18 



with gasoline will come about slowly and by the time such condi- 

 tions exist, the Section expects to have secured enough experi- 

 mental data upon which to base another more definite and tech- 

 nical bulletin. 



The main series of tests were made upon Engine No. i,* in 

 eight horse power, four cycle, water cooled horizontal engine using 

 a make and break igniter. A complete thermal efficiency test was 

 not made. The temperature of the jacket water was taken merely 

 to determine the condition under which the engine was working, 

 but the amount used was not determined. 



The brake horse power was determined by means of a Prony 

 brake and a speed indicator, and the indicated horse power by 

 the number of explosions and the area of the indicator cards. A 

 device was designed for counting the number of charges exploded 

 in the engine. Indicator cards were the means of determining the 

 proper timing of all events of the cycle, and were taken quite 

 frequently to determine the least opening of the fuel valve which 

 would give a full card with high maximum pressure. The point 

 of ignition was such as to give greatest area to indicator card. 

 That is, the maximum pressure from the explosion of fuel was 

 brought about at such a time as to give the line, showing the rise 

 in pressure, a forward inclination of about 4 or 5 degrees t Igniter 

 mechanisms of different designs require such variable lengths of 

 time to act that the point of release of this mechanism is of little 

 value. 



Engine No. 2 was similar to No. I except that it was of the 

 vertical type and rated at three horse power. 



Engine No. 3 was a two horse power, two cycle, water cooled 

 horizontal engine using a jump spark ignition. 



* Valuable assistance with the engine tests has been rendered the Section by 

 the Lennox Machine Co., of Marsha lltown, Iowa, for which we desire to express 

 our appreciation. 



tGas Engines by F. R. Hutton. 



