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Interesting Steam Engines , From the last days of steam power in the USA ...
Recently I have come upon a steam powered dredge boat that operated on the inland rivers of the USA from 1934 to 1973. It has some of the most interesting steam engines on board that I have ever found, and I am spending some time studying them. They represent, in many respects, the final stages of development of steam power in the USA.
The main engines (there are 2) are each rated at 600 Hp, with double expansion, double acting cylinders. This means that there is a double acting high pressure cylinder, and one the same piston rod there is also the piston for the double acting low pressure cylinder. These engines are laid out almost horizontal, on just a very slight incline.
The piston stroke is 84 inches. The piston rod of course comes out to a cross head where it is joined to the connecting rod, but in this case it is not called a connecting rod but rather it is called a "pitman." (That is river boat terminology.) The pitman is much longer than a customary connecting rod might be expected to be. In this case, the pitman is 336 inches long, a very, very long connecting rod. The pitman is made of ash wood, reinforced with steel plates on the top and bottom. The crank radius is 42 inches. The valve mechanism is quite complex, and very, very heavy. The "reach rods" as they are called that actuate the valve mechanism are approximately 2.25 inch solid steel rods, anywhere from 80 to 125 inches long, so there is tremendous inertia in the valve mechanism. The top speed on this engine was 16 rpm, so dynamic effects were not extremely large, but there must have been some with all that moving mass.
At the present time I am trying to gather enough dimensional data to put together a kinematic simulation for the engine. Because it is so very large, I have to get help simply to measure the parts; I can't reach from one end to the other in most cases. Eventually I hope to make a dynamic simulation, but that will take even longer because I will have to estimate all of the moving masses, a tedious job.
The other engine of interest is a three cylinder, upright, triple expansion steam engine rated at 1300 Hp. It is absolutely beautiful, like a piece of fine sculpture! I have not had much opportunity to explore it as yet, but it promises to be even more interesting than the main engines. It too is a crosshead engine with double acting cylinders.
On both of these engines, the lube systems are quite different from anything we would do today. They are separate little boxes, housing the pump and an oil reservoir. I would really like to take one apart, but that is not permitted. In each case, there is a shaft that goes cross ways through the box. On one end, there is a small hand crank for emergency oil supply (a person can stand there and turn the crank). On the other end of the shaft, there is what appears to be a simple little crank that is invariable connected through some sort of cobbled up linkage to a reciprocating point on the engine. Apparently, inside on that side there must be ratchet drive so that the shaft will rotate continuously with a reciprocating input. The oil comes out the top, through a sight glass and into tubing through wihch it is distributed to the bearings. It appears to be a very heavy oil, say SAE 70 or higher. These little oil pumps are not manufactured by the engine builders but were a purchased item, simply added to the engine and not designed into it at all.
http://mechanical- engineering. in/forum/ index.php? showtopic= 936&pid=1327&st=0&#entry1327
The main engines (there are 2) are each rated at 600 Hp, with double expansion, double acting cylinders. This means that there is a double acting high pressure cylinder, and one the same piston rod there is also the piston for the double acting low pressure cylinder. These engines are laid out almost horizontal, on just a very slight incline.
The piston stroke is 84 inches. The piston rod of course comes out to a cross head where it is joined to the connecting rod, but in this case it is not called a connecting rod but rather it is called a "pitman." (That is river boat terminology.) The pitman is much longer than a customary connecting rod might be expected to be. In this case, the pitman is 336 inches long, a very, very long connecting rod. The pitman is made of ash wood, reinforced with steel plates on the top and bottom. The crank radius is 42 inches. The valve mechanism is quite complex, and very, very heavy. The "reach rods" as they are called that actuate the valve mechanism are approximately 2.25 inch solid steel rods, anywhere from 80 to 125 inches long, so there is tremendous inertia in the valve mechanism. The top speed on this engine was 16 rpm, so dynamic effects were not extremely large, but there must have been some with all that moving mass.
At the present time I am trying to gather enough dimensional data to put together a kinematic simulation for the engine. Because it is so very large, I have to get help simply to measure the parts; I can't reach from one end to the other in most cases. Eventually I hope to make a dynamic simulation, but that will take even longer because I will have to estimate all of the moving masses, a tedious job.
The other engine of interest is a three cylinder, upright, triple expansion steam engine rated at 1300 Hp. It is absolutely beautiful, like a piece of fine sculpture! I have not had much opportunity to explore it as yet, but it promises to be even more interesting than the main engines. It too is a crosshead engine with double acting cylinders.
On both of these engines, the lube systems are quite different from anything we would do today. They are separate little boxes, housing the pump and an oil reservoir. I would really like to take one apart, but that is not permitted. In each case, there is a shaft that goes cross ways through the box. On one end, there is a small hand crank for emergency oil supply (a person can stand there and turn the crank). On the other end of the shaft, there is what appears to be a simple little crank that is invariable connected through some sort of cobbled up linkage to a reciprocating point on the engine. Apparently, inside on that side there must be ratchet drive so that the shaft will rotate continuously with a reciprocating input. The oil comes out the top, through a sight glass and into tubing through wihch it is distributed to the bearings. It appears to be a very heavy oil, say SAE 70 or higher. These little oil pumps are not manufactured by the engine builders but were a purchased item, simply added to the engine and not designed into it at all.
http://mechanical- engineering. in/forum/ index.php? showtopic= 936&pid=1327&st=0&#entry1327
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