Engine was designed to work into a keel condenser in a 24” hull.  Re-use of condensate in the boiler precludes the use of oil in the cylinder which has to rely on any lubrication it can get from the use of saturated (ie un-superheated) steam.  To reduce wear under these conditions most bearing surfaces are of cast iron and bearing pressures have been kept low by the use of a balanced slide valve and piston rings with minimum outspring.  To avoid the problem of springing these small gapped rings over a solid piston, this is built up of ‘washers’ - which also have the big advantage that these can be lapped individually to give very close ring clearances, in the order of ‘tenths’, and give an excellent seal.  The only non C.I. bearing surface exposed to steam is the self lubricating ‘Rulon’ rod seal.
 To prevent excessive condensation of the unsuperheated steam, the cylinder is both jacketed and lagged and the jacket becomes the reservoir supplying the internal admission slide-valve.
 Internal iron surfaces are all protected from rust by flooding with Shell ‘Ensis’ fluid after running.
 Measured power at 100 PSI,  1800 RPM, running non-condensing was approx 1/32 HP.
 

 PROBLEMS: -  1.  The jacket should have been provided with its own independent, circulating, steam supply.
                         2.  It proved very difficult to get rid of all the Ensis fluid at the start of a run, before connecting to the condenser.