
No crankshaft, no problem: Toyota's free piston engine is brilliant - ilamont
http://www.roadandtrack.com/go/out-of-turn-toyota-engine
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zackmorris
I drew almost this exact same picture in high school, along with just about
every other kid interested in internal combustion engines (before I knew what
a horizontally opposed engine was, like the boxer engine in Subarus). I'm just
glad to see a car company talking about it, because the way we do it now with
transmissions is pretty much ridiculous. This engine is roughly 7 times weaker
than it should be, because Nikola Tesla had a 110 horsepower turbine in 1913
[https://en.wikipedia.org/wiki/Tesla_turbine](https://en.wikipedia.org/wiki/Tesla_turbine)
which was unfortunately ahead of its time because the country was barely
getting wired with electricity at that point.

But today a 95% efficient generator connected to a 95% efficient motor for 90%
overall transmission efficiency would be worth it on a turbine or Stirling
engine running at 40-50% efficiency (maybe 40% overall at the wheels). Compare
that with an old gas guzzler from the 70s running at 25% efficiency with maybe
an 85% efficient transmission for 20% efficiency at the wheels. Not to mention
that cars used to weigh twice as much which halved city fuel economy again,
and lacked regenerative breaking which halved it again, and so on and so
forth. It’s no wonder that cars used to get 10 mpg when what I would argue are
relatively simple engineering changes could have raised that to 30, 50, even
100 mpg. It’s almost like they were deliberately designed to be as inefficient
as possible…

~~~
pjc50
They were designed for cost-effectiveness in an era of cheap fuel. Electric
transmission wasn't feasible on the car scale until cheap microelectronics
arrived. It was confined to diesel-electric locomotives.

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programminggeek
What people might not think about so much is that weight reduction is as
important if not more important than the advancements we make in the engine.

When Rocky Mountain Institiute was working on their hyper car concept, I
believe the researcher said that weight reduction was more important than
electric or gas engine.

I think he said something like for every pound you save, you actually reduce
an extra 2-3 pounds of supporting materials elsewhere. Lighter cars need less
HP, you can reduce some of the support bracing as it's not as heavy of a
vehicle, etc...

Making cars super light would do a lot of good and so every time I see a giant
battery for electric cars or a 2nd engine to act as a backup, I wonder how
much that is costing in terms of weight and MPG.

~~~
wspeirs
Along with a weight reduction, they said that, "It can also be run like a
diesel, using compression rather than a spark plug to ignite its fuel
mixture." This is important as spark plugs require a decent amount of energy
to function.

~~~
tnorthcutt
_spark plugs require a decent amount of energy to function_

Are you sure about that?

According to [0], "To ignite a stoichiometric air-fuel mixture (14:1)
approximately 0.2 milliJoules of spark energy are required. Very rich or lean
mixtures can require as much as 3 mJ."

[0]
[http://www.mr2.com/TEXT/DavidKucharczyk/ignition.html](http://www.mr2.com/TEXT/DavidKucharczyk/ignition.html)

~~~
schrodinger
(0.2 millijoules * 6 * 3000) / minute = 0.06 watts

So yea, not much...

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mentos
Seems like needing the piston to change directions is a waste of momentum.
What about a similar design where a ball is propelled around the inside of a
circular doughnut to generate electricity?

~~~
chiph
Too hard to seal. Ask a RX8 owner about rotor apex seals sometime. The bane of
their existence.

In this new motor there's nitrogen on the other end of the piston that
provides "rebound". It's probably inside the coolant jacket as well to prevent
expansion and the loss of efficiency that would bring.

~~~
kabdib
Ex RX-7 owner here. Not much room in the back of one of those things, but I
always had room for cans of oil :-)

Wonderful cars. I'd buy an RX-9 if they ever built one, but they're never
going to. So I have to motorcycle instead, could be worse :-)

~~~
nathanstitt
Same. Mine didn't burn much oil, but would refuse to start when the engine was
warm because of the weak compression. Would fire right up when it was cool
though.

Loved how it handled and the 9,000 rpm redline.

~~~
busterarm
It sure is a pain in the ass when that happens. I have a chipped ECU so I
don't have to get out and pull the fuse to get it started, but I haven't
installed it yet.

One of my cats is gutted and my exhaust is rusted to hell - right now my fuel
economy is shit (~10mpg). This should actually improve when I put the Racing
Beat exhaust in but then I have to upgrade the injectors and air intake and
port the turbo.

My 10th Anniversary is still bone-stock and I'm sad about having to change it.

------
thesz
What is forgotten here is a reduction of vibrations.

The crankshaft works as a (cheap) synchronizer for piston movement and can
reduce vibrations when phases are aligned in special way.

Motor vibrations are big deal - they take energy and also reduce quality of
car.

~~~
maxerickson
It's mentioned obliquely:

 _Even better, a two-cylinder FPEG is inherently balanced_

I guess electronic timing is also up to the task of keeping things running
smoothly without mechanical synchronization.

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IgorPartola
If you enjoyed this article, check out [http://jalopnik.com/what-its-like-to-
ride-in-a-car-with-the-...](http://jalopnik.com/what-its-like-to-ride-in-a-
car-with-the-camless-engine-1529865968)

------
Stolpe
I remember seeing something similar to this a year ago in a documentary series
concerning the small Swedish supercar manufacturer Koenigsegg. See it here:
[https://www.youtube.com/watch?v=Bch5B23_pu0&list=PLHa6PXrV-y...](https://www.youtube.com/watch?v=Bch5B23_pu0&list=PLHa6PXrV-
yIgnXSYFT07BouKhEhyFuWnf). It sounds really interesting.

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stephengillie
All it needs to do is generate motion, so they made it like those flashlights
you charge by shaking them. Reciprocal! What will be revolutionary will be
performing this with some kind of rotary engine.

~~~
arethuza
The Jaguar C-X75 almost made it into production - and it had miniature gas
turbines linked to generators feeding the batteries and wheel motors:

[http://en.wikipedia.org/wiki/Jaguar_C-X75](http://en.wikipedia.org/wiki/Jaguar_C-X75)

Given the current popularity of hybrid hyper-cars from Porsche, McLaren and
Ferrari it would be interesting to see if something like the Jaguar is tried
again.

~~~
tomswartz07
Much older than that was the Chrysler Turbine car:

[http://en.wikipedia.org/wiki/Chrysler_Turbine_Car](http://en.wikipedia.org/wiki/Chrysler_Turbine_Car)

This was quite literally a lower power jet aeroplane turbine used to power the
car.

I would imagine that this would have been great on fuel economy on the
highway, but terrible in cities.

~~~
arethuza
That seems to have used a "conventional" mechanical transmission rather than
using the turbine to generate electricity to feed the electric motors.

Still pretty cool though!

~~~
MBCook
If you're interested there is a very good book called Chrysler's Turbine Car:
The Rise and Fall of Detroit's Coolest Creation.

[http://www.amazon.com/Chryslers-Turbine-Car-Detroits-
Creatio...](http://www.amazon.com/Chryslers-Turbine-Car-Detroits-
Creation/dp/1613743459)

------
zevyoura
>Even better, a two-cylinder FPEG is inherently balanced and would measure
roughly 8 inches around and 2 feet long. An engine of that size and type could
generate 15 hp, enough to move a compact electric vehicle at highway speed
after its main drive battery has been depleted.

Is 15 HP really enough to move a car at highway speeds? I had a CBR250
motorcycle that produced 22-24 HP and weighed around 350 pounds, and it was
not particularly great on the highway. It's hard for me to imagine a car
that's 3+ times heavier with less horsepower being safe on a highway.

------
alkoual
This could be used as a transition from gas to battery cars. Why? Currently
one of the most important reasons holding back companies from producing
electric cars is the lack of good batteries, but with this, companies can
produce cars that convert gas to electricity in order to drive an electric
motor. After a few years, when gas becomes even more expensive and batteries
get better, we can switch this mechanism to batteries, and that's it.

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ChuckMcM
Pretty cool, and I wonder if you could build the piston with two "heads" and
put a cylinder head on either end and just shoot it back and forth. Magnetics
of course have a hard time at high temperatures, so I'm not sure how you
generate the stator field reliably.

~~~
bradleyland
The problem would be startup and shutdown timing. Any circumstance where you
had a "missed" ignition (which occurs more often than you'd think) would
result in a catastrophic failure (pistol slams in to the opposing head).

------
snowwrestler
Anyone know why hybrids don't use turbine generators? As I understand it, they
are more efficient than even the best reciprocating engine. Aside from solar
and wind, every large-scale generating station uses turbines, for example.

~~~
TheLoneWolfling
IIRC, turbines are really ineffecient at small scales.

It's only when you get up to large scales that they start making sense.

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hyperliner
Pardon my ignorance, but the video does not show and I am interested to see if
they modified the system, but what draws the piston back towards the spark
plug?

~~~
tnorthcutt
It's not drawn, it's pushed, by the pressure built up in the "gas spring
chamber".

------
IgorPartola
I believe this is what Chevy Volt does, and it's brilliant. There are two
reasons I like this design. First, the fossil fuel engine in the Volt spins at
only three pre-defined speeds so it can be optimized better. By contrast, your
normal car engine has to run at both 900 RPM and 6500 RPM, with the best fuel
economy somewhere between 2000 and 3000 RPM. Heck, you could shut the Volt's
engine entirely while it's "idling" and not have to worry about stop & go
traffic: the engine is independent of the wheels.

Second, and this is admittedly more long term, it doesn't really matter what
type of engine you put into the Volt. This thought was presented to me by one
of their dealers, but it makes a lot of sense. The current engine is a "tried
and true" gasoline job. But if Chevy found that diesel or bio fuel, or natural
gas worked better, they could swap it out without redesigning the rest of the
drivetrain.

I may sound like a walking billboard for the Volt, but I am honestly not. I
don't own one, and do not work for Chevy/GM. I do happen to think that the
Volt is the best compromise between price, range on batteries, and ability to
drive long distances. While Tesla's are very cool, I think the Volt is a much
more gradual transition from gas to electric.

~~~
masklinn
> I believe this is what Chevy Volt does

The article's point is not to about "diesel-electric" systems (where the ICE
acts solely as a prime mover for a generator and the wheels are always driven
electrically). That's old news in both transportation in general (it's been in
use in trains and ships since the early 20th century) and in hybrids ("diesel-
electric" is sometimes called "series hybrid" or "range-extended electric
vehicle" in cars).

It's about a new engine design[0] where electric generation is merged into the
piston itself: a "normal" diesel-electric engine has a regular diesel engine
(or more generally ICE) with pistons driving a crankshaft which drives the
driveshaft, which is connected to a generator.

Here the design does away with the crank and driveshaft: the piston itself is
a rotor, and the casing becomes the stator, doing away with mecanical
transmission altogether: the piston and its cylinder become a linear
generator.

[0] not quite that new, the first patent on free-piston engines[1] for linear
generators dates back to 1959. The new part is getting a design to actually
work in a vehicle[2].

[1] a free-piston engine is an engine without a crankshaft transforming the
piston's linear movement into rotational movement

[2] the crankshaft does not just transform motion and lose energy, it also
synchronises pistons and limits the piston's course. But if the
piston+cylinder is a self-contained generator, I guess you can treat each
piston as a single-piston linear engine? Which would limit the usual issues of
multiple free-piston engines.

edit: formatting, footnotes

~~~
IgorPartola
Thanks for the explanation.

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Already__Taken
It's also a big deal having electronic controlled valves, you can make them
have a square profile for maximum flow rates.

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marknutter
Why was this article removed from the front page of Hacker News?

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daraosn
Reminds me of
[http://en.wikipedia.org/wiki/Mazda_Wankel_engine](http://en.wikipedia.org/wiki/Mazda_Wankel_engine)
Good think this seems to be efficient, but I would like that instead they
would be putting more focus on improving batteries rather than gas motors.

~~~
sharemywin
until you get most of your grid power from solar your still using fossil fuels
for power.

~~~
wtallis
About 30% of US electricity is produced from nuclear power or non-solar
renewable sources. Solar may be a hot topic, but it's nowhere near being the
top alternative to fossil fuels.

~~~
rational-future
US =/= world. Solar is growing far far far quicker than nuclear.

------
adrow
Previous discussion:
[https://news.ycombinator.com/item?id=7677197](https://news.ycombinator.com/item?id=7677197)

