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!).

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.

A long overdue update:

Progress has been interrupted by the need to rebuild my microlight engine, following an in-flight failure and forced landing in a random crop field. No damage to man or machine (apart from the dropped valve, piston, rod and barrel!) and the landowner was more interested in taking photos of the aeroplane in his field than complaining about it. He even helped with the recovery.

The radial engine now has its auxiliary drives gearbox on the back of the crankcase, containing 2:1 reduction bevel gears driving a vertical shaft which drives the main oil pump.

In progress is the oil tank, which also acts as the engine mount. The tank design is a short cone, for which I had to make a set of versatile bending rolls. These will later be adapted to roll the exhaust collector ring from 38mm stainless tube.

Photos of the bending rolls and the oil tank in progress added to the album.

The timing of the Gatwick drone event was extraordinary, both as a distraction from the chaos in parliament and with respect to the sale of the majority of shares in the airport to a French company on the 27th December.

With the tin foil hat on... one might suspect that the event could have been brought to a conclusion very quickly if there was a will to do so.

As usual, there will likely be a knee-jerk response, introducing legislation which causes cost and inconvenience to legitimate users while having no effect on those with malicious intent.

One last photo to round off the year.

A 'dry' assembly with all the 'front end' parts in place. This marks the completion of the induction side of the engine. Next will be the oil supply, scavenge, oil tank, primary drive and ignition systems.

New photo - the first of the inlet tracts loosely assembled.

Now I need to practice Tig welding thin stainless tube a lot.

Yes, indeed I did!

I never owned a motorcycle trailer. I helped out the guys at Freewheel https://www.freewheeluk.net/ many years ago when they needed to design a subframe for an overseas customer who had a Kawasaki Zephyr. I had a Zephyr at the time, so the subframe was designed around my bike and I had the opportunity to try it out.

I second the proposal for a trailer. If you bolt a sub-frame to the bike, supporting a standard tow ball behind the rear wheel and below spindle height, you can tow a conventional two wheel trailer. I have ridden this set up and it is surprising how little difference it makes to the bike.

For me, Paramotoring has now given way to microlighting.

Aside from flying, almost anything with moving parts interests me. I also dabble in a little amateur electronics.

Bikes seem to be a recurring theme here - I currently ride a Triumph 1200 Tiger and I've built a few, including a Panther (British 600cc single) with a whole array of hidden features.

Another couple of photos added, showing the mechanism for engaging the high supercharger speed. A cable will pull on the long end of the curved lever, pulling the ends of the brake band together. When assembled, the brake band sits around the ring gear carrier shown in the other photo.

I had a chap come to visit last week, who is also building a radial engine. I am not the only person in the world mad enough to embark on such a project!

Hi Hann,

I don't consider myself patient. The engine is a hobby, so I work on it when the mood takes me and step back from it as soon as it starts to feel like work. For that reason, there is no projected date for firing up.

I see Bren quite regularly on Tuesday evenings at the Old Buckenham bike night. Very nice chap!

More photos added to the album and more progress.

The supercharger housing has been bored to the profile to fit the impeller, using a fiendishly bodged copy technique which worked rather better than expected. I have not yet bored the holes for the inlet tracts to the cylinders. The inlet tracts will be fabricated from stainless steel and I have a better chance of boring the holes to match the geometry of the fabricated parts than the other way around.

In the meantime, the supercharger parts are assembled and the SU carb hung on the front, looking like it means business.

In other news, I am now the holder of a NPPL(M) and my aircraft passed inspection. I may be gone for some time...

As our 20th wedding anniversary was coming up, my wife asked me to get something 'to spice things up in the bedroom'.

I bought her a small, potted rubber tree.

"There you are", I said, "It's a latex fetish starter kit".

On 05/06/2018 at 17:56, alan_k said:

Well done Pete on the GST, plus of course your continued work on the radial engine.

Thanks Alan. I've just completed the last couple of hours solo at the weekend, so I'll be sending off for my license this week and getting a permit on my Thruster, G-BZNP.

Another photo added - Supercharger housing.

This one is guaranteed to raise accusations of having a CNC mill hidden away in the back of my garage. All the machining was carried out on my manual mill, using an improvised profile copying device. Kiwi dropped in during the process and has seen how it's done. I'll add some photos of the process in the coming days.

A few more photos added to the album. The supercharger (it'd be rude not to) impeller is fabricated around a cone, turned using my home made radius turning attachment. Nine of each of two sizes of impeller vane are cut from 2mm steel, with tabs which fit into the slots on the cone. Each vane is TIG welded at the back of the cone where the tab goes through, then the whole assembly is brazed, using the TIG torch at lower current to accurately heat and draw the Sifbronze material along the join (mostly) without forming blobs and puddles. The assembly is finally trued in the lathe.

PS I have now passed GST for the microlight, so look out for G-BZNP at an airfield near you (provided its not too far from me).