The most difficult project?

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The most difficult project?

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  • #781883
    Tony Martyr
    Participant
      @tonymartyr14488

      The double Tangye

      In my life I’ve completed several ‘big’ model projects including the Mastiff, the Reeves triple expansion engine, a 3.5” William locomotive, a Beam engine and finally the Reeves Double Tangye engine. All but the Tangye have been given away. I found the machining of that double Mill engine the most challenging of all my projects. It was obviously a company that liked big complicated castings!

      Added to the expected difficulties was the fact that the thin end parts of the two trunk standard castings were chilled and required localised grinding with a Drexel set up on the tool post.

      The 7 equally spaced cylinder and head bolts are an interesting exercise when complete interchangeable is desired and machining the connecting rods out of rectangular bar is quite challenging.

      When I was an apprentice one of our tests was to machine, then hand scrape the white metal bearings of an in-line shaft with three bearings; this engine has four bearings in line the outer two being in housings set at an angle to the horizontal.

      I’ve ran it once on steam, but to avoid corrosion it now occasionally runs only on compressed air, the speed governor has too much stiction to operate subtly but it’s smooth and powerful. It sits on my bedroom window ledge and is a source o, until now, private pride because it was the most difficult of all to get absolutely right.

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      #781884
      JasonB
      Moderator
        @jasonb

        I’ve never been convinced that the 4 bearing shaft is right. It’s a bit like the Clarkson Compound, cobbled together from two models of singles but the surplus two bearings were never removed. Tangye had it right with just the two angled ones

         

        #781886
        Chris Gunn
        Participant
          @chrisgunn36534

          Tony, I recently bought a set of castings from a guy who had started it, but not done a lot, maybe now I know why, I was getting ready to make a start soon.

          He has ground the base and deeply centred all the holes for the 2 trunk standard castings, maybe not a good idea, i would be inclined to make them first and spot the holes through when construction was further advanced, what do you think?

          Chris Gunn

          #781888
          Chris Gunn
          Participant
            @chrisgunn36534

            Jason our posts crossed, have you made one?

            Chris Gunn

            #781891
            JasonB
            Moderator
              @jasonb

              No but if I did I would be thinking seriously about cutting a section out of the bed casting or starting from scratch so that the inner bearings could be done away with.

              I’d also do the two part flywheel as I have made one of those before.

              As for machining I’d get the two frames either onto the base or a machining plate and set up on the cross slide. Between ctrs bar to do the two trunk guides parallel and horizontal then swing the plate 90 degrees to do the bearing housings.

              #781893
              Tony Martyr
              Participant
                @tonymartyr14488

                Chris, I used a dividing table to drill the 7 holes in the two cylinder heads the used them as drilling jigs to drill the holes in the standards. I used the lathe as a horizontal borer to machine the standards but it is a tricky intermittent cut and I had to use the Drexel grinder to get a decent finish in the cross head bore due to patches of chilled hard surface.

                #781894
                Tony Martyr
                Participant
                  @tonymartyr14488

                  Jason, What supports your opinion is the fact that the halving joints of the inner bearings are horizontal while the outer are angled, I don’t think that is a sensible design and certainly makes work difficult. I got all four bearings taking load by using a straight alignment bar and shimming up the inner bearing stands which were made 10thou too short. It is a heavy flywheel but it all runs very smoothly.

                  #781895
                  JasonB
                  Moderator
                    @jasonb

                    Agreed, the different angles just don’t look right.

                    Sounds like it may be worth giving your castings a roasting Chris, there is a Clarkson in there somewhere.

                    20241030_154702

                    #781916
                    Chris Gunn
                    Participant
                      @chrisgunn36534

                      Thanks folks for all the tips, I better get on with it, no excuses. Jason, a good idea to get it all in one piece before machining, maybe that is why the holes have been started, Thanks

                      Chris Gunn

                      #781934
                      Tony Martyr
                      Participant
                        @tonymartyr14488

                        Chris,

                        Good luck, I think it is a very engaging project that requires a degree of ingenuity to complete just using a Myford and a pillar drill

                        IMG_0148

                        #781938
                        Nicholas Farr
                        Participant
                          @nicholasfarr14254

                          Hi, I saw this one at the Midlands ME in 2016.

                          Double Tangye#!

                          Double Tangye#2

                          Regards Nick

                          #781940
                          Tony Martyr
                          Participant
                            @tonymartyr14488

                            I really don’t see the purpose of two governors when the cylinders are coupled on the same shaft

                            #781941
                            Tony Martyr
                            Participant
                              @tonymartyr14488

                              Looking at Nick’s photos I think the straight shank connecting rods are of composite construction, which is a hell of lot easier job than turning the tapered rods out of one piece of rectangular bar!

                              #781962
                              Ian Hewson
                              Participant
                                @ianhewson99641

                                Here’s a few pics of mine built 15 year’s ago.

                                Ian

                                DSCF0737DSCF0745DSCF0746DSCF0749

                                #782046
                                Chris Gunn
                                Participant
                                  @chrisgunn36534

                                  I really don’t see the purpose of two governors when the cylinders are coupled on the same shaft

                                  Tony, just read the original construction articles, and Westbury mentions that in the case of full size engines, when demand for power was low, they would uncouple one con rod, and just run the engine with a singe cylinder. I guess this is why 2 governors were fitted, each controlling one cylinder, presumably the governors were set identically when running on 2 cylinders?

                                  Ian and Nick, your pics have really got me going, just having a tidy up, and then i will get going on my set of castings.

                                  Thanks Chris Gunn

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