Discussion on “chattering wheel slip in electric motive power” (Eaton), New York, February 9, 1916. (see proceedings for February 1916)

S. T. Dodd: It occurs to me that chattering wheel slip is exactly the same phenomenon which has been reported on a good many European side-rod locomotives. Of course, the European designers have had more experience than we have had in designing various types of side-rod locomotives, and there have been reported in the foreign technical press several failures of this type of locomotive. I have in mind principally a couple of reports in German papers in regard to the Loetchberg locomotives. These locomotives, as you will remember, have characteristics which would increase the possibility of such a thing occurring. They have two very large motors of about 1300 h.p. each, geared to jack shafts the jack shafts tied together by Scotch yokes, which in turn are connected to the driving axles by side rods. In the papers I have in mind, they describe the disturbance in these locomotives, as a “shuddering” motion occurring at speeds of 20 to 25 miles an hour. This is so intense as to break the cranks and the Scotch yokes, sometimes by tearing them apart by tension, and sometimes crushing them by compression. The papers I have made reference to discuss mathematically the motions and the stresses which occur in such a frame work as that, showing that these forces are proably due to the building up of mechanical resonance between the springing of the driving rod on one side, and the inertia of the very heavy armatures on the other.