From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Page from an automotive journal detailing engine component testing and comparative performance analysis.
| Identifier | ExFiles\Box 50\3\ Scan044 | |
| Date | 27th January 1921 | |
| January 27, 1921 AUTOMOTIVE INDUSTRIES THE AUTOMOBILE 167 water circulates through a standard radiator such as is used on the car. The radiator is cooled by circulating water from an outside source around the outside of the radiator; that is, the cooling medium is water instead of air as used in the car. However, since the water passing through the engine has the same resistance as in the car, it has the same temperature drop, for the quantity circulated is the same in each case. The temperature of the engine water is controlled very easily by this apparatus, and car conditions are duplicated. The temperature of the engine water outlet was kept at 150 deg. fahr. for all the tests. Fig. 14 is a photograph of the connecting-rod, inlet valve, exhaust-valve, piston-pin and the pistons. The connecting-rod length is 11 in., the weight complete with bearings is 46.35 oz. and the center of gravity is 2.60 in. from the center of the crankpin end. Two pistons are shown at the upper part of the photograph. The one to the left gives the 4.25 to 1 compression ratio; the one to the right gives the 5 to 1 compression ratio and is of the constant-clearance type. At the bottom the latter piston is shown from a different angle. A set of 4.25 to 1 compression pistons of the constant-clearance type was not available for the comparative tests; however, ⅛-in. wide piston-rings were used in each case and the 4.25 to 1 compression pistons were relieved at the side in an endeavor to give the pistons approximately the same bearing area as the other pistons. The cylinder clearance given the low-compression pistons was 0.005 to 0.006 in. and that of the high-compression pistons 0.0015 to 0.0025 in. The weight of three ⅛-in. wide piston-rings is 1.82 oz.; that of the 4.25 to 1 piston, 13.52 oz.; that of the 5 to 1 piston, 18.65 oz.; and that of the piston-pin, 5.60 oz. The weight of the complete engine without the clutch is 660 lb. The weight of the complete powerplant, engine, clutch and transmission is 780 lb. Testing Apparatus A Weston tachometer was used to indicate the speed. This was checked repeatedly by a revolution counter throughout the entire range of speeds used. The engine cooling-water temperature was obtained by a radiometer calibrated for the range used. Particular care was used in weighing the fuel for each run. Two fuel tanks were used, one for a general supply and the other for weighing the fuel consumed in 120 sec. The time interval was obtained from the second hand of a watch and the use of a three-way valve connecting the two tanks to the carbureter. Both tanks were equipped with gage glasses so that the level of gasoline could be kept almost the same. This scale balances readily within 1/100 oz., even when the rubber tubing connected with the fuel line is in place. During the tests the windows of the laboratory were opened and the room temperature kept close to 65 deg. fahr. on all the runs. The average barometer readings for comparative tests Nos. 1 and 5 were 30.23 and 30.22 in. of mercury respectively. The gasoline used was Target brand, made by the Western Oil Refining Co. The weight of a sample gallon was 96.80 oz. and the heat value per pound was taken as 19,500 B.t.u. in the calculation of the thermal efficiencies. Comparative Tests Fig. 15 shows the engine characteristics at full load with the 4.25 to 1 compression ratio. The maximum brake mean effective pressure comes at 1000 r.p.m., with a considerable reduction at 400 r.p.m. due to the delayed inlet valve timing. The maximum fuel economy is 0.613 lb. per b.hp. per hr. The mechanical efficiency is very good at low speed but drops off rather fast as the speed increases. The peak of the power curve is at 2600 r.p.m. Fig. 16 shows the results of tests Nos. 2, 4A and 3, in terms of miles per gallon for 4.5, 3.5 and 2.5 rear axle gear ratios and 4.25 to 1 compression ratio. It will be noticed that a material increase in mileage is obtained as the engine load factor is increased by changing the rear-axle gear-ratio. Fig. 11 (above)—Section of cylinder head showing short cast-in intake manifold Fig. 12 (below)—Vertical section of 2-in. carbureter used in the tests Fig. 14—Parts of engine used in test. Of the two pistons at top, the one nearer the center gives the 4.25 to 1 compression ratio, while that at the right gives a 5 to 1 ratio and is of the constant clearance type. Another view of the latter is seen at the bottom | ||