While Mr. Chanute was with us, a good deal of time was spent in discussion of the mathematical calculations upon which we had based our machine. He informed us that, in designing machinery, about 20 percent was usually allowed for the loss in the transmission of power. As we had allowed only 5 percent, a figure we had arrived at by some crude measurements of the friction of one of the chains
when carrying only a very light load, we were much alarmed. More than the whole surplus in power allowed in our calculations would, accord to Mr. Chanute's estimate, be consumed in friction in the driving chains. After Mr. Chanute's departure we suspended one of the drive chains over a sprocket, hanging bags of sand on either side of sprocket of a weight approximately equal to the pull that would be exerted on the chains when driving the propellers. By measuring the extra amount of weight needed on one id e to lift the weight the other, we calculated the loss in transmission. This indicated that the loss of power from this source would be only 5 percent, as we originally estimated. But while we could see no serious error in this method of determining the l oss, we were very uneasy until we had a chance to run the propellers with the motor to see whether we could get the estimated number of turns.
The first run of the motor on the machine developed a flaw in one of the propeller shafts which had not been discovered in the test at Dayton. The shafts were sent at once to Dayton for repair and were not received again until November 20, having been gon e two weeks. We immediately put them in the machine and made another test. A new trouble developed. The sprockets which were screwed on the shafts, and locked with nuts of opposite thread, persisted in coming loose. After many futile attempts to get them fast, we had to give it up and went to bed much discouraged. After a night's rest we got up in better spirits and resolved to try again.
While in the bicycle business we had become well acquainted with the use of hard tire cement for fastening tires on the rims. We had once used it successfully in repairing a stop watch after several watchsmiths had told us it could not be repaired. If tir e cement was good for fastening the hands on a stop watch, why should it not be good for fastening the sprockets on the propeller shaft of a flying machine? We decided to try it. We heated the shafts and sprockets, melted cement into the threads, and scre wed them together again. This trouble was over. The sprockets stayed fast.
Just as the machine was ready for test, bad weather set in. It had been disagreeably cold for several weeks, so cold that we could scarcely work on the machine some days. But now we began to have rain and snow, and a wind of 25 to 30 miles blew for sever al days from the north. While we were being delayed by the weather we arranged a mechanism to measure automatically the durations of a flight from the time the machine started to move forward to the time it stopped, the distance travelled 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 travelled through; and a counter took the number of revolutions made by the propellers. The watch, anemometer and revolution counter were all automatically started and stopped simultaneously. From data thus obtained we expected to prove or disprove the accuracy of our propeller calculations.
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