The second Field Steam Bike owned by Henk van der Wal Part 2
This arrangement was very successful and no annoyance was experienced by the rider of the cycle. The steam whistle—a very effective device—was fitted on the top of the case.
The steam temperature was originally controlled by thermostat, but eventually a small loop of tube was fitted at back of case in a small box with a Mica window for observation by the rider, which proved very successful. Steam pressure varied from 200 to 1,000 p.s.i. and a foot pedal was arranged to operate the safety valve, which otherwise blew off at 1,400 p.s.i.
The burner was a modified Simpson vaporising type, specially made by the late W.H. Simpson, the oil burner specialist of Hastings. It was pre-heated by methylated spirits or acetylene for about three minutes before switching over to paraffin.
The engine was a special type of single-acting poppet valve design, using simple expansion. Bore was 45 mm., stroke 80 mm. It was built to use hot steam at as much as 1400 p.s.i. and was run at 10,000 r.p.m. on test-although I do not believe in such high speeds. The poppet steam admission and exhaust valves were operated by phosphor bronze tappet guides and cam followers. Variable cut-off, 0.80 deg., was obtained by a sliding camshaft, driven by two easily accessible bronze gears wheels. The two cylinders were cast in special hard quality close-grained cast iron, and splash lubrication from the aluminium crankcase proved adequate.
This is the engine from Field #1 but it is almost identical to the second engine
This engine gave great power for it’s size, much more than the best petrol motor-cycle engine, and it ran without viabration. On test it twisted a steel transmission shalft of about ¾ in. dia. Through a full quarter turn.
Transmission was by chain to counterhaft and thence to the rear wheel. To the countershaft was fitted a foot-operated “dog” or “claw” clutch to give a free engine for warming up and to make wheeling about in garages relatively easy. This shaft drove the ¾ in. stroke fuel and water pumps, which were vertical and driven by eccentrics, all fitted in an aluminium case and splash lubricated. Pump delivery was controllable and the fuel was led to the small brass pressure chamber seen at the rear just above the countershaft
The exhaust steam was led through the 2 in. diameter brass tube to therear of the machine. This tube was sealed at the end and contained a number of small diameter copper tubes in which the feed water flowed before reaching the condenser, thus forming an effective feed water heater and assisting the condenser. From the end of this brass tube a smaller tube conveys the exhaust steam back to the first part of the condenser, fitted underneath the countershaft and consisting of a number of thin flattened brass tubes on edge. Then it is collected into a cross tube which, in turn, has a number us small diameter tubes rising up in front of the generator case to the main water tank. No air or circulating pumps were used, the condensate been forced up by the pressure of the exhaust steam to the tank.
The fuel pump, with variable delivery, kept the small pressure chamber supplied—15 p.s.i. being used when standing and up to 45 p.s.i. when running. The fuel supply could be further controlled by hand adjustment of a needle valve on burners supply.
The machine could be ridden away from all cold in a few moments, the burner requiring about three minutes pre-heating, as noted previously, then the rider mounted and as soon as the steam gauge a showed sufficient pressure, the cut off lever--it looks like a gear-lever--was moved to “start” position, and away you went. Should the engine be on dead centre one small push by foot was sufficient.
The rider had to be careful to remember to always sit on the saddle before moving the cut-off lever to start position. The acceleration was so rapid that it was easy to be left behind. All this was in silence and with complete freedom from “choked” exhaust fumes, blue smoke, etc.
Fuel and feed water supply was controlled from the handle-bars and gave no difficulty.
I had some interesting and sometimes exciting trips with this machine. I used to turn at six in the morning and run till 8 a.m. round the district on the country road. So quite was the machine, the engine being silent and only the humming of the tyres being audible, that sometimes, as I came up from behind sleepy cyclists they would awake with a start and nearly fall off their bikes. The steam siren, which was fitted to supplement the whistle, also had an interesting effect. When used in the early morning near road junctions it would sometimes cause windows to be hastily thrown up to frame startled faces. Such times were not suitable for tarrying, and I never waited to witness the after-effects.
After riding an i.c. engined motor-cycle, I had to be very careful not to enter corners or approach road junctions too fast. The silence made speed deceptive, and more than once I had to keep straight on at a cross-road. It was usually found, on returning from a trip, that the speedometer, which registered to 80 M.P.H., was thrown out of gear!
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