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).
Report comparing exhaust valve temperatures on a standard 25/30 cylinder head versus a modified head with a lowered water jacket.
| Identifier | ExFiles\Box 106\5\ scan0174 | |
| Date | 12th November 1936 | |
| 524 55L Rm{William Robotham - Chief Engineer}/Mths.{Reg Matthews}35/AP.12.11.36. To Hs.{Lord Ernest Hives - Chair} from Rm{William Robotham - Chief Engineer}/Mths.{Reg Matthews} c. to E.{Mr Elliott - Chief Engineer} c. to By.{R.W. Bailey - Chief Engineer} c. to E/TGD. Exhaust Valve Temperatures. We have been comparing the exhaust valve temperatures on the standard 25/30 Cylinder Head and on Cylinder Head to LeC.5222 in which the water jacket is lowered. From our tests it will be seen that the valves of the standard Cylinder Head are actually quite considerably cooler than the valves on LeC.5222, the reason for this may be in the actual shape of the exhaust ports, there is a tendency on LeC.5222 for the gases to be thrown back on to the valve. The attached curve BV.98 shows the difference in temperature of the valves in the two heads, it will be noticed that the maximum valve tmperature is reached at the position of maximum economy in each case, although with LeC.5222 the specific consumption is lower at the position of maximum economy than with the standard head. The end inlet ports on LeC.5222 are slightly larger than on the standard head and this may have for some reason improved the distribution and also made for a freer inlet for the gases. The power output is slightly higher with LeC.5222 head although the compression ratio of the heads was exactly the same in each case, namely 6.0 : 1. The attached curve BV.97 shows the power output of each head. We also tried the effect of varying the tappet clearance on the standard head to see what effect the extra duration of seating would have, with the normal tappet clearance of .006" the temperature was 837°C. and with .010" clearance 830°C. whilst at .015" clearance the temperature had dropped to 820°C., no further increase in clearance up to .025" had any further effect, the temperature remaining constant at 820°C. These figures were all taken at the maximum economy position. In order to try and improve the LeC.5222 head we are going to fit a larger valve in view of the figures taken with the varying tappet clearances, we are at the same time going to remove one or two obstructions in the ports. The reduction of specific consumption is interesting and will be dealt with further when we try larger inlet ports, the improvement of consumption is from .625 to .600. Rm{William Robotham - Chief Engineer}/Mths.{Reg Matthews} Attached curves BV.97, 98, 99. | ||