74 PRESIDENTIAL ADDRESS — SECTION A. 



Engine used in Tests: It was decided to carry out the tests 

 on an ordinary motor-car engine, isolating it from tlie car so 

 that the various observations might be more readily made. 

 This engine was of the ordinary four-cylinder vertical Otto 

 cycle type, as built for motor-car work, with the cylinders cast 

 in pairs. The cylinder diameters were 3^ inches, and the stroke 

 4^4 inches. The valves were arranged in side pockets, and the 

 magneto, carburettor, and exhaust pipe were arranged ua the 

 same side. The ordniary type of water cnxulation was htted, 

 the cooling fan being disconnecced during the tests. The valve 

 timing ana ignition remained the same throughout ail tests. 

 This was a very inetlicient engme, but as tne tests were mainly 

 comparative from the point 01 view of fuel, this was not con- 

 bidered of very great moment, especially as the engme was 

 tnoroughly overhauled before the series 01 tests was inade and 

 carefully inspected before beginning a new test to ensure that 

 it was in good running condition. 



Arrangements for Tests : In order to ensure greater accuracy 

 in carrying out the tests, and to enable the results obtained to 

 be checked, arrangements for complete thermal efticiency tests 

 were made so that heat balances could be constructed. The 

 engine was mounted on a rigid testing stand, and the cranli 

 shaft connected by means of a universal joint to the shaft of 

 the water-cooled brake wheel, which was carried on ball bear- 

 ings, so as to eliminate friction. The brake arm rested, 

 through a knife edge, on the platform of a small sensitive 

 balance, and the load was kept perfectly constant during the 

 period of each test by means of an adjusting screw operated by 

 hand. Water passed from the town mains through the jackets, 

 and the calorimeter which absorbed the heat in the exhaust 

 gases. All thermometers and other measuring instruments used 

 were carefully calibrated before the tests. The temperature of 

 the exhaust was measured by means of an electric thermo-couple, 

 specially arranged and calibrated for the tests. The analysis of 

 the exhaust gases were effected by means of the Orsat apparatus, 

 sometimes in duplicate, and also by means of continuous samples 

 capable of being examined more closely in the labdratorv for 

 otiier constituents. 



In order to maintain the l)est mechanical operating condi- 

 tions of the engine, it was decided to secure the services of 

 experts in the " tuning up " and running of petrol motors, and 

 the works manager of a local garage and an expert motor 

 mechanic were selected for this jiurpose. 



Particulars of Pud Used: The chcnnc.il and ])hysical i^ro- 



perties of the fuels used have already been given. The calorific 



valves were detennined by means of the Mahler Bomb calori- 

 meter. 



