Part one by Ramon Wilson

When my first 'vintage' diesel was made about six years ago it did not take long to discover that treasure trove of all matters I/C -  the 'Model Engine News' (MEN) web site. Set up and run by the late Ron Chernich in Australia this labour of love of has provided many hours of entertaining information on all sorts of interesting I/C subjects on a monthly basis right up until Ron's illness got the better of him.

Now, I've always had a passion for diesel engines having owned many, mostly basic, versions over the years but when I saw this I was totally spellbound.

The description showed it to be an 'Atomatic 4' an Italian design and built by one of the 'Engine Boys' Les Stone. The engine features on one of MEN's 'tribute pages' where you can see that Les is a prolific builder of some truly superb engines. With that help from MEN and some photos and measurements from Eric Offen, who just happens to own one, there was also treasure in the form of an advertisement with a cut-away drawing...

...and another picture of a display board.
The cutaway answered questions on the intake and delivery system - note there is no needle valve - and the front mounted crank driven rotor disc was a complete surprise. The fuel tank sits over the crankshaft which although unusual in UK engines was frequent in Italian designs. It kept the engine short from an installation point of view and gave it a more streamlined look which was no doubt a selling point. One thing that threw me though was the internal backplate cast in situ albeit with a hole in it and a separate mounting plate. I could not understand the reason for the knurled screw set in the middle of this either but this would be revealed at a later date.

These two images were printed off along with images of Les's version and various parts carefully measured.

With the bore and stroke known it was possible to approximate other dimensions and from these create a reasonable set of working drawings for a 5cc capacity engine.

Swarf production got underway with two milled blocks and two bored holes.

When I first drew this out I could not fathom why the case was cast with an integral back-plate which then had a hole in it. I decided to leave the plate out and make it a straight through bore. Something obviously fitted into the hole but it would be a while before I could make a guess based on a image on the net and one which, I'm certain, was confirmed recently on some drawings. I was convinced it is a crankcase pressure relief valve - no doubt intended to be used in conjunction with a timer to cut the engine on free flight models.

Bearing in mind the two blocks are primarily in case a boo boo occurs I have decided to do one as first drawn - without the integral plate - and the other as per the prototype.

It proved difficult to hold in the four jaw to bore the case, so I resorted to the face plate putting some 2.5mm MDF board behind for the tool to break into.

Despite having had my workshop for many years my clamping kit is, to say the least, minimalist. Along with a few small home made ones I have four of these clamps left over from the Unimat which preceded my 'first' lathe (ML10). Nice and small they are constantly in use and allow for clamping in tight spots. The 'packing' is a series of 25mm bar cut into varying lengths and drilled through 6.5mm and counterbored to take a 6mm caphead. This enables screwing to the faceplate if desired to keep the packing from  falling away and, as here, they can also be pressed into service as counterweights. All clamping, lathe or mill is done using caphead screws of various lengths from 8mm to 120mm - anything required over that then it's out with the studding.

With the case bores and those for the liners done next up was to mill out side clearance for the con-rod. This was a 'deep' hole and that long series finger mill bought for a quid 'just in case' finally saw some use.
Milling the transfer ports came next - another 'deep' and basically out of sight operation. A small shell mill made for the Super Tigre build was pressed into service - just needing a longer shank this time.
Then finally milling the exhaust ports in at 30 degrees. The position was found by indicating off a plug gauge used for boring the case pushed into the hole.