Thank you Phillip.
Here is the completed and aligned valve and reversing system for both cylinders of the V-twin. All of the other components of the turret engine have been turned off.
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complete valve linkage small.jpg [ 29.85 KiB | Viewed 4116 times ]
Two straight, simple rectangular section rods connect the crossheads to the tips of the T-links. These two reciprocating rods completely replace and supplant the elaborate cam driven valve gear more typical of 19th century steam engines. This excellent simplification worked because one cylinder of a 90-degree V-twin is always a quarter of a revolution ahead of the other cylinder.
Here is the complete engine, ex-crankshaft.
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ex crank small.jpg [ 38.09 KiB | Viewed 4115 times ]
We know the USS Monitor used a standard, off-the-shelf V-twin "donkey" engine supplied by the Clute brothers of Schenectady. I think it was a rolling mill engine -- already developed and proved in iron works and mills. The features of V-twin rolling mill engines include reliable and sudden start/stop operation, quick reversing, high starting torque, the ability to operate without a flywheel, and stall-proof starting. They were also called "reversing engines." There is a print of one here:
http://www.prints-4-all.com/cgi-bin/cat ... 011875916#The specific engine I have modeled in Rhino3D, the turret engine for the USS Monadnock launched in 1864, was supplied by the Atlantic Iron Works in Boston. How closely does it resemble the original Monitor's turret engine?
In the Scientific American for December 12, 1863, on page 372, there is a long article entitled "The Monitors". This volume of the Scientific American (V9) can be downloaded as a pdf from Google Books. The article is dense with specifications and dimensions for the original USS Monitor and for the nine Passaic class monitors that followed it. For all these monitors, according to the article, the turret engines had a 12 inch bore and a 16 inch stroke. The USS Monadnock also used a 12-inch bore. By CAD measurement inside the cylinder I get a maximum possible stroke of about 16.5 inches. The crankshaft throw is 7.993 inches, suggesting a 16-inch stroke exactly. From the USS Camanche photos posted above, I would say the Monadnock and the Camanche also had essentially the same turret engines.
Finally, here is a CAD analysis of an overhead view of the USS Monitor's crank and crankcase. The original image from which these lines were lifted is in the Stevens McCord collection. Net of it, the USS Monitor turret engine was designed with a 16-inch stroke. The bore I have not yet pinned down.
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File comment: Dimensions taken from the Stevens collection confirm 16-inch stroke
Stevens-McCord 16-inch stroke small.jpg [ 71.93 KiB | Viewed 4072 times ]
As a practical matter, I intend to use the USS Monadnock engine modeled here to finish the CAD model of the USS Monitor turret drive. It is an approximation of the original, but it may be the best approximation we find until the actual USS Monitor turret engines are recovered from underwater.
My guess is that this newer, Boston-built Monadnock engine varies in some details from the Clute Bros original of 1861 -- but that the size (i.e. bore & stroke), power, valve gear and controls of the turret engines were essentially unchanged from the USS Monitor to the USS Monadnock. Subjectively it seems to me that the double reversing gear, the camless valve drive, and the single master control lever all ring true.
Michael