Design and operation of the planetary mechanism (PMP) DT-75M

Construction of components and assemblies of the chassis of the DT-75m tractor

CONTENT

• Introduction

DT-75 (75M,RV,N,D,E) is a general-purpose tracked agricultural tractor. The most popular caterpillar tractor in the USSR. In 2008, the Volgograd Tractor Plant celebrated the 45th anniversary of the launch of the DT-75. The tractor has gained a good reputation due to its successful combination of good performance properties (simplicity, efficiency, maintainability) and low cost compared to other tractors of a similar class. Over such a long period of time, the DT-75 was modernized several times: it was modified externally and internally, usually for the better. As of 2009, more than 2,741,000 units of tractors were manufactured. In August 2009, another modernization of the tractor rolled off the plant assembly line. The restyled tractor is equipped with a new cabin and a plastic hood, a new economical and environmentally friendly Finnish Sisu engine, the production of which was launched at the Vladimir Tractor and Motor Plant. It has a new index VT-90V (Trade name “Agromash 90 TG”). The signature color of the tractor has changed from red to blue-gray with orange color inserts. The production of the previous obsolete design DT-75DE is still ongoing. An industrial modification of the DT-75 tractor is the T-90 tractor, which differs from the base model in the presence of support hinges for hanging the front blade and front hydraulic cylinders for controlling it. In addition, the T-90 has different transmission ratios.

• Purpose, design and principle of operation of the chassis of the DT-75m tractor

The DT-75 tractor is designed to perform agricultural, road, construction, reclamation, loading and unloading and transport work. It is used in agriculture and forestry, peat mining and land reclamation in conjunction with various machines and implements. Depending on the configuration, the DT-75 tractor has the following modification:

DT-75N with SMD-18N engine

DT-75D with A-41 engine (D-440-22)

DT-75RM with RM-120 engine

hydraulic control and drive system

rear linkage

single-speed power take-off shaft (540 rpm or 1000 rpm)

front removable ballast weights.

Tractor suspension carriage DT-75

Purpose of components and assemblies of the DT-75m chassis

The clutch is dry, double-disc, permanently closed. The gearbox and rear axle are mounted in one housing. The rear axle has two single-stage planetary rotation mechanisms with band brakes, providing reliable braking of the tractor both in forward and reverse. The planetary mechanism allows you to reduce the effort on the tractor turning control levers. The chassis consists of drive and guide wheels, support rollers with rubber bands, four balance suspension carriages and two track chains.

Construction of components and assemblies of the chassis of the DT-75m tractor

Initially, the tractor was equipped with a closed automobile type cab, all-metal, two-seater, sealed, unified with the cab of the GAZ-51 car. The seat is adjustable according to the weight and height of the driver. The DT 75M tractor had a cabin with a deeper stamping of the cabin ceiling (the height above the driver’s head was increased) and control levers bent towards the tractor driver. Since 1978, the tractor has been equipped with a new sprung cab and tail.

To improve visibility, the cabin of the new model is shifted to the right of the tractor axis, and the fuel tank of increased capacity is located on the left side of the cabin. However, many operators were unhappy with the new panoramic cab.

Interesting fact: although the new cabin is more comfortable than the old one, a tractor with a new cabin cannot cultivate the soil under tree canopies (the height of the cabin interferes). As a result, the plant began to receive letters from consumers asking them to return the car-type cab.

Operating principle of the DT-75m tractor chassis

To support the tractor on rollers that roll along the caterpillar, the DT-75 suspension is used. It is elastic and has excellent balance, due to which the tractor moves smoothly, even when mounted implements are used. Each DT-75 suspension carriage (there are four in total) has the same design and is mounted on axles - two carriages on each side.

Each of these carriages, which plays an important role in the DT-75 chassis, is a bogie composed of internal and external balancers, which are connected to each other by a swing axis. The support rollers are installed in pairs at the lower ends of the balancers, while at the top of the balancers a cylindrical spring spring is pushed apart.

To change the direction of movement of the running caterpillar branch, a DT-75 guide wheel is used. It also prevents the track chain from losing tension. The wheel is mounted at the front of the tractor on two tapered roller bearings, which are pressed from the lower end onto the crank axle.

The DT-75 tensioning mechanism regulates the tension of the tracks. This device is composed of a bracket, a coupling bolt, a flange and a nut. The front bracket connects the mechanism to the crankshaft.

Each DT-75 support roller (there are also four of them) guides the track with the help of rims and does not allow it to sag. There are two such rollers installed on each side of the tractor.

The DT-75 track consists of links that articulately connect the fingers. Inserted into the link eye holes, the pins are held on the outside by stamped heads that prevent them from falling out. From the inside, the fingers hold cotter pins and washers. Each track is a complex steel casting with seven lugs grouped on each side: three on the outside, four on the inside. The center outer eye is a thick lantern that is used to engage the link with the teeth of the drive wheel.

Tractor gearbox

As in the original model, the DT-75M is equipped with a similar seven-speed transmission, which is quite unpretentious in operation.

Transmission DT-75M

The DT-75M gearbox is a four-way, 7-speed gearbox. It is possible to retrofit the box:

• reverse gear;
• creeper.

The tractor box mechanism operates on constant mesh gears. The gearbox used in the design allows the tractor to reach speeds of up to 9.3 km/h. The minimum possible speed of movement of the tractor is 0.34 km/h, which can be achieved by installing an optional creeper. It also increases the maximum speed of the tractor to 11.49 kilometers per hour.

Not available: