The main manufacturer of stationary engines in the USSR was the Ulyanovsk Motor Plant. Since 1952, the assembly of a family of unified UD engines with different cubic capacity and power began at the production facilities of the plant. The main field of application of such engines is the drive of generators in portable power plants, as well as various agricultural, construction or road equipment.
Total information
In 1967, the range of engines was expanded by units based on the ZAZ-966 engines of the Kommunar plant. One of the engines based on the Zaporozhets engine was a single-cylinder four-stroke UD-15. With a cylinder displacement of just 0.245 liters, engine power is 6.5 forces at 3600 rpm of the crankshaft. This power is achieved when the carburetor throttle is fully open. In practice, the UD-15 engine operates under the control of a speed limiter and develops long-term power of no more than 4 forces. In the photo below - a single-cylinder engine generating station.
The second engine of the new family was the larger two-cylinder UD-25. The motor with a working volume of 0.490 liters has a long-term power of about 8 forces. Structurally, the UD-25 engine is maximally unified with a single-cylinder counterpart. One of the features of the engines was the camshaft drive scheme, in which the gears are located directly inside the crankcase. In the photo below - a two-cylinder UD-25.
Both engines have a low compression ratio (6 and 7 units, respectively) and can operate on gasoline with an octane rating of at least A72. According to the instruction manual for the UD 15 engine, the unit has the following overall dimensions and weight:
- length - 410 mm
- width - 455 mm
- height - 535 mm,
- weight - 41 kg.
Modifications
All stationary UD units are available in various versions, featuring attachments. The UD-15 engine was not an exception, which was supplied to customers in the basic version and in the version with the “G” index for driving the electric generator. The photo below shows such an option for the motor.
The generator version of the engine was distinguished by a transitional bell mounted on the crankcase for mounting the generator and the presence of a ring gear on the flywheel. To start such a unit, an ST-351V electric starter with a voltage of 12 V was used. Another difference between the versions was the spark plug. On the UD-15 engine, a model A10N or CH200 candle is used, and on the UD-15G generator motor there is a SN302-A candle.
Carter
The main detail of the UD-15 engine is the aluminum crankcase of the tunnel circuit. It has a separate housing for the front bearing of the crankshaft, which is bolted. In the front wall of the crankcase there is a place for installing a gear pump and a pressure reducing valve for adjusting the pressure in the lubrication system. On the outside of the crankcase there is an axis for the foot pedal of the engine.
The design of the crankcase provides a ventilation system through a special valve located near the magneto drive. Gases that burst into the crankcase through the valve enter the rubber pipe and then into the air filter of the motor.
Shafts and engine pistons
One of the main characteristics of engines is the use of ball bearings as crankshaft bearings. The front bearing is mounted in a removable housing, and the rear is pressed directly into the crankcase. This design allowed to increase the engine resource and greatly simplified repair work.
On the front of the shaft is the so-called “lubricating bearing”, which distributes the oil supply from the pump. In addition to it, a camshaft drive gear and a flywheel are mounted on the front end of the shaft. The other end of the shaft has the shape of a cone on which a coupling is mounted to drive the units.
The camshaft is mounted on bushings made of bronze tape. The valves located in the heads are driven by rods and rockers. The valve cover and engine head are clearly visible in the photo.
The UD-15 design uses aluminum pistons with two compression and one oil scraper rings. In the design of the pistons, a specially shaped skirt is used, which minimizes the risk of sticking when heated. Each cylinder has its own cast iron with developed external fins. The inner surface of the cylinder acts as a mirror.
Heat exchange
The main characteristic of the engine is the cooling system. At UD-15, a forced air supply from a fan, made at the same time as the flywheel, is used for this. The direction of air flow is set by the casing system. The intensity of the air intake into the fan is regulated by a blind system in the inlet channel.
Mixture formation
To power the UD-15 engine, a K-16M or K-45M carburetor is used (on a motor with 2 cylinders). The design of the carburetor allows you to use it in conjunction with the speed controller. Speed control is carried out by two spring-loaded balancers. As the revolutions increase, the centrifugal force moves these balancers to a certain point. When it is reached, the balancers begin to move the throttle of the carburetor through the thrust, thereby reducing speed. Regulator springs can change the tension to set the speed.
To supply gasoline from the tank, a diaphragm fuel pump is installed on the crankcase. The working drive of the pump is implemented from a separate cam on the camshaft of the engine. To pump gasoline into the carburetor at startup, a manual drive is provided. Air filtration is carried out by an inertial filter with an oil bath.
Grease
The lubrication system of the UD-15 and UD-25 engines is identical. To store the oil supply in an amount of 1.5 liters (3 liters for a motor with two cylinders), the lower part of the crankcase is used. From there, it is fed under pressure to the bearings of the engine and to the centrifuge for cleaning. Refined oil is supplied to lubricate the bearings of the connecting rods and the gas distribution mechanism. In this case, oil is supplied to the engine valve boxes through the actuator rod of one of the valves. Oil flow back from the box goes through a separate pipe. For use in engines, the cheapest mineral oils of summer and winter grades can be used.
To control the oil pressure there is a mechanical pointer. The protrusion of the rod of the pointer by 3 mm is considered the norm of pressure. Optionally, an arrow gauge MTS-16U can be installed on the engines. For its installation in the crankcase there is a hole closed by a threaded plug. This hole is used to fill fresh oil. To drain, there is a second plug on the bottom of the crankcase.
Ignition and start
The UD-15 engine is equipped with an ignition system from a conventional single-spark magneto M-137 (two-spark M-151 on UD-25). The design of the unit provides constant control of the angle of the moment of supply of the spark to the spark plug of the engine. All magneto units are located in a zinc alloy housing. The drive is carried out from the gears of the speed regulator using an additional coupling.
The start of a conventional UD-15 engine is carried out by the kick-starter pedal . The kick-starter is a lever with a gear sector, which engages with the gear on the crankshaft flywheel shaft. This gear is equipped with a ratchet mechanism that disengages it after starting the engine. The reverse stroke of the starter pedal is provided by a spring.
Application today
Stationary engines UD-15 were widely used on various agricultural machinery, for example, on the MTZ-05 motoblock. In addition to Ulyanovsk, motors were assembled at factories in Petropavlovsk (Kazakh SSR) under the designation PD or SK and in Kherson under the SM index.
Currently, engines are widely used on home-made equipment - tractors and motor boats. In the photo below - a homemade walk-behind tractor.
Reviews about the UD-15 engine are mostly positive. One of the main conditions for the trouble-free operation of the engine is timely and regular maintenance with cleaning the engine edges from dirt. The only drawback is the lack of high-quality spare parts, so many engine instances are disassembled into donor parts.