1965 Honda RA272E 1.5-litre V12
1965 Honda RA272E 1.5-litre V12: For the new 1961 1.5-litre formula1 only Honda and Ferrari raced a V12 engine during that formula. Honda produced a strikingly transversely placed cylinders 60 degree V12 engine. The east-west layout incorporated the complete power train as an integrated package.
The engine cam-drive gearing was completely of the gearing to the transverse transmission. This drive was taken from a spur gear at center of crankshaft, which made it into 2 short stiff vee-sixes as far as the crankshaft was concerned. At a reduction of 1.85:1 it drove a short transverse shaft, from which 2 skew gears drove shafts going downwards to the gear-type oil scavenge pumps mounted in the sump.
From the transverse shaft another gear pair drove yet another east-west shaft, this long shaft was driven at a further reduction of 1.21:1, so this shaft turned at 44.7% of engine speed. On the right end of this shaft was the multiple-disc clutch that drove the gearbox -2 more transverse shafts- at another reduction of 1.14:1 through a pair of gears that could easily be changed to adjust the overall ratio. On the long shaft’s left end was the engine’s single water pump with twin outlets which delivered coolant directly to passages cast into the block and heads. Coolant outlets went also to a manifold which was integral with the magnesium inlet camshafts covers of both cylinder banks.
Near the center of the long shaft was a spur gear from which drive progressed up to the V12 center of all 4 camshafts. A large idler gear at the center of each cylinder head drove its 2 cam gears, the gearing from the long shaft to these idlers established the necessary half speed ratio for the cams.
From the top of the gear at center of the rearmost exhaust camshaft another gear drove the fuel injection distributor that was used for the developed version of the engine, as used in the 1965 RA272E Honda; it first raced in 1964 as the RA271 with 6 twin-throat downdraught Keihin carburetors. A single central 10mm NGK spark plug was used. Valve inclination from vertical were 30 degrees for the inlets and 35 degrees for the exhausts. 2 conventional coil springs closed each valve, the springs were shrouded in long skirted cup tappets which slid in bolted-in carriers in the head.
Hollow camshafts were made in pieces and joined together inside its central drive gear. 4 narrow needle bearings supported each 3-cylinder camshaft. A single aluminum alloy casting constituted the cylinder head for each 6-cylinder bank. In an unique Honda process the head was cast around chamber roofs made of an aluminum-bronze alloy which bonded to the head material. These formed the complete surface of the pen-roof combustion chamber and provided durable valve seating and spark plug threading. The spark plug recesses were cast open then closed later by inserted cups, a construction which allowed maximum control of the casting cores.
Fully skirted pistons with crescent cutouts for crank counterweight clearance. 2-thin compression rings and 1-oil ring were used. Steel I-section con-rods were used.
One single complex aluminum heavily ribbed casting constituted both the RA272E cylinder block and its gearbox and final drive housing. After installing all gears and reciprocating parts, its bottom was closed by another large aluminum casting that provided a sump for the entire unit. The complete assembly weight was 215kg.
Wet cylinder liners, ribbed around their circumference and sealed at bottom end by O-rings in groves in block. Liners were clamped directly by the cylinder head and 16 studs. Cylinder liner to head gasketing was by mean of sealing rings in grooves in top of liner. The crankcase casting extended down past the crank centerline, which was carried in 7 main bearings. An earlier version had an extra bearing flanking the central drive take-off gear. All the bearings used were rollers bearings, so the RA272E bottom end only required low-pressure lubrication to the main bearing, which then distributed overflow oil to the rollers big-ends through slinger rings. A build-up crankshaft was used.
Stroke/bore ratio 0.81:1.
Compression ratio 10.5:1.
Con-rod length 119mm.
Rod/crank radius ratio 5.1:1.
Main bearing journal (center) 40mm, the next 2-outwards 36mm, the next 2-33mm, the outermost mains 30mm.
Con-rod journals were similarly like the mains, with the outer 4-27mm, the inner 2-32mm.
Inlet valve 24mm.
Exhaust valve 22mm.
Inlet valve lift 7mm.
Exhaust valve lift 6mm.
Valve timing at 1mm lift:
Inlet opens 30 degrees BTDC.
Inlet closes 40 degrees ABDC.
Exhaust opens 30 degrees BBDC.
Exhaust closes 30 degrees ATDC.
Inlet pressure 1Atm.
Peak power 230BHP@12000RPM.
Piston speed corrected 20.6m/s.
Peak torque 157Nm@11000RPM.
Peak bmep 192psi.
This engine holds the record for using the smallest cylinder diameter with a 4 valve combustion chamber (58.1mm). While the 1951 BRM type15 V16 holds the record for using the smallest cylinder diameter ever in F1 (49.5mm).
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