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Stephenson's Rocket--Working Model

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  • #46
    I'm getting close to making a start on the Stephenson's Rocket cylinders. I went to my metal suppliers this week and bought a 12" length of 1 1/4" square brass. This will give me enough material to make two cylinders and two steam chests.---and maybe 4 cylinder end caps but I'm not sure yet. There's going to be a bit of finagling, because this brass is 1 3/4" across the diagonals and the bore in my lathe spindle is only 1 1/2". I don't want to waste any of the brass, because that 12" length cost me $50. I will probably hold one end in my four jaw chuck and use a live center to support the outboard end. I can turn the outboard ends of both cylinders in one set up, but I can't bore the cylinders in the same set up, so I"ll have to think more about this.
    Brian Rupnow

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    • #47
      Originally posted by Rich Carlstedt View Post
      There is a set of stationary drawings for rocket at
      https://www.modelengineeringwebsite....y_model_1.html

      What is the CAD format you wish to convert Brian ?

      Rich
      Rich, do you know the pedigree of these drawings, what they were based on? Is it the old Stuart model? That draftsman is certainly prolific, amazing what he's put out....but there is never a comment on where they came from, what is his goal or how closely they follow the original. Basic things one needs in deciding to build. Is it an "artistic interpretation, redraw of something, through research original and rivet counted from trips to the museum? With a sense of the pedigree it really dissuades one from pursuing a build
      .

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      • #48
        Maybe I'm missing something but..... Why would you not cut the brass stock into two parts to let you do the cylinders and chests on opposite ends as pairs instead of working with the one whole length? Is there not a combination of these parts where work on one end for one or the other won't let you hold it for accurate work on the other end at each stage?

        Just as a fer instance example... If you did two cylinders back to back at some point you might need to make an expanding arbor and hold from the bore to do outside work? But prior to that you'd have some amount of the original square OD to work with? So the only waste would be the final parting cut and any light facing at the split line between parts?
        Chilliwack BC, Canada

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        • #49
          The 1 1/4" square brass is 1 3/4" across the corners, and the i.d. of my lathe spindle is only 1 1/2".
          Brian Rupnow

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          • #50
            Now---If I've done this right, there should be two identical cylinders in there. It is set up so that each cylinder, when sawed from the square stock should be the right diameter and have a 1" long "spigot" attached to one end of each cylinder, to mount it in the three jaw chuck for boring. After the cylinder has been bored, the 1" stub length will be cut off and turned to give me four cylinder end caps.
            Brian Rupnow

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            • #51
              And now you know how I spent my Monday. Everything went very well, no drama. There is more machining yet to be done on the cylinder bodies, but not today.
              Brian Rupnow

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              • #52
                The outside of the rectangular areas of the cylinder have been machined this morning, all except for the radiused area. This was simple stuff, with the cylinders held in my milling machine vise. The rest of the things I have to do are mostly all rotary table work, so I need shafts mounted in each of the cylinders for my 3 jaw chuck on the rotary table to hold onto. I could have made an expanding arbor to mount the cylinders on, but this works just as well. I cut a couple of 5/8" cold rolled steel shafts, long enough to stick out each end about 1", and Loctited the shafts into place. After all my machining is finished, a bit of heat applied to the cylinders and the shafts slide right out. If any loctite residue remains in the cylinder it will easily come out by running a 5/8"reamer thru.
                Last edited by brian Rupnow; 05-20-2020, 07:09 PM.
                Brian Rupnow

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                • #53
                  Shopgeezer was asking how I machined the radius on the cylinder. This is a picture of my set-up. I'm end-milling with a 1/4" diameter endmill. The endmill is cranked down until it contacts the part and is locked there. The travel stops on the front of the mill are set to keep me from running the endmill into the larger diameter bands at each end of the cylinder. The mill bed travels in the X axis to the extent of the travel stops, then cranked back, and the rotary table is indexed about three degrees, then repeat---and repeat---and repeat. Eventually you will have milled all the way around to the next "flat" surface on the cylinder. It will need a bit of file and sandpaper cleanup, but it works very well.
                  Last edited by brian Rupnow; 05-20-2020, 07:10 PM.
                  Brian Rupnow

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                  • #54
                    I always consider it a huge success when I have to drill and tap 20 holes, drill 20 clearance holes, and all the parts fit together!! Tomorrow I will probably work on steam chests.
                    Brian Rupnow

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                    • #55
                      Originally posted by Mcgyver View Post
                      Rich, do you know the pedigree of these drawings, what they were based on? Is it the old Stuart model? That draftsman is certainly prolific, amazing what he's put out....but there is never a comment on where they came from, what is his goal or how closely they follow the original. Basic things one needs in deciding to build. Is it an "artistic interpretation, redraw of something, through research original and rivet counted from trips to the museum? With a sense of the pedigree it really dissuades one from pursuing a build
                      Good Question Mcgyver.
                      I did some research a few years ago on this very engine and there are a few variables.
                      Yes, Julius is certainly prolific and a splendid Model Engineer. The original Rocket was rebuilt several times and as a result it had several cylinder configurations.
                      I can find no real scale noted by Julius and his model seems to be for a 7 1/2" gauge track based on axle dimensions . The Kensington Science (London) Museum engaged some model builders
                      in 1904-08 to build a model replica in 1/8th scale and to make accurate drawings ( The Museum sells them - probably about 100 Pounds now ) The drawings were done and a model built and was on display ( 25 years ago ). The problem is the "true scale" . The wheels on the model are 6 15/16" gauge ** , so to make it a fit , you need to add 8 % to all dimensions which puts the scale at 1 : 7.4 instead of 1:8 ..."if " the Science Museum drawings are correct ? The Science Museum Scale Boiler is 5 1/2" in diameter , while Julius's drawings show 9 inches (~) , hardly a 8 % difference and so it is hard to tell what scale and axle adjustments were made. we also don't know if the large size is to allow for better boiler operation, His was for wood construction ( well Maybe ??)
                      For Purists , there are two excellent books on Rocket
                      A scientific review (superb !) called " The Engineering and History of Rocket ' by Bailey & Glithero (1999)
                      and
                      Stephenson's Rocket 1829 onwards -Owners Workshop Manual by Richard Gibbon - A Science Museum publication (2016) Haynes Publishing UK & USA

                      Henry Ford had a full size Replica built In England about 1920 and I do not know where those drawings came from and may have been original prints ? That engine is at the Henry Ford Museum

                      ** at 8 to 1 , the Proto Track would have been 4'-7 1/2"min, 4'-8"most likely

                      Rich
                      Last edited by Rich Carlstedt; 05-22-2020, 10:33 PM.
                      Green Bay, WI

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                      • #56
                        This morning I finished up the two steam chests. I had the outside machined yesterday, which involved 4 jaw set-up in my lathe to turn the round spigot. This morning I put the 4 holes in each corner and the cavity in the center. Once again the machining Gods smiled on me and everything bolts together!!
                        Brian Rupnow

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                        • #57
                          Today we have some steamchest covers and some pistons and piston rods. One noteworthy thing here---these small steam/air engines are not very forgiving of a non-concentric alignment between the pistons and piston rods. To get around that, I turn the pistons to 0.050" oversize, then screw the piston rod into the piston (they are both threaded #10-24) and coat the threads liberally with J.B. Weld. After it sets up for 24 hours, I will grip the 3/16" diameter piston rod in my lathes 3 jaw chuck, and finish turning the pistons to the correct sliding fit into the cylinders.
                          Brian Rupnow

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                          • #58
                            Agree about finishing the pistons on the rods. Any particular reason you choose JB Weld over Loctite?
                            I cut it off twice; it's still too short
                            Oregon, USA

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