One of the main differences between Paxman's Class B and Class C engines appears to be that the Class C was mounted on a girder frame. The only description of Class C engines published by Paxman, that I am aware of, is that which appears in Catalogue No. 32 of June 1883 (pp 39-40). The description is reproduced below with the usage of bold type and capital letters following that in the catalogue. The opening paragraph suggests that the Class C was introduced shortly before the catalogue was issued in June 1883.
IMPROVED HORIZONTAL HIGH-PRESSURE STEAM ENGINES,
WITH OR WITHOUT CONDENSER.
These engines are of an entirely new design, and present many important improvements. They are especially suitable for large Electric Light Installations; also for driving Machinery in Mills and Manufactories of all kinds, Pumping Machinery, &c.
They are made sufficiently strong to work up to 120 lbs. Steam pressure when required, at a small extra cost. The ordinary working pressure is 80 lbs.
As will be seen in the Engraving, these Engines are mounted on a massive Cast-Iron Girder Frame, which gives great rigidity to the Engine throughout. This frame is so made that the Condenser may be removed or attached at any time by simply breaking the Joint. When the Condenser is removed a Cross Girder piece is fitted to stay the ends of the Girder frame.
Engraving of Class C Engine from the 1883 catalogue.
The Cylinder is of large area, made of Cold Blast Iron, with a separate liner, which forms the Steam Jacket. It is lagged with hair felt and Spanish mahogany, polished and secured with Brass Bands. Indicator Cocks and a double grease cup are provided ; also drain cocks, coupled with bright rods, and fitted with ebony handes.
The Crank-Shaft, Piston Rod, Cross-head Pin, Slide Rods, &c., are of Steel.
The Motion Bars are of neat design, and large proportions for wear, and carefully planed. The two top bars are fitted with large oil cups, with polished covers.
The Connecting Rod and Straps, Eccentrics and Rods, are of the best Forged Iron, finished bright, and fitted with Gun Metal Bearings at each end.
Each Engine is fitted with our Patent Automatic Expansion Gear, which varies the cut-off from 0 to five-eighths of the stroke ; also our new Patent Adjustable Governors, which act directly on the Expansion Valve. These together keep the Engine under the most perfect control, and allow it to run with great steadiness, however varied the load may be, especially adapting it for Electric-Light purposes.
All the Bearings and Glands are made of the best Gun Metal, and are extra large to allow for wear and many hours' continuous running.
The Fly-Wheel is extra large and of ample weight to keep the Engine running steadily.
The Condenser is of the Injector type, self-contained in one casting. The Air-Pump is double acting. The Piston, Valve, Seats and Guards are of Gun-Metal, The Disc Valves are of India-Rubber. It is complete with Injection Valve and Pipe, Overflow Pipe, and improved Vacuum Gauge.
Each engine is complete with Stop Valve, special large Lubricators, Spanners, &c.
PARTICULARS OF IMPROVED HORIZONTAL HIGH-PRESSURE STEAM ENGINES
Page updated: 06 JAN 2009