SABINE Mk 2

TWO STROKE ENGINE

By Jan Ridders

One of my earlier experimental engines was not viable. It was the Pendulum 2-Stroke. I had thought that it would be fun to design a 2-stroke engine in which the piston is held in motion by a pendulum instead of by a conventional flywheel. It should have the looks of a clock in which the pendulum is not powered by a spring, but by a working piston which runs up and down in a glass cylinder as a result of a two-stroke combustion process.

When the Pendulum 2-Stroke was not found to be viable, I decided to rebuild this engine with a flywheel instead of a pendulum. In this way I could keep a relatively large portion of the engine and it would still yield a nice engine. In fact, it was a variant of the Pressure-controlled two-stroke Sabine engine and so I baptised this design the ‘2-stroke Sabine MK2’ which has the following differences with his predecessor:

- Simpler and more compact design;

- A glass cylinder containing a graphite piston;

- A double flywheel construction;

- Easy carburettor variant.

To be honest, the Pendulum 2-Stroke would have been more innovative and spectacular but you can’t force physics.

The figures below illustrate the design:


I took over here the 2-cycle concept of Pressure controlled 2-stroke Sabine with the difference that here the cylinder is made of glass and the piston of graphite. A system with two ball valves and an expansion tank automatically takes care of the suction of the fresh gas mixture from the carburettor, the compression thereof, and the flushing of the cylinder at the moment when the piston passes the exhaust opening in the cylinder in its lowest position. In contrast to the standard two-stroke process here the fresh gas is injected at the top of the cylinder instead of through an inlet opening in the wall of the cylinder.

As I with several of my IC engines I have here the glass cylinder cut from a 20ml Fortuna Optima syringe whose inner diameter is extremely accurate with a roundness of 0.01 millimetre or less. This is a precondition to having a well-fitting graphite piston.

I myself obtained a few of these syringes from a fellow modeller so I have never bought myself such a syringe until now . But suppliers for this "Fortuna Optima" syringes are everywhere on the Internet; simply type "Fortuna Optima syringe" into Google Search (or "Fortuna Optima syringe"),see the picture below:


The carburettor is a variant of my universal Petrol Vapour Carburetor using the same principle. This variant is a simplification where I used a small spice jar as gasoline tank. At the top side it is closed by a metal cover with the lead for the inlet of the outside air and the outlet with the controller for adding outside air; impossible to be easier, I think. This vertical version also fits better in the relatively compact design of the engine.

I have applied here two coupled flywheels, one at the cylinder side of the vertical support with the eccentric for the connecting rod and one on the other side with a Neodymium magnet for controlling the reed switch for the spark-ignition. This also serves as a flywheel start-up pulley with two holes for a start-up tool in the hand drill.

Apart from some small dimension differences the ball valve system is identical to that of the Pressure controlled 2-stroke Sabine.
Below an animation of this 2-stroke process:


The expansion vessel that can be seen on the cross section (not on the animation) is intended to limited the compression pressure under the piston. A too high pressure would brake the engine severely. This pressure needs only to be just enough to flush the cylinder well, with the fresh gas mix at the time when the piston is in its lowest position and the outlet opening is opened.

I used the spark system according to alternative 2 that you can find at http://modelengineeringwebsite.com/Blokker_alternatives.html

I have CAD plans for this engine that are available for every one interested; click here for a request.