One of the largest manufacturers of tractors in the USSR and in modern Russia is Vladimir motor-tractor plant (vmtz). The most famous model of the plant was a small wheeled tractor T 25, which was manufactured from 1966 to 2000. During this time, through the gates of the plant were more than 800 thousand cars.
T 25 and its modifications are equipped with two-cylinder diesel engine D 21. The engine was developed by designers vmtz as part of a family of engines, which includes three-, four - and six-cylinder diesel engines. Engine specifications D 21 is quite consistent with the requirements of a tractor of this class requirements. All versions were equipped with air cooling system. General view of the tractor with the engine of D 21 is shown in the photo below.
The Engines were widespread unification in many parts. Was identical to the details cylinder-piston group, camshaft (except the camshaft).
The Main part of the engine of D 21 is a cast iron crankcase (so-called block-Carter), a closed bottom stamped oil pan. Inside the case are three crankshaft main bearing caps and a pair of the supports of the camshaft and balance shafts. To increase the rigidity of the axle bearings of the crankshaft is located above the bottom plane of the block. Inside the unit is made channels for supplying oil from the gear pump to the bearings.
To the rear of the crankcase is attached a cast of the flywheel housing of the engine. In front of the gear motor is located to drive the camshafts and auxiliary units. The gear unit is closed by a removable cover. All major units of the engine installed on the crankcase or casings the front and rear of the motor.
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On the left side of the motor (in the direction of the tractor) is the pump for fuel supply and piping supply of fuel to the pump and to the injectors in the cylinder heads. On the same side are the headers intake and exhaust. On the intake manifold is the glow plug used for preheating of air. Additional heating is used to facilitate engine start at low temperatures.
On the front of the engine located in the neck of the oil filling, the inlet of an axial fan and a counter of hours worked. On the same axis with the fan arranged in the generator. The entire Assembly is secured by a clamp to the cover of the gear unit. The drive is provided by belt drive from the crankshaft. On the pulley shaft there are marks of opposite dead points in the first cylinder (identified as TDC and BDC) and mark the beginning of fuel injection in the first cylinder (label T). Also on the front of the engine D 21 mounted dipstick and a filter system for the filtration of fuel.
On the right side of the motor includes a decompressor that is used to facilitate starting the engine. This mechanism connects the cylinder chamber with the atmosphere and can be used to emergency stop diesel. The same side in the cylinder heads are installed nozzles fuel injection. The cylinders are covered with a casing in which is pumped to the cooling air. At the bottom of the engine closest to the flywheel housing with an electric starter.
On top of the unit there are two holes to set the individual cylinders. The side of each there are a couple of additional holes for the rods tappets.
Cylinders are made of cast iron and is equipped with a mounting flange and eighteen thin cooling fins. Between the ribs there is a gap of 8 mm for the circulation of cooling air. The ribs are asymmetric on the circumference of the form.
The part of the fan rib is shorter, and on the opposite side – long. This is made for more uniform cooling of the cylinder. With front and rear ends of the ribs are made short to reduce mitrinkova distance and the overall length of the motor as a whole. Also on the ribs made the cutouts for the studs.
Because the cylinder material is special abrasion-resistant cast iron, the mirror is made directly on the inner surface. When worn or damaged cylinder just replaced.
Each cylinder of the engine 21 D has an individual head of aluminum in which are located the intake and exhaust valves, the opening of the decompressor and the injector.
Head and cylinder are attached four studs, screwed into the block body. Heads and cylinders are interchangeable. For cooling the head is equipped with eleven ribs. At the top of the head there are guide bushings for valves and studs for the rocker arm shaft of the valve train. In the lower part of the pressed heat-resistant cast iron valve seats.
Inside the head there are channels for the intake and exhaust that go on the left side. To these channels on the studs to fasten the intake and exhaust manifolds.
Pistons of aluminum are in its design the combustion chamber. The camera has a spherical shape and is made in the bottom of the piston.
To ensure reliable operation, the piston has threecompression and two oil scraper rings. In the groove under the oil ring is provided with holes for draining shot rings oil.
The Piston has different diameters along the length to reduce the likelihood of sticking during operation. The upper, more thermally loaded part of the piston has a smaller diameter than the piston skirt. This solution allows to equalize the thermal expansion of parts in the process.
Article in other languages:
AR: https://tostpost.com/ar/cars/6860-d-21.html
BE: https://tostpost.com/be/a-tamab-l/12269-ruhav-k-d-21-kanstrukty-nyya-asabl-vasc.html
DE: https://tostpost.com/de/autos/12271-motor-d-21-konstruktionsmerkmale.html
ES: https://tostpost.com/es/coches/12278-el-motor-d-21-caracter-sticas-constructivas.html
HI: https://tostpost.com/hi/cars/6867-21.html
JA: https://tostpost.com/ja/cars/6865-d21.html
KK: https://tostpost.com/kk/avtomobil-der/12272-oz-alt-ysh-d-21-konstruktivt-k-erekshel-kter.html
PL: https://tostpost.com/pl/samochody/12262-silnik-d-21-cechy-konstrukcyjne.html
PT: https://tostpost.com/pt/carros/12258-motor-d-21-caracter-sticas-do-projeto.html
TR: https://tostpost.com/tr/arabalar/12274-motor-d-21-yap-sal-zellikleri.html
UK: https://tostpost.com/uk/avtomob-l/12270-dvigun-d-21-konstruktivn-osoblivost.html
Alin Trodden - author of the article, editor
"Hi, I'm Alin Trodden. I write texts, read books, and look for impressions. And I'm not bad at telling you about it. I am always happy to participate in interesting projects."
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