This is the engine I was thinking of earlier, conceived by the, alas, now defunct Saab. Interesting Engines: Saab’s Variable Compression Engine – Spannerhead A much simpler design that the Nissan with, I'd have thought, real potential.
It's another way of doing it, sure. But moving the entire cylinder head and barrel assembly (including the camshaft drives, induction and exhaust connections, cooling and lubrication systems) with respect to the crankcase does not look simple to me. It introduces a host of complications which the Nissan patent avoids. In the 1950s there was a tiny cyclemotor engine, the Lohman, which had variable compression ratio by means of a junkhead which could be screwed in or out on a quick thread, controlled by cable from the handlebars. This system would not scale up satisfactorily to a full-size engine.
I can see that there would be complications in the drive to the camshafts. It sounds like a model aero engine with a cable operated contra-piston. I'm not surprised it couldn't be scaled up.
The Deltic was a great marine and rail engine of the 1940s/50s, but it never featured variable compression ratios.
Again, the Jumo/Gemini layout has some advantages, but variable compression ratio is not among them. And that is (or was) the subject under discussion here. If you find unusual engines amusing, go to Douglas Self's Museum site and fill your boots: Unusual Internal-Combustion Engines for Autos etc.....rates refinancing
By the way, this Atkinson patent design from 1887 provides not only for a variable compression ratio but for the expansion stroke to be longer than the compression stroke (sic). Who would have thought that was even possible?
See also "Some Unusual Engines" by LJK Setright. Remember him @Pete1950 ? It seems my copy might be quite valuable now.
I never spoke to him but he lived on the same road as me in 1970 - Wensleydale Road, Hampton on Thames. He could often be seen typing away of an evening in his study, which faced the road. His Missus used to drive the family Bristol with some verve...
I believe it was originally designed to drive propellers on airships - a very weird engine. Whoever came up with three crankshafts, onw rotating the opposite way to the other two, and no cylinder heads had a very strange sense of humour !
I knew a guy who bought a nato patrol boat with two of these things in it, each of which produced a lot more power than the version which powered a Deltic locomotive. Sadly he never did get the engines to start and ended up flogging them to a railway society.
I reckon that Duke engine idea came partly from variable swash plate pumps where you could alter pump flow by varying the angle of the swash plate. Used to have them on some GTs very neat piece of engineering IMHO Could have it wrong but I thought the Deltic had its origins in the Jumo 205, which was developed for the JU-86P It's 2 stroke Diesel, it was then redesigned into the Deltic by Napier for marine use My opposite number on a Deltic experience day, apologies for my crap photography and the video is way too long, it was made to give to the guy driving as memento Apologies having spent a good deal of my life trying to understand what was going on inside Gas Turbines, engine design and all the variations fascinate me...................I'm convinced that's why the missus fell for me :Angelic:
If you think the Deltic is weird how about this? A 3 cylinder 2-stroke with 3 crankshafts and no cylinder heads! More here: Michel Opposed Piston Diesel Engines Sorry for taking this off topic from Variable compression engines to weird engines>
