ptwizz

No significant progress on the radial. I've made some of the exhaust bypass valves in between other things. The new business has quickly become a 50/50 mixture of assorted contracts and another business designing and manufacturing parts for 1930s Ford hot rods. This is still leaving me enough time for engine building, but my attention has been focused on engines for my model aircraft. No promises, but I hope to get back onto the final stages of the radial next year. On another note, I have now sold my fullsize aircraft - it was my most expensive toy and wasn't getting played with enough. I would like to get back into paramotoring at some point in the not too distant future.

There has been very little progress on the radial recently, partly because I have started my own business. I am offering design and prototyping services. Rates are flexible - depending on how interesting the work is. My skillset is mostly in mechanical engineering, with some capability in electrical systems. If you have any ideas you would like to pursue, I am happy to discuss with no obligation, whether it's a tiny device to mount your GPS or a paramotor trike frame. Business email: PTwissellengineering@gmail.com. Thanks to Simon for allowing me to promote my business here.

I did the same thing with valve springs - used only the outer springs where the Dnepr has double springs. Have you though how you might fit your engine in a bike? It's pretty big to get handlebars and arms around and indeed to see over it! A friend of mine is building a much smaller radial to go in a bike, using Honda 125cc OHC cylinders and heads.

Hi Tim, when I ran the calculations for the slave rod bushes, I was quite surpised that the little end bushing (from the Dnepr design) was substantially larger than required. A little further investigation revealed that the little end bush diameter is goverened not by the bearing load, but by the requirement for stiffness in the gudgeon pin. This my slave rods have 21mm little end bushes and 16mm bushes where they connect to the master rod. I assume the HE15 pin is a typo? How do you harden HE15?

Hi Tim, have you seen the radial engines group on groups.io https://groups.io/g/RandREngines? Well worth joining if only for the archive, but not very active for a while. I am still fiddling with bits and pieces, various tedious brackets etc. Otherwise, all the engine needs to run is for me to finish the ignition system. I have put that aside for a while, to avoid the temptation to start the engine before everything is finished. I'm absolutely happy to share information. On the radials group, among other stuff, is my spreadsheet which calculates balance for radials up to 11 cylinders. Can you post a photo of your engine as it stands?

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.

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.

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.

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.

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!).