3.9. Pistons and rods
The basic sizes of the piston, rod, piston finger and piston rings
The piston is made of an aluminium alloy and covered by a layer of tin for improvement прирабатываемости. A piston skirt in cross-section section oval, and on height the conic. Therefore to measure diameter of the piston it is necessary only in a plane, perpendicular for a piston finger and on distance of 52,4 mm from the piston bottom.
The aperture under a piston finger is displaced from a symmetry axis on 2 mm in the right party of the engine. Therefore for correct installation of the piston in the cylinder about an aperture under a piston finger there is a label «П» which should be turned towards a forward part of the engine.
Pistons of the repair sizes since 1986 for all models of engines are made about the increased on 0,4 and 0,8 mm in external diameter. Till 1986 pistons of next repair sizes were issued: for engines 2101 – with increase at 0,2, 0,4 and 0,6 mm; for 21011 – with increase at 0,4 and 0,7 mm.
Piston rings are made of pig-iron. The external surface top компрессионного rings is chromeplated and has бочкообразную the form. Bottom компрессионное a ring – scraper type (with выточной on an external surface), фосфатированное. The maslosemnoe ring has cuts for oil removed from the cylinder and an internal twisted spring (dilator).
Piston finger – steel, tubular section, запрессован in the top head of a rod and it is free врашается in piston lugs.
Rod – steel, shod, with a demountable bottom head in which loose leaves шатунного the bearing are established. The rod is processed together with a cover, therefore at figure assemblage on a rod and a cover should be identical.