Production years: 1989–? The first six "Don-1500" grain combines built at the "Rostselmash" plant arrived at Keila railway station on 15 June 1987, and by autumn 1988 more than a hundred were already working on Estonian fields. The "Don-1500" was undoubtedly a big leap in quality for the so-called domestic combine industry, and just like the "Yenisei 1200-N" combine, which first worked on our fields in autumn 1986, the "Don" was usually compared with the SK-5 "Niva", the most common combine here at the time. Let's look at the features of the "Don-1500" assembly by assembly: Header. The combine has a 6-metre header. Instead of the crank and connecting rod knife drive familiar from earlier combines, the "Don-1500" used a so-called wobble plate mechanism (as on the East German E 280 self-propelled forage harvester). Compared with the "Niva", the reel is also sturdier, especially its central shaft. To clear blockages, the feeder conveyor transmission and the twin auger can be run in reverse. For road travel the combine comes with a trailer for transporting the header. Setting the header into working or transport position was, however, considered rather awkward and time-consuming here compared with the East German "Fortschritt" E 516B combine introduced a few years earlier. In practice the build quality and reliability of the header made at the Tula plant proved unsatisfactory. Nor did the combine and the header, made at different plants, always arrive at the farm at the same time, so quite a few "Don-1500"s initially worked with the header of an SK-6 "Kolos" combine. The thresher follows the usual layout and is in many respects similar to that of the "Niva". It is 1500 mm wide, and the 10-bar threshing drum is 800 mm in diameter. A single-section concave (wrap angle 130 degrees) is used. There is no feed beater in front of the drum, and the straw beater has six blades. Partly threshed heads pass through a re-thresher similar in design to that of the "Yenisei 1200-N". The straw walker consists of five walkers, each with seven steps. Compared with the "Niva", the crank radius of the walker crankshafts was increased from 50 to 60 millimetres, which promotes more intensive separation of the straw mass. The walkers are 482 mm longer than those of the "Niva". The separating areas are noticeably larger than on the "Niva": whereas the "Niva" has 4.2 and 2.1 square metres of walker and cleaning shoe area respectively, the "Don-1500" has 5.74 and 3.9. To reduce grain losses, the grain and tailings auger housing is made as a single assembly. The grain tank is twice the size of the "Niva"'s (6 cubic metres), and the unloading auger turns almost two and a half times faster, so emptying the tank takes relatively little time. The unloading auger drive and moving it into working and transport position are controlled electro-hydraulically. Hydraulic vibrators at the bottom of the grain tank ensure fast and thorough emptying. The straw collector is similar in design and operation to that of the "Niva", but one and a half times larger (9 and 14 cubic metres respectively). When the straw collector is full, the operator is alerted by a sound and light signal. If the operator does not notice, the straw collector empties automatically. The hydrostatic transmission allows smooth travel both in the field and when turning. A three-speed gearbox is also used, giving three ranges: 1st gear 0–5 km/h, 2nd gear 0–10 km/h and 3rd gear 0–20 km/h. The same speeds are available in reverse. The combine has low-pressure tyres, 30.5-32 on the drive wheels and 18.4-24 on the steered wheels. Cab. The comfortable, quiet, air-conditioned cab of the "Don-1500" with its wide view gave the operator very good working conditions compared with earlier combines, especially the "Niva" (though not compared with modern combines made by "Western" firms). An electronic monitoring system checks the operation of 19 assemblies. The operator is alerted by sound and light signals if the threshing drum deviates from its nominal speed. In addition, several operations, such as unloading the grain tank, changing the drum speed and the grain tank vibrator, are controlled electro-hydraulically. If grain losses from either the straw walker or the cleaning shoe exceed the permitted limit, the operator is also alerted by a sound and light signal. Engine. The combine has an SMD-31A diesel engine with 162 kW (220 hp). In practice, however, the introduction of the "Don-1500" did not go smoothly on every farm: there were many of the design and manufacturing faults typical of Soviet machinery of the time, and the reliability of the so-called domestic electronics left much to be desired. The first series-built "Don-1500" combines left the factory in 1986; around the turn of the decade it was replaced by the slightly improved "Don-1500A", which eliminated the main shortcomings of the earlier model. Deliveries of these combines to Estonia stopped with the change of regime and the transition to a market economy in the early 1990s. About ten years later, in 2003, OÜ "Flint Kaubandus" in Kõo, Viljandi County, began importing and selling the "Don-1500B", a further development of the old Dons. Today "Don-1500" and "Don-1500A" combines built in the last years of the Soviet Union can still be seen here and there on Estonian fields in autumn, but their number is falling year by year. One of them stands at the Järva-Jaani Old Tech Park as a reminder of a stage in the history of our farm mechanisation that is coming to an end.