The Pennsylvania Railroad for many years had operated a specially designed car for the purpose of accurately measuring the distance above or adjacent to the tracks of objects such as bridges, tunnels, stations and rock cuts above or adjacent to the tracks.

 

      The demand for increased speed to shorten travel time by both present-day industry and the business world, also the ever increasing size of passenger and freight cars and commodities in open top cars, coupled with large motive power, has caused the railroad to provide more clearance for movement of equipment. The trend of larger equipment and larger commodities in open top cars has made the gathering of clearance information of growing importance.

 

     The Pennsylvania had spent many millions of dollars to increase clearances for handling traffic. In the 1950's, the Panhandle Division Tunnel project between Pittsburgh, PA and Dennison, OH cost alone was over eight million dollars.

 

     With the increased speed and more frequent train schedules, together with the vast increase in traffic experienced during World War II, it became necessary to develop a means of measuring clearances of structures along the railroad with greater speed and accuracy without interference to the regular flow of traffic. This had not been possible with the clearance car that was operating prior the '50's. Therefore it had become obsolete and was dismantled in mid-1950.

 

     The Pennsylvania Railroad was able to accomplish the challenge of more accurate measurements with its new clearance car #497125. The car was designed by the Mechanical Department and the Chief Engineer's Clearance Department and was built at the railroad's Altoona Works in Altoona, PA in 1950. The first test run was made over the Middle Division on November 7, 1954 measuring the Spruce Creek Tunnel (22 miles east of Altoona.

 

      The car used in the construction of the Clearance Car was a former inspection car and of the P-68 passenger type of that time. It is divided into five compartments. The head end (or front) is the template room where all the measuring instruments are located.      On the exterior of the car there are a total of 126 measuring instruments (called feelers). The template room is the location of the gauges that record the measurement of each feeler. The feelers are divided into four groups:(1) the oval template called the 'Horse Shoe", (2) the "Main" templates (one on each side of the car) called the Main", (3) the "Right foot' template and (4) The 'Left Foot" template.

 

Horse Shoe:
    It is hydraulically adjustable, and can be raised one two, three, or four feet, which gives you the ability to measure from 17' to 21' above top of rail. When the horseshoe is down (normal or travel position), the lowest feeler (which is number 30) is eight (8) feet above top of rail. At this point, the horseshoe curves over the top of the car on a five-foot radius. The horseshoe has a total of sixty (60) feelers. There are thirty (30) on each side of the centerline of the template. Feelers 28, 29 & 30 are six (6) inches apart and the remaining are three (3) inches apart. They are numbered from the top (or center of the horse shoe) starting at number one (1). When traveling between measurements, the horseshoe is in a down position and all feelers are in a down and locked position.

 

Main Templates:
      There are two main templates in fixed positions, one on each side of the car. Each one has 26 feelers, the lowest feeler is 2 feet, 3 inches above top of rail and the highest feeler is 11 feet, 6 inches above top of rail. Starting at the 2 feet, 3 inch position, the first 14 feelers are 3 inches apart, up to 5 feet, 6 inches. Then from 5 feet, 6 inches to 11 feet, 6 inches, the remaining 12 feelers are 6 inches apart. When traveling between measurements, all feelers are in a closed and locked position.

 

Foot Templates:
       There are two-foot templates, one on each side of the car. Each has 7 feelers which are spaced three inches apart. When in the down position the bottom feeler is 6 inches above top of rail and the top feeler is 2 feet above top of rail. These templates are hydraulically controlled and are lifted through wells in the car floor to the up position when in transit. This is to prevent striking objects along the right of way, However, the feelers must be closed and locked before raising the templates.

 

Operator of the Car:
      The car is entered through the template room which designates the front of the car. At first sight, the controls and gauges for each feeler seem quite complicated, but are actually quite easy to comprehend. These instruments consist of three main parts: (1)feelers attached to an outside gear box,(2)a length of teleflex cable which passes through special brass tubing, (3) the indicator quadrant with gear box and magnifying glass.

 

      The feelers which are on the outside of the car are 36 inches long and are made of half-inch aluminum tubing with a tip of six inch hardened tool-steel on each end This assures longer wear and a more accurate measurement. 

 

   Each feeler is attached to a shaft extending from the outside gear box Both shaft and feeler fittings have serrations which allows for a more delicate adjustment on dead center. The feeler is secured to the shaft by means of two washers, locknut and damp bolt. One washer is made of spring steel, slightly cup-shaped, with protruding legs bearing against a fiber washer. The purpose is to obtain proper friction so that the feeler will not swing back too freely or be too rigid when making contact with structures. The flexible cable which passes from the outside gear box through the brass tubing to the gear box on the indicator quadrant is of special design, developed during WWII for aviation and marine controls. On the outer circumference of the quadrant is a white scale with black numbers, with increments of 1/8th of an inch, from zero to thirty-six (O to 36"). The scale is calibrated so that its readings indicate the exact clearance measurement taken by the feeler in that position This is all incased with an opening over which is attached a magnifying glass with a hairline marking on the underside, this indicates the proper position for reading the scale. Also attached to the quadrant indicator is a handle for extending or retracting the feeler, as required, and a stop-hold for locking the feeler in a closed position.

 

        The car has an intercom system with two-way speakers and headphones in the template room and a two-way speaker in the recording room for constant communication between the two rooms during its operation.

 

      From the rear of the template room, you can access the observation dome by means of two small ladders on each side, allowing for inspection of overhead structures and tunnels. A seat for this purpose is provided on each side of the dome.

 

        The next compartment consists of a stainless steel kitchen with an electric refrigerator, sink with running water and a stove that burns charcoal, wood or coal. This is on the right side of the car (when facing the rear of the car). On the left is the washroom that has three wash basins with cabinets and mirrors with electric outlets above each one. There is also one shower room and a private toilet room. Continuing on to the rear of the car, we enter the sleeping compartment with standard Pullman-type upper and lower berths. This section also has lockers for each man's personal effects and storage for bed Linens.

 

    The next compartment we come to is the office. The operation of the car is directed from this area. It is equipped with a desk where the readings of each feeler is recorded on a clearance diagram. The information is received over the intercom system from the two men in the template room. This compartment also contains a table, chairs and filing cabinets, in which track charts, maps and current clearance diagrams are stored it is also used as a lounge or dinning area.  

 

    A generator is located in the last compartment of the car and is used to power all electric equipment. A ladder is located in this room directly over the center line of the rear truck for access through a hatch in the ceiling to the rear template. It allows for measuring overhead bridges and other structures which are more than 21 feet above top of rail. The measuring is done by means of a telescoping gauge that can be extended to the underside of a bridge or another structure. At that point, the car is stopped and the gauge is extended to the underside of the structure being measured The gauge is graduated for direct reading in feet and inches above top of rail.

 

      The clearance car is moved over the railroad in regular passenger service when traveling between headquarters and working locations. It is not a self-propelled car and when taking measurements, it is moved with a locomotive and rider car for the train crew. When measuring, the clearance car is operated as a Special Passenger Train.

 

      At the beginning of a day's work, the first structure to be measured is located on a track chart in the recording room. The mileage, location and type of structure to be measured is obtained from the structure's own clearance diagram. It also indicates how the templates and feelers will be set and which ones will be used. If the horseshoe is needed, the setting will be determined from the clearance diagram. This information is then relayed over the intercom to the men in the template room. As the train approaches the structure, it will slow down to about 5 M.P.H. and stop about two car lengths from the structure to be measured. At this point, the crew in the template room will make all of their settings and extend all feelers that an necessary. The train will then move through the structure at about walking speed pace. As the car moves through slowly, the feelers striking the structure are brushed back, which in turn form the contour of said structure designating the exact distance from the centerline of track and above top of rail. When clear of the structure the train will stop and the crew will record the measurements on a clearance diagram. The scale on the diagram is one-half inch to the foot. Each structure is recorded on a single diagram and a separate diagram is used for each track. 

 

    The clearance car is usually operated by a crew of three men under the direction of the Clearance Engineer. Each has specified duties; two in the template room and one at the recording desk. The two men in the template room operate the templates, feelers, and horseshoe while observing the structure being measured and report any unusual conditions. The man in the recording room plots the measurements on a clearance diagram, also recording unusual conditions and keeps a record of the date and the mileage of the car and all structures measured.

 

    The car was usually out on the system measuring from April to late October. The rest of the year the crew was in the office compiling the field notes. The individual structures were then complied on a single sheet showing all structures between any two junctions or interlocking's. Also, a sheet was made for each track. Copies of these sheets were made and forwarded to the Regional and Division Engineer, M. of W., and the Transportation Department's Clearance Bureau, who did the routing of high and wide loads for the PRR.      

 

    This car reduced more than 75% of the time in actual measuring and recording time over the previous car. Upon completion of recording the measurement of a structure which takes only a few minutes, the diagram is complete and the clearance of a structure can be determined immediately.

 

    This car was also leased to other railroads, as the PRR owned the only car of this type. It traveled over the RF&P, VIRGINIAN, N&W, GREAT NORTHERN, ROCK ISLAND, LONG ISLAND, and THE MILWAUKEE ROAD (from Chicago IL to Seattle. WA), etc.

 

H. Earl Snyder composed this article. He was a Clearance Car Operator on PRR # 497125 from 1959 to 1963. All photos used in this article are the property of H. Earl Snyder