I've installed a clearance gauge at a team track to check correct loading of e.g. flat cars. That is the same position and purpose as it is used in Germany.
Now I read clearance gauges are used in the US e.g. in front of tunnels to give the break man possible on top of a boxcar a last and final warning.
Could you provide some advise where and for what purpose clearance gauges are used in the US (in the timeframe 1950 - 1960).
Reinhard
The device you have called a clearance gauge in US practice is called a 'telltale,' and is meant to warn anyone on top of a car that it's time to duck, get down an end ladder or jump!
The key element was a series of weighted ropes or light chains that had their bottoms six inches below the upcoming low-clearance point, which could have been anything (tunnel portal, overhead bridge, pipeline, even low-hanging telephone wires.) The support structure was about six feet higher, and could have been anything from a cable between two poles to a fairly substantial triangular or box truss like a signal bridge. Or the telltale ropes could be hung from a higher bridge in advance of the low point (say, highway bridge ahead of a tunnel portal.)
If someone on a car top was brushed by a hanging telltale, that was his warning that he was about to be swept off the top of the car. The accepted reaction was to drop flat, get off the roof walk and hang on! The alternative? SPLAT!!!
Telltales disappeared just after roof walks were outlawed, but still could be in use where cars which load from the top and still have roof walks (grain hoppers, for example) could be moved while someone was topside closing and securing the loading hatches. (If anyone knows for sure, please advise!)
Chuck (modeling Central Japan in September, 1964 - where roof walks and telltales were unknown)
This http://www.walthers.com/exec/productinfo/683-128 is the device I'm asking about.
It is called a clearance guard in the Walthers online catalog. However, it matches also the description of a telltale.
I guess I have to move it to a tunnel portal.
The updated devices are known as high/wide load detectors. The Espee had them in Texas to protect through truss bridges. I noticed about 5 years ago that the UP had taken them out of service. I remember them in service up until 1995, but between then and a few years ago, I don't know when they turned them down. I also have no idea when they were originally installed.
Basically they are a steel framework that was built around the ROW with a wire running on the inside. If the wire was hit by something hanging off the side or protruding above too far, it would alert the crew in the locomotive via radio, just like most all other detectors. They seemed to be a headache for the signal maintainers because I would see them servicing the high/wide load detectors relatively often. If I remember correctly, there was also either a dragging load detector or hot box detector in the same locations as well. I want to say that they were about 2-3 miles from the structure they were protecting, but I would have to do a little research to verify that.
The telltales on the Boston & Maine in the 1950s were 1/4-inch steel or iron rods hung from loops on the crossbar that extended over the tracks. There were several of them spaced about six inches apart. If you ran into one, you would really know it. I never saw anyone actually riding on top of a car; that practice ended long before my time. As far as I know the RR didn't take them down until they abandoned a line or branch, or made major improvements.