wim an expansion mun no rm than an I and .i mmprmun mm mmhi, mm the Chatterton simpm W um urnmmmu, llypiireimnsion engines Fm Hon mmugh muhumcally-npcmluil nimm mm, mm coupled plpm lmm w rylinden phmcd lmdcgrcc apart induced a flow cm into me cylmd u "out live urn ~r than was needed torcomhmtmn, [lircxmwScnmgmtnolthccngmcmternnll) ItisaninlnglungldndApparently s m nnupilulstalctwu} nihilmcxmx me tworsnoke cycle In gm mum pom u. .u. exceptionally ugh: engine 46 : SOME UNUSUAL ENGlNES that the morecomplete-expansion cycle is practical only for engines that are not frequently operated at light loads. The mean cylinder pressure during the latter part of the expansion stroke tends in light-load operation to be near to or even lower than the friction mean pressure, and when this happens the hyperexpansion portion of the cycle may involve a net loss rather than a gain in efciency. The principle might best be employed for engines such as are used in pipeline pumping stations where great reliability, long life, and good fuel economy, are required. Running on a fuel such as methane, a large hyperexpansion engine might be a good proposition; but a large engine is not subjected to the restraints on turbocharger e'iciency that prompted the design of the little Simplic. It is not difcult to see applica tions for the latter driving small pumps, generators, and the like. Nor is it diicult to resist the argument that these considerations should have been discussed in the chapter on unusual charging and scavenging. What, after all, is the turbocharger or the exhaust power turbine if it is not a more complete expansion device? All this must be accepted; but the unworldly simplicity and apparent crudity of construction of the Chatterton Simplic gives it a place here, Permission to reproduce pages 43 to 46 of "Some Unusual Engines" by L.J.l(. Setright (Mechanical Engineering Publications Limited, 1975) on the website insulatedpulseenginecom has been granted by The Institution ofMechamcal Engineers.