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Tile minim~~m oil film thickness in a dynamically loaded cone n d bearing of a high-speed, fuel injected, 2.8 litre, V-6 nec1ivt.g-ro(1, big-end bearing of a /ti$-speed gasoline engine has (60") gasoline engine; bore a n d stroke were 93 r~~m and been studied experimenlolly and tkeoretically. The theoretical cal-68.5 mm whilst was 9.2:1; c~~l r~t i o~~ were cc~rried outfir bolh rigid and elastic bearings. The the engine had a brake l o kW a t 5800 rlmin and a maximum torque o f 216 N.m at 4000 rheoly k (~Lso w~ed to explore the effects on the experimental results rlmin; the crankshaft had four main bearings. ($ (L it~echnnicnl scissor linkage and of l/te assumption that there isT h e big-end bearing shells were ungrooved, their dino rli.slorlion or cavilntioit. Coinpanions are made between the ameter a n d width being 54.0 m m a n d 16.5 m m respectively. llreory I L I I (~ ex/)e?Zment of the effects of cranksitaft speed and lu-The bearing material was copperllead on a steel backing bricc~nt visco.sily.with a ca. 10 p m thick leadltin overlay; the total thickness of the shell was 1.4 mm. Oil was fed to the bearing via a -

Conformational energies have been calculated as functions of the internal rotation angles about the C-C bonds for n-perfluorobutane in the neighbourhood of its trans and gauche conformations, and for polytetrafluoroethylene (FTFE) in the vicinity of its all-trans form. The energy equation consists of a semi-empirical " 6-exp " potential for the interactions between non-bonded atoms, a dipole-dipole interaction term, and a three-fold " intrinsic " torsion potential having a barrier height Eo for each bond undergoing rotation. The various parameters were adjusted to reproduce CONFORMATIONAL ENERGIES OF (CF,), Jernigan and Flory,lo and Scott and Scl~eraga,~~ for example, provide detailed information about the intramolecular energies of polymethylene and the lower n-alkanes. Iwasaki,ll De Santis, Giglio, Liquori and Ripamonti,12 and McCullough and Mchlahon l 3 calculated intramolecular energies of PTFE as a function of rotation angle about the CF,-CF2 bonds. The effect of varying the parameters in the semiempirical expressions was not investigated, however, nor were energies calculated in the vicinity of the gauche minima of n-perfluorobutane. McCullough and McMahon l 3 and De Santis and co-workers l2 considered. contributions to the intramolecular energy from attractive and repulsive interactions between non-bonded atom pairs, while Iwasaki l1 included an additional contribution from dipole-dipole interactions between the C-F bonds. The inclusion of this latter term would seem to be desirable and has been taken into account in the present calculations. In the earlier calculations,ll-l the ecergy equations did not include a contribution from an intrinsic torsion-potential term. The effect of including such a term in the semiempirical energy expression for the perfluoroalkanes should be investigated, in view of its importance in the expressions for the n-alkane~.~. 4* 6-10 INTRAMOLECULAR ENERGY