Following initial steam trials of the Bull Engine, it was decided to remove the engine's cylinder head for a closer inspection of the engine's piston and piston rings. This is believed to be the first time a cylinder head had been removed from a Cornish Beam Engine in preservation.

 

The Bull Engine is fitted with a patent piston arrangement, in which the main engine piston contains four annular pistons, which act to push the main piston ring against the inner wall of the cylinder.

 

From our investigations it was found that this system (also fitted to the Grand Junction 90 inch Engine) was not working correctly, and a large volume of steam was leaking past the piston during the engine's power stroke. Hence, we took the decision to dismantle and refurbish the annular pistons and the main piston ring, before re-fitting them to the engine for further testing.

 

Three more test runs were made of the engine (with the cylinder head still removed) and any leakage past the piston ring noted. Finally, following two sucesful tests, the cylinder head was put back on to the engine, ready for more steam trials to commence.