June 30, 1917
MEDFORD YOUTH NOW OVERHAULING ARMY AEROPLANES
Seely Hall, who enlisted in the aviation corps of the United States army, writes as follows to his father, Court Hall, from the United States aviation school, North Island, San Diego, California:
"I am still in the machine shops. I don't know what they are going to make out of me. But as I keep going up, I feel that I am making good.
"I have now been in the machine shop six weeks. I first started in the valve and cylinder department. Have overhauled my first aeroplane motor. It certainly made me feel happy to be able to do this work. In fact I think I am the happiest boy in the world.
"They have some of the best motor men in the world here, and they are very nice to me. I consider myself very fortunate in being able to work with such high class mechanics.
"Everything has its own separate adjustments here. The motors are taken down by one set of men and put up by another set. The same way with the bearings, cylinders, etc. It is the little things that the average mechanic overlooks that really hurt a motor. There are so many small things that one can do to make a motor run like new. Airplane motors are overhauled after every fifty hours flight, and we set everything by a thousandth of an inch.
"The pistons are weighed every time a motor is taken down to see if they are of the same weight. They must weigh within an ounce of each other or it would cause vibrations. The bearings must have two-thousandths of an inch play, yet still be able to spin the motor without the least friction. We set the motor five-sixteenths of an inch advanced on the pistons. and it makes all the difference in the world with an motor.
"I intend to learn everything possible in the mechanical line before I fly. That is if they leave me here."