13 thoughts on “Old Engines”

  1. I’ve been using Slick 50 with every oil change in my old truck for years. But recently I saw a youtube where they tested it to destruction in 2 lawn mower engines. Slick 50 caused the engine to run cooler but it actually siezed sooner than just plain oil. Then I came across this video.

    This popped out at me from your linked article, “With three times as many bearings as a conventional engine, durability was a concern…”

    I definitely think I may switch to Bestline.

    1. In some places they lubricate gasoline engines with palm oil. That leads to interesting experiments and some Youtube videos. Petroleum based lubricants weren’t the only option. You can drive cars long distances on cooking oil, which is pretty cool to know in a post apocalyptic world.

        1. The benefit/cost ratio of the Clean Air Act and its extensions has been estimated to be ~40. I’d not want to give that up just to drive the Batmobile.

  2. “With three times as many bearings as a conventional engine, durability was a concern…”

    is that an increase from 2 to 6 bearings or 20 -60?

    1. The connecting rod connects the piston to the crankshaft, so there’s some sort of rotational connection at each end of the rod, so that’s two bearings per cylinder. This Lexis thingie has six bearings per cylinder. Multiply that by the number of cylinders, so probably going from 12 to 36, but also inserting two electric actuators per cylinder. The connecting rod is under a lot of stress and a failed rod is one of the more common failures in a piston engine (“a thrown rod”), so sticking two actuators and four more bearings per cylinder does seem to be introducing many more future points of failure. The wiring harness seems like another potential problem: these actuators need to be powered and controlled, so the wires are going to be flexed thousands of times per second…

      1. It looked to me as though a single through-shaft could turn the compression ratio adjusters of all six cylinders at once. A single bi-directional harmonic drive rotary actuator could do the twisting. The wires powering the actuator would be outside the engine and no more subject to vibration damage than any other set of wires under the hood.

        1. So you’re picturing two shafts bent sort of like the crankshaft (clearly straight shafts wont work)? I don’t think a correctly shaped shaft is possible, but that’s going to require some actual analysis to find out.

      2. At 7200 RPM, which is a pretty high redline, the engine is turning 120 revolutions per second – not “thousands of times per second.” And passenger car engines almost never see redline anyway. And thrown rods almost never happen on reasonably maintained passenger car engines; a blown head gasket is probably the most likely major mechanical failure mode that requires a teardown, and even that is really unlikely without overheating the engine. Modern passenger car engines are quite reliable mechanically.

        1. Oops, you’re right, I was thinking multi-thousands RPMs then forgot to divide by 60 for motions/second.

          I did almost exactly this a few years ago in a post on a message board about a bicycle power meter, where the manufacturer specified it took a force measurement every 0.01 seconds and my mind thought this wasn’t often enough since typical cadences are in the neighborhood of 70-90 RPM…

  3. Can’t you get many of the advantages of variable compression ratio with variable valve timing? VVT is pretty much state of the practice now; my inexpensive Toyota Corolla has it.

    1. I think you can. I think they’re varying to overall compression ratio without introducing a difference between the upstroke and down stroke.

      In an inline engine I’d do something that is perhaps simpler. Move the crank shaft up and down relative to the cylinders. One end of the crankshaft would drive a spur gear (1) that meshes with a second spur gear(2) that’s roughly horizontally level with the first and which drives the transmission.

      The crankshaft bearings and spur gear 1 would have an arm at both ends of the block that pivots its axis (centered on spur gear 1) around the axis of spur gear 2, so that it stays meshed as the arms rotate. The arms could be moved up and down with something like a jack screw.

      It doesn’t take much travel to drastically alter the compression ratio, so the crankshaft wouldn’t move in much of an arc, and wouldn’t be offset much from the line of the cylinders, so it shouldn’t introduce much extra wear on the cylinder walls and pistons.

      It should have the same effect as slightly raising and lowering the cylinders and cylinder heads relative to the crankshaft.

      The idea was probably already patented long long ago, but I’ve never bothered to look.

      1. That sounds complicated. In an engine with variable valve timing, you just close the intake valves later. Some air is pushed back out of the cylinder, so effectively the compression stroke is shortened. The downside is that engine power is also reduced (because less air is being compressed), but that’s ok if the engine is operating well below max power (which is usually the case in an automobile.) In effect, the engine can operate in the Atkinson Cycle at lower power, increasing efficiency.

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