The shafts, made of larger and heavier tubing, arrived from Dayton on November 20. When they were tested again, a new difficulty appeared. The sprockets, which were screwed to the shafts and locked with nuts of opposite thread, kept coming loose. This was a small problem, and yet the brothers did not at once see any way to solve it. They went to bed discouraged. The next day, however, they tried, as they often did, something they had learned in the bicycle business. They had found a great variety of uses for the kind of cement intended for fastening tires to rims. Once they had used it successfully in fastening the hands of a stop-watch that several watchsmiths had said was beyond repair. Why not try tire cement on those sprockets? They heated the propeller shafts and sprockets, poured melted cement into the threads and screwed them together. There were no more loose sprockets. Just as the machine was ready for test, bad weather set in. There was rain or snow for several days and a wind of twenty-five to thirty miles an hour from the north. But while being delayed by the weather the Wrights were not idle. They busied themselves contriving a mechanism to measure automatically the duration of a flight from the time the machine started to move forward to the time it stopped, the distance traveled through the air in that time, and the number of revolutions made by the motor and propeller. A stop-watch took the time; an anemometer measured the air traveled through; and a counter took the number of revolutions made by the motor. The watch, anemometer, and revolution counter were all automatically started and stopped simultaneously. During this time, the Wrights occupied themselves also in making tests of the strength of the wings, as well as many satisfactory tests of the engine. During a test of the engine, on November 28, they discovered that one of the recently strengthened tubular shafts had developed a flaw and cracked! With winter almost upon them, there was no time to trust to express service in getting the shafts to Dayton. Orville decided he would go there at once. Instead of tubular shafts, they would use solid tool steel, necessary, it seemed, to take up the shock of premature or missed explosions of the engine. Not until Friday, December 11, did Orville get back to camp. (En route, he had read in a newspaper of the last unsuccessful attempt to fly the Langley machine over the Potomac at Washington.) It didn’t take long to install the new propeller shafts and the next afternoon, Saturday, the machine was again ready for trial. But the wind was so light that a start could not have been made from the level ground with a run of only sixty feet permitted by the monorail track to be used. Nor was there enough time before dark to take the machine to one of the near-by hills, where, by placing the track on the steep incline, enough speed could be promptly attained for starting in calm air.