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ptwizz

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ptwizz last won the day on April 29

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About ptwizz

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    Paramotor Club 500.
  • Birthday 03/03/1963

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  1. Another image added, showing construction of exhaust bypass valves. Since the engine is intended eventually to be installed in a road vehicle, it will need to run with exhaust silencers and possibly catalytic converters. Radial engines are notorious for expelling unburnt fuel and oil at startup. To avoid damage to the exhaust system, the bypass valves allow the engine to be started on open stubs, then diverting exhaust through the cats and silencers when it has settled down. Each valve contains a swinging flap, with a disc on each side which closes into a conical valve seat. The flap will be spring loaded into the 'normal running' position. Start position (open stubs) will be achieved by moving the flaps with a bowden cable.
  2. ptwizz

    Radial Engine Build

    Off topic - Radial engine build gallery
  3. On Sunday, the temperature in my workshop finally exceeded 15C, warm enough to pour polyester resin and have a first try at casting a distributor cap. I have added an image to my album showing the result. https://www.paramotorclub.org/gallery/category/1-member-albums/ A couple of lessons learned and another attempt will follow when the weather sorts itself out. First attempts are in clear polyester, as it allows me to see whats going on with the moulding and can be used for bench testing the ignition system.
  4. ptwizz

    IMG_20191211_175828.jpg

    If you can't make it good, make it Shiny* (*Copyright Harley Davidson)
  5. Hi Alan, I suspect your PIC work is far beyond what I am doing. I am running a few lines of code, essentially a couple of DO-WHILE loops to calculate the advance and dwell periods in the 'down time' between firing events, then using those values to time triggering of a FET which drives the coil. My first attempt was an ambitious all singing & dancing behemoth which could not run fast enough on a 1MHZ pic, even for my max 3500rpm.
  6. More pictures added to the gallery. The oil pumps have been tested, the photo shows the scavenge pump on test, circulating a mix of air and oil. The pump was run like this at 1800rpm for 4 hours. It became only slightly warm and there was no appreciable wear visible afterwards. A more elaborate setup was used with a manifold simulating the oil system loads and housing temperature and pressure sensors. This setup was run at 3°C (a cold morning in the workshop) and then heated to 90°C and the pump was able to supply oil through the temperature range at the required pressure from 250rpm. I've made the 'works' of the distributor and a mould for the cap (Halfords are completely out of 7 cylinder distributor caps!). The cap will be moulded in clear polyester for trials, so I can observe any errant arcing inside. The distributor uses an optical sensor and I have written my own software to run on a PIC to control the advance and dwell.
  7. ptwizz

    IMG_20200106_090125.jpg

    Distributor base and internals
  8. ptwizz

    IMG_20191211_175828.jpg

    Distributor cap mould
  9. ptwizz

    IMG_20191111_142220.jpg

    Oil pump test.
  10. More Progress. The Primary Drive Case houses the 55mm wide toothed belt drive, the starter motor and the clutch assembly. The case comprises a front plate (which bolts to the rear of the oil tank), a rear plate (which provides a mount for a gearbox) a number of spacers and four strips of aluminium bent to form the 'wrappers' of the front and rear halves. The parts for one half are assembled with the wrapper strips clamped in place and are then fixed together using the 'Technoweld' process. For those who are not familiar with Technoweld (or Lumiweld, or other trade names), it uses rods containing antimony and heat from a propane torch. The antimony alloys with the aluminium at a temperature lower than the melting point of the parent metal. It is often described a 'aluminium brazing'. I have found it to be strong and effective in many applications, including repairing motorcycle engine and gearbox cases. The assembly shows no distortion from heating. Applying the heat and rods from the inside gives a very clean finish on the outside (and some singed eyebrows!).
  11. ptwizz

    IMG_20190908_115441.jpg

    Part for rear half of Primary Drive Case
  12. ptwizz

    IMG_20190908_115406.jpg

    Loosely arranged parts of Front half of Primary Drive Case
  13. ptwizz

    IMG_20190908_185611.jpg

    Assembled front half of Primary Drive Case
  14. More pictures added to the album. The oil tank assembly was tack welded together and brazed. Both front an rear faces were machined and grooves cut for the large O rings which will seal the tank to the back face of the crankcase and the front face of the primary drive case. Bosses are fitted at the top for the oil return from the cooler and for the oil filler cap. When the auxiliary drives assembly is fitted, the main oil pump has an external O ring which seals into the boss fitted at the bottom of the tank. The upper end of the auxiliary drive shaft sit below a hole in the top of the tank. The distributor will be fitted and sealed to the top face of the tank at that location.
  15. ptwizz

    2018-06-24 09.15.37.jpg

    Machining outside of supercharger housing
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