The "Ideal" First IC Project
This is a question I'm frequently asked and it's a difficult one to answer. I lean towards a compression ignition (CI) type, purely from an ideological predisposition (and because I love the smell of ether fumes in the morning 
). This is probably an actual negative to modern builders who have no experience with operating this type of engine, compounded with the increasing difficulty of obtaining the correct fuel, or even the ingredients to mix your own! But all that aside, let's look at characteristics that are important:
- A proven, developed design with enough prototypes made to iron out bugs due to manufacturing tolerances, etc.
- A displacement of somewhere in the 0.09 to 0.15 cuin range (1.5 to 2.5 cc). Much smaller than this and the parts require watchmaker skills; larger and mistakes become expensive. Additionally, the bore of engines in this range is "sweet"; beginners will have no great difficulty achieving the required finish and uniformity. Above and below though, extra care and effort are required.
- No screw-cutting required. While I believe the ability to cut accurate threads is ultimately mandatory for all model engineers, reports from some first-time builders suggests that removing it from the equation for the first attempt is a distinct positive.
- Just simple turning, drilling, and tapping operations required—no special tooling, milling, or slitting required. These things too should be part of a model engineer's skills inventory, but they can come later.
- No bush for the crankshaft; simply a reamed hole in the crankcase makes for one less thing to worry about. Pressing in a bush presents some 'gotchas', as does using a Locktite fit. Easier to skip it. Engine life and performance will be reduced, but we can live with that—many commercial engines have!
- Builders' choice for ignition type: glow, CI (diesel), maybe even spark. Some early English engines like the ED Mk III offered both CI and glow heads out of the box. This would let the builder use the system they are most familiar with, then try the other after confirming that the engine will run.
The question of using a casting for the crankcase verses one hogged from a lump of aluminium is contentious. A casting simplifies things. Machining it is generally the first task as other parts will be made to fit it. This provides the beginner a grand opportunity to have an expensive mistake when skills and confidence are at their lowest. On the other hand, a "hogged" case requires even more skills, but permits a few stuff-ups at an acceptable cost in material and time (to obtain a replacement that is, not in the overall effort invested). But this comes at the expense of either a dependency on milling operations, or a lot of sawing and filing—both of which are skill requirements we wanted to avoid.
If pressed, right now I'd recommend the ML Midge, or the Schroeder Deezil. The Midge is smaller than I'd prefer, and requires hogging the case. The Deezil is the right size, but requires screwcutting. The Owen Mate would be another contender, but as the crankcase extrusion is no longer available, a builder is faced with both hogging and screwcutting! All these engines are proven designs and have been successfully tackled by many first time builders with positive results. But late this month, two alternatives surfaced that have all the features on the list, provided you accept that castings are an acceptable risk. What are they? Wait for next month... .
ETW and the Deltec
Editorial
