Do It Yourself?
Among those people who start out as amateur racers, some will develop a role as an engineer and learn to understand the shortcomings of their production engines in the quest for more horsepower. Of those people, most will choose not to increase horsepower further, but instead focus on other areas of improvement. This could be on the vehicle itself or on using a stronger engine.
A few people though will not want to accept horsepower limits, and will choose to develop their own engine. Since this is definitely not the fastest and easiest route, we should give them our compliments now. As all of us with experience of engine development know all too well, the actual development begins with the first engine start-up, not before, which is why taking the initiative to build one's own engine deserves the compliment.
There are a some basics though that need to be understood before such an initiative can be realised. For example, one should know whether to use existing components or to make them yourself. In all honesty, I have not seen many amateur racing projects where all the parts were made from scratch. In most projects, some components are sourced from production units, and are typically components that did not fail in the first place.
In the example I want to use here - single-cylinder competition engines - the builder uses mostly production parts such as gearboxes and crankshafts, as well as smaller parts such as valves, valve springs and so on. Parts designed from scratch and produced using prototyping processes are crankcase housings, covers and cylinders. The remaining parts are often those based on standardised parts with engine-specific modifications, such as pistons where the piston head and valve pockets are often made to spec.
I don't want to give too many details about the engine concept (yet), but I can say that the engine is destined for a racing series in northern Europe. Normally the regulations for the single-cylinder racing series, the Supermono, permit engine capacities of up to 800cc. This engine, however, throws in an enormous swept volume of well over 1000 cc - from a single cylinder!
Where a rule of thumb says that any racing piston over 100 mm in diameter will lead to disaster, one can imagine how big this piston is. This of course also affects the crankcase design. As can be seen from the photos here, the design of the engine is quite basic.
The parts shown in the photos are machined castings, all produced by the designer/racer himself, with some advice from a number of friends and interested followers. To give an idea of size, the visible bolt heads are M8, which means the cooling ribs for example will not damage easily.
A closer look to the top end, both with and without the cylinder head installed, reveals a similar approach - keep it simple and use appropriate dimensions.
Some readers may be very interested to read more about this engine, but because the aim of this article is to provide an insight into the kind of initiatives involved in designing and making your own blocks and heads, more in-depth information will have to wait until a future article.
During my search among amateur racers and engineers, I have seen a number of fascinating engine projects, not just in terms of the different levels of design maturity but also the drive which these engineers have in realising their ideas. Creating these kinds of parts forces us to think about their specific functions in the engine, something which has kick-started careers as race engine engineers.
There is plenty of interesting information to share on privately built amateur race engines, so look out for future articles on the subject.
Fig. 1 - Side view of a self-made horizontal single-cylinder race engine. Cylinder and cylinder head cast and machined, crankcase machined from solid
Fig. 2 - Top view of cylinder head and support to the frame
Fig. 3 - Top view into the cylinder, showing the basic approach and shape of the self-made engine components
Written by Dieter van der Put