This is a demonstration model of a walking beam steam engine. A key feature of the model is its ability to demonstrate the complex mechanism controlling the valves which fed pressurized steam to the engine. That mechanism is quite similar to the design contained in United States Patent Number 9,582 awarded on February 15, 1853 to Horatio Allen and D.G. Wells. The patent is titled “Adjustable Cut-Off Gearing for Poppet-Valve Engines.”
To allow the students to visualize operation of the engine model, a hand crank turns the crankshaft which in turn causes all the parts of the engine to move as if it were operating. The students were then able to see the details of the timing and control of the valve mechanisms.
Mr. Allen was an engineer of significant accomplishment working on locomotives, steamships, bridges and tunnels. He became President of the New York Novelty Iron Works in 1842, and his early patent design for valve gear was used in the engine built by that company for the steamship Adriatic. Novelty Iron Works continued to make engines for many steamships through the Civil War years.
The model is constructed of metal and wood frames and mounted on a large wood base. All of the key elements of the Allen and Wells valve gear patent are illustrated by the model. A full description of the workings of the valves and diagrams showing the complete design of the patent can be found in the patent document online at the United States Patent and Trademark Office website, www.uspto.gov.
This twenty dollar gold coin was produced at Moffat & Company's mint in San Francisco, California around 1853. Moffat & Company was a major player in the production of California private gold coinage. First issuing its own coins, then coining the fifty dollar “slugs” for the United States Assay Office of assayer Augustus Humbert. This 1853 double eagle is one of the last coins struck by this prolific California pioneer coiner. Obverse and reverse designs bear a close and deliberate similarity to those used on the "official" double eagle of the same period produced by the U.S. Mint for regular circulating coins.
Obverse: Liberty head, “Moffat & Co.” on crown, 13 stars around, dated 1853 below.
Reverse: Liberty eagle with thirteen stars around its head, “San Francisco California/Tweny D.”
