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Building the Trevithick Engine

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  • Building the Trevithick Engine

    The Trevithick was a train engine built in or about 1805. It did prove that it could carry ten tons of freight as well as passengers for a short period of time, but was so heavy that it kept breaking the tracks. Other associated failures, and then finally a boiler explosion which killed four men was the end of the Trevithick. Similar engines were used for pumping stations for a few years after that, but it never really caught on as a commercial engine either. Richard Trevithick, the man who designed this engine died in poverty as an old man. The external gearing and an absolutely enormous flywheel make it an ideal hobby engine to build, because there is so much visual stuff happening when this engine runs. It has a very interesting steam admission valve, which sets directly in line with the cylinder body itself. I have attached a beautiful rendering that was sone as a 3D model by someone. Julius DeWall of New Zealand made absolutely marvelous detail drawings of this engine, however I don't plan on my engine being nearly as complex as the drawings Julius made, so I will more or less be developing this one "from scratch".---Brian
    Brian Rupnow
    Design engineer
    Barrie, Ontario, Canada

  • #2
    There is one full size working replica of the Trevithick train engine: https://www.youtube.com/watch?v=K40XrR67fas

    Trevithick's train was built in 1802, and it wasn't until 1829 that Stevenson's now famous Rocket won the Rainhill trials. There were others between those two - Blucher, Locomotion and the Lancashire Witch amongst others. A fascinating period of rapid design and development.

    Should make a great project Brian!

    Ian
    Last edited by Ian B; 08-27-2020, 09:41 AM.
    All of the gear, no idea...

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    • #3
      Here is a bit of information about the original inventor, and some insight into the story behind the engine. The most complex part of what was built was the steam valve which was built into an extended portion of the cylinder. I have no doubt about my ability to recreate the overall machine, but if I can't come up with some better info about the steam valve I may have to do something a bit different there.
      https://www.youtube.com/watch?v=rul0iazn3d8
      Brian Rupnow
      Design engineer
      Barrie, Ontario, Canada

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      • #4
        As in all things, I have to determine what scale I want to build this engine at. That is going to be easy for me this time, because the largest gear I can cut on my milling machine is 108 teeth, which is 4.584" outer diameter. All other components will have to be scaled to accommodate this known part size.
        Brian Rupnow
        Design engineer
        Barrie, Ontario, Canada

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        • #5
          Looks very interesting. Specially the valve mechanism which looks relatively simple but has a number of critical dimensions.
          I will be watching with great interest.
          Larry - west coast of Canada

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          • #6
            So, based on ratio and proportion, and the fact that my largest gear is going to have 108 teeth, this lets me establish that the smaller gears at the drive wheels are going to be 50 teeth and the small drive gear is going to be a 36 tooth. All three of these gears are tied to the large gear by a function of adding the pitch diameters together and dividing by 2. I arbitrarily select the horizontal distance between gears, and so now they are fixed in position and can not be moved. No thought has been given to the width of the Trevithick yet, because that will be dependent on the diameter of the boiler.
            Brian Rupnow
            Design engineer
            Barrie, Ontario, Canada

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            • #7
              The largest gear I've actually MADE is 108 tooth. So far we don't have much, but the basic proportions are blocked out. If I don't go and eat some lunch I'm going to fall of my chair!!
              Brian Rupnow
              Design engineer
              Barrie, Ontario, Canada

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              • #8
                It appears to be driven only on the starboard side wheels even though all the wheels (in the first gorgeous rendering) include a gear. I suppose this is to keep all wheels interchangeable, even though half of them or more complex than need be? Or did I miss something?
                "A machinist's (WHAP!) best friend (WHAP! WHAP!) is his hammer. (WHAP!)" - Fred Tanner, foreman, Lunenburg Foundry and Engineering machine shop, circa 1979

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                • #9
                  mickeyf--I think it was a mistake on the beautifully rendered model. I don't think the real Trevithick had an extra set of gears that weren't needed.
                  Brian Rupnow
                  Design engineer
                  Barrie, Ontario, Canada

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                  • #10
                    Originally posted by brian Rupnow View Post
                    I have no doubt about my ability to recreate the overall machine, but if I can't come up with some better info about the steam valve I may have to do something a bit different there.
                    https://www.youtube.com/watch?v=rul0iazn3d8
                    Some details and explanation on the valve, John.

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                    • #11
                      John--I already have that---see post #3. Thanks ---Brian
                      Brian Rupnow
                      Design engineer
                      Barrie, Ontario, Canada

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                      • #12
                        Trevithick was better known for his mine pumps, wasn't he? I have some period engineering books from the 1920's that mention him in connection with the Cornish mine pumps. I had no idea he attempted a railroad.

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                        • #13
                          Just as I was reaching a point where I didn't want to go any farther without more knowledge about the cylinder and valve, Julius from New Zealand has came thru with a bunch of drawings and saved me. Thank you Julius, from the far side of the world!!!

                          Brian Rupnow
                          Design engineer
                          Barrie, Ontario, Canada

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                          • #14
                            Brian- To make the model a little more realistic, I would look into increasing the pitch of the gears your going to cut.
                            See here:
                            https://youtu.be/wOGYZC-IJPQ.
                            This video has some good views of the period construction of a couple of things.

                            Give it a look.

                            Sid

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                            • #15
                              The only gear-cutters I have are 24 DP.---Neat video!!
                              Brian Rupnow
                              Design engineer
                              Barrie, Ontario, Canada

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