760 REPORT— 1897. 



works the exhaust valves, which, as usual, have a small lap ; the other eccentric 

 lias a large negative angular advance, and controls the ad mission valves, which 

 are set with -J-inch clearance. This separation of the admission and exhaust 

 valve gear allows the cut-off to be prolonged to about § stroke without changing 

 the action of the exhaust valves. 



A single powerful bail governor is given control of the cut-off valves for all 

 three cylinders ; but any set of valves may be disconnected from the governor, 

 and then the cut-off by those valves may be raised by hand while the engine is 

 running. It is the practice in the laboratory to allow the governor to retain con- 

 trol of the high-pressure admission valves only, those for the other cylinders 

 being adjusted for each test by hand. This arrangement throws a very light duty 

 on the governor, so that with the aid of a heavy fly-wheel it regulates the 

 engine very closely, and successive indicator diagrams from the several cylinders 

 are very nearly identical. 



Intermediate receivers, each several times as large as the cylinders connected 

 to it, are placed between the high and intermediate and between the intermediate 

 and low-pressure cylinders. In each receiver there is placed an efficient reheater, 

 made of copper tubing. 



The several cylinders are provided with steam jackets on the heads and the 

 bands. A proper system of pipes and valves allows steam to be supplied to or 

 excluded from any steam jacket or either receiver reheater. The condensed water 

 from the jackets of any cylinder, or from either reheater, is collected in a closed 

 receptacle and measured by displacement, five such receptacles being provided. 



The steam-piping is arranged so that boiler steam may be supplied to any 

 cylinder independently ; and the exhaust pipes from the several cylinders are so 

 connected that various combinations of compounding can be made. For example, 

 steam may be exhausted from the middle cylinder into both receivers, and may 

 then pass into both the small and the large cylinders, which then act as low- 

 pressure cylinders. The exhaust steam in any cate is finally condensed in a 

 surface condenser, and is collected and weighed in two tanks on scales. 



Tests on this engine are made as a part of the regular class work in the steam- 

 engineering laboratory, all observations and calculations being made by the 

 students. But the work is all under the careful supervision of competent instruc- 

 tors, who also calculate all the results to give a standard with which the students' 

 calculations are compared. It is our experience that this method gives at once 

 the best instruction to the students and very reliable results, which have been 

 published from time to time for the information of engineers. The paper of which 

 this is an abstract gives a rksume of all the tests that have thus far been made. 



The standard time for an engine test is one hour, which has been found to be 

 abundant, provided the engine has been running a sufficient time under constant 

 condition when the test is begun. "When steam is supplied to the jackets of the 

 cylinders during the test fifteen or twenty minutes' preliminary running is enough, 

 but when steam is not admitted to the cylinders one hour is required, it being the 

 habit to start the engine when cold by first warming all the cylinders by aid of 

 the steam jackets. 



Tests have been made on the engine running as a triple-expansion engine, and 

 also running compound, using sometimes the small cylinder and the large cylin- 

 der, and sometimes the intermediate and the large cylinders. The several com- 

 binations have been tested, both with and without steam in the jackets. The 

 best results have been attained when the engine is run triple-expanding, with 

 steam supplied to the jackets on the heads and the barrels of all three cylinders. 

 With a boiler pressure of 150 pounds, and with cut-off at one-third stroke for the 

 high-pressure cylinder, the engine develops 150 horse-power at 90 revolutions per 

 minute, and uses 13-7 pounds of steam per horse-power per hour, or 2-?3 R.T.TI. 

 per horse-power per minute. 



When no steam is supplied to the jackets of any of the cylinders the engine 

 runs 270 B.T.U. per horse-power per minute, so that the ratio of th.« heat con- 

 sumption with and without steam in the jackets is 



233:270 = 1:1-16. 



