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Sun and planet gearing to obtain 2:1 ratio for 4 stroke engine?

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  • Sun and planet gearing to obtain 2:1 ratio for 4 stroke engine?

    I'm just watching a bit of YT before heading off to bed and came across a video showcasing James Watt's work around against the usual crank on an engine. The interesting thing is that it produces an inherent 2:1 gearing ratio.

    I'm too tired to try to figure out how it might be used in a four stroke model engine... But tomorrow I'm going to think about it. My first thought is that it could operate in connection with the exhaust valve on a simple utility engine style model.
    Chilliwack BC, Canada

  • #2
    James Watt used the sun and planet gear because James Pickard had a patent on the simpler crank. It was far more complicated and probably a lot more expensive to manufacture. It wasn't that the sun and planet was a superior way to convert linear motion to rotational motion. He WAS aware of the crank and of it's superiority. But he simply did not want to pay royalties. When that patent expired, Watt promptly abandoned the sun and planet and virtually all engines since then, both steam and IC, have used the crank.

    The sun and planet does have a 2::1 gear ratio meaning the shaft goes twice as fast (two revolutions for each back and forth strokes of the piston) as a crank would drive it. This is probably OK with a steam engine which generates a lot of power and torque at slow speeds. This is shown by a steam locomotive starting to pull a heavy, multiple car train from a dead stop with no transmission to allow the pistons to operate faster. They just push it into motion via brute force. But IC engines are a lot happier when spinning at higher speeds and generally work best with the crank and it's slower shaft speed. Try "popping" the clutch in a stick shift auto with the car at rest, the transmission in third gear, and the engine running at speed. The car may jerk, but the IC engine will likely just stop. In fact, virtually all auto transmissions are gearing those IC engines DOWN, not up. So if you simply want an IC engine that demonstrates that this can work with no load on it, go ahead and knock yourself out. But if you are going to use it for anything practical, then I suspect that the sun and planet gearing is not the way to go.
    Last edited by Paul Alciatore; 04-01-2021, 05:32 AM.
    Paul A.
    SE Texas

    And if you look REAL close at an analog signal,
    You will find that it has discrete steps.

    Comment


    • #3
      In the model engineering world, many of the best rules for efficient, simple, cheap engines don't apply. People are constantly challenging themselves to do something different, just to see if it can be done. I was recently looking through an article on a Phil Duclos engine. He was wondering if there was a way to operate an exhaust valve without gears at all. He came up with a ratchet mechanism that would open the valve every other stroke. Better than using a gear ratio and cam? Maybe not but it was more fun.

      Then there was an automobile engine, NSU maybe, with an overhead cam that did not use gears, belt or chain. It was driven synchronously by two links that provided rotation to rotation movement. That may not have been a world beating mechanism, but it's always been imagination and the 'what if' thinking that moves industry forward.

      Go for it, BC.
      .
      "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

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      • #4
        I think I have seen the actual mechanism at the Science Museum in London.

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        • #5
          That's crazy how someone could have patented something so damn simple --- it's like patenting the wheel fer cri-sakes....

          I hate the way that kid says patent... it's annoying so I did not watch the whole thing...

          Comment


          • #6
            The patent office mostly looks to see if something has a PRIOR patent. And that is the big reason why obtaining a patent is so expensive and time consuming. Widespread, prior use also counts and yes, cranks do go back to prehistoric days.

            Apparently James Pickard wrote it up in such a manner that it was or seemed to be a unique idea as far as piston engines were concerned. Water wells in ancient Greece may have had cranks, but they did not have pistons.

            Anyway, that is my take on it. I do know that the patent thing WAS why Watt didn't originally use the crank. And, as I said, he was aware of it and of how much it did simplify any piston engine. So, as soon as James Pickard's patent expired, he did switch over to using the crank on all of his engines.

            And that is history. It is also why history can be so very interesting: real people with real world problems that they find solutions for. And, with such wonderful stories in history, I want to personally shoot every history teacher who ever asked for a date on a history exam. The date that something happened is far, Far less important and far, Far, FAR less interesting than the story behind what happened.



            Originally posted by A.K. Boomer View Post
            That's crazy how someone could have patented something so damn simple --- it's like patenting the wheel fer cri-sakes....

            I hate the way that kid says patent... it's annoying so I did not watch the whole thing...
            Paul A.
            SE Texas

            And if you look REAL close at an analog signal,
            You will find that it has discrete steps.

            Comment


            • #7
              see if it can be done. I was recently looking through an article on a Phil Duclos engine. He was wondering if there was a way to operate an exhaust valve without gears at all. He came up with a ratchet mechanism that would open the valve every other stroke. Better than using a gear ratio and cam? Maybe not but it was more fun.
              My Olds vertical model has this sort of mechanism to operate the exhaust valve, it works great. And, it IS fun to watch.

              Comment


              • #8
                Originally posted by Paul Alciatore View Post
                The patent office mostly looks to see if something has a PRIOR patent. And that is the big reason why obtaining a patent is so expensive and time consuming. Widespread, prior use also counts and yes, cranks do go back to prehistoric days.
                Of course, there was not much prior use of a crank IN THAT WAY, simply because the steam engine was new, and few other things existed (if any) that would use a crank in that way. And of course it was the BRITISH patent office, a long time ago, with their own rules and definition of what was "patentable".

                However, the US patent office does not do what you say they do.

                They CLAIM they do, but they do not. Many years ago, at a prior employer, we noticed that the patent office had issued TWO patents, each of which covered, the same thing as part of the patent. Clearly they had not done their patent search, let alone a "prior art" search, properly. And our court district was known for never invalidating a patent, not that we would have spent the 2 million (estimated by our attorney) to clear it up so that we could use that portion of the expired patent.

                For a while, they were so bad that we speculated that they would allow the wheelbarrow to be patented, so long as it was painted pink.
                Last edited by J Tiers; 04-01-2021, 08:17 PM.
                CNC machines only go through the motions

                Comment


                • #9
                  Originally posted by A.K. Boomer View Post
                  That's crazy how someone could have patented something so damn simple --- it's like patenting the wheel fer cri-sakes....

                  I hate the way that kid says patent... it's annoying so I did not watch the whole thing...
                  I believe he is using the correct pronunciation.

                  Comment


                  • #10
                    Originally posted by The Artful Bodger View Post

                    I believe he is using the correct pronunciation.
                    LOL...... it is patent(#1) that patent (#2) is a word that has at least two pronunciations. One in UK and "derivative countries", while both pronunciations are used, depending on the meaning of the word in context, in the US.
                    CNC machines only go through the motions

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                    • #11
                      Originally posted by The Artful Bodger View Post

                      I believe he is using the correct pronunciation.
                      Yeah --- same with "tissue" and "schedule" as in the way Jean Luke Picard says them --- again --- annoying...

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                      • #12
                        It is called the "Queen's English" and that is the way we like it.

                        Comment


                        • #13
                          Originally posted by Paul Alciatore View Post

                          ......................I want to personally shoot every history teacher who ever asked for a date on a history exam. The date that something happened is far, Far less important and far, Far, FAR less interesting than the story behind what happened.
                          Far easier to grade a student based on their ability to memorize a simple number than it is to gauge their ability to grasp a concept and its significance.

                          Comment


                          • #14
                            Originally posted by The Artful Bodger View Post
                            It is called the "Queen's English" and that is the way we like it.
                            That is patently obvious (#1).
                            CNC machines only go through the motions

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