In the Soviet Union, various model sections, which usually existed at the palaces of pioneers, were very widespread. The main activity of young modelers was the independent production of models of aircraft and ships with various types of engines.
General information
The simplest models were equipped with the so-called rubber motor, which was a twisted bundle of rubber strips. One side of the harness was fixed on the body of the model, and a propeller or propeller was attached to the other. Older modellers built models and models equipped with several types of engines:
- electrically powered;
- piston compression type;
- piston with glow ignition of the mixture.
Compression motors are simple in design and do not require separate starters. That is why they are the most popular. The mixture is ignited by compression, while the volume of the chamber is regulated by a special device.
Motor design
The MK-17 engine was made famous at the timeaircraft modeler and master of sports in this discipline V. Petukhov. The date of development of the motor is not exactly known, but by 1954 the first samples already existed. The designer set himself the goal of creating a reliable engine in start-up and operation that could be used by novice modellers.
The design of the motor was very simple, which predetermined its prevalence. Serial production of the MK-17 Junior engine was carried out at the Znamya Revolyutsii plant (Moscow). Structurally, the motor consists of the following main parts:
- Cast silumin crankcase.
- Replaceable cast iron sleeve.
- Crankshaft.
- Smooth piston with connecting rod and pin.
- Spool valve and replaceable diffuser.
- Cylinder head with multiple ribs.
- Counter piston and screw to move it.
Next, a general description of the MK-17 aircraft model engine, which is typical for all model compression engines, will be given. The motor shaft rotates on a pair of ball bearings that are pressed into the bottom of the crankcase. The shaft has a counterweight and a neck with one free end. A connecting rod is put on this neck and a spool is driven, which serves to supply fuel. A pin is installed on the upper part of the connecting rod, connecting it with a cast-iron piston. The upper part of the piston has the shape of a cone, while the counter-piston has a reciprocal recess. A diffuser and a primitive carburetor are installed on the back of the engine, which made it possible to regulate the amount of fuel supplied whenhelp of a needle. The diffuser was produced in two sizes - small and large. The first option was used by novice modellers, and the second by more experienced ones. The spool assembly is installed through a cardboard gasket with four screws.
An aluminum head with six thick ribs was installed on top of the crankcase. The head was attracted by three screws and fixed a replaceable sleeve. There were windows in the walls of the sleeve through which a fresh mixture was supplied and exhaust gases were emitted. The exhaust windows were located under the head mounting plane. The cylinder displacement was only 1.48 cu. see
Thanks to all the improvements, the power has increased, which has reached 165 watts, and the maximum engine speed (up to 12 thousand per minute when working with a propeller). The weight of the motor was about 130 grams.
Fuel
The MK-17 engine could only use a special mixture as fuel. Its composition necessarily included sulfurous ether, which has a high volatility and a low flash point. It was this component that provided the self-ignition of the mixture. Additionally, the fuel composition included kerosene and castor oil, which provided lubrication of all rubbing elements. The proportional ratio of components is almost equal (35% of kerosene and ether, and the rest is castor oil).
Currently, carburetor cleaner is used instead of ether to start MK-17 engines.
Launch
To start the motor, you mustfill the tank with fuel, loosen the counter-piston fixing screw a few turns and turn the shaft by hand. In this case, you should pinch the diffuser hole with your finger. Some fuel will get inside the engine. Then it is necessary to sharply turn the motor shaft by the screw. If there are no flashes or they are single, then it is necessary to increase the compression ratio by tightening the screw in the head. Then turn the shaft again and try to start the motor.
After starting, you need to set the required speed with the needle and vary the position of the screw in the head, achieving the most stable operation. The motor is stopped by closing the diffuser or closing the needle.
Revisions and alterations
Under the refinement of the motors meant a reconciliation of the real gas distribution diagram with the passport documentation. At the same time, purge windows in the sleeve were trimmed or the sleeve was replaced with a new one in case the windows were too high.
One of the most common engine modifications is installing a glow plug in place of the counter piston screw. The counter-piston itself was removed from the cylinder. This alteration turned the MK-17 compression engine into a glow engine.
