racing. That’s kinda what we do down here. We like big trucks, noisy cars, and bizarre racing. Tractor pulling is popular down here, too.

If you don’t know, tractor-pulling is an odd sport where you hook a tractor to a weighted sled and try to pull it a specified distance (usually 300 feet or 100 meters). On top of the sled is a sliding weight which is geared to the wheels so that it moves forward in proportion to the distance pulled, making the front of the sled dig into the dirt, making it harder to pull the farther you pull. Unsurprisingly, that takes a lot of power. I’ve seen pictures of tractors with as many as five or six supercharged V8s, tractors with 18-cylinder radial engines, tractors with two diesel V12s, and tractors with helicopter turboshaft engines.

I always assumed tractor pulling was exclusive to American rednecks. Clearly, I was ignorant, because a lot of the really good tractor-pulling videos are from Germany, the Netherlands, and Australia, where it’s apparently a really popular sport. And my favorite tractor by far is the German “Dragon Fire.” I don’t care if you don’t like big engines or tractor pulls. I insist you watch this video of Dragon Fire in action.

As much as I like big engines and weird engines, I’ll freely admit that tractor pulling seems a bit excessive. Five supercharged V8’s? Just looks silly to me. Like a truckload of engines collided with a truckload of bad Ikea chandeliers.

Dragon Fire, though, has a more elegant solution. Well, kind of. It depends how you define “elegant,” I guess. Dragon Fire isn’t powered by a bunch of V8s. It’s powered by a single 42-cylinder radial engine: the Zvezda M503, built for use in Soviet missile boats. The 503 has 42 cylinders (6 rows of 7). It weighs five times (almost five and a half times) as much as my car. It displaces 143 liters (which is about the volume of a bathtub, according to Wolfram Alpha). In its stock form, it produced nearly 4,000 horsepower. And it’s a diesel, too.

I should mention that the M503 powering Dragon Fire is running on methanol, not diesel fuel. And it, apparently, produces closer to 8,000 horsepower, which is absolutely ridiculous, and which makes me happy.

The Swashplate

swash20plate20motor3

(From the website of Douglas Self, who’s compiled a whole bunch of awesomely weird engines.)

I wouldn’t want to be the guy who proposed that design. I’m sure some stuffy executive looked at that, took out his monocle, took his cigar out of his mouth and said “Stop bringing me nonsense and bring me a real engine!” But the swashplate engine is real, and it’s pretty damn cool. It operates just about the same as any other piston engine, but instead of turning a crankshaft, the swashplate engine pushes on an eccentrically-mounted disk. Not only does this squeeze four (or more) pistons into a compact package, but it also eliminates the heavy crankshaft and provides a natural gear reduction. Apparently, while it has been used on a few cars, and was considered for use in airplanes, its main use is as the powerplant in torpedoes, where its small frontal area and corresponding tiny drag is vital.

For some reason, I really like the swashplate engine. It’s about as far as you can take a traditional fixed-cylinder design. It’s just delightfully weird, and it’s weird that it actually works. (Make it any weirder, and you’ll get awesome stuff like the Duke engine, which didn’t make the list because its cylinders aren’t fixed, and that was one of the arbitrary qualifications I came up with.)

I also like that the swashplate engine has been built in Lego form, by the awesome YouTuber DrDudeNL.

The Chrysler A57 Multibank

18ncol1fdw8s5jpg

(Found via Jalopnik.)

When the United States entered World War 2 in 1941, apparently, Chrysler was tasked with producing a high-power engine for the M4 Sherman tank as quickly as possible. They delivered a 30-cylinder engine. 30 cylinders isn’t as many as 42, so the A57 shouldn’t be as impressive as the Zvezda M503. But it is, for my money. Because Chrysler did a clever thing to meet the deadline. To allow them to use existing engineering, they didn’t exactly build a 30-cylinder radial. They built a 30-cylinder engine made of five Chrysler I6 engines, attached to the main output shaft by gears. Here’s what that looked like:

chrysler-a57-multibank-gears

(From Old Machine Press.)

Using five existing I6s saved Chrysler design time, and they already had the machinery set up to make I6s, so they didn’t have to retool any factories, presumably. The A57 really is just five straight-6 engines stuck together. That’s the kind of Mad Max/McGyver creativity I like. Sure, the engine only produced 450 horsepower, but it was surprisingly compact, and I love this kind of simple innovation.

Honorable Mentions

I wanted to include the Junkers Jumo 205, but I’m running long as it is, and I already talked about opposed-piston two-stroke engines when talking about the Napier Deltic. I wanted to include the Duke Engine, but it’s got rotating cylinders, which disqualified it. For the same reason, I didn’t talk about the weird rotary radials developed early in piston-engined flight. I didn’t include the Wankel rotary engine, because it has no pistons. I didn’t mention awesomely weird concepts like the nutating engine or the gerotor combustion engine for the same reason. Plus, there’s only so much time in the day, and I’ve taken up enough of yours. But if you’ve got any weird engines you think I should’ve included, leave them in the comments. I might stick then in an addendum later on.

Cars, physics, Space, thought experiment

A Toyota in Space

I talk all the time about the weird nerdy epiphanies I had as a kid. One of those epiphanies involved driving a car around on the outside of a space station. I realized that the car would have to bring along its own air supply, because an internal combustion engine can’t run on vacuum. I know that sounds obvious, but when you consider I was like nine years old at the time, it’s almost impressive that I figured it out. Almost.

Now that I’m older, I realized “Hey! I can actually figure out how much air I’d need to bring with me!” Conveniently, the worldwide craze for automobiles (some say they’ll replace the horse and buggy. I think that’s a pretty audacious claim, sir.) means that all sorts of vital statistics about gasoline engines are known. For instance: the air-fuel ratio. It’s as simple as it sounds. It’s the mass of air you need to burn 1 mass unit of fuel. The “ideal” ratio is 15:1: combustion requires 15 grams of air for every gram of fuel burned. Of course, if you’ve watched Mythbusters, you’ll know that stoichiometric (ideal) mixtures of air and fuel detonate, often violently. You don’t actually want that happening in a cylinder. You want subsonic combustion: deflagration, which is rapid burning, not an actual explosion. Supersonic combustion (detonation) produces much higher temperatures and pressures. At best, it’s really rough on the. At worst, it makes the engine stop being an engine and start being shrapnel. So, in practice, mixtures like 14:1 and 13:1 are more common. I’ll go with 14:1, although I freely admit I don’t know much about engines, and might be talking out my butt. No change there.

Either way, we now know how many mass units of air the engine will consume. Now, we need to know how many mass units of fuel the engine will consume. There are lots of numbers that tell you this, but for reasons of precision, I’m using one commonly used in airplanes: specific fuel consumption (technically, brake specific fuel consumption). The Cessna 172 is probably the most common airplane in the world. It has a four-cylinder engine, just like my car, though it produces 80% more horsepower. Its specific fuel consumption, according to this document, is 0.435 pounds per horsepower per hour. The Cessna engine produces 180 horsepower, and my car produces 100, so, conveniently, I can just multiply 0.435 by 100/180 to get 0.242 pounds per horsepower per hour. Assuming I’m using 50% power the whole way (I’m probably not, but that’s a good upper limit), that’s 50 horsepower * 0.242, or 12.1 pounds of gasoline per hour.

So, we know we need 12.1 pounds of gasoline per hour, and from the air-fuel ratio, we know we need 169.4 pounds of air per hour. That’s all fine and dandy, but I’m not sure how much room 169.4 pounds of air takes up. Welders to the rescue! According to the product catalog from welding-gas supplier Airgas, a large (size 300) cylinder of semiconductor-grade air has a volume of 49 liters, and the air is stored in that bottle at about 2,500 PSI. (I don’t know what you actually do with semiconductor-grade air, but it’s got the same ratio of gases as ordinary air, so it’ll do.) At room temperature, the bottled air is actually a supercritical fluid with a density 1/5th that of water. Therefore, each cylinder contains about 10 kilograms (22 pounds) of air. Much to my surprise, even when it’s connected to an air-hungry device like an internal combustion engine, a single size-300 cylinder could power my car for over seven and a half hours.

But you guys know me by now. You know much I like to over-think. And I’m gonna do it again, because there are a lot of things you have to consider when driving a car in a vacuum that don’t come up when you’re driving around in air.

Thing 1: Waste heat. This is a major issue for spacecraft, which live in a vacuum (unless you’ve really screwed up). The problem is that there’s only one good way to expel waste heat in a vacuum: radiation. Luckily, the majority of automobile engines are already radiator-cooled. Normally, they depend on heat flowing from the engine to the cooling water, into the metal fins of a radiator, and into the atmosphere. In vacuum, the cooling will run engine-water-radiator-vacuum. The engine produces 100 horsepower at maximum, which is about 75 kilowatts. A radiator operating at the boiling temperature of water radiates about 1,100 watts per square meter, for a total area of 68 square meters, which means a square 27 feet (8.2 meters) on a side. You could play tennis on that. Luckily, the radiator is two-sided, which cuts the radiator down to a square 19 feet (5.8 meters) on a side. It’s still going to be larger than my car, but if I divide it into ten fins, it would only be absolutely ridiculous, rather than impractically ridiculous. That’s already my comfort zone anyway.

Thing 2: Materials behave differently in a vacuum. Everything behaves differently under vacuum. Water boils away at room temperature. Some of the compounds in oil evaporate, and the oil stops acting like oil. Humans suffocate and die. To prevent that last one, I’m going to have to beef up my car’s cabin into a pressure vessel. And since I’m doing that, I’ll go ahead and do the same to the engine bay, so that I don’t have to re-design the whole engine to work in hard vaucuum. I’ll make the two pressure vessels separate compartments, because carbon monoxide in a closed environment is bad and sometimes engines leak.

I’ll also have to put a one-way valve on the exhaust pipe, because my engine is designed to work against an atmospheric pressure of 1 atmosphere, and I feel like working against no pressure at all would cause trouble. I’m also going to have to change the end of my exhaust pipe. I’ll seal it off at the end and drill lots of small holes down the sides, to keep the exhaust from acting like a thruster and making my car spin all over the place.

Thing 3: Lubrication. A car’s drivetrain and suspension contain a lot of bearings. There are bearings for the wheels, the wheel axles, the steering linkages, the universal joints in the axles, the front and rear A-arms… it just goes on and on. Those bearings need lubrication, or they’ll seize up and pieces will break off, which you very rarely want in engineering. Worse, in vacuum, metal parts can vacuum-weld together if they’re not properly protected. We can’t enclose and pressurize every bearing and joint. That would make my car too bulky, for one. For two, there would still have to be bearings where the axles came out of the pressurized section, so I’ve gotta deal with the problem sooner or later. Luckily, high-vacuum grease is already a thing. It maintains its lubricating properties under very high vacuum and a wide range of pressures, without breaking down or gumming up or evaporating. We’ll need built-in heaters to keep the grease warm enough to stay greasy, but that’s not too big a hurdle.

Thing 4: Tires. My car’s owner’s manual specifies that I should inflate my tires to 35 psi (gauge). I’ll have to inflate them to a higher gauge pressure in vacuum, since they’ll have almost no pressure working against them. If I don’t, they’ll be under-inflated, and that’ll make them heat up, and in vacuum, that goes from a minor problem to a potentially fatal tire-melting and tire-bursting disaster. Actually, I think I’ll eliminate that risk altogether. I’ll do what most rovers do: I’m getting rid of pneumatic tires altogether. Because my car’s going to be fast, heavy and have a human passenger, I can’t do what most rovers have done and just make my wheels metal shells. I need some cushioning to stop from rattling myself and my car to pieces.

nasa_apollo_17_lunar_roving_vehicle

That’s Gene Cernan driving the Lunar Roving Vehicle (the moon buggy). It’s about five times lighter than my car, but it proves that airless tires can work at moderate speed. Michelin is also trying to design airless rubber tires for military Humvees, and while they don’t absorb shocks quite as well as pneumatic tires, they can’t puncture and explode like pneumatic tires. So I’m going with some sort of springy metal tire, possibly just composed of spring-steel hoops or something like that.

Thing 4: Fuel. If I was sensible, I’d have chucked the whole idea of powering a vacuum-roving Toyota with a gasoline engine. (Actually, I’d have chucked the whole idea of a vacuum-roving Toyota and started from scratch…) We know I’m not sensible, so I’m going to demand that my Lunar Toyota run on gasoline. 10,000 liters of gasoline (I like to mix units, like an idiot) will let me drive 42,500 kilometers. Enough to go around the Moon’s equator three (almost four) times. You might think that carrying a small tanker’s worth of gasoline to the Moon is an impossible feat, but when you consider that the mass of my car (about 1,000 kilograms) plus the mass of all that gasoline (7,300 kilograms) plus tankage is less than the weight of the Apollo Command-Service Module and the Lunar Module, not only does the Apollo program seem that much more audacious and impressive, but it becomes possible to talk sensibly (sort of…) about putting my car, my air tanks, and a lifetime supply of gasoline on the Moon. That also takes care of…

…Thing 5: Getting my car on the Moon. We can just use a Saturn V, or wait for the engineers to finish building the Falcon Heavy or Space Launch System. Lucky for me, the rocket scientists have already solved the problem of landing a heavy vehicle, too: the ballsy sky-crane landing used during the Curiosity rover’s descent would almost certainly work just fine for my car, since it’s only 200 kilograms heavier than Curiosity. The fuel and air can just be landed under rocket power, or by expendable airbags.

So it wasn’t all that insane for my nine-year-old self to imagine driving an ordinary street car around on the Moon. That is, from the point of view of fueling and aspirating (ventilating? aerating? Providing air to, is what I mean…) the engine and the passenger. But the physics of driving around in vacuum and/or under low gravity pose another challenge, and that challenge is interesting enough to get a post of its own. Watch this space!

Cars, physics, thought experiment

A City on Wheels

Writing this blog, I find myself talking a lot about my weird little obsessions. I have a lot of them. If they were of a more practical bent, maybe I could’ve been a great composer or an architect, or the guy who invented Cards Against Humanity. But no, I end up wondering more abstract stuff, like how tall a mountain can get, or what it would take to centrifuge someone to death. While I was doing research for my post about hooking a cargo-ship diesel to my car, another old obsession came bubbling up: the idea of a town on wheels.

I’ve already done a few back-of-the-envelope numbers for this post, and the results are less than encouraging. But hey, even if it’s not actually doable, I get to talk about gigantic engines and huge wheels, and show you pictures of cool-looking mining equipment. Because I am, in my soul, still a ten-year-old playing with Tonka trucks in a mud puddle.

The Wheels

Here’s a picture of one of the world’s largest dump trucks:

liebherr_t282_1

That is a Liebherr T 282B. (Have you noticed that all the really cool machines have really boring names?) Anyway, the Liebherr is among the largest trucks in the world. It can carry 360 metric tons. It was only recently outdone by the BelAZ 75710 (see what I mean about the names?), which can carry 450 metric tons. Although it doesn’t look as immediately impressive and imposing as the BelAZ or the Caterpillar 797F, it’s got one really cool thing going for it: it’s kind of the Prius of mining trucks. That is to say, it’s almost a hybrid.

I say almost because it doesn’t (as far as I know) have regenerative braking or a big battery bank for storing power. But those gigantic wheels in the back? They’re not driven by a big beefy mechanical drivetrain like you find in an ordinary car or in a Caterpillar 797F. They’re driven by electric motors so big you could put a blanket in one and call it a Japanese hotel room. The power to drive them comes from a 3,600-horsepower Detroit Diesel, which runs an oversized alternator. (For the record, the BelAZ 75710 uses the same setup.)

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Cars

The 1964 Chrysler Turbine Car

Not even a week after writing a post in which I considered putting a turboshaft engine in an ordinary car, I discovered that it’s actually been done. More than once. Most of the attempts are by hobbyists, but a few big car companies actually tried it out.

One of these was the 1964 Chrysler Turbine Car. It was powered by a 130-horsepower turboshaft engine. I’m no car expert, but from what I’ve read, it looks like it was an amazing machine. High take-off torque. Simpler cooling requirements. No need for oil changes. Longer lifespan. Fast start-ups even in cold weather. Could run on diesel, unleaded gasoline, kerosene, aviation kerosene, vegetable oil, and, reportedly, tequila.

Unfortunately, the project fell through. Only 50 Chrysler Turbines were ever produced, and only 9 are known to have survived, and only a few of those still have working engines.

Somebody really needs to bring the turboshaft back. You wanna sell more cars? Do something cool like putting a turbine in a production car.

Cars, physics, thought experiment

Supersonic Toyota? (Cars, Part 2)

A while ago, I wrote a post that examined, in much greater and (slightly) more accurate detail what speeds my 2007 Toyota Yaris, with its stock drivetrain, could manage under different conditions. This post is all about Earth at sea level, which has gotta be the most boring place for a space enthusiast. Earth at sea level is what rockets are built to get away from, right? But I can make things interesting again by getting rid of the whole “sensible stock drivetrain” thing.

But first, since it’s been quite a while, a refresher: My Yaris looks like this:

2007_toyota_yaris_9100

Its stock four-cylinder engine produces about 100 horsepower and about 100 foot-pounds of torque. My drivetrain has the following gear ratios: 1st: 2.874, 2nd: 1.552, 3rd: 1.000, 4th: 0.700, torque converter: 1.950, differential: 4.237. The drag coefficient is 0.29 and the cross-sectional area is 1.96 square meters. The wheel radius is 14 inches. I’m totally writing all this down for your information, and not so I can be lazy and not have to refer back to the previous post to get the numbers later.

Anyway…let’s start dropping different engines into my car. In some cases, I’m going to leave the drivetrain the same. In other cases, either out of curiosity or for practical reasons (a rarity around here), I’ll consider a different drivetrain. As you guys know by now, if I’m gonna do something, I’m gonna overdo it. But for a change, I’m going to shoot low to start with. I’m going to consider a motor that’s actually less powerful than my actual one.

An Electric Go-Kart Motor

There are people out there who do really high-quality gas-to-electric conversions. I don’t remember where I saw it, but there was one blog-type site that actually detailed converting a similar Toyota to mine to electric power. That conversion involved a large number of batteries and a lot of careful engineering. Me? I’m just slapping this random go-kart motor into it and sticking a couple car batteries in the trunk.

The motor in question produces up to 4 newton-meters (2.95 foot-pounds). That’s not a lot. That’s equivalent to resting the lightest dumbbell they sell at Walmart on the end of a ruler. That is to say, if you glued one end of a ruler to the shaft of this motor and the other end to a table, the motor might not be able to break the ruler.

But I’m feeling optimistic, so let’s do the math anyway. In 4th gear (which gives maximum wheel speed), that 4 newton-meters of torque becomes 4 * 1.950 * 4.237 * 0.700 = 21 Newton-meters. Divide that by the 14-inch radius of my wheels, and the force applied at maximum wheel-speed is 59.060 Newtons. Plug that into the reverse drag equation from the previous post, and you get 12.76 m/s (28.55 mph, 45.95 km/h). That’s actually not too shabby, considering my car probably weighs a good ten times as much as a go-kart and has at least twice the cross-sectional area.

For the electrically-inclined, if I was using ordinary 12 volt batteries, I’d need to assemble them in series strings of 5, to meet the 48 volts required by the motor and overcome losses and varying battery voltages. One of these strings could supply the necessary current of 36 amps to drive the motor at maximum speed and maximum torque. Ordinary car batteries would provide between one and two hours’ drive-time per 5-battery string. That’s actually not too bad. I couldn’t ever take my go-kart Yaris on the highway, but as a runabout, it might work.

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Uncategorized

Forget flying cars. I want a submarine car!

The metal container powered by the explosion of million-year-old liquefied algae which transports me over long distances (My car. Yes, I know I’m a smart-ass.) is a 2007 Toyota Yaris hatchback. It’s a decent enough car, I suppose. It looks about like this:

(Many thanks to the nice person on the Wikimedia Commons who put the photo in the public domain, since I lost the only good photo of my car before it got all scruffy.) According to its specifications, its engine can produce 106 horsepower (79 kilowatts), it weighs 2,326 pounds (meaning it masses 1,055 kilograms), and has a drag coefficient of 0.29 and a projected area of 1.96 square meters (I love the Internet). Those are all the numbers I need to calculate my car’s maximum theoretical speed. I’ll be doing this by equating the drag power on the car (from the formula (1/2) * (density air) * (velocity)^3 * (projected area) * (drag coefficient)) with the engine’s power. I will be slightly naughty by neglecting rolling resistance, which for my car, is usually negligible.

1. Maximum speed on Earth, at sea level: 135 MPH (217 km/h or 60.19 m/s). I may or may not have gotten it up to 105 MPH once, so this estimate seems about right. Worryingly, according to the spec sheet for my tires, they’re only rated up to 112 MPH…

2. Maximum speed on Mars: (Assuming I carry my own oxygen, both for me and for the engine.) 538 MPH (866 km/h, 240.50 m/s). I would break the speed record for a wheel-driven land vehicle (Donald Campbell in the BlueBird CN7) by over 100 MPH. And probably die in a rapid and spectacular fashion. But that’d be all right: I always wanted to be buried on Mars.

3. Maximum speed on Venus: (Assuming I avoid dying in burning, screaming, supercritical-carbon-dioxide-and-sulfuric-acid agony.) 36 MPH (58 km/h, 16.23 m/s). Unfortunately, the short-sighted manufacturers didn’t say whether my tires are resistant to quasi-liquid CO2 at 90 atmospheres. The bastards.

4. Maximum speed underwater: This is the one we’re all here for! Water is dense shit and puts up a lot of resistance, as anyone who ever tried running in a swimming pool can attest. Maximum speed: 15 MPH (23 km/h, 6.52 m/s). Wolfram Alpha tells me I’d only be driving half as fast as Usain Bolt can run. I shall withhold judgment until we clock Mr. Bolt’s hundred-meter seafloor sprint.

5. Maximum speed in an ocean of liquid mercury: (Assuming we filled my car with gold bricks to keep it from floating to the surface. Also, why is there an ocean of liquid mercury? That’s horrible.) Maximum speed: 6 MPH (10 km/h, 2.74 m/s). I can bicycle faster than that (although not in a sea of mercury, admittedly). Of course, mercury is so heavy that, even if our sea was only 5 meters deep, the pressure at the seafloor would be high enough to make my tires implode. Which would, of course, be the least of my problems.

6. And finally, just for fun, my maximum speed in neutronium. Neutronium is what you get when a star collapses and the pressures rise so high that all its atoms’ nuclei get shoved together into one gigantic pile of protons and neutrons. It’s just about the densest stuff you can get without forming a black hole, and my car could push me through it at a whole 0.1 microns per second, which is only fifty times slower than the swimming speed of an average bacterium.

I’ve now spent far too long imagining myself being crushed by horrible pressures. I need to go lie down and imagine myself being vaporized, to balance it out.

Sublime Curiosity

A zoo for thought experiments.

Tag Archives: engine