First installation of the HBD prototype
From March 27 to March 30 I was in Übach-Palenberg in Northwest Germany and attended a Fremo (Friendscircle of European Modelrailroaders) meeting. Along with the H0-USA and H0-RE groups we had set up a 47 meter long N-scale layout.
Bernd Schneider, initiator of the "americaN" module standard, has put together a report of the meeting, which you can find on the americaN website. It's in German only, but the pictures and the layout plan should give you an idea. Follow this link for some more impressions.
On the west end of the layout, just before the staging yard, the Hot Box Detector was mounted on an 80 cm long module. It had not been landscaped, besides of some electrostatically applied grass fibers, as this was to be the first field test of the device.
How it worked operationwise
During the first two sessions, we just let the detector send its messages without affecting our traffic. At the beginning of the third session, we decided it was time to implement it into our game. As the module was very close to the western staging yard, we ignored any hotbox on westbound trains. Eastbounds, however, had to stop and inspect the train, and passenger and intermodal trains could proceed afterwards without any restriction. All other trains had to set out the affected cars on the next siding (JK Coal), where they were picked up by a local and taken to the repair shop. There were additional "bad order" way bills, and the method worked great.
Defect percentage had been set to 2.5%, and that was okay, given the fact that most trains were a bit shorter than 100 axles, and only eastbounds were affected. For longer trains, it would probably be better to decrease it.
Technical aspects
The device worked flawlessly for all three days of operation. Axles were counted with an accuracy of over 99 percent. Speed detection and length calculation worked well, but the latter was not as exact as I had wanted it to be. Maybe I'll change the sensor arrangement to give better defined distances between known points (sensors). On the other hand, during passage any variation of train speed, which can only be maintained constant with regulation-equipped decoders, affects the outcome of length calculation.
More than once it seemed that the HBD sent "ghost" messages without any trains nearby, but there was a human culprit to it: to demonstrate the function, someone had passed with a hand over the sensor and triggered the device. Funny, isn't it?
Conclusion
This first field test proved the concept of the device feasible. The Hot Box Detector added a lot of fun to the game of model railroading, especially because of the randomness it acts with.