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Long-stroke single-piston reconfigurable internal combustion

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(+3, -8)
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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.

MaxwellBuchanan, Jan 27 2008

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]


       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).   

       // Acceleration is rapid initially, //   

       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.   

       Traffic lights located close to the point of departure may also introduce rather more interest than is desireable into the journey.
8th of 7, Jan 27 2008

       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.
FlyingToaster, Jan 27 2008

       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.
MaxwellBuchanan, Jan 27 2008

       //unless supported in a liquid medium//   

       where do people keep coming up with this concept that floating in a liquid medium somehow makes one immune to G forces?
jhomrighaus, Jan 27 2008

       //where do people keep coming up with this concept that floating in a liquid medium somehow makes one immune to G forces?//

       it spreads the pressure out better.

       anyways I like the "InterCity Ballistae" idea better
FlyingToaster, Jan 27 2008

       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.   

       Now, have a bun for the artillary driven crankshaft-type-differential idea that explodes its way across town. [+]
quantum_flux, Jan 27 2008

       Well...I don't think you have something there.
M Carter, Jan 27 2008

       Is that a medical opinion?
MaxwellBuchanan, Jan 28 2008

       Have you been looking at Pennington Autocars?
Ned_Ludd, Jan 28 2008

       //it spreads the pressure out better.//
As in, "it transmits it almost perfectly"?
coprocephalous, Jan 28 2008

       //piston stroke between 6,562ft and 9,842ft long// Yes, an we would have to offer both metric and imperial versions, depending on whether you live in a metric or imperial road system.
MaxwellBuchanan, Jan 28 2008

       You can't take it in the Lincoln Tunnel.
elhigh, Jan 28 2008

       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).
marklar, Jan 28 2008

       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..
quantum_flux, Jan 28 2008

       //You can't take it in the Lincoln Tunnel.// Oh yes you can. Getting it out again would be the problem.   

       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.   

       Reversing, incidentally, involves the same process without first unbolting the crank end.
MaxwellBuchanan, Jan 28 2008

       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.
MaxwellBuchanan, Jan 28 2008

       The kilometric version won't sell in the States - we're bringing out an imperial model soon.   

       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.   

       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.
MaxwellBuchanan, Jan 28 2008

       //The ignition cycle happens only once per journey. //   

       "A journey of a thousand miles begins with a single step." Confuscious   

       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.
quantum_flux, Jan 28 2008

       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.
Blisterbob, Jan 29 2008

       Parallel parking would get interesting.
acurafan07, Jan 29 2008

       But getting out of a tight space is child's play.
MaxwellBuchanan, Jan 29 2008

       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?
BLTurner, Jan 29 2008

       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.
MaxwellBuchanan, Jan 29 2008

       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.
globaltourniquet, Jan 29 2008

       //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.
MaxwellBuchanan, Jan 29 2008

       Can't I just climb in the front door, climb out the back door, and be where I want to go?   

       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.
RayfordSteele, Feb 01 2008

       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.
sninctown, Jan 02 2014


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