Free Pision Engine

Is it a myth that two stroke engines MUST burn oil.

I cant see why a new take on two stroke cant include a clean burn system?...

In this design, I wonder if you could use the magnetic field as a bearing? Between that, air bearings, and an oil free ring setup, you may not need any oil at all. How would that effect maintenance and life?

Could you use a self lubricating metal for the seals like Bronze? Or would that not stand up to the heat/abuse?

The reason for a simple 2-stroke gasoline engine burning oil is that a 2-stroke engine lacks the intake and exhaust stroke. Instead, those cycles are part of the work stroke. At the end of the work stroke, the cylinder needs to be "flushed" in order to replace the exhaust gasses with fresh air and fuel vapors.

You can use a blower to flush the cylinder but this requires additional hardware. The method of choice for simple 2-stroke engines is using the crank case as a compressor. When the piston goes up during the compression stroke, the vacuum of the crank case draws in the gas/air mixture from the carburettor. When the piston goes down during the work stroke, the crank case is pressurized and this pressure is used to flush the cylinder when the piston is all the way down. This method requires to add oil to the gasoline in order to lubricate the crankshaft and piston.

The blower allows to fill the crank case with oil for cooling and lubrication purposes. Using a blower for a gas engine is not a good idea since you have a flammable mixture under pressure. If the blower leaks or the engine backfires, the engine can catch fire or blow up easily. In a diesel engine, all the blower does is to handle fresh air, the fuel is added right before the work stroke inside the cylinder.

A 2-stroke gas engine must use the crank casing as a compressor for safety reasons and this requires adding oil to the fuel for lubrication. The lack of cooling from splashing oil requires a very crude design because the piston will heat up a lot and can become stuck in the cylinder. This decreases efficiency dramatically. On the other hand, the crude design also decreases costs since you don't need a complicated cooling system for the cylinder as well. So while a 2-stroke gas engine is very inefficient, it's cheap and very simple which also makes it very reliable.

There's another effect which decreases the efficiency of 2-stroke gas engines which also prevents the use of a good catalytic converter. Flushing the cylinder can't be done well. Either you replace not much exhaust gasses or you flush fresh mixture right through into the exhaust pipe. Most who had a motorcycle using such a simple 2-stroke engine know that removing the "shock disc" of the muffler will increase the engine power dramatically. The "schock disc" reflects the shockwave of the exhaust gasses. The returning shock wave stop gasses from escaping the engine to keep as much unburned fuel as possible inside the engine. By removing the disc, the cylinder is flushed much more rigorous but at the same time, a lot of unused fuel will escape. Your motorcycle will burn more than twice as much fuel but is significantly faster.

A 2-stroke diesel can flush all the way it likes, there is no unused fuel present in this stage of engine cycle. The fuel is put in right before the work stroke. So while a 2-stroke diesel is more complicated due to the blower, it has an oil sump in the crank case and no efficiency deficits from flushing. The only real disadvantage of a 2-stroke diesel design is that you can't turbo charge it!

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The idea of an engine with just a moving piston isn't new at all. There were many designs meant to be used as pumps and compressors. They all didn't make it onto the market since plenty of exhaust gasses mix with the medium you pump or compress. Water is contaminated with oil and poisonous exhaust gasses and so is compressed air. You can't breath what comes out of your jackhammer and you can't pump water into the environment.

The design to generate electricity that way has many flaws, too. The piston doesn't perform a sine wave movement so you won't be able to generate plain AC. You need a power converter! Also the shock waves of the combustion shake the magnets ruining them. And the wider the gap between magnet and coil, the lower the efficiency so the piston must have a very tight bearing which becomes destroyed when the thing heats up - or you use a very crude design with low electric efficiency.
And if you need a power converter anyway, why not using a super efficient fuel cell in the first place?

first: the difference you cite is not between a gas and diesel motor but between a carbureted and fuel injected motor.
second: Mr Cummins would be inclined to disagree with you on the impossibility of turbocharging a two-stroke diesel.
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The difference is between an engine with direct fuel injection and other systems. It doesn't make much sense making a simple engine and then use a highly expensive injection system.

Of course you can turbocharge a 2-stroke, it's not the 2-stroke itself that prevents turbo charging. It's the valveless principle which make the common 2-stroke so simple, reliable and cheap. Of course you can add valves and then equip anything a 4-stroke engine can have.

Of course you can. Most early diesel tractors had pretty crude and simple 2-stroke diesel engines.

The most famous engine was the "Lanz Bulldog" engine invented in 1918 by Fritz Huber. Originally it was designed for crude oil as a stationary engine, then used in a farming tractor which became also known as "the Bulldog".

Here are some diagrams too look at:
www.lanz-bulldog-homepage.de/src/tech/gluehkopfmotor.html

Like the common gas 2-stroke engine, it uses the crankcase as the blower but it uses indirect injection as classic diesel engines use.

The problem of building up soot and spitting burning chunks of soot was fixed by using a cylinder filled with iron wool in the exhaust pipe. This was how the muffler was invented, it's primary function was to prevent torching fields and barns but it also reduced the engine noise so it was kept even after the soot problem was really fixed.

The injection pump is nothing but a cylinder hit by a cam at the correct time. The accelerator just rises and lowers the cylinder so the accelerator controls the amount of fuel squirted into the glow head.

As seen in the diagrams, the some early crude oil versions were started using spark plugs. Light gasoline was added from a second fuel tank to start the engine. The injection jet had to set to spray "wide" so the gas vapours reach the spark plug. When the engine was running for a while, you had to stop adding gasoline and set the injection jet to spray "narrow".

The later diesel Bulldogs method to start them was to set a blowtorch filled with petroleum under the "bulldog's head" and wait until it glows red hot before the engine can be started. The "bulldog's head" of the diesel version is pure design of the cover keeping the actual head hot. The early crude oil version heads looked like a bulldog's head for technical reasons.

well, that certainly does look light and simple... how many horsepowers to the pound does it develop?

a simple two stroke - aka chainsaw engine, uses the crankcase as a supercharger. therefore, there is no crankcase oil, and as I am sure you know, gasoline is an excellent solvent for cleaning oil off of metal parts.
so you could certainly make a two stroke engine with a blower and an oil filled crankcase - at the expense of cutting the horsepower per pound in half. but you can't make a permanently lubricated crankcase with a constant flow of fuel-air mix through it.