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Radial engine build


ptwizz
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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.

 

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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.

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  • 1 month later...

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...

Edited by ptwizz
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Superb work, and i admire your steadfast comittment to such a huge project, it`s all i can do to summon the enthusiasm to change my bikes` oil these days..

When do you think it`ll be ready to fire up?

 

Well done on the NPPL..

 

BTW, we have a mutual aquaintance - Bren (works in the builders merchants near you)?

Edited by Hann__
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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!

 

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  • 3 months later...

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!

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  • 2 weeks later...
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  • 4 months later...

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.

 

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  • 4 weeks later...

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.
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  • 3 months later...

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!).

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  • 4 months later...

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.

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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.

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  • 3 months later...

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.

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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.

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  • 11 months later...

Hi Ptwizz. Awesone post,  excellent creativity to circumnavigate engineering problems. I have also been building my own designed radial for past 3 years. Interesting to see how you made the master rod, very clever,  I made mine in  2 separate assemblies as well but like a cotton real. I machined crankcase from 11 inch billet and I am using VW bettle heads and barrels. I went for 5 camshafts and 5 carbs. Mine is 5 cylinder , 2200cc , will run at 2000rpm. What stage are you at now, have you got to run yet. I am rushing to get the basic engine running this summer. Would be great to share some info with you,  all the best tim 

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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?

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Engine made with basic machinery like you. I thought the interconnecting rods might be a little weak so made new ones which set me back. Assembled the engine to get the cam timing sorted. Timing is minefield because of the low rpm I will be running. I looked at Harley's which varied massively and also the engine on my PA28 (fly from White Waltham)which has similar rpm. In the end I settled on what I think should be OK. Compression ratio i am aiming for just over 7:1.  I changed the design of the master-rod many times and settled for phospher bronze main bearing which will be pressure fed. The interconnecting rods are ally and didn't want to weaken them with the oil hole at the knuckle pin end so drilled in from the inside of the rod lightening groove instead of the outside like the piston pin. 

It is quite amazing the forces involved when it is turning which is why I think 2000rpm with max 2500rpm will be safe. 

I am familiar with the Kinner balance formula which I am using. Bob weights are finished now and nearly ready to balance.

I am using a slave test pin to hold the 2 crank webs together for balancing then I will press the crank together. The main pin I machined from HE15 and had hardened and tempered. I think I went to just over Rockwell 40 to prevent it being too brittle.

The pushrods i used were basic VW rods which are light weight ally but incredibly strong. I cut them to correct length and turned the rods down on one end until the hardened steel insert fell out, then pressed it back in with rod the correct length.

The top end is all exposed, no lubrication so I will fill the pushrods which are hollow with grease for lube of the rockers and tappetts  cheers  Tim 

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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?

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My piston pins are 22mm as supplied with pistons and the knuckle pins are 18mm.

The main pin was made from H13 – orvar material  , you were correct.

I have fitted weaker  valve springs as the engine is low rpm engine to offload the cam drive train. I have oil tank beneath the crankcase and large oil return holes in the front chamber (cam and tappet area) and one between the 2 lower cylinders. I will use a driven fan on the front of the engine to blow air over the 5 cylinders.

I would like to fit the engine to a motorbike if it runs well enough. I have a donor bike with shaft drive , but thats a long way off. 

I am fitting a window in the front chamber of the crank case for viewing and hope to fit a window in the rear back plate as well.

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