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Last, best estimate

Writers Aviation posted on Jul 19, 2017
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Description


Now that I have run off into the exotic expansion of the internal combustion engine I would like to simply present a Rolls-Royce Merlin. I make no claim it is a Packard licensed version. I also make no claim it has two overlapping superchargers for high altitude use where it truly shown. I, myself, like to examine things like how the connecting rods were joined to the crankshaft where the lack of stagger between the banks meant both rods from a cross section of the Vee wanted to join a single crank throw at the same place. The Allison solved this with knife and fork like a Harley Vee twin. This Merlin solved it with one rod directly on the crankpin and the other running on a sleeve projecting out of the first rod. The big ends were thus concentric not like on a radial engine master rod. The Merlin also cross bolted the main bearing caps for the crankshaft into the sides of the block of the crankcase thus achieving a rigidity used later in NASCAR by Ford. My Hurricane model render on Renderosity has no internal modelling to avoid some issues. The red color? You tell me! I am not aware of anyone using Rootes or screw type compressors for superchargers on high performance aircraft in WW-II and the Farman 2 speed mechanism as well as the overlay of two stages on the Packard-Merlin was a means of avoiding overpressure at takeoff and climb while delivering thin high-altitude air to the carburetor. For a large Rootes type blower in before WW-II, look into the Auto-Union Grand Prix car. For turbocharger see P-47 “Thunderbolt” and B-17. The Merlin displacement was slightly smaller than the Allison v-12 of the same era. I won’t quote it as I have seen 1640 as well as 1650 cubic inches. About 26.9 liters is a good place to look. Twenty-eight liters is the Allison. The operating rpm is an issue for the two engines where the propeller reduction gearing was once a Cleveland air races question. Direct drive was the use on the prototype Hurricane with a two-bladed propeller. As speeds got up to 3000 or even 3300 rpm even a propeller governor and variable pitch was not enough to allow direct drive. This write up is made long after I used Von Mises book to design my own kit plane and mathematically explored all these issues with the formulas in that book including the use of pure hexane for fuel. I used Mathcad and the NASA recommended gaCAD for these calculations. Symbolic logic converted to calculations is easier that was than with a TI-83 or TI-84 graphing calculator with the TI-84 being able to do airfoil estimate of cambered and cusped airfoils used in the 1930’s and in gas turbines today.

Comments (1)


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Richardphotos

8:11PM | Mon, 24 July 2017

they restored the exterior, but I wonder about the internal workings. very good clarity


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Photograph Details
F Numberf/3.5
MakeNIKON CORPORATION
ModelNIKON D3200
Shutter Speed1/60
ISO Speed800
Focal Length18

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