Transcript Document
Tomislav Skračić, MA Undergraduate English Course for MARINE ENGINEERS 3nd Semester Essential reading: SPINČIĆ, A., PRITCHARD, B., An English Textbook For Marine Engineers 2., Pomorski fakultet, Rijeka 2009. LUZER, J., SPINČIĆ, A., Gramatička vježbenica engleskog jezika za pomorce, Pomorski fakultet, Rijeka 2003. Lesson 3 – Connecting Rods Lesson 3 Connecting Rods KEY WORDS piston rod - klipnjača, stapajica connecting rod - ojnica: kod crosshead engine gdje su povezani piston rod → crosshead → connecting rod → crankshaft connecting rod - klipnjača, stapajica: kod trunk piston engine gdje je njome direktno povezan piston → crankshaft crosshead (n.) - križna glava in essence - u biti, u suštini thrust (n.) - potisak, poriv channel section - U-profil I-section - I-profil "marine" type design - ojnica s "brodskom" izvedbom donje glave, tj. ležaj u dvodjelnom kućištu pričvršćenom za petu ojnice fixed centre design - ojnica s fiksnim središtem Lesson 3 Connecting Rods KEY WORDS "crankpin end" - glava letećeg ležaja = big end bearing bolted - spojen vijcima rod shank - tijelo ojnice rod foot - peta ojnice distant piece - podloška, distancioni element (npr. "shim") shim (n.) - podložna pločica, podložak za reguliranje zračnosti top dead centre (TDC) - gornja mrtva točka (GMT) thickness (n.) - debljina compression ratio - omjer kompresije clearance (n.) - zračnost, razmak piston (n.) - klip, stap trunk piston - klip (s produženim plaštem kod motora bez križne glave) Lesson 3 Connecting Rods KEY WORDS bearing metal groove (n.) bush (n.) bushing (n.) interference (n) fit (n.) fit (v.) rod eye bored bore (n.) - ležajni metal - žlijeb, utor, kanal - klipna očica, stapna očica, bukola - rupa, otvor za osovinicu. "Bolcen" ulazi u bushing. - rupice koje se nalaze i na bukoli i na osovinici moraju se poklopiti radi podmazivanja - pristajanje, prijanjanje - postaviti, podesiti, ugraditi "it fits perfectly" - oko ojnice - izdubljen… - provrt, otvor, kalibar Lesson 3 Connecting Rods The connecting rod connects the crankshaft directly to the piston or, as in some other designs, to the crosshead. It is a running component connecting the crankshaft to the piston (in trunk piston engines) or to the crosshead (in crosshead engines). It has both linear (reciprocating, up-and-down) and rotational (rotary) motion. Connecting Rods The connecting rod does this important task of converting reciprocating motion of the piston into rotary motion of the crankshaft. It consists of an upper forked section which fits on the crosshead bearings while the lower part fits on the crankpin bearing. Connecting Rods 1. DEFINITION A running component connecting the crankshaft to the piston (in trunk piston engines) or to the crosshead (in crosshead engines). It has both linear (reciprocating, up-and-down) and rotational (rotary) motion. 2. FUNCTION Primary function: to transmit the push (pressure, thrust) of the piston to the crankshaft, either directly or indirectly. Secondary function: (in most designs) to convey cooling oil to the pistons which demands for a quite a large diameter passage. Connecting Rods TYPES a) Marine type: The large end bearing is seperate from the rod which has a palm end (T-shaped end) b) Fixed centre design: The upper half of the crankpin box makes part of of the connecting rod. c) Fork and blade type: Vee engine connecting rods. d) Articular type: Vee engine connecting rods. Types of Connecting Rods – MARINE DESIGN In the marine type design the rod large end, called “crankpin end”, consists of a separate bearing housing (or box) divided in two parts, bolted to a foot on the rod shank. A distance piece, known as compression plate or shim, is interposed between the foot and the box to permit the piston to be moved nearer to or farther from the cylinder head at top dead centre. Its thickness is chosen so as to ensure correct compression ratio. Types of Connecting Rods – MARINE DESIGN Types of Connecting Rods – MARINE DESIGN Types of Connecting Rods – FIXED CENTRE The simpler construction of the fixed centre rod does not have this adjustment and relies on accuracy to ensure correct clearances. With a few exceptions medium speed diesel engines have trunk pistons with the result that pistons and connecting rods have to be fitted together before being assembled into the cylinder. The methods of assembly and overhaul tend to influence the design of the large end. Connecting Rods Exercise 1 – Complete the sentences: The connecting rod does the important task of ____________ . It consists of an upper forked section which fits on ____________ while the lower part fits on ____________ . Connecting Rods Exercise 2 – Complete the sentences: The connecting rod connects the crankshaft directly ____________ or, as in some other designs, to ____________ . It connects the crankshaft to the piston (in ____________ piston engines) or to the crosshead (in ____________ engines). It has two motions: ____________ (reciprocating, up-and-down) and _____________ motion. Connecting Rods Exercise 3 – Complete the sentences: In the marine type design the rod large end, called “crankpin end”, consists of a ____________ divided in two parts, bolted to a foot on the rod shank. A distance piece, known as ____________ or shim, is interposed between the ____________ and the box to ____________ the piston to be moved nearer to or farther from the cylinder head at ____________. Its thickness is chosen so as to ensure correct compression ____________. Connecting Rods Exercise 4 – Complete the sentences: The simpler construction of the fixed centre rod does not have this adjustment and relies on accuracy to ensure ____________ . With a few exceptions medium speed diesel engines have trunk pistons with the result that pistons and connecting rods have to be fitted together before ____________ . The methods of assembly and ____________ tend to influence the design of the large end. Connecting Rods Exercise 5 – Complete the sentences: The primary function of the connecting rod is to transmit _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ , either directly or indirectly. Its secondary function is to _ _ _ _ _ _ _ _ _ _ _ _ , which demands for a quite a large ____________ passage.