THE SILSBY ROTARY STEAM FIRE ENGINE.

The distinguishing feature of this engine will be found in the fact that, in both the cylinder and pump, the rotary type is substituted for the reciprocating or piston principle.

Fig. 412.

The larger sizes of these engines, Fig. [411], are hung on platform truck springs in front and on half-elliptic springs in the rear, and are braced and stayed to withstand violent shocks in the rapid driving over pavements. Although fitted to be drawn by horses only, they can be supplied with rope reel and drag rope.

Fig. 413.

The Silsby steam cylinder consists of two rotary pistons or cams, mounted on steel shafts and working together within an elliptical steam-tight case. Live steam from the boiler enters at the bottom of this case, and in its passage presses apart their long teeth or abutments, causes the two cams to rotate, and exhausts from the top into the tank and feed-water heater; these cams are provided with teeth or cogs, adapted to mesh with corresponding recesses in each other, so that a steam tight joint is maintained between them and leakage thereby prevented from passing directly upward into the exhaust.

The sides of these cams have their arcs turned to fit the heads of the case, and are so adjusted that, while being practically steam tight, allowance is made for expansion and contraction. In the ends of the longest teeth of the revolving cams are placed removable packing strips, which are forced outward into contact with the cylinder walls by means of springs. These packing strips may be removed through openings in the sides of the cylinder, and readjusted to take up the wear, which is confined to the ends of these adjustable strips. This can be done without taking the pump or cylinder apart.

Fig. 414.

Fig. 415.

The construction of the pump is similar to that of the cylinder; in this there are three long teeth in each cam instead of two. One shaft of the pump is coupled to the corresponding shaft of the cylinder, there being outside gears on both cylinder and pump to compel a uniform motion of the cams and to equalize the pressure. This construction secures a transmission of power at once direct and positive in Fig. [412].

The stuffing-boxes, used on both cylinder and pump, are self-adjusting, reduce friction and insure tightness. Valves are entirely absent from the pump and cylinder. The water ways being large, anything liable to enter the suction will pass through the pump without injury or interruption; the pump requires no priming, but when started will immediately without the aid of a check valve lift water vertically any required distance up to 29 feet.

The construction of the boiler ordinarily supplied with this engine is shown in Figs. [414]-[415]. In the fire-box hangs a series of circulating water tubes arranged in concentric circles and securely screwed into the crown sheet. These drop tubes are closed at their lower ends by means of wrought-iron plugs welded in, and within each of them is placed a much smaller and thinner tube, which latter is open at both ends. The cooler water in the boiler descends through the inner tube and is thus brought directly into the hottest part of the furnace, whence, after being for the most part converted into steam, it ascends through the annular spaces between these inner and outer tubes.

The gases of combustion pass from the fire box to the stack through smoke flues, the lower ends of which are expanded into the crown sheet, and the upper ends into the top head of the boiler.

Fig. 416.

TABLE OF EFFECTIVE FIRE STREAMS.

USING 100 FEET OF 2¹⁄₂-INCH ORDINARY BEST QUALITY RUBBER-LINED HOSE BETWEEN NOZZLE AND HYDRANT, OR PUMP.

Smooth Nozzle, Size	³⁄₄-inch.
Pressure at Hydrant, lbs.	32	43	54	65	75	86
Pressure at Nozzle, lbs.	30	40	50	60	70	80
Pressure Lost in 100 feet, 2¹⁄₂-inch Hose, lbs.	2	3	4	5	5	6
Vertical Height, feet	48	60	67	72	76	79
Horizontal Distance, feet	37	44	50	54	58	62
Gallons Discharged per Minute	90	104	116	127	137	147
Smooth Nozzle, Size	⁷⁄₈-inch.
Pressure at Hydrant, lbs.	34	46	57	69	80	91
Pressure at Nozzle, lbs.	30	40	50	60	70	80
Pressure Lost in 100 feet, 2¹⁄₂-inch Hose, lbs.	4	6	7	9	10	11
Vertical Height, feet	49	62	71	77	81	85
Horizontal Distance, feet	42	49	55	61	66	70
Gallons Discharged per Minute	123	142	159	174	188	201
Smooth Nozzle, Size	1-inch.
Pressure at Hydrant, lbs.	37	50	62	75	87	100
Pressure at Nozzle, lbs.	30	40	50	60	70	80
Pressure Lost in 100 feet, 2¹⁄₂-inch Hose, lbs.	7	10	12	15	17	20
Vertical Height, feet	51	64	73	79	85	89
Horizontal Distance, feet	47	55	61	67	72	76
Gallons Discharged per Minute	161	186	208	228	246	263
Smooth Nozzle, Size	1¹⁄₈-inch.
Pressure at Hydrant, lbs.	42	56	70	84	98	112
Pressure at Nozzle, lbs.	30	40	50	60	70	80
Pressure Lost in 100 feet, 2¹⁄₂-inch Hose, lbs.	12	16	20	24	18	32
Vertical Height of Stream, feet	52	65	75	83	88	92
Horizontal Dist. of Stream, feet	50	59	66	72	77	81
Gallons Discharged per Minute	206	238	266	291	314	336
Smooth Nozzle, Size	1¹⁄₄-inch.
Pressure at Hydrant, lbs.	49	65	81	97	113	129
Pressure at Nozzle, lbs.	30	40	50	60	70	80
Pressure Lost in 100 feet, 2¹⁄₂-inch Hose, lbs.	9	25	31	37	43	49
Vertical Height of Stream, feet	53	67	77	85	91	95
Horizontal Dist. of Stream, feet	54	63	70	76	81	85
Gallons Discharged per Minute	256	296	331	363	392	419
Smooth Nozzle, Size	1³⁄₈-inch.
Pressure at Hydrant, lbs.	58	77	96	116	135	154
Pressure at Nozzle, lbs.	30	40	50	60	70	80
Pressure Lost in 100 feet, 2¹⁄₂-inch Hose, lbs.	28	37	46	56	65	74
Vertical Height of Stream, feet	55	69	79	87	92	97
Horizontal Dist. of Stream, feet	56	66	73	79	84	88
Gallons Discharged per Minute	315	363	406	445	480	514

N.B.—Mr. John R. Freeman, member of the New England Waterworks Association, should have the credit of this carefully arranged table.—See also page [125] for data relating to Nozzles.

The Clapp & Jones piston engine in design has features peculiar to itself; Fig. [416] represents one of six sizes, adapted particularly to city service.

Fig. 417.

The illustrations, Figs. [417] and [418], show the vertical pump as built for the larger engines: namely, the sizes known as Extra First, First, Second, Third and Fourth. The complete engine corresponding to the detailed views is shown by Fig. [416] on the preceding page.

The principal details are very clear in this engraving. The steam and water ends, together with the crank and reciprocating mechanism, are compactly arranged and the complete structure which comprises these parts is rigidly self-contained. The steam cylinders and valve chest are cast in a single piece and while this part is firmly secured to the boiler, all steam and exhaust connections are entirely independent of these fastenings.

The Clapp boiler is represented in Fig. [419]. Reference to the annexed illustration makes clear the special features of this boiler, which consist chiefly of a series of spiral water-tube coils arranged within the fire-box. The coils are of copper and are produced by the seamless drawn process. Each coil is connected separately to the boiler, and the spiral form of these tubes permits freedom for expansion and contraction without strain on the terminal joints. The connections and the ends of the tubes are made by means of threaded nipples, jam nuts and corrugated copper washers, and the joints thus made insure tightness, yet admit of ready disconnection at any time.

Fig. 418.

The lower ends of the coil tubes are directly joined to the hollow fire-box walls and the upper terminals are arranged to discharge the circulated water over the crown sheet. This upward movement of the water within the spiral coils is caused by the application of heat to the outer surfaces of the tubes, and the circulation thus set up induces a corresponding downward action in the leg of the boiler. The circulation, therefore, continues without interruption so long as fire is maintained on the grate. In operating this boiler the water should be carried a few inches above the level of the crown sheet, but owing to the protection afforded by the constant distribution of water over the crown sheet, the limit of safety is not reached until the water is nearly out of the fire-box leg.

Fig. 419.

An improvement in the design of this boiler is the water-circulating deflector, which was devised to occupy the central space within the coil tubes. This deflector comprises an additional sectional unit, and its action coincides with the functions served by the coil tubes. The prime object of this device is to break up and direct the gases of combustion in a manner that adds to the heat-absorbing qualities of the coil tubes. See Figs. [420], [421].

Fig. 420.

Extending from the crown sheet to the top head are the smoke flues, which are securely expanded at both ends, and through which the gases of combustion pass from the fire box to the stack.

The Clapp & Jones Village Engine. By the illustrations, Figs. [422], [423], [424], etc., it will be noted that the cylinders and pumps are disposed horizontally and are fitted in a self-contained manner between bars, which also serve as the main frame of the engine.

The steam cylinders are 8 inches diameter; the pumps 4³⁄₈ inches, and the stroke common to both is 7 inches. These sizes are properly proportioned for effective work and the boiler power provided is ample to drive the pumping mechanism to its rated capacity of 400 gallons per minute.

Fig. 421.

The pumps are fitted with gates permitting two lines of hose to be worked either independently or at the same time without interference. The machine is mounted on half-elliptic springs, front and rear, and the weight of the boiler and pumps is distributed equally over both axles. The front pair of wheels turn completely under the goose necks, and the engine can therefore be turned on either hind wheel as a pivot. The arch of the main frames under which the wheels pass in turning is immediately forward of the boiler, and the advantage to be noted in this connection is the reduction in the over-all length of the entire machine. The front axle is equipped with a rope reel, and the pole is arranged for either hand or horse draft. The wheels are fitted with brakes, which are operated from the rear footboard. The engine weighs about 4,400 pounds. A detail description of the pump and valve gear follows.

Fig. 422.

The valve gear of the Clapp & Jones village engine is simple yet controls the moving mechanism of the two pumps working in unison. Each pump is driven directly by its own steam cylinder, and the steam valves are actuated by the positive movement of the opposite piston rod. The principle is substantially the same as practiced in the “Duplex” pump construction, and may be readily understood by reference to the detailed views which are given of these parts in other portions of this work.

Fig. 423.

The steam cylinders and pump are self-contained, and aside from the distinctive difference in the reciprocating gear the design of the steam and water ends does not differ from the vertical engines of the Clapp & Jones type.

On these engines intended for use in cold climates a “thaw-pipe” is attached, at the engineer’s side, inside the frame, and is used in extremely cold weather to prevent the feed-pump, as well as the main pump and connecting pipes, from freezing. It is operated by means of a small globe valve. If it is desired to warm the main pump, the two-way cock used in feeding the boiler should be turned as when feeding directly from the main pump, when steam will have access both to the main pump and the feed-pump; but care must be observed not to heat the main pump too warm. When the two-way cock is closed, and also when it is open as when feeding from the tank, the steam goes only to the feed-pump.

After using it to warm the main pump, the two-way cock, should be closed; otherwise, if the check-valve should happen to stick fast, the water would pass out of the boiler through the main pump.

Fig. 424.

Always keep the globe valve closed when not in use. It will be observed that the vacuum chamber upon the suction pipe is located within the air chamber upon the discharge passage.

The valves of this pump are formed by heavy rubber rings which surround the pump barrel, as shown in Fig. [423], therefore there can be no hammering of these valves when the pump is at work.

The rubber rings have slots cut into them at each side of each valve so that each valve can open and close without stretching the rubber bands. The steam valve is of the well-known rocker type. The plungers have no packing excepting water.

Fig. 425.—See page [122].