Tilly built a 20 HP engine with four upright cylinders, which was specially built to be installed on the airplane built by John Duigan in 1908.

From Appendix 7: The J.E. Tilly engine was made in Melbourne and had 4 vertical cylinders in line, and was air cooled. It gave 20 HP and was installed on the Duigan biplane.

“The Tilly engine on a biplane”

From Appendix 12: The four-cylinder engine is shown below in a drawing,

"Engine in John Duigan's biplane"

“Diagram with drawing of Duigan's airplane”

-The engine is an upright, four-cylinder engine, which had air-cooled cylinders and water-cooled cylinder heads.

-At 1,800 rpm it gave 25 HP.

“The Tilley on Both Sides"