Small Internal Combustion Engine Design — Cooling and Associated Parameters, Heat Rejection Methods 670526
In the case of small, lightweight aircooled engines the fin design is of utmost importance. The basic consideration is to make maximum use of the material in the cylinder to obtain maximum heat transfer for minimum material used. The trapezoidal fin approaches the ideal construction and is more effective than either the rectangular or triangular types.
The author illustrates how thinner fins mean better utilization of material, together with an additional advantage in that cooling surfaces are doubled and the amount of heat transferred is increased. An important point to be considered is the spacing of the fins so that airflow is not reduced between them. Finally, provisions must be made for the disposition of foreign materials, which may block airflow, if the engine is to operate in a dirty environment.