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 a 'Ramp' type cylinder head with a standard Bentley head on a single-cylinder test unit.
| Identifier | ExFiles\Box 133\2\ scan0059 | |
| Date | 26th July 1934 | |
| X4706 To Sg.{Arthur F. Sidgreaves - MD} c. to Wor.{Arthur Wormald - General Works Manager} c. to Rg.{Mr Rowledge} c. to E.{Mr Elliott - Chief Engineer} c. to By.{R.W. Bailey - Chief Engineer} c. to Lr.{Mr Ellor} He/GRP.15/KM.26.7.34. Single Cylinder Bentley Unit. Period covered by this report: 20th March to 21st July, 1934. This engine has completed a further 80 hrs. 20 mins. actual running time since the last report was issued. The work carried out during this period consists almost entirely of a comparison between the "Ramp" type cylinder head (Lec.3739) and the normal Bentley head (Rh.{R. Hollingworth}1517). Summary. Comparison of "Ramp" and Std. Heads. The "Ramp" Head in its present form (Lec.3739) is inferior for power up to 2750 r.p.m. (max. loss of 2.7% at 1800 r.p.m.). Above 3000 r.p.m. there is an appreciable improvement which gradually increases to 5.5% at the power peaks, ultimately reaching 14.5% at 4500 r.p.m. The power loss below 2750 r.p.m. is due to detonation, as this loss disappears when running on anti-detonating fuel. With regard to audible detonation the Ramp is very inferior. At 1000 r.p.m. the detonation is 88% greater than std. Above this speed the detonation falls off very slowly and is not zero until a speed of 3500 r.p.m. is reached; whereas the std. head is clear at 2200 r.p.m. If the detonation of the Ramp head is reduced to the level of the std. head by retarding the ignition, then the power of the former falls below that of the latter until a speed of 3150 r.p.m. is reached. Reviewing the possibilities of fitting the Ramp head to the six-cylinder car engine, we find that - (1) In its present form, detonation would rule it out. (2) The cause of the greater degree of detonation is either plug-position or reduced turbulence through larger inlet valve and/or at end of compression stroke. | ||