Wednesday, March 20, 2013

Go Go Gadget Generator!

There's nothing wrong with using electric motors to turn a car's wheels. As a matter of fact, there's a lot right with it, starting with the fact that electric motors produce peak torque from the jump-off, which can make for great big smoky burnouts.

The downside is that it's hard to carry volts around in a lightweight, portable, easily-refilled form. Given current and near-future battery technology, pure electrics are going to be confined to urban runabout duty for quite a while yet.

Slapping an electricity-generating motor on board is the current fix for this shortcoming and most applications use fairly conventional piston engines in this role, although Jaguar has been dabbling with micro turbines for the chore. Meanwhile, some Jerries have let their gadget freak flag fly and come up with this solution. If you're not using the pistons to turn the wheels, there's no real need to have them physically connected to anything, is there?


Fuzzy Curmudgeon said...

Stunningly simple. But the best technology usually is.

JD Rush said...

How in the hell do you keep that timed?

And OMG, Fairbanks Morse still makes horizontally opposed engines. (Sorry, wiki-wandered there) I don't keep up with oddball diesels, just the ones I play with.

BGMiller said...

Gotta admit, that's kind of clever.
And a really clever person could build the generator into some form of self contained module that plugs into the vehicles system. It would fit really well with some of the modular vehicle concepts that have been proposed.


Jay Dee said...

There is an apocryphal story that the Chevy Volt was invented when a GM development engineer was frustrated by the limited range of the all electric drive line under test and hooked up a Northern Freight trailer carrying a genset and gas tank; shade tree engineering at its' finest.

Anonymous said...

I was against electric cars until my brother pointed out that coal-powered cars hurt Gaia more than gasoline.

As long as we are making men in sandals cry, I am for it.

Shootin' Buddy

RevolverRob said...

Simple and looks like it could be effective. But I await a test of the technology before providing fully judgement.

I like it thus far.

Joanna said...

That may be the sexiest thing I see all day. I loves me some applied lateral thinking.

Tam said...

Shootin' Buddy,

"I was against electric cars..."

I don't care what's turning the wheels; all I'm looking at are the Chrondeks.

Anonymous said...

I care. I want the maximum damage to the Earth possible. Kill the Earth AND make hippies cry.

Now, let me ask you this, if given the choice of running your car on coal or the tears of a hippe, would you not have a preference?

I thought so.

Shootin' Buddy

Joseph said...

Fuzzy Curmudgeon said...
Stunningly simple. But the best technology usually is.

Did you actually look at the picture of the actual device? I don't think I'd call that "simple". At least not as simple as the Briggs & Stratton on most small generators or even large diesel generators. I wonder as well what's required to keep it in time and how long those gas springs are going to last.

I think it's neat, but they oversimplified the video and ignored requirements like cooling.

I kept thinking of the underpants gnomes while watching the vid.

Anonymous said...

The French (peugeot) are working on a compressed air hybrid.

The concept is quite clever, use the compressed air to drive the car for acceleration and "high demand" spikes, and the engine-engine is sized for "base load+".

The BIG advantages are:

A. Pressure tanks and such are well understood and can be made safe from all but the sort accident where a pressure tank going off with bang is just the cherry-on-top of a much bigger light & sound show.
B. Compared to batteries, very LIGHT. Less mass is good.
C. My understanding is the engine act as both compressor and driver (alternately, partially) so no extra "junk" to haul around.
D. Uses existing infrastructure

Early Beta test make little cars go from 30-50mpg to 100+.

I'll believe it when I see it, but it sounds cleverer than hauling a stupid heavy load of low energy density batteries a round.

Anonymous said...

Finally. Way back when, I was part of a couple racing engine projects in which we reconfirmed that as horsepower increased dramatically the powerband narrowed, equally as dramatically. No surprise there, but what was a surprise was how much fuel consumption per HP was reduced in that narrowed powerband.

Enter the idea of a small, very high efficiency single-rpm turbocharged diesel driving an alternator. Add a small battery pack to handle those brief periods when you need 120% of alternator output and, IMHO, you have an mpg winner. IIRC, VW has been selling 55-60 highway mpg turbo diesels in Germany (can't remember if it's the Jetta or Golf platform) for a few years; EPA doesn't like that particular model so VW imports other versions here.

Copper cable is lighter and routes easier than driveshafts, and direct drive motors at the drive wheels eliminates transmission and differential power loss. What's not to like?

Armed Texan said...
This comment has been removed by the author.
Tam said...

Armed Texan,

You mean like this one? ;)

Anonymous said...

You'd be better served by a small, purpose built gas turbine.

They too will burn nearly anything, are more efficient, and would work well with a set of drive motors at each wheel.

perlhaqr said...

Anonymous @10:08: Maybe not "go bang", but I'd believe the possibility for turning the compressed gas tank into an unguided missile is higher.

Still, way better than batteries, both in terms of weight and speed of fill-up, which is the real deal-killer for me on EVs. I can refuel my '72 Satellite in 10 minutes. After I burn down the charge on a Fisker Karma, I'm not going anywhere for 12 hours. I imagine very high pressure air takes a bit longer to fill up than gasoline, but probably nowhere nearly as long as recharging batteries.

And yeah, putting a compressed air outlet at your normal gasoline filling station is a pretty easy retrofit. Heck, you could even put the tank underground like the gasoline jobbies, and run the lines through the regular gasoline dispensers.

Fuzzy Curmudgeon said...

@Joseph, yes, I looked at it. And the concept is stunningly simple. I didn't say that the implementation would necessarily be easy.

perlhaqr said...

Anonymous @10:11: You're thinking of the VW Lupo, a eurocar running on a 1.3l 3 cylinder turbodiesel. I'm not sure it's the EPA objecting so much as the DOT, those things are dinky. Then again, they let the bloody SMART in, so, I dunno.

The Lupo is a "3l car", which means it takes less than 3 liters of fuel to travel 100 km, which is 78.4 mpg (American gallons) equivalent. They sell both the Jetta and Golf (and a Passat) here as TDI models, and the TDI Golf will do 55 mpg in full American trim.

As ever, though, the best thing to do (from an efficiency perspective) would be to get the DOT to back off on safety requirements. The last gen Mk5 Golf (which is the latest I can find a value for, production ended in 2009, though the latest Mk6 is still on the Audi/VW A5 platform) has a curb weight of ~3500 lbs, where the Mk1 Golf topped out at ~2200 lbs (which is what the Lupo weighs). Build a car that weighs that little, with a very modern turbodiesel powerplant, and you can have a real sized car that makes 60 mpg easily, and possibly even more.

foxmarks said...

Like JD Rush pointed out, this isn’t quite all the “gee-whiz” it seems. F-M’s diesels, the Napier Deltic engine, and some Kraut flying machines from 80 years ago used opposing pistons with a common chamber. Separating the engine from the motor is the essence of a diesel locomotive.

Making it all fit in a useful car is still cool, just not that cool…

perlhaqr said...

Ok, so, about the actual post: So, I see how it's supposed to work as an IC engine, but how is it a "generator"? Are the pistons magnetic?

Joseph: I think the "gas springs" are just the backside of the pistons. So presumably they'll last as long as the rings on the front side of the pistons do.

bob r said...

Re: Timing. The linear "generator" can also function as a linear "motor". Add appropriate position sensing (very simple) and electronic control (not so simple) and drag/boost can be applied to each piston to assure it arrives at "TDC" at the correct time.

Linear motor are used for very precise positioning and can achieve very high acceleration. For more than you probably want to know:
Moving large mass at 90 meters per minute with micron accuracy:
Description of linear motor CNC
Linear motor CNC 50 meters per minute machining full size car body prototype:

Tam said...


"F-M’s diesels, the Napier Deltic engine, and some Kraut flying machines from 80 years ago used opposing pistons with a common chamber."

Yes, I know.

"Separating the engine from the motor is the essence of a diesel locomotive."

Yes, I know.

Go look again.

This isn't just a plain old diesel with its crankshaft hooked to a generator like on the 6:05 out of Hartford, the pistons aren't connected to anything. There is no crankshaft. The... for lack of a better term... "connecting rods" (which don't connect to anything) serve as the "rotors" (which don't rotate) while the cylinder walls are the stators.

Anonymous said...

The concept of a narrow power band combustion engine driving a generator, and electric motors at the drive wheels, makes me think of the Ferdinand tank destroyer. Before he got into the Nazi armor business, Dr Porsche also built a car that ran on the same principle.

Carmel IN

The Raving Prophet said...

A packaging benefit to that kind of design is that it can be mounted very low in the vehicle. Depending on the design, it can even go underneath the passenger cabin. That frees up space up front for any needed battery pack (if desired) or more cargo room (if you run out of ideas). With the engine located that low you also seriously lower the center of gravity of the vehicle so it's not only handling better but it is also rather unlikely to flip over if the driver can't keep even a good handling vehicle out of trouble.

Nifty design, I hope it can be developed into a useful powerplant for automotive use. Unfortunately not every nifty technology can develop into a state where it is a reasonable replacement for the ever-evolving reciprocating piston internal combustion engine (the Otto and Diesel engines we do so love).

Sigivald said...

perlhaqr asked: Ok, so, about the actual post: So, I see how it's supposed to work as an IC engine, but how is it a "generator"? Are the pistons magnetic?

One must assume that, yeah.

They do say it's a linear generator, so the presumption is that there are coils in the cylinders around the rods attached to the piston heads, and magnets being moved through them to generate power.

Anonymous said...

perlhaqr said...

Anonymous @10:08: Maybe not "go bang", but I'd believe the possibility for turning the compressed gas tank into an unguided missile is higher."

I agree, one presumes they cocoon the bottle in car structure away from edges, have pressure release values that blow if temp rises too much, or G forces spike (like in an accident - airbags deploy => tank discharges quickly but without "fuss") I think their point is for all the problems a high pressure air tank might have, it's just AIR and the tech is VERY well understood and robust which more than we can say for batteries that seem to burst into flame at unfortunate intervals etc...

Also it's the car itself that recharges the pressure tank - again - presumably via regenerative braking, so no doofuses at the "gas station f-ing around with ultra high pressure air lines.

Like another commenter above, I'm always surprised we have seen a diesel/gas generator electric hybrid with battery to handled the acceleration spikes and sub 10 mile journeys.

I wonder if the genny + battery powering drive motor combo is just too inefficient. i mean effectively you need a the genny to provide 100% power the car at cruise + some extra to recharge the short range battery for acceleration.

You think such an obvious combo would be on the streets if it made sense.

Billll said...

Connect the rods to something like those "shake weight" powered flashlights we saw a few years ago, and now you're generating electricity from reciprocating motion.

The question I guess is how much?

I suppose you could gang a bunch of them together and run only as many as you need.

Kristophr said...

Shooting Buddy: Which is why I a want an SUV with a Nuclear-electric battery. To make eco-tards cry.

I think Jaguar is on the right track ... turbines are just more efficient than piston engines when allowed to run at designed RPMs.

Running an electric car with an airliner's APU has a lot of potential ( heh ).

montieth said...

Come on, say "Freikolbenlineargenerator" 3 times fast.

Stranger said...

35KW output. About 28 horsepower with no battery, enough to get you home, and with almost unlimited power with the right battery and leads. With 4WD and regenerative braking.

For a conventional 3500 pound fourdoor, Zip to the Ton in about eight seconds. And with a lot more of the weight between the frame rails, or stubs...

Driving the Dragon would be a whole lot of fun. Almost as much fun as riding it. For the driver.

A passenger used to a barge would get much the same thrill as the passenger in the Gordon Pepsi commercial.


global village idiot said...

How do the pistons reciprocate?

I can see if they were connected to a secondary rod with the same function as the crankshaft, but I don't see it in their schematics.

If they've built the thing I'm sure they've sorted out how to make it reciprocate - it'd just be worth it to see it.

Compressed-air engines are relatively easy to build. Friend of mine has an engine in development which is scalable to everything from golf-carts to duallies.


Anonymous said...

This is nothing new. Free piston engines have been around since, oh, the 1930's. They come into (and go out of) fashionable imagination about every 15 years or so.

The upside of free piston engines is that they're seemingly simple compared to common internal combustion recip engines, the ability to vary your compression ratio (and therefore your extraction stroke) and therefore the ability to run on different fuels (gasoline, diesel/distillate or bunker oil).

OK, sounds great. So if they've been around since the 1930's, why haven't we seen someone put them into a vehicle or application where everyone has seen them before?

Because their overall thermal efficiency isn't a huge improvement over the Otto-cycle gasoline engine. There is an improvement, but it's not a big increase... and not as big an increase as using some common sense and already very well-developed technology like a turbocharged direct injection diesel engine with a compression ratio starting at about 18:1 before the boost is factored in. Recent work in diesel engines is putting their thermal efficiency over 50%.

A free piston engine, very well designed and tuned with the right working gas in the bounce chambers might achieve thermal efficiencies in the 40%+ area. Otto-cycle gasoline engines are at in the 20's. If you wanted to play with free-piston engines and high efficiencies, why screw around with this kind of engine when the Stirling engine (which is external combustion) design has been around even longer, and has approached the thermal efficiency of diesel engines?

OK, let's cut to the chase. Want to have a wicked high-mileage car? Go learn about diesel engines. Learn about the Carnot cycle, how "suck, squeeze, bang, blow" engines achieve efficiencies and how a turbo takes otherwise wasted energy out of the exhaust stream and stuffs it back into the engine.

Then hook one up to a generator in an electric car. Presto! You have 80 to 100 MPG without breaking new ground or frittering away millions on R&D. While the (typically government-funded) researchers pursuing these cute novelties get the press and the "hope and change" crowd all worked up, diesel engines have been getting work done at high efficiencies for decades.

If you want to see the company that's getting for-real 100+ MPG autos done in R&D for several years now, go look at Volkswagen. While everyone else is chasing squirrels, they're achieving results in something that people might actually a) afford and b) drive.

The problem in the US is that the blithering idiots at the EPA are now selected from the ranks of CARB, who are anti-diesel luddites.

Ed said...

Diesel powered electric hybrids are already developed:

Tim said...

I'll take a gas turbine to power my generator, thanks. There's a reason they don't use piston engines at power stations.

Dave in Indiana said...

Remember bumper cars? With our government dreaming up ways to tax us by the mile I see a possible Rube Goldberg solution that could possibly save money on winter snow removal. Enclose roads, basically turn them into tunnels with an electrified ceiling, no snow or rain can get in so no snow and ice removal expenses in the winter. Make electric cars with a pole that reaches up and drags on that electrified ceiling, just like in the bumper car rinks in amusement parks. Heck, the government could even eliminate traffic congestion by adjusting the voltage when needed to increase or decrease speed as needed to maintain flow. WHAT? It's the government, it's there to help! /sarc

Tam said...


"I'll take a gas turbine to power my generator, thanks. There's a reason they don't use piston engines at power stations."

It's a scale thing. The problems with microturbines as encountered by Jaguar are that they require large intake and exhaust passages which are hard to muffle, and the intake plays hob with the aero.


"How do the pistons reciprocate?"

The sealed cylinders act as air springs.

Anon 6:12,

What is this die-sel of which you speak?

Aesop said...

Yes, but being the government, the first electrified tunnel roads will be constructed in Economic Opportunity Zones from Key West to the Florida mainland, in Ward 9 of New Orleans, and alongside the Mississippi River from Minneapolis to the Delta. What could possibly go wrong?

David aka True Blue Sam said...

I read about the Loudmouth in Mechanix Illustrated a lifetime ago, and the free piston system has stuck in my head ever since. They ran the loudmouth on acetylene, and used its exhaust to propel a go-kart. A good picture of it here:

Brad K. said...

What I was thinking, was what about the model airplane crowd -- could something like the .040 Golden Bee be replaced with a suitable sized, free piston pair?

And, I think it likely that the reciprocating nature of the piston motion would likely make any electrical output sort of cyclical. Something like what I learned in the Navy to call "alternating current". Here, though, the piston runs through once out-and-in cycle, where in a regular generator the rotor turns through one pole to the next.

Situation easily rectified!

Anonymous said...

"A free piston engine, very well designed and tuned with the right working gas in the bounce chambers might achieve thermal efficiencies in the 40%+ area. Otto-cycle gasoline engines are at in the 20's."

This reminds me about why Silicon chips are still kings of the heap despite Gallium Arsenide and etc... challengers that keep cropping up, that theorhetically are better:

Amount of R&D on "alternate" chip materials = X x 10 million per annum, Amount spent on Si chips research= XX x BILLION + amount invested in SiChip factories infrastructure = Billions _per_ _factory_

So any non Silicon Chip design not only has to fight the entire WORLD of very bright science and engineering hardware guys beavering day and night to make Si better, but also has to line up BILLIONS in seed money to build a special factory to make them ( and years to build it) by which time the Si guys have caught up and can roll the new designs into production in months.

Same holds true against gas/diesel reciprocating engines, you have to be AWFULLY good, reliable and cheap to beat'em.

Oh and power plants: you'd be amazed how many small plants are "big arsed diesels" rather than turbines.

The big diesels are easier to maintain in most places, & burn cheap fuel and are reliable like grim death.

Goober said...

My bone stock un modified 2001 Golf vw diesel avarages 50 miles per gallon, Peaked at 57 miles per gallon in the best tank I've ever put through it, and will do a smokey burnout through second gear.

The future is in diesel. Now if we could just get the EPA to recognize that.

The Old Coach said...

German engineers are a PITA much of the time, because they keep inventing solutions to non-existent problems (I dare you to ask me how I know!). But every so often they come up with a winner.

Oakenheart said...

The pistons are air sprung, and they're directly connected to 2 linear motor / generators. The linear motors have position sensors give feedback to the ECU, the ECU commands battery power to the linear motor for compression, direct injection makes a squirt, Spark plug fires, linear motors operate as generators as the pistons fly out, generated DC pulse is conditioned and fed to battery. Intake and exhaust ports are set up like a two stroke, cut into the cylinder. Motion of the pistons is entirely controlled by the ECU. The cylinder is sleeveless, nickle silicon carbide coated and water jacketed. Looks very viable as a generator, less mass, less friction, no losses changing linear motion to torque, and less moving parts. It doesn't even need oil if the sleeve is coated and you use a fuel that lubricates. Very neat.

No, I don't have any inside information, and that may not be entirely accurate, but it fits the cutaway, and it's how I'd do it if I tried to build one.

Wish I came up with it.

Anonymous said...

@Anon 10:51 AM, March 21, 2013:

Yep, I've seen the remains of power plants in central Nevada that were big-arsed Fairbanks-Morse diesel gensets that ran the entire town until the late 1970's.

We're talking RPM's of 600 RPM at full throttle.

The reason why diesels have such a bad rap in the US is that we allowed GM/Detroit to perpetuate the stereotype of soot-belching diesels for so long in public transport. Those old bus systems with Detroit two-stroke diesels belched huge clouds of soot coming off a stop... because the Detroits were meant for OTR trucking or industrial use at rated RPM, not as a stop-n-go diesel.

But because our national energy policy is created and enforced by a bunch of liberal arts majors who believe in the power of Unicorns and Alternative Energy Fairies, we're going to turn our backs on the technology that the rest of the world will use in their cars. Europe's auto fleet is now about 40% high-efficiency turbodiesels and climbing quickly - with over 50% of their new car sales being diesels with very high mileage engines.

Justthisguy said...

I mind something I read in Aviation Week back in the '80s, I believe it was. There were all kinds of strategic weapon proposals back then, and one of them was to have lots of cruise missiles powered by free-piston diesel gas generators driving turbofans. These were to be launched by the hundred from big airplanes made of composites, flying randomly over our own territory.

Plastic Diesel-Missile Bombers. Yup, I thought that was just funny , and still do.