This blog is named after a series of articles written by Doctor P. H. Van der Weyde and published in Manufacturer and Builder Magazine in 1889 and 1890. The more I learn about Doctor P. H. Van der Weyde -- I'll share more about him in future posts -- the more I like him. Here is the third of four parts, in which he discusses the Beach Pneumatic Subway. Read more about it on my cable car site.
The text is taken from the Library of Congress' American Memory site (http://memory.loc.gov/ammem/index.html).
The Pneumatic Rolling-Sphere Carrier Delusion.
BY DR. P. H. VAN DER WEYDE.
THIRD ARTICLE.
The next practical application of the pneumatic principle was made by A. E. Beach, of the Scientific American, who, in 1867 exhibited at the same place (the American Institute Fair) a round wooden tube, 300 feet long, suspended by iron straps from the ceiling rafters, so that it occupied no floor space, and as he rightly considered the atmospheric pressure upon a piston in a comparatively small tube insufficient to propel considerable weight, he returned to the original conception of Valiance in 1825, and placed the whole car in the tube. It is evident that then he could obtain the enormous propelling power produced by the atmospheric pressure of about half an atmosphere upon the surface of a circle of some 6 feet in diameter, or 30 square feet, which, at the rate of only 8 pounds per square inch, is over 24,000 pounds. It is evident that such power is capable of propelling quite a big train of cars. The car, moving on rails, was propelled by a ventilator wheel in the shape of a propeller, which produced either a blast or suction, by revolving it in alternate directions. A platform at one end, accessible by stairs, supported the propeller, which sent the car, containing more than a score of passengers, outward and backward with the greatest ease.
One year later, in 1868, he built a round tube, or tunnel, 400 feet long under Broadway, New York city. It was 9 feet 3 inches in diameter; the experimental car in use was 25 feet long, and had a seating capacity for 25 to 30 passengers.
Mr. Beach also devised a plan to substitute, in place of the lamp-post post office letter boxes, a simple slot for the reception of letters and small parcels which allowed them to fall through the hollow post into a subterranean tube, through which they would be carried to the central post office by means of an exhaust pump operating continually there. Trials on a small scale proved eminently successful; but the probability that the tube might be choked up by a superabundance of letters, which occasionally might be deposited during the busy hours of the day, caused the abandonment of this plan.
This leads us back from the pneumatic railways to the main subject under discussion -- the pneumatic dispatch systeam, about which we wish to correct an omission, so as to do justice to the first inventor. This was a Danish engineer, named Medhurst, who, in 1810, conceived the idea of carrying mails in a pipe, by creating a vacuum in front of a traveling piston, inside of which letters were to be placed. Years after, in 1832, he conceived the project of driving cars by the same means. The piston being united to the front car by a rod passing through a longitudinal opening in the top of the tube, this opening was closed by a water valve, which opened to let the rod pass, and closed behind, ready for the return trip. The use of a water valve made it necessary for the railway to be perfectly level, and for this reason the plan was soon laid aside, until, in 1835, Pinkas made it a success by substituting an elastic valve for the water valve, as mentioned on page 242, November number.
A few years after, Mr. Beach constructed his pneumatic passenger railway in New York city, Albert Brisbane obtained an appropriation from Congress of $12,000 for constructing an underground pneumatic dispatch between the Capitol and the United States printing office, operated by rolling balls, for which he claims to have obtained a patent about 18 years ago, which makes the date 1871. As Mr. Needham claims to have obtained a patent for the rolling balls some ten years previously, the granting of a second patent for the same thing was an error on the part of the patent office -- in case the statements are entirely correct, which a search in the patent office records only can decide; but such a search must not be expected to be made, except when a sufficient monetary interest is at stake, especially since the patent office reports of that time are not provided with a yearly alphabetical index, as is the case at present.
Mr. Brisbane also states, that after spending $6,000 more than the appropriation amounted to, the enterprise failed, because a portion of the tubes had to be laid in quicksand, which caused them to settle. However, N. J. Van Der Weyde, CE., a son of the writer, who some years ago was employed in Washington as superintendent in the construction of a new sewage system, states that there is no quicksand, but only two kinds of soil, one very hard and the other more soft -- not so soft, however, as to cause any impediment in the construction of the brick sewers. This raises the suspicion that the vibration caused by the continuous rolling of the heavy balls is the true cause of the settlement, and if so, it is another serious objection to the rolling-ball system, brought out by practice.
Next in order comes the introduction of the pneumatic dispatch principle at the different stations of the telegraph and post offices in London, and also in the Western Union Telegraph building in New York, intended to connect the different floors, the office for receiving and delivering messages being in the basement, while the operating room is on the the seventh floor, just under the battery room on the eighth floor. There were introduced there in 1872 twenty brass tubes of 2 1/4 to 3 inches in diameter, in which well-fitting leather cylinders of some 10 inches long are propelled exclusively by suction produced by an exhaust Root blower. Such leather cylinders are very appropriate to receive the rolled up messages, while rolling balls of 2 inches interior diameter would be inadequate and very inconvenient; so that the idea of rolling balls was not even thought of, especially since a great portion of the tubing was vertical.
About the year 1880, long tubes were laid under the streets of this city, connecting the telegraph office with the leading newspaper offices down town, while other tubes were laid to Wall street, and still others to the branch telegraph office up town, at Fifth avenue and Twenty-third street. It was at once discovered that the Root blower was utterly unable to work tubes of a mile and more in length, in addition to which the great noise that would be made by six such blowers would be highly objectionable in the building. Therefore, it was concluded to work the long tubes by the positive and silent blast of large pistons, which were introduced to operate them, one side being worked by blowing for transmission, and the other side by suction for the receiving of dispatches. The pistons for the four air pumps have 32 inches diameter, and are directly connected with the steam pistons of 20 inches diameter, while the stroke is 3 feet. They move perfectly noiseless, within the moderate velocity of 30 to 40 strokes per minute. The total capacity of the four engines and air pumps is 500 H.P.
In order to be satisfied respecting the superiority of the positive blast produced by pistons moving silently and propelling sliding message carriers in comparison with the noisy rotary blowers, and still more noisy balls rolling with thundering effect through iron tubes, worse than the noise of a bowling alley, one has only to visit the lower basement in the Western Union building and watch the operation.
In our next will be given some critical remarks on the last exhibition of pneumatic transmission by rolling balls, now in operation at Marion, N. J., a few miles west of New York city.
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