O.S. LA .65 11 c.c. Model Diesel Engine

This is a plain bearing model aero engine intended for sport model aircraft. It was only ever offered by O.S. with glow ignition. It is now long out of production.

The engine has been converted to diesel operation by removing the factory glow head and installing a suitable diesel conversion head. The diesel head shown in the video was made by Andrew J. Coholic of Canada in 2005. It is similar in construction and operation to the well-known U.S. made Davis Diesel Development (DDD) conversion heads, offered to aero-modellers in considerable variety for many years in the 1980's and 1990's.

Two issues were identified during this run:

1. The carburettor rotor valve is seized open. Hence it is running at full speed.

2. There is an air leak in the remote needle valve assembly. Small bubbles may be seen in the clear fuel line leading to the carburettor. The main needle "O" ring is perished. The result is the admission of air to the fuel line.

The above issues will be addressed and further test runs undertaken.

Propeller: Master Airscrew "K" Series 13 x 8

Fuel Composition:

1. 35% Di-ethyl Ether
2. 25% Castor Oil (lubricant grade)
3. 38.5% F-34 AVTUR
4. 1.5% AMSOIL Diesel Cetane Boost (2-Ethyl Hexyl Nitrate)