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 a Society of Automotive Engineers (S.A.E.) journal discussing engine valve clearances, material properties, and hydraulic lifter compensation.
| Identifier | ExFiles\Box 158\5\ scan0023 | |
| Date | 1st March 1939 guessed | |
| 114 S. A.{Mr Adams} E.{Mr Elliott - Chief Engineer} JOURNAL (Transactions) Vol. 44, No. 3 exhaust gases or condensed products formed by the combustion of gasoline containing 10 cc per gal of tetraethyl lead-ethyl-dibromide at any temperature below 1600 F (870 C). No attempt is made to add or detract, or even criticize this list, it being quoted to bring out the fact that, in five of the seven requirements, “high temperature” is stressed. Since this factor is so predominating and is the cause of the majority of difficulties, it seems only logical that any progress that can be made to reduce temperatures will aid in bringing outstanding results. The data presented in Fig. 12 are a graphical representation showing the effect temperature has on the ultimate strength and hot hardness⁴ of two typical valve steels. The relative values of ultimate strength and hot hardness chosen for this particular plot are based on the more or less approximate relationship between Brinell hardness and ultimate strength, namely, multiplying Brinell hardness by 500 gives a rough approximation of the ultimate strength. Curve A is the strength of a widely used hardenable steel and B is that of a typical austenitic type. These curves clearly illustrate the desirability of reducing temperatures from the viewpoint of improvement in the strength factor; as, for example, a reduction from 1400 to 1100 F increases the ultimate strength from 19,000 to 43,000 lb per sq in. Likewise, the austenitic type follows the same trend. These data also bring out the relative difference between hardenable and austenitic types of steel as far as hardness is concerned at high temperatures. The hot hardness data indicate there is a distinct relationship between it and the ultimate strength and illustrate clearly the fallacy of using room-temperature hardness figures as criteria of high-temperature operation. The hardenable types generally average 1 1/2 to 2 1/2 times the hardness of the austenitics at room temperature whereas, as the temperature reaches the red zone the austen- Fig. 9 – The two curves illustrate the two extreme cases encountered in the variation in clearance between the valve and its cam 1. The physical properties at room temperature shall not be affected by repeated heating to 1600 F (870 C) and cooling in air. 2. The material shall not warp or become brittle at any temperature between room temperature and 1600 F (870 C). 3. The tensile strength at 1600 F (870 C) shall not be less than 25,000 lb (11 tons) per sq in. 4. The tip hardness at room temperature shall not be less than 75 scleroscope. 5. The stem and head hardness shall not be less than Rockwell C-52. 6. The Izod value at room temperature shall not be less than 10 and, between 1000 F (540 C) and 1600 F (870 C), it shall not be less than 25. 7. The steel shall not corrode in air or in the presence of ⁴“Hot Hardness Data,” courtesy S. D.{John DeLooze - Company Secretary} Heron and O.{Mr Oldham} E.{Mr Elliott - Chief Engineer} Harder. Fig. 10 – The sketch shows schematically how the hydraulic lifter accomplishes its compensation Fig. 11 – This relation between inlet-valve opening and exhaust closing has the clearance change illustrated as “aircraft” at idling or cold conditions Graph Text: Fig 9 Y-axis: Clearance Fig 9 X-axis: Cold, Idle, Low Speed, Full Load, High Speed Fig 9 Curves: Aircraft, Automotive Fig 11 Y-axis: Lift of Valve Fig 11 X-axis: Crank Deg Fig 11 Curves/Labels: Exhaust Closing, Top Dead Center, Inlet Opening, Running, Starting | ||