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A number of ideas have been proposed
on
this site for engines which are more
efficient, more powerful or mechanically
simpler than the conventional I.C.E.
For non-engine fanatics amongst you, I
should explain that
one
of the main problems with the
conventional engine is that the
pistons
reciprocate. Not only must this
reciprocating motion be converted into
rotary motion (via a fairly complex and
wear-prone system of cranks and
bearings), but the need to reverse the
direction of the pistons and cranks
hundreds of times per second leads to
tremendous loadings and energy
wastage.
The Wankel engine, as well as less
practical alternatives, seeks to overcome
these limitations by creating rotary
motion
more-or-less directly. Nevertheless,
there
is still a conversion to be done after all
this, since the movement of the car itself
is substantially linear. Efficiency losses
arise in the clutch, gearbox, rear
differential and wheel bearings necessary
to convert the rotary output of the
engine
into linear motion of the vehicle. A
further
drawback is that the tyres (US: tires) on
the driven wheels suffer additional wear
due to the shear forces imposed by
acceleration.
I therefore propose an alternative engine
configuration which may overcome some
of these limitations. This configuration
has the advantage of having minimal
moving parts (and, above all, no
reciprocating parts).
The engine itself is mounted
longitudinally
in the car - its long, narrow design
allows
it to be installed in the space which
would
normally be the prop-shaft tunnel. A
single horizontally-mounted cylinder
runs
axially from the front of the engine to the
rear, with the usual inlet and exhaust
valves and spark-plug in the cylinder
head, which is at the front end. The
cylinder bore will, typically, be larger
than
that of a conventional four-stroke
engine,
and the stroke will (for a typical small
urban car) be on the order of 2-3000m
and is calibrated to correspond with the
desired journey distance.
In place of a regular crank connected to a
crankshaft, this engine has a crank of
slightly greater length than the stroke of
the single cylinder. One end of the crank
attaches to the piston in the usual way.
The other end of the crank is widened
into
a broad plate (a bit like the 'mushroom
head' of conventional engine valves, but
much more robust), and has five holes
for
fixing bolts.
In operation, the engine starts with the
piston at the 'top' (in this case, front) of
its
travel, close to the cylinder head.
(Considerations of compression ratio,
etc,
are basically the same as in conventional
engines.) The widened distal end of the
crank protrudes just beyond the rear of
the car and, using the five bolt-holes, is
secured to a solid structure. At this
point,
obviously, it's imperative that the vehicle
is pointing in the desired direction of
travel.
The ignition cycle happens only once per
journey. Fuel in the headspace of the
cylinder is ignited, driving the piston
backward relative to the cylinder. Given
the rigid fixing of the crank, this equates
to a forward motion of the cylinder and,
thence, of the vehicle itself. Acceleration
is rapid initially, but decreases during the
completion of the detonation phase.
Ultimately, the vehicle is brought to rest
when the crank reaches the limit of its
travel.
As you will appreciate, this design of
engine is ideally suited to use in long
vehicles. Although the engine could be
incorporated into compact cars, their
range would be compromised.
Linear Piston Engine
Linear_20Piston_20Engine
You could make this marginally less impractical by implementing the "...have all the pistons pointing down and towards the road at the rear of the car at about 45 degrees, then they can punt the car along." idea I suggested here... [hippo, Jan 28 2008]
Pennington Autocar
http://www.histomob...et/472/732601_1.jpg
cylinders as frame rails [Ned_Ludd, Jan 28 2008]
Pennington Autocar
http://images.googl...%26hl%3Den%26sa%3DG
about half-way down the page [Ned_Ludd, Jan 28 2008]
[link]
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This is an adaption of the concept of the "spigot mortar" which has been in practical use since the early 20th century (perhaps even before that). |
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// Acceleration is rapid initially, // |
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Indisputably, this will be so. While it may be possible to produce a vehicle capable of retaining its structural integrity when subject to such accelerations, it is doubtful that any human occupant would survive the forces involved, unless supported in a liquid medium. |
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Traffic lights located close to the point of departure may also introduce rather more interest than is desireable into the journey. |
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You don't actually *need* a piston... in fact (except for the eventual need for stopping), it probably works for a more extended period of time without one. |
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Granted, there are a few technical issues to
resolve. However, I like to think that
whatever this concept lacks in feasibility, it
makes up for in impracticability. |
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//unless supported in a liquid medium// |
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where do people keep coming up with this concept that floating in a liquid medium somehow makes one immune to G forces? |
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//where do people keep coming up with this concept that floating in a liquid medium somehow makes one immune to G forces?//
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it spreads the pressure out better.
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anyways I like the "InterCity Ballistae" idea better |
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A person who drove into a wall going 65 mph would fly through the windshield because there wouldn't be enough friction on the butt to change that person's momentum fast enough. Now, air doesn't have as much viscoscity as a liquid fluid does, and hence the liquid would impart a larger shear force on the body slowing it down more before it hit the windshield. That is why a car-pool is safer if you have your SCUBA on. |
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Now, have a bun for the artillary driven crankshaft-type-differential idea that explodes its way across town. [+] |
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Well...I don't think you have something there. |
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Is that a medical opinion? |
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Have you been looking at Pennington Autocars? |
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//it spreads the pressure out better.//
As in, "it transmits it almost perfectly"? |
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//piston stroke between 6,562ft and
9,842ft long// Yes, and we would have to
offer both metric and imperial versions,
depending on whether you live in a metric
or imperial road system. |
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You can't take it in the Lincoln Tunnel. |
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There is not a major problem with flying through the windscreen, the problem is whatever object stops you. If your car hits a brick wall and is filled with liquid, you will stop instantly, which is no less harmful to your body than being strapped to the front bumper (US: fender). |
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Well, its safer to slow down a little bit before you hit the windshield. Of course, the added mass and pressure of a suddenly impacted car-pool fluid would easily blow out your windshield before you did unless it was designed to take that kind of high pressure impact.. |
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//You can't take it in the Lincoln
Tunnel.//
Oh yes you can. Getting it out again
would
be the problem. |
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For emergency situations and long
journeys, a hand-winch can be use to
manually retract the piston, after
unbolting
the crank end from its starting point.
Said
crank end can then be reattached at
your
current position, allowing you to
continue
on your way. |
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Reversing, incidentally, involves the
same process without first unbolting
the crank end. |
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UnaBubba, you seem to be missing the
versatility of this vehicle. Its choice of
destination is not limited in any way by the
stroke-length of the engine, as long as
you remember to start from the right
place. |
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The kilometric version won't sell in the
States - we're bringing out an imperial
model soon. |
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Yes, I suppose a simplistic
interpretation would compare it with a
rocket sled on a single rail. However,
the rail itself is not a rail but the crank
connected to the piston, and there is no
rocket as such. And it goes on wheels.
Apart from that, very similar. |
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A further advantage of this vehicle is
that if, after arriving at your destination,
you find you've forgotten something,
you can simply walk to the back of the
car and you will be at your departure
point once more, whence you can
retrieve it. Few other cars offer this
feature. |
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//The ignition cycle happens only once per journey. // |
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"A journey of a thousand miles begins with a single step." Confuscious |
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If by journey, you mean the average distance you travel per explosion, and it takes a thousand mini-journeys to travel one complete journey, then I think you have something there. |
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This might fall in line with the random destination vehicle. You just climb in and dissappear the moment you twist the ignition key...where you went, no one knows but you did leave behind a rather curious grease spot. It could also be termed the "Terminal" car....the accelleration would be almost instant with the very messy results ending up in the rear seat. |
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Parallel parking would get interesting. |
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But getting out of a tight space is child's
play. |
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This basically a rocket engine with a giant metal rod stuck up its rear. Would this be correct comparison or have I misunderstood this idea? |
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The latter, I'm afraid, at least to an extent.
A rocket engine spews all manner of stuff
out of its rear end, and said stuff is lost
forever to the rocket. This, in uttermost
contrast, is merely a very long single-
cylinder engine, in which the crank pushes
directly against wherever it is that you
don't want to be, in order to move you to
where you do want to be. At no time does
the crank, piston or anything else of
significance part company with the vehicle. |
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For me to get to New York in such a car, it would need to be as long as from here to Kansas. This is good. I mean, I rarely need to get to New York, but at least I know it would fit all of my kids. |
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//For me to get to New York in such a car,
it would need to be as long as from here
to Kansas.// Not necessarily. I think
you're probably starting from the wrong
place. |
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Can't I just climb in the front door, climb out the back door, and be where I want to go? |
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The rocket would be more efficient, I'm afraid. At least it could be said to coast, which is what this thing will be doing through most of its travel as the gas explosion is only effective to a certain change in displacement and pressure. And don't forget about the backpressure that the underside of this rather useless piston will have to push out of its way to travel along its tube.
Essentially yes, it's a rocket with a plug up its arse. |
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Orienting the axis of the piston at an angle to the
horizontal, and utilizing falling-rate springs in the
suspension, could optimize the handling vis a vis
urban traffic obstacles. |
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//a rocket with a plug up its arse// |
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To spare its feelings, could we instead call it an alienated monorail? |
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