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Posted: Jul 24 2012, 03:03 PM
11% Armaments Designer
Member No.: 1,377
Joined: 24-July 12
Every one to stand out from the crowd, Diamond Star engines used in their commercial and marine applications, such as trucks, small boats and trains utilise SLEEVE VALVES rather than poppet valves operated by a cam shaft or rockers.
The basic layout of the engine is a V12, consisting of 12 individual cylinder sub assemblies bolted onto a common crank case. Atop the blocks are 12 individual dead heads, (so called because the engine has no working parts in the cylinder head, they are simply drilled out for the fuel injector).
Inside the each block there are 6 sleeves and 6 pistons. In the crank case there are 3 cranks. The main central crank has the connecting rods for the 12 pistons which move up and down like a regular V12 engine. The second and third cranks are what drive the sleeves. These sleeves, via individual bevel gears by each piston. To line up with the exhaust and intake ports, rotation is at top and bottom dead centre.
The sleeves are drilled in 4 places, these line up with ports drilled out in the cylinder walls of the block. The intakes being in the valley of the V, the exhausts being on the outside of the V.
Each head is machined to have fins which increase surface area of the block, allowing better transfer of heat into the air. The front of the block has a high pressure oil driven fan which draws air in and across the valley of the V between the blocks, whilst a cover goes over this portion, creating an airbox. As the Airbox is blocked off at the rear, air can only leave through the gaps between individual cylinders. Similar in the Air cooled engines made by Tatra and Magirus Deutz.
Maintenance : When major engine work is required, cylinder, piston etc., its is possible to remove a single complete cylinder assembly without engine removal or even removing the engine sump or oil. A 12 cylinder engine can undergo a top end rebuild over 12 daily down time sessions ( 1 cylinder per day ) and go to work each day, rather than be taken off the road for complete engine removal, rebuild and replacement. This is a particularly useful facility for emergency and military use. The modular construction of the engine drastically reduces the number of spares which need to be held. As the piston heads have rings, each individual head can be checked during this time, allowing rings to be replaced as needed.
Each bank of cylinders has its own exhaust, this exhaust flows through the drive stage of a turbocharger. These turbochargers are coupled to the intake , allowing air that has passed through the air filter modules at the back of the cab to be then forced into the intake manifolds. This set up also has a hydrostatic coupling between the engine flywheel and the turbocharger, allowing it to be spooled up before the exhaust has generated sufficient pressure to get the turbine section of the turbocharger spinning, this makes for a more respomsive turbo by reducing turbo lag
The front of the engine is home to the alternator and compressor unit, these are driven by a V-belt assembly. Being air cooled, there is no requirement for a water pump or radiator, this makes for a simpler engine. With the engine not having any rocker heads, the lubrication requirement is much reduced, the oil pump is situated within the sump assembly. Oil filters are situated to the left hand side of the sump.
To transfer heat into the cabin heating system, with no water circuit, the oil is used, with a small radiator type heat exchanger situated in the heater matrix. Oil is pumped here from the sump by the gear driven oil pump.
maximum power 750bhp from the 17.2 going to 1000 for the 24 litre, with peak power being at around 1500RPM, with the never exceed engine speed being 2500RPM.
Back in the 1940s, these engines were developed, though only had 5 years of serious development, Poppet valves had had up to now 112 years of development. and given MODERN materials, these engines could be developed to a high degree of reliability to rival standard piston engines.
as for the ports sealing, they would have no worse sealing issues than a Detroit 12V71 or similar, a 2 stroke diesel engine.