UD is an abbreviation for stationary engines

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

Starting from the 50s, the USSR produced stationary engines, which were widely used in civil and military fields. The key developer and manufacturer of such engines was a motor plant in the city of Ulyanovsk. According to the name of the plant, all engines had the UD index - this meant an abbreviation for the Ulyanovsk engine, and for the method of starting from a foot starter - “Top-top”.

General data

The first production models of UD engines were equipped with a lower valve timing scheme. Such a scheme ensured the simplicity of the engine design, but did not have reserves for modernization. At the end of the 60s, a family of engines appeared in the production program of the plant based on the units of serial ZAZ-966 engines from the cars of the Kommunar plant. The family included two units:

1. Engine UD-15 with one cylinder.
2. Motor UD-25 with two cylinders.

Both engines were forced air-cooled and overhead valves. In fact, the UD-25 engine was half of the standard Zaporozhets engine. The technical documentation indicates the power of 12 horsepower. It should be noted that the powermotors UD - these are the values for long-term operation. This is an important point in identification.

Currently, the production of both types - the UD-25 and UD-15 engines has been discontinued. They can be purchased at sales of decommissioned military equipment complete with various units. The most common stationary installation with a UD engine is a generator station. The photo below shows just such a design - the AB-4 army generator.

Electric start version

Modification of UD-25G, equipped with a cast transition crankcase. On one side, the crankcase was attached to the engine housing, and a generator was installed on the other side. There was a landing hole on the transition crankcase for the ST-351B electric starter. The starter was powered by a 12-volt battery, which was installed on a special pallet. The engine flywheel was equipped with a ring gear and a special disconnecting clutch. The photo clearly shows the crankcase of the flywheel of the UD-25G engine.

Optionally, these engines were equipped with a sealed and shielded ignition system. Thanks to this improvement, the system worked smoothly in the rain and did not create radio interference. The weight of the UD-25G engine was 66 kg.

Reduced motor

UD-25S version, equipped with RO-2 gearbox. The crankcase of a single-stage gearbox was directly on the engine. The gearbox lowered the speed by more than two times. Such a unit has been widely used to drive variousmechanisms that required a reduced speed for operation.

Among such devices were various centrifugal pumps, compressors, railcars, road and agricultural machinery. The weight of the geared UD-25S is 61 kg.

Gearbox Service

The UD gear motor is a rather highly loaded unit, which is not recommended to be operated at minimum speed. The reason lies in the centrifugal clutch, which starts working only after 1,000 revolutions. Up to this point, slippage of the clutch frictions occurs, leading to their premature wear. The maximum speed of UD is 3,000 per minute. It is at this speed that the speed controller is set at the factory. The photo in the article shows the nameplate of the UD-25 engine.

The engine gearbox needs a constant check of the oil level, which must be carried out every 100 hours of operation. The oil should be changed every 400 hours. It is better to drain hot oil, so this work is done immediately after the engine stops.

Other engine options

The UD-25 engines and their modifications were produced by a number of enterprises in the republics of the USSR:

• In the Kazakh SSR, in the city of Petropavlovsk, there was a plant that produced units under the designations PD or SK.
• In the Ukrainian SSR in the city of Kharkov, the production of similar motors under the index SM.

These motors were used on a par with the Ulyanovsk power units and had similarmodifications. In the photo in the article you can see a generator set with a UD-25 engine.

Repair and maintenance

The UD-25 engine is capable of running on any type of gasoline with an octane rating ranging from 70 to 76. The design of the engine allows the use of leaded gasoline. To lubricate the engine, depending on the ambient temperature, it is necessary to use winter or summer grades of oil. Neglecting the type of oil leads to insufficient lubrication of the components and engine failure.

Before each engine start, the oil level in the crankcase should be checked and topped up in a timely manner. When operating the engine, it is necessary to carry out a set of service works every 100 and 200 hours. Minor maintenance requires cleaning the spark plugs and lubricating the magneto and kickstart ratchet assemblies.

Major maintenance of the UD-25 engine involves removing the cylinder head and checking the tightness of the valves. At the same time, the condition of the rings and cylinder mirrors is checked, the absence of backlash in the piston pins. The combustion chambers are cleaned of possible deposits and the oil in the crankcase is changed. In this material, you can consider the UD-25 engine from above.

During the operation of the motor, it is necessary to control the clearance in the valve drive mechanism every 100 hours of operation, which should not exceed 0.2 mm. The check is carried out with a probe on a cold engine.

When the cylinder mirrors wear out, they are not polished, but changedentirely. One of the features of the repair of the UD-25 engine is the correct installation of valve lifters. One of them has a through channel inside, which serves to supply oil to the valve box. When installing, this tappet must be fourth from the flywheel.