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  • Homebuilt engine

    Hello all,

    I am a student pilot (3-axis) and new to this forum. I have a project in progress which, while not strictly microlight related, may be of interest to some.

    I am in the process of building a 7 cylinder radial engine of 2300cc with a projected output around 100BHP at 3500rpm.

    The engine uses motorcycle cylinder heads (pushrod OHV) and barrels. These are from the ubiquitous Dnepr.

    The images show the whole engine in CAD and the assembly of crankshaft, master and slave rods and pistons.

    The crank is machined from EN24T and is a bolt-up assembly, split at the crankpin.

    The rods are machined from aluminium 2014A-T6 with EN24T steel side plates for the master rod and SAE660 bronze bushes.

    The pistons are machined from aluminium 2618-T6511. The slipper design avoids the traditional challenge of machining elliptical skirts.

    This engine will never fly. I expect it to weigh around 120kg dry and I wouldn't like to trust the Dnepr parts at full power for any period of time.

    There is a plan to use the engine, but that's another story for another day.

    If there is any interest, I have a series of photos of the various machining operations and components. So far I have made the crank, rods, pistons, 2 oil pumps and I'm partway into the maincases.

    Attached files
    Pete T.

    "A closed mouth gathers no feet".

  • #2
    Homebuilt engine

    The engine now has a crankcase, shown with the crank, rods and pistons fitted.
    It's getting very heavy and the next job is to fabricate a test stand.

    Attached files
    Pete T.

    "A closed mouth gathers no feet".

    Comment


    • #3
      Homebuilt engine

      What a shame it wont fly...sure looks nice.
      "When once you have tasted flight...you will forever walk with your eyes turned skywards..."

      https://www.youtube.com/user/nickjaxe/videos.

      Comment


      • #4
        Homebuilt engine

        Wish you'd got into a V-Twin, using bits cannibalised from the industrial motors, that would fly.

        Impressed

        Kev
        G-KEVA
        BMAA 5696

        "If anybody ever tells you anything about an aeroplane which is so bloody complicated you can't understand it, take it from me: it's all balls."

        R.J. Mitchell :- Designer of the Supermarine Spitfire

        Comment


        • #5
          Homebuilt engine

          Hi Peter,

          Best wishes with your project.

          My plan was to manufacture a small Radial when I retired as it has loads of advantages when it comes to both the manufacture and when fitted to a plane,
          I was fitting a small model radial to a push bike when a bit of a disaster stopped play and forced a change in direction.

          Common heads with an easily machined crankcase with the conrod assembly being the small price to pay, it would have had total loss oil injection and with direct drive been light enough for SSDR but the best bit would have been the noise.

          Maybe two on the Lazair for that different experience ;-)
          Mick Broom
          Member 909
          Shadow G-MWTN

          Comment


          • #6
            Homebuilt engine

            Thanks for the kind words.
            I designed the engine so that I could make and modify all the parts in my own workshop. Materials were selected with availability and manufacturing in mind.
            I had looked at what would be needed to get the engines weight down to a plausible 80kg. Most of it is just more machining, but working out exactly where I can remove material from is a significant analysis exercise.

            The design could easily be adapted to use heads from an industrial engine. One could argue that a radial is what you get when you started designing a V twin but didn't stop.

            I recently saw some pictures of a bicycle with a modern model radial installed. It's in a museum and labelled as an early 20th century French machine!

            Once I have my PPL(M) and a healthy number of hours, I'd like to build a WW1 lookalike SSDR. Maybe then I could look at building a radial (or rotary) to fly.
            Pete T.

            "A closed mouth gathers no feet".

            Comment


            • #7
              Homebuilt engine

              Looking more like an engine. Temporary assembly to verify CAD model.

              Attached files
              Pete T.

              "A closed mouth gathers no feet".

              Comment


              • #8
                Homebuilt engine

                That's beautiful work Peter. Admiration to you! Tell us though, how you will get exhaust and inlets onto the cylinders, it's a bit close between!

                Comment


                • #9
                  Homebuilt engine

                  The cylinder heads will be modified. I will machine away the exhaust stubs and fit studs for mounting flanged exhausts. I have modelled the inlet and exhaust plumbing in CAD and there is about 3/8" clearance between the inlet bends (facing forward and towards the crank axis) and the exhaust bends (facing rearward and away from the axis).
                  The pipes (inlet and exhaust) will be 1-1/2" stainless. Mandrel bends are available with 1D (i.e. 1-1/2") centreline radius. Probably not ideal for gas flow, but the supercharger will help with that.
                  Pete T.

                  "A closed mouth gathers no feet".

                  Comment


                  • #10
                    Homebuilt engine

                    Explanation made plain, thanks Peter and best wishes for a cracking project.

                    Comment


                    • #11
                      Homebuilt engine

                      Cam ring and timing gears:
                      The cam ring has 3 intake lobes and 3 exhaust lobes. It runs at 1/6 crankshaft speed and rotates in the opposite direction to the crankshaft.

                      I have created a few spreadsheets to calculate component loads, valve events etc. The most recent calculates balance of all the major moving parts for any radial engine up to 9 cylinders and it's a monster!

                      Attached files
                      Pete T.

                      "A closed mouth gathers no feet".

                      Comment


                      • #12
                        Homebuilt engine

                        Wow... fantastic project... and superb workmanship.

                        You may be interested in this thread (If you are not already aware)

                        http://www.homebuiltairplanes.com/forums/light-stuff-area/12860-radial-engine.html

                        Comment


                        • #13
                          Homebuilt engine

                          Thats a lovely piece of engineering Peter....any more pictures??
                          "When once you have tasted flight...you will forever walk with your eyes turned skywards..."

                          https://www.youtube.com/user/nickjaxe/videos.

                          Comment


                          • #14
                            Homebuilt engine

                            Thanks for the complimentary comment. I have had a brief break from the radial build, but I'm back on it now.
                            I've mostly machined the tappet ring (sits around the cam ring and supports the tappets and pushrod tubes) and immediately found that I had incorrectly located some tapped holes in the crankcase. I have now fixed the issue by machining threaded plugs, staking them into the holes and re-drilling and tapping in the correct location.
                            I'll finish the tappet ring and then post a few pictures.
                            Pete T.

                            "A closed mouth gathers no feet".

                            Comment


                            • #15
                              Homebuilt engine

                              More progress: The tappet ring is in place, the swinging tappets manufactured and assembled. Pushrod tubes have been turned, heads modified for proper seals, pushrod ends have been turned from silver steel and hardened.
                              When I came to check pushrod lengths on the job, it became apparent that the Russian rockers were all over the place. They are steel castings which are scruffy and poorly machined. They had to go, so I have created another 50 hours work for myself. I am now machining aluminium rockers with roller tips and improved geometry.

                              Attached files
                              Pete T.

                              "A closed mouth gathers no feet".

                              Comment

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