A calculation indicated that 305 revolutions of the propeller would be required to produce 100 pounds thrust. Later, actual measurement showed that only 302 instead of 305 propeller turns were required, or just under one per cent of the calculated amount. The propellers delivered in useful work 66 per cent of the power expended. That was about one-third more than either Hiram Maxim or Professor Langley in their attempts at flying had ever been able to attain. For two reasons the Wrights decided to use two propellers. First, they could in that way obtain a reaction against a greater quantity of air, and at the same time use a larger pitch angle; and, by having the propellers run in opposite directions, the gyroscopic action of one would neutralize that of the other. The propellers were on tubular shafts about ten feet apart, both driven by chains running over sprockets, somewhat as on a bicycle. L. M. Wainwright, president of the Diamond Chain Company, of Indianapolis, became interested in the Wrights’ transmission problem, and gave them valuable advice. The Wrights found that the chains would have to be run through guides to prevent slapping and to overcome undue stresses on the machine. They adopted tubular guides and found that they could cross one of the chains in a figure eight and thus have the propellers running in opposite directions. Not until September 23 was all in readiness for the Wrights to set out for Kitty Hawk. They were able to make good connections with a boat and arrived at camp two days later, on a Friday. Discussing en route what they hoped to accomplish, neither had the slightest doubt about the fulfillment of their dreams. Besides being full of confidence they also felt the exuberance of excellent physical condition. Orville was now thirty-two years old and Wilbur thirty-six. Five foot ten and a quarter inches in height, Wilbur was the taller of the two by a little more than an inch and a half. Orville weighed 145 pounds, about five more than Wilbur. Each of them had grayish-blue eyes and they might have been recognized as brothers, though in their own family Wilbur at that time was considered “more of a Wright” in his facial conformation. Orville looked a little more like his mother. Both were suitably built for bird men. Plenty of annoyances, difficulties, and delays were still to be faced. When they reached their camp near Kill Devil Hill, the Wrights found that a storm had blown it from its foundation posts. They repaired the shed and also built a new one. With two sheds they had enough space for housing both the 1902 glider and the power machine, and also for a better workshop.