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'[TECH]:: One stroke multi-piston per cylinder line'
Radically new engine designs almost always aren't.
Unusual & highly promising engine implementations almost invariably fail to
Even the most plausible designs almost always meet the above two "rules"
All that said, this one *LOOKS* promising and new.
One stroke multi fuel, pistons have no sideforces, conrods slide straight,
smaller engine size and weight per swept volume than conventional designs,
aiming at about 5% energy efficiency gain over conventional engines.
Spokesman on video below sounded very cool calm and collected, & *seemed*
to know his stuff. Whther it would actuually work as well as they claim I
cannot tell. Murphy says no.
I don't know, but, I do see an extra connecting rod plus the connecting link per cylinder that must be accelerated and decelerated for every crank rotation. That's a lot of mass (weight) for F=MA, which means power wasted. Also there are many more bearing surface where rotation is occurring and that's more wasted power. Plus difficult to locate the sparkplug for good flame spread and air/fuel/exhaust flow looks poor, when thinking "Hemi" smooth flow. :)
On 8/24/2011 10:50 AM, RussellMc wrote:
|On 24 Aug 2011 at 13:40, Carl Denk wrote:
> I don't know, but, I do see an extra connecting rod plus the connecting
> link per cylinder that must be accelerated and decelerated for every
> crank rotation. That's a lot of mass (weight) for F=MA, which means
> power wasted.
I think that's a very popular misconception, I hope I can explain without offending. At first it seems like a no brainer: the connecting rod has some mass, in a reciprocating engine the connecting rod is pushed up and down very quickly, accelerated from zero speed to maximum and back down to zero again exactly two times for every 1 revolution of the crankshaft to which it is connected, surely then it must take some "power" to do so? And surely one might assume the heavier the con rod and the faster the engine the more "power" would be wasted?
In reality however the crank shaft/flywheel and the other rotating masses store kinetic energy. Accelerating the reciprocating parts takes kinetic energy out of storage, and decelerating them puts it back in again. Like a big capacitor. There are losses due to friction, as usual, but there is no net loss in energy from accelerating and decelerating the mass itself. With F = MA remember that deceleration is negative acceleration.
Admittedly the speeding and accelerating of various masses is not entirely smoothed out by the crank/flywheel and thus there is vibration which is undesireable... but in itself not a significant factor in overall engine efficiency.
> Also there are many more bearing surface where rotation is
> occurring and that's more wasted power. Plus difficult to locate the
> sparkplug for good flame spread and air/fuel/exhaust flow looks poor,
> when thinking "Hemi" smooth flow. :)
> In reality however the crank shaft/flywheel and the other rotating masses store
> kinetic energy. Accelerating the reciprocating parts takes kinetic energy out of
> storage, and decelerating them puts it back in again. Like a big capacitor. There are
> losses due to friction, as usual, but there is no net loss in energy from accelerating
> and decelerating the mass itself. With F = MA remember that deceleration is
> negative acceleration.
That's true for "SHM" (simple harmonic motion) rotary motion. But I
suspect that it may not be fully true of the linear piston and conrod
arrangement. To the extent that they can be modelled as a mass on the
end of a rotary SHM part they will store and return energy, bit if you
disconnect the linear piston and cross bar mass it does not store
energy (I think) unless you have elasticity in the connecting rod -
which they do not seem to have and which would be "interesting" to
produce. Mayhaps the proper picture is mid way between the piston and
crossbar mass being part of the SHM cycle and partially part of a
linear cycle. Hopefully for them I'm completely wrong and it's all
|Hello Pic List
Long time reader but not poster.
This engine does have some advantageous features but is not as strong a
design as they say. While I do see advantages: piston life and
vibration. This inclusion of two pistons does not double power. Their
is only one combustion chamber. The draw back of this design is
significantly more parts. Two pistons, connecting rods for each
Note that a simple opposing cylinder arrangement manages most of the
same vibration goals and this is not common. Vibration is more related
to the fluctuating torque which this design still has.
Regarding efficiency, the standard Otto cycle efficiency is limited by
the compression ratio and the ratio of the specific heats of the gas
being compressed. So if we want to minimize friction and maximize
efficiency a large change in volume for a small movement is required.
Or, maximize piston area and minimize stroke. This is limited by the
force the connecting rod linkages must handle.
Friction is a running engine is very low do to hydrodynamics. Pistons
do not rub agains the cyclinder walls they float on a very thin film of
Interesting clever design. I am not holding my breath for a ICE
On Thu, 2011-08-25 at 13:40 +1200, RussellMc wrote:
>> Regarding efficiency, the standard Otto cycle efficiency is limited by
>> the compression ratio and the ratio of the specific heats of the gas
>> being compressed.
> Theoretically, but it is necessary to get the maximum amount of the
> correct fuel/air ratio into and exhaust out of the combustion chamber.
> This is where gas dynamics enters. We all know how much on a standard
> engine, the intake and exhaust manifold design effects the power output.
> It appears this would be a design issue to getting good power out of the
> engine. :)
Note that it's "supercharged" of necessity.
Works for my MR2 :-).
As someone mentioned, frictional losses ("side loads", et al)
are modest. After thermodynamic considerations, the most
significant factor (usually) is pumping losses.
It's not obvious how this design fares better, in either respect
M. Adam Davis
On Fri, Aug 26, 2011 at 6:48 AM, Andrew Kettner <vianet.ca> wrote: kettnera
> This inclusion of two pistons does not double power. Their
> is only one combustion chamber.
This is the marketing claim that sets off the BS detector for me.
"Four pistons in the same space as a conventional engine fits one"
doesn't mean four times the power, or the same power at 1/4 the space.
Further, I agree with you on the moving parts issue - there are more
individual moving parts. Chain breaks, and you've destroyed the
engine. One of the links breaks, and you've destroyed the engine. Not
only are there more points of failure, but it appears as though the
design would cause damage if any small failure occurred due to the
I don't quite understand or trust their claim regarding single stroke
operation. At first I thought they meant that with one piston having
two combustion chambers, they could have two stroke on each end and
count it as a single stroke, but their animation does indeed show
combustion happening at each end on each stroke. What I don't
understand is, even with the pumps they've built in, how do they
manage to clear the exhaust and inject the fuel/air prior to
combustion and still maintain efficiency? It's still a piston based
IC engine - their design doesn't make single-stroke any more
practical, efficient, reliable, or inexpensive than it would be to
make a "conventional" IC engine single stroke. Am I missing
something? Does their design make single stroke more useful than our
current engines, or is that just something they're claiming because
they don't know any better?
Addressing only single stroke aspiration issue - and only lightly.
> It's still a piston based
> IC engine - their design doesn't make single-stroke any more
> practical, efficient, reliable, or inexpensive than it would be to
> make a "conventional" IC engine single stroke. Am I missing
> something? Does their design make single stroke more useful than our
> current engines, or is that just something they're claiming because
> they don't know any better?
IF you can do single stroke you ~ double power and power density wrt a
2 stroke and ~~~4x wrt a 4 stroke. .
They have an air compressor which they use to aspirate the cylinder
because, as they note, with a single stroke you cannot use the piston
to acquire its own charge.
I have not attempted to follow their diagrams to see how they actually
propose to do this.
Does Kiwi "single-stroke" = "two-cycle" in Gringlish
M. Adam Davis
I was getting confused with my terminology.
A two stroke engine fires once per revolution, per cylinder. When
monolith engines says "single stroke" I think they do mean to claim
that one cylinder is getting two combustion cycles per revolution.
It's a silly marketing claim, it's just a two stroke engine with two
Which makes me wonder - when they say they are attempting first trials
with a "two stroke" design, does that mean they are actually running a
four stroke cycle on two ends of one cylinder?
It's as clear as mud, and only makes me more skeptical about their claims.
On Fri, Aug 26, 2011 at 2:26 PM, John Gardner <gmail.com> wrote: goflo3
> Does Kiwi "single-stroke" = "two-cycle" in Gringlish?
> A two stroke engine fires once per revolution, per cylinder. When
> monolith engines says "single stroke" I think they do mean to claim
> that one cylinder is getting two combustion cycles per revolution.
> It's a silly marketing claim, it's just a two stroke engine with two
> cylinders combined.
> Which makes me wonder - when they say they are attempting first trials
> with a "two stroke" design, does that mean they are actually running a
> four stroke cycle on two ends of one cylinder?
Again, I have not followed their demonstration in detail BUT I gain
the impression that they are talking about a genuine "1 stroke"
Imagine a horizontal cylinder with a combustion space at left and
right end and a single piston sliding in the cylinder. Splitting the
piston into two halves allows you to do mechanical things in the
middle but it is still conceptually a single piston.
Piston starts at left, unfired charge in left space. Unknown condition
in right space.
Fire left charge and piston moves left to right.
When piston arrives at far right there is a fresh charge in right
space and an unknown charge in left space.
I say "unknown" as you could eg exhaust the left space as the piston
travels l to r and then fill it with new charge as it moves r to l -
which is a conventional 2 stroke except that there is a second space
working to its right. This makes the "2 x 2 strokes connected
together" claim reasonable but its still different than just two 2
Arguably you CANNOT have a stroke as every 2nd stroke would have to
"suck" to do so. ie if you power the piston l to r from 1 side then it
is not making power on the l side when you power it r to l from the r
side. To that extent the "2 x 2 strokes" claim is unavoidable.
When they say they will try it as a 2 stroke 1st they may mean they
will use eg just l side.
However, when they mention their air pump they say it is necessary as
a 1 stroke cannot self aspirate, which suggests they really think they
are doing something more.
In the same way as you cannot make a 1 stroke you must have an odd
number of "points" in a vehicle turn in a street if you start off
going forwards. eg you can have a 1 point turn (= U turn), a 3 point
turn or a 5 point turn etc.
Where appropriate I do 2 point turns by starting off backwards :-).
Care must be taken not to confuse others to the point that accidents
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