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Building the Trevithick Engine

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  • Boys, we're going to start down a new path today. I'm very disappointed that I didn't get this engine to run with the 4 way valve and I really, truly thought that I would. Ah well, so much for unbridled optimism. The change of course is going to involve a more conventional steam slide valve on the cylinder. Due to restrictions based on everything having to fit inside the boiler, I am going to have to gear the crankshaft to a "camshaft" and mount the eccentric strap and eccentric on the camshaft. (it will revolve at the same speed as the crankshaft.) This means that the steam-chest will hang from the underside of the existing 3/4" diameter x 3" stroke cylinder, similar to the way it did on the Stephenson's Rocket. I will be getting rid of all of the exterior valve control rods and guides, and the rings with built in rod guides will revert back to being just simple rings around the ends of the boiler. The only visible difference is going to be at the smoke-stack end of the engine, where it will be possible to see the extra set of gears to operate the cam shaft, and different method of mounting the crankshaft and cam shaft. If this sounds like a lot of extra work, well, yes, it will be.-However, it's Covid time. Can't visit friends, can't go out for entertainment, can't even see my grandchildren nor take out good-wife for a restaurant meal. I'm just happy to have something fun to do!!!

    Brian Rupnow
    Design engineer
    Barrie, Ontario, Canada

    Comment


    • So you are no longer interested in building a Trevithick Engine, but will be content to build something that (mostly, sort of) looks like it from the outside?

      Comment


      • Doctor Mike--You have it right. Most of my 40 engines "look like something visually but aren't technically the same". I have no shame in doing this. I only pursue this hobby because it is fun. When it becomes frustrating because a certain design doesn't run the way I had hoped, then I move on.
        Brian Rupnow
        Design engineer
        Barrie, Ontario, Canada

        Comment


        • Wasn't trying to "shame" in any way, was just asking the question. This is the first of your builds I've followed, and I'm just getting used to your style.

          I must admit I don't understand the way you can toss aside days or weeks of work at the first sign of difficulty - and with this 4-way valve it looks (to me) like you are sooo close to making it work and you are throwing it out!

          I do understand that I don't have to understand, this is you being you and enjoying your hobby.
          I'll not clutter your threads with any more suggestions or comments.

          Comment


          • Dr Mike- I'm sorry if I rattled your chain a bit.--No foul intended. I build a lot, and I post a lot, and there are some people who enjoy jumping on me with both boots if I don't do things quite as they expected. I haven't thrown out the baby with the bath-water. Although I haven't had success with the 4 way valve, I will still use everything I built except the four way valve. If there were more things I could do to use the 4 way valve successfully, I would try and do them. I tried many different settings on the adjustable sliders, and that didn't work. I shortened the radius arm above the valve, and although that made a difference the engine still didn't run. There wasn't really much more that I could do, far as I can see. The four way valve isn't going to be discarded. I will keep it and try at some future date to make it work controlling a cylinder. I do have many models running with a conventional slide valve controlling the cylinder, so I'm reverting to something I now works.---Brian
            Brian Rupnow
            Design engineer
            Barrie, Ontario, Canada

            Comment


            • Well, I don't know of other steam engines using this valve design, which by itself says a lot. People who've developed successful valve motion designs back in day, we still say their names.
              I don't view this as a failure Brian, more of a proofing of the flaws in the original design. Never mind the fact the piston resides inside the boiler!!

              Comment


              • RB211 ---All of those men were giants. At the beginning of the 1800's, when nobody had done these things before, they did the equivalent of the moon landing and the first trip to Mars. I stand in awe of these guys. True, some of their machines didn't work well, but the fact that they worked at all is mind boggling. I have worked in engineering for 55 years, and I can truthfully say that I have only met two or three men who could stand shoulder to shoulder with Trevithick and Stephenson. I play at it because I love it---Always have.
                Brian Rupnow
                Design engineer
                Barrie, Ontario, Canada

                Comment


                • Just finished the big three hour "clean-up, slick-up, put all my tools away in the correct place" dance. I try and put my tools away as I use them, but when I get into the final lap of building something I get so excited that nothing gets put away properly. When I walk into my little machine shop and the floor "crunches", I know that it's about time for a sweeping and vacuuming. My apologies to everyone who hoped to see this run with the 4 way valve.---I did too. My apologies to anyone who I may have snapped or snarled at on the forums. I'm not normally like that. This project hasn't stopped. Very little of my work will be lost, even the cylinder will remain the same. The 4 way valve gets tossed, and I gain a cam shaft and conventional slide valve to control the cylinder. Don't go away please. There is more to come, and I promise, it will be interesting.---Brian
                  Brian Rupnow
                  Design engineer
                  Barrie, Ontario, Canada

                  Comment


                  • Originally posted by RB211 View Post
                    Well, I don't know of other steam engines using this valve design, which by itself says a lot. People who've developed successful valve motion designs back in day, we still say their names.!
                    Actually, the Corliss Engine has 4 valves that operate in essentially the same manner as this 4-way valve, each of them can be individually tuned for optimum efficiency. The Corliss Engine is considered the pinnacle of steam engine design and efficiency, until it was replaced by the development of steam turbines.
                    Last edited by DrMike; 10-20-2020, 06:59 AM.

                    Comment


                    • Two 25 tooth gear blanks turned and that's all she wrote for today. O.D. and hubs are turned to size from 1144 stress proof steel. Center hole has been drilled and reamed to 5/16" diameter. Next time you see them they will have teeth cut and be mounted in place.
                      Brian Rupnow
                      Design engineer
                      Barrie, Ontario, Canada

                      Comment


                      • Originally posted by RB211 View Post
                        Well, I don't know of other steam engines using this valve design, which by itself says a lot. People who've developed successful valve motion designs back in day, we still say their names.
                        I don't view this as a failure Brian, more of a proofing of the flaws in the original design. Never mind the fact the piston resides inside the boiler!!
                        The cylinder inside the boiler was actually a master stroke, but nobody knew it!

                        So, later, designers had to bring part of the boiler TO the cylinder, in the form of a steam jacket to prevent condensation from lowering the power and efficiency. How much smarter to have it inside the boiler, where it costs no extra steam or heat..... Steam sent to the jacket was lost, but steam in the boiler is not. All the losses in the piping are avoided, the cost is minimal in lost steam.

                        Of course, the engine had to become far more efficient before the condensation losses became important.

                        1601 2137 5683 1002 1437

                        Keep eye on ball.
                        Hashim Khan

                        If you look closely at a digital signal, you find out it is really analog......

                        Comment


                        • Hi Jerry--Nice to hear from you. Doing something a bit new and different. Normally, when steam-chests are used with a cylinder they are either both machined as one part from the same piece of material or soldered together, and all of the steam passages are internal inside the walls of the cylinder. In my case, I am retrofitting a steam-chest onto a cylinder which was previously operated by my 4 way valve. The steam lines are going to be external to the cylinder. I will solder brass "hose barbs" into the steam-chest and run flexible neoprene lines from the steam-chest to the cylinder ports. ( I know I cautioned against doing that but needs must.) I have never seen that done, but I can't think of any reason that it won't work.
                          Brian Rupnow
                          Design engineer
                          Barrie, Ontario, Canada

                          Comment


                          • Wouldn't it be better to use small copper lines inside the boiler with fittings or soldered joints. Then you wouldn't have to worry about them blowing off.
                            Larry - west coast of Canada

                            Comment


                            • Cuttings--Yes, it would be better. I'm making parts right now. When I go to assemble them I will think about that some more.
                              Brian Rupnow
                              Design engineer
                              Barrie, Ontario, Canada

                              Comment


                              • It feels like I must have been taking "slow pills" today. I managed to work all day and make only one part. This is the sub base for the new slider valve. The four shcs in the corners attach it to the cylinder. The four tapped holes are where the steam-chest bolt to it. The tapped holes in the ends are drilled galleries that needed to be plugged after the fact, so they were tapped and #10 set screws threaded in to act as plugs. There will be three tubes soldered into the block, two on one side and one on the other side. I still have some internal de-burring to do.
                                Brian Rupnow
                                Design engineer
                                Barrie, Ontario, Canada

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