"The circumference of a wheel is 8 feet; that of its axle is 16 inches; the weight, including friction, is 85 pounds. How great a power will be required to raise it?
"A power of 70 pounds on a wheel whose diameter is 10 feet balances 300 pounds on the axle. Give the diameter of the axle.
"An axle 10 inches in diameter fitted with a winch 18 inches long is used to draw water from a well. How great a power will it require to raise a cubic foot of water, which weighs 621⁄2 pounds?"
The first mail in the morning brought word that the whole of the partly prepared stuff for the boat had been shipped by "fast freight," and that it would reach its destination in the course of a few days. The paper patterns, directions, and all necessary instructions for building would be mailed at once.
IV
MAKING A GASOLENE LAUNCH
Two or three days after Mr. Gregg had talked over the principles of the wheel and axle, with the children, Fred received notice that a consignment of wood-work was at the station awaiting his orders. Mr. Gregg made immediate arrangements with the railway people, and by the time he got home from his office, the stuff was being unloaded by the boys, who carried it piece by piece into the workshop, each section being laid by itself in the order in which it was to be put in place in the boat. Printed instructions were in the equipment for laying the keel, setting up the frames, and even for taking the stuff out of the packages and putting it in heaps, so that it could be readily picked out when wanted for use.
Each rib was numbered, and marked or stamped "right" or "left," and all the pieces were cut off to the right length and to the right bevel or angle to suit the positions they were to occupy, as specified in the printed instructions. This made the setting up an easy matter, requiring only care, patience, and a fair knowledge of the use of wood-working tools. That Fred possessed these qualities, was partly due to the training he had received in the technical school, and partly to his natural aptitude for picking up methods, ideas, and new applications.
Fred, George, and Mr. Gregg himself, were much interested in the selection of the various materials, and when the plank that was to form the keel had been unpacked, George was anxious that it should be laid down on the bed that had been prepared for its reception. He was quite disappointed when he found it considerably shorter than he had expected the boat to be. It was explained to him, however, that the overhanging of the stern, and therefore shortening of the forefoot, or stem, necessitated the keel being shorter than the boat would be when measured over all on top. The keel was found to be a fine piece of tough oak, nicely dressed, made the proper shape at each end, bored and gained to receive the stern post, the stern ribs, and side stanchions. Everything was marked, and each timber was sized so that it would fit in place snugly without using a tool on it, except a hammer or mallet.