Walter Minor
The Walter Minor was a piston engine for general aviation by Czech manufacturer Walter Engines AS. The OHV engine was produced as a four-cylinder Walter Minor 4 - III and as a six- cylinder Walter Minor 6- III and found wide use. During the production of the four-cylinder version was set in 1960 in favor of the successor of Walter M332, the production of the Minor 6- III at least until 1972 ran on, where it was installed in the first copies of the Zlin Z -526. Him then took over from the Walter M337.
The development of the engine began in 1929. Starting from 1930 the series production of the engines was taken, whose main design feature was the hanging cylinder with air cooling. The steel cylinders were rotated together with the cooling fins of solid material. The surfaces were nitrided. Had the cast of an aluminum alloy cylinder heads, in addition to bores for the two spark plugs, each one inlet and an exhaust valve made of steel, which have been controlled by means of push rods and rocker arms. The cylinder with the cylinder heads were mounted with four bolts on the crankcase. The aluminum pistons had three compression and one oil scraper ring. The connecting rods had a double - T- profile and consisted of polished aluminum. The big ends were split and had a bronze bearings in a steel shell. The forged and fully machined crankshaft consisted of a chrome - vanadium steel alloy and was stored for five or seven times in bronze bearings. The propeller thrust forces were recorded by a radial ball bearing in the front of the crankcase. This was designed in three parts and consisted of the actual crankcase as well as an upper and a front cover, all of which were made of a thermoset magnesium alloy. It was the crankshaft and on the left driven by spur gears camshaft. Developed by Walter himself carburetor had a manual mixture control, a cold-start device and an accelerator pump and was suitable for aerobatics, including a special nozzle for the flight back was. The Minor 6- III had two carburetors. The supply was secured by a diaphragm fuel pump. For the ignition two fully shielded systems of scintillation were used which had an automatic ignition advance. The lubrication was carried out by a dry sump recirculation system, for which a gear pump with suction and pressure level behind made on the crankshaft. Lubrication could be modified for aerobatics operation. The propeller was driven directly.
For attachment to the airframe two motor mount, for the two suspension points were present on every page served. The engine is started by either a manual or an electric starter.
The Minor 4 - III was the drive for the built under the name of Zlin Z -381 last version of the Bücker Bu 181, approved by the several pieces after 1955 in Germany.