||Build the Elliott Bay Triple
For the experienced machinist & fitter, these engines are faithful replicas of small engines from the Golden Age of Steam. We supply them as castings and drawings. You become the Victorian Era machinist, then fitter, then operating engineer.
Spend the same time making a correct engine as an incorrect one. Most other "casting kits" available do not resemble Victorian engineering either in function or form. Most lack the purposeful grace of the iron casting, and few are designed to heat engine fundamentals. Some use inappropriate alloys or they confuse stationary or railway engine practice with the requirements of marine use. With our engines you re-create the established practice of 100 years ago. With few exceptions, adherence to Victorian practice is the most practical, cost-effective, and enjoyable way to go.
The engine to the left is the Elliott Bay triple being lowered into the Elliott Bay fantail hull owned by David Porter of Sunset Beach, California. The boiler (not shown) is a charcoal- fired, ASME Code Elliott Bay boiler which at 40 square feet heating surface pushes the boat at its hull speed of 7 knots. This particular engine was specially fitted with a Lowe pump for air and feedwater; however, the engine is supplied with castings for air, feed, and auxilary pumps driven from each of the three crossheads. Cylinder dimensions are HP 2.75, IP 4.375, LP 6.5 and stroke is 4 inches. Both the HP and IP valves are piston; LP is slide. Each of the three valvegears has cut-off adjustment, and, the builder has a choice of "split" or "closed" top end connecting and eccentric rods. The kit consists of 96 castings and 144 drawings. Crankshaft casting is supplied. Bar stock and fasteners are not supplied. Price $4,600. Drawings $300.
Our triple expansion marine engine is a reduced-size replica of engines made for torpedoboats in the 1890s. We did not simply scale down dimensions, but we checked original texts used by designers back then to determine cylinder diameters, bearing areas, valve events, etc. The same part that was a casting 100 years ago is a casting in our kit, and it is made of the same metal. Here we admit, however, that we have adopted a modern bearing bronze that is resistant to galling with gravity lubrication up to 600 rpm, and we supply bronze stock for you to turn rings. And, we will substitute aluminum for iron bedplate if the customer wants to save 40 pounds (18 Kg) weight and can get the part deep annodized black after machining. Fifteen of these engines have been or are currently being built in six countries. Five of these engine are being built in England, the traditional source for small marine steam.
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The Triple Kit's Castings
This photo shows many of the triple kit's castings layed out on a table. The engine in the background is the same engine pictured above. In foreground are valvegear bearings and immediately behind are mainbearing caps and boxes (that are fitted into the bedplate); to the Left are two of three bronze pump bodies, and to their right are reversing levers and eccentrics. In midground are pistons, bottom and top cylinder covers, and cast ductile stock for making rings for all three cylinders and valves (directly behind pumps).
The triple also has independent cut-off adjustment on each cylinder, so the engineer can "take a card" on the engine and balance the work to be done by each cylinder. I had the good fortune to be tutored by the late Cliff Blackstaffe on the advantages of independent cut-off: the first launch we built commercially had a two-cylinder compound engine that had gag screws on the weighshaft bellcranks. It ran "ragged" until Cliff began to work the screws in and out on both valve gears until the engine began to run smooth--even for a compound. Cliff was one of the last "19th century marine engineers" even though he was born in the 20th. See his articles in STEAMBOATS & Modern Steam Launches, available from this website, Model Engineer, and Light Steam Power. Triples are inherently smooth because their cranks are equally positioned at 120 degrees, and the ability to refine cut-off can make them nearly vibrationless. This triple pushes our 23-foot hull at 7 knots at 400 rpm at 100 psi; it will operate as slowly as 20 rpm. While it's cylinder walls are designed with a 10x hoop strength "safety" factor at 300 psi, this engine captures the pleasures of marine engineering at low pressure.
What do we mean by the term fitter? Fitting
was a trade that has nearly died out but
that was essential in machine manufacturing before precision manufacturing,
and was an essential
task in producing engines. Fitters took over after the machinists. With
trammels, gauges, and hand-scrapers they
brought an assembly of machined parts into tolerance and alignment. Imagine,
for example, aligning a ten-foot-high cast column of a marine engine;
the underside of
its base had to be painstakingly scraped
away to "tip" the
column into position at its top. Ten-thousandths off the base
to move the top over by thousandths. Even with boat-sized engines
, more than machining is needed. As Cliff Balckstaffe often
reminded, "It was the fitters, not the machinists, that made
rivalries for smoothness and quietness among
the trans-Atlantic liners. "
To see an Elliott Bay Triple being built, go
to Peter Cowie's Website at: http://www.users.bigpond.net.au/cowiepeters/ .
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Greg Linden of Sedalia, Colorado (former commander of a Navy tugboat with a triple expansion engine) supplied this photo of cylinder boring. On the left, the cored passageways leading to the IP cylinder from the adjacent piston valve can be seen; the cutter has just finished first cut on the LP bore. Note the relief cuts in the bores of the finished block which all "run-by" of the pistons to prevent moraine build up, a requirement for long life.
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