Pretty sure you’re right, although my brain had to churn on the problem for a bit.
As a mental exercise, though, what would it take to make the geometry work? If the V-shaped connecting rod had telescoping ends (rigid in alignment, but variable in length), I think that would be possible. Maybe even if only one arm of the V was telescoping.
I only ask because I’ve seen so many unusual mechanical linkages over the years, like the Scotch Yoke earlier in this thread.
I don’t think you could practically do it, unless you were able to come up with a design which continuously varies the vee angle. variable-length conrods would seem to lead to a lower expansion ratio, which would kill efficiency.
even radial engines have to have a “master” connecting rod, which the rest of them connect to.
Oh, I wasn’t thinking of efficiency, just if the geometry worked. And I wonder if there are other applications that use a telescoping rod with similar properties (total length, min/max length ratio, sideways forces, etc.).
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even radial engines have to have a “master” connecting rod, which the rest of them connect to.
Connected V8 piston rods would produce linear motion where they join assuming they are firing simultaneously and whatever they join to is constrained to linear motion like a compressor piston. I think firing 180 degrees apart would follow some sort of arc. The linear motion could at least power a piston compressor or something like that, not sure if the arc has any value at all. If they weren’t somehow synchronized that joint will be all over the place.
Thanks for the replies…anyway, another question: I saw a proposal made by a British inventor (Heron?) to replace the poppet valves with a rotating sleeve valve at the head, It would rotate to expose the exhaust and intake ports. This looks like a difficult job, but it would save the complexity and act faster than the poppet valves. i haven’t been able to find anything with a Google search.
Sleeve valves were WWII-era tech. See Sleeve valve - Wikipedia
And returning to your OP question, I’d still like to see a picture of what you think the word “opposed” means in the context of engines in a V configuration. As far as I (and IMO everybody else) can determine, V-ness and opposed-ness are impossible to have in the same engine.
I simply took it a meaning cylinders which share a crankpin because they’re in the same position on opposite banks.
You are correct-i only saw a diagram of this engine, quite a while ago.
Should have thought of that. It’s like taking a V pair from a radial engine, and the crankshaft would constrain the rod ends to traveling in a circle. They don’t have to be quite aligned as they would for a fork or offset end, just shift by the width of the rod.
Another question: several american manufacturers experimented with extremely long engines (V-12; V-16). These engines required extremely long crankshafts-did these engines experience crankshaft failures? Metallurgy in the 1930s was not very refined, I imagine the challenge of machining such a long shaft would be a tough nut.
Just guessing here, probably only slightly more problems than with shorter shafts, and only proportional to the increased length. They would have been made heavier and metallurgy wasn’t really primitive at the time either. They may not have had all the alloys and techniques now available, but they could cast quality steel and lathes were accurate enough. The failures would have been primarily from the inability to detect to internal flaws in the metal.
I seem to recall that the Cadillac V-16 in particular did suffer from some odd operating and failure issues from its double-V8 design and long crankshaft.
Most engines converted from one design to another seem to have problems. GM’s V-8 diesels and variable-displacement engines of the 1980s were disasters. The engine in the Porsche 944 (half a 928 V8) is so phenomenally expensive to rebuild that pristine 944/956s are junked out if the engine goes bad. I seem to recall a VW/Porsche flat six that was an extended VW engine, not a true Porsche design, and had issues. The few V-16 engines of the early era were doubled V8s, with problems. About the only successful conversion I can think of is the previously mentioned GM 231 V6, which was 6/8ths of a smallblock V8, and had good enough engineering to survive for more than a decade. I think some owners and most mechanics hated it, though, and there is the infamous issue of the models (designed for GM’s never-born Wankel) in which the engine had to be lifted to change the spark plugs.
The pistons share a crank journal, not a connecting rod. And that’s common.
Especially in modern engines, long engines have problems with crankshaft torsion causing timing inconsistencies which get worse at the extreme ends of the engine.
Also, for a given displacement, a lower number of cylinders (e.g. a 6.0 liter V8 vs. a 6.0 liter V12) will be a bit more efficient due to lower ratio of cylinder surface area to volume.
Plus they’re just a plain PITA to fit in anything anymore.
There was an interesting one in Formula 1 in the 1960s. At one point, the rules specified a maximum engine size of 1.5 liters. BRM (British Racing Motors) ran a 1.5 liter flat-8. When the rules changed in the next year to allow 3.0 liters, BRM stacked two of their flat-8s to make a 64-valve H-16 with two crankshafts geared together. It wasn’t a big success, but did win one race.