|Cross section showing the flexible beam on the front two drivers.|
If the narrative is correct then the purchase and abandonment dates do not seem right to me. It must have been purchased earlier in 1862 and abandoned when Burnside ordered the destruction of the Aquia line during the Antietam Campaign, sometime in October, 1862. The USMRR rebuilt the Aquia line starting on 17 November. It was ready in about 10 days time. The Aquia train log I have shows the USMRR Aquia line in operation in early December. I think it unlikely they would have abandoned an engine in December when they were operating the line. Also, the Confederates were running trains to Fredericksburg at this time.
So, it ran on my railroad, but the (suspicious) dates indicate a few months before I model. Not much a foobie at all.
What is a flexible beam engine? Baldwin developed it to allow his 6 and 8 coupled engines to negotiate tight curves found on American railroads. European locomotives had rigid 6 and 8 coupled engines, but they did not ask these engines to traverse tight curves. Here is a more detailed explanation from "The Illustrated Catalog of Locomotives."
Its principal characteristic features are now matters of history, but they deserve here a brief mention. The engine was on six wheels, all connected as drivers. The rear wheels were placed rigidly in the frames, usually behind the fire-box, with inside bearings. The cylinders were inclined, and with outside connections. The four remaining wheels had inside journals running in boxes held by two wide and deep wrought-iron beams, one on each side. These beams were unconnected, and entirely independent of each other. The pedestals formed in them were bored out cylindrically, and into them cylindrical boxes, as patented by him in 1835, were fitted. The engine-frame on each side was directly over the beam, and a spherical pin, running down from the frame, bore in a socket in the beam midway between the two axles. It will thus be seen that each side-beam independently could turn horizontally or vertically under the spherical pin, and the cylindrical boxes could also turn in the pedestals. Hence, in passing a curve, the middle pair of drivers could move laterally in one direction—say to the right—while the front pair could move in the opposite direction, or to the left; the two axles all the while remaining parallel to each other and to the rear driving-axle. The operation of these beams was, therefore, like that of the parallel-ruler. On a straight line the two beams and the two axles formed a rectangle; on curves, a parallelogram, the angles varying with the degree of curvature. The coupling-rods were made with cylindrical brasses, thus forming ball-and-socket joints, to enable them to accommodate themselves to the lateral movements of the wheels.
Colburn, in his "Locomotive Engineering," remarks of this arrangement of rods as follows:
"Geometrically, no doubt, this combination of wheels could only work properly around curves by a lengthening and shortening of the rods which served to couple the principal pair of driving-wheels with the hind truck-wheels. But if the coupling-rods from the principal pair of driving-wheels be five feet long, and if the beams of the truck-frame be four feet long (the radius of curve described by the axle-boxes around the spherical side bearings being two feet), then the total corresponding lengthening of the coupling-rods, in order to allow the hind truck-wheels to move one inch to one side, and the front wheels of the truck one inch to the other side of their normal position on a straight line, would be √602+12 - 60 + 24 - √242-12 = 0.0275 inch, or less than one thirty-second of an inch. And if only one pair of driving-wheels were thus coupled with a four-wheeled truck, the total wheel-base being nine feet, the motion permitted by this slight elongation of the coupling-rods (an elongation provided for by a trifling slackness in the brasses) would enable three pairs of wheels to stand without binding in a curve of only one hundred feet radius."
I made this animated gif to illustrate the action of the special truck.
The Baldwin flexible beam engines were designed to burn coal. Did it burn coal on the USMRR? Maybe. The USMRR did have some coal burning engines. For example, this excerpt from a letter from Devereaux to Haupt in 1862 describes some coal burning engines obtained from the B&O and used on the USMRR Manassas Gap line.
We have only one coal light engine, never used for freight. On Monday week, Col. McCallum seized from Baltimore & Ohio Road three heavy coal burners for the special purpose of aiding me in sending forward Ord's Division. They were on the road when you came, but had done the duty they were procured for and I still kept them, and to meet the demands that might occur by keeping them, I ordered coal. This was last week. The engines did not get out of coal till yesterday, Monday.
Col. McCallum telegraphed me this A. M.: "I ordered a car load of soft coal for you on Friday from Georgetown, and the party agreed to deliver it at Alexandria by Saturday night. He has had some trouble in getting vessel to take it, but has succeeded in getting vessel this morning, and promises to have the coal in Alexandria some time tonight." I therefore must say that neither I nor my men could have done more, and, moreover, more than three-quarters of your locomotives on Gap Road are wood burners. Coal burner 70 being broken, leaves only two coal engines in use. The 70 has her steam chest perforated and her cylinders out of order, and is of no use. And I did not propose to do anything to her, as on our own broken machines we have plenty of work day and night. (see Page 57-58 of Reminiscences of General Herman Haupt)
Note the Coal Burner 70 was a B&O Winans 0-8-0 Camel built in 1851.
Did the Washington burn coal when on the RF&P? I have not found any evidence that it did, but I am not ruling it out. Perhaps more research will find out.