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Building the Trevithick Engine

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  • #76
    Your flywheel looks really good and the nice thing about a water jet is it doesn't induce any stresses into the steel. But I suppose it could release some that are already there.
    Larry - west coast of Canada

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    • #77
      That is why the waterjet cutters generally supply A36 or G40.12 hot-rolled steel.--There are very few stresses "built into" this material.
      Brian Rupnow
      Design engineer
      Barrie, Ontario, Canada

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      • #78
        I haven't ran off. There is a lot of time spent on fitting and creating new platework, and I didn't want to post every single part that I made. The cylinder is fitted into the boiler, with a little bit of design change to allow for clearances. The plate stands that support the boiler and provide bearing surfaces for the axles are almost finished, but as you can see, they haven't been drilled for axles yet. Tomorrow I will finish those plates and machine two more that run parallel to the boiler, and drill and tap the boiler shell for the bolts which holds the end stands in place. The wheels are going to be the last parts made for this engine. I can actually go ahead and make all the parts required to make the engine run without finishing the wheels and the gears.
        Brian Rupnow
        Design engineer
        Barrie, Ontario, Canada

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        • #79
          Todays job was to finish all of the axle brackets and assemble them to the boiler shell. This gets a bit tricky, because with no real suspension, if things are a bit off you end up with one wheel out of the four "up in the air".--It won't matter so much on this model, because it's not going to be a high miler, but I do like to get it right.
          Brian Rupnow
          Design engineer
          Barrie, Ontario, Canada

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          • #80
            This is taking shape nicely, Brian!
            I cut it off twice; it's still too short
            Oregon, USA

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            • #81
              Thanks Tim---It is a most interesting project.
              Brian Rupnow
              Design engineer
              Barrie, Ontario, Canada

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              • #82
                Originally posted by brian Rupnow View Post
                ... I can actually go ahead and make all the parts required to make the engine run without finishing the wheels and the gears.
                I am hazy about how it can run properly without being connected to the flywheel crank. Without that connection only air pressure (from the rotary valve) reverses the direction of piston motion. Is there always an air cushion at stroke's end to prevent it from banging against the cylinder head?

                Allan Ostling

                Phoenix, Arizona

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                • #83
                  Aostling--Look at the completed model. The piston rod drives a beam which rides on the cross head guides, extended out beyond the front of the engine. There are drive links (or connecting rods if you prefer) going from that moving beam back to the flywheel and an offset arm on the ends of the shaft which support the flywheel. Yes, there is a gear on the end of that shaft, but it's not needed to make the engine run.
                  Brian Rupnow
                  Design engineer
                  Barrie, Ontario, Canada

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                  • #84
                    I see it now. I mistakenly thought the flywheel was one of the wheels you were referring to as unnecessary for proper running.
                    Allan Ostling

                    Phoenix, Arizona

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                    • #85
                      What's the setup in post #79?

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                      • #86
                        In post #79, the tapped holes that the base bolts to are very close to the outside edges of the boiler body. I drilled and tapped one hole, then used one bolt to hold the base in place and drilled/tapped the other three holes in the boiler using the frame as a drill guide. That kept the drill from wanting to wander out of place down the side of the boiler.
                        Brian Rupnow
                        Design engineer
                        Barrie, Ontario, Canada

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                        • #87
                          And behold, the great horned beast!! Is it not a beautiful thing? I think it's a Rupnowsaurus!!!
                          Brian Rupnow
                          Design engineer
                          Barrie, Ontario, Canada

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                          • #88
                            You know that saying about "Old dogs can't learn new tricks".--Not really true---I'm an old dog and I'm still learning new tricks. The cross-head on this engine (purple colored) has a long protrusion welded on top of it that operates the rotary valve. The fact that it is quite long will make the cross-head want to bind as it moves under pressure from the cylinder. This is technically called an "overturning moment". The way to overcome that binding is to make the area on the cross-head which slides along the cross-head guides as long as possible. Since that is probably the next thing I'm going to build, an update to the 3D model was called for.
                            Brian Rupnow
                            Design engineer
                            Barrie, Ontario, Canada

                            Comment


                            • #89
                              Today I finished the cross-head, and I'm quite pleased with the results. In the 3D model I posted yesterday, I thought that the extended bearing surfaces added to the cross-head looked kind of "clunky", so I changed the design after I had posted the model, and made the two extension pieces from round brass, which extend completely thru the rectangular body. They are loctited in place. The vertical part of the cross-head which operates the valve control rod is silver soldered to the cross-head main body.
                              Brian Rupnow
                              Design engineer
                              Barrie, Ontario, Canada

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                              • #90
                                Today is a "banner day", as I have completed the cross-head and cross-head guides, and my air cylinder and rotary valve are moving the cross-head thru it's travel. Everything is a bit herky-jerky right now, because everything is new and stiff. Once it has been operated a number of times, any "tight spots" will be smoothed down and the travel will be much smoother.

                                https://www.youtube.com/watch?v=-8n-...ature=youtu.be
                                Brian Rupnow
                                Design engineer
                                Barrie, Ontario, Canada

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