CHAPTER IV.
FACTS AND GENERAL INFORMATION RELATING TO PNEUMATIC TUBES.
DEFINITIONS 124
INTERMITTENT AND CONSTANT AIR-CURRENT 125
LAWS GOVERNING THE FLOW OF AIR IN LONG TUBES 126
LAW OF PRESSURE 128
USES OF PRESSURE CURVES 130
LAW OF VELOCITY 130
CHARACTERISTICS OF THE VELOCITY CURVE 132
USES OF VELOCITY CURVES 133
QUANTITY OF AIR USED 134
TEMPERATURE OF THE AIR 135
HORSE-POWER 136
EFFICIENCY 137
PRESSURE AND EXHAUST SYSTEMS 138
LAWS EXPRESSED IN MATHEMATICAL FORMULÆ 141
MOISTURE IN THE TUBES 142
LOCATION OF OBSTRUCTIONS IN TUBES 143
PREFACE.
I have been prompted to prepare this book by the frequent inquiries made regarding the details of our system of pneumatic tubes. These inquiries have come from people interested in our company, from others interested in companies that have purchased the right to use our apparatus, from people desirous of becoming interested in a pneumatic-tube business, from would-be purchasers of pneumatic tubes, and from people interested in pneumatic tubes from a scientific, engineering, or mechanical point of view. This book is not intended to be a treatise on pneumatic tubes. In the first chapter I have given a brief sketch of what has been done in the application of pneumatic tubes from the earliest records to the present time. The second chapter contains a description of the postal tubes in Philadelphia, and the third chapter describes our system in detail. Following this is a short chapter explaining the theory of pneumatic tubes, or the theory of the flow of air in long pipes, stating the more interesting facts and relations in as plain and simple a manner as possible. Mathematical formulæ have been purposely avoided.
Several plates showing the Philadelphia postal line have been kindly loaned to me by the Engineers’ Club of Philadelphia. They formerly appeared in a paper read by Mr. A. Falkenau before that club. I have also to thank the and Drill Co., the B. F. Sturtevant Co., the Wilbraham-Baker Blower Co., and J. B. Stewart for the use of electrotypes of their machines.
B. C. B.
October 6, 1896.
THE
BATCHELLER PNEUMATIC TUBE SYSTEM.