Mohave County miner and our mineral wealth., 1920-07-03

The following is the second install ment of an abstract from his paper which has been pronounced by experts as the most authoritative treatment of the subject ever made. MT. Norton is widely known as a transportation engineer, tire expert and as the author of "Motor Trucks of America" and "The Motor Truck as an Aid to Business Profits. The Subject is covered in three installments. The third and last will appear in this sec tion next week.
 In the first installment of this ser ies the mechanical features involved inchanging from solid to pneumatic
 equipment were discussed. Let us now look at the practical operating features that must be considered in determining which type of tire will make the truck most efficient in ser vice.
 Broadly speaking, the efficiency of a truck in performing it's function de- pends upon the amount of time or money, or both, that it saves for the shipper, as compared with any other means of haulage. While it is diff cult to separate all the factors bear ing on these two items, they may be roughly classified as follows:
 The factors effecting time are: Dis tance of hauls; traffic congestion; speed of delivery; regularity of de- livery; condition of roads-(effect on speed of truck); number of trips per day, and time out for repairs, etc.
 The factors effecting money are: amount of pay load and overload; con- dition of road-(effect on tires and truck); number of trips per day; cost of upkeep, and cost of substitute equipment.
 In what way does the tire equipment bear on these factors? To begin with, the operator must pay from 75%e to 225% more for pneumatic than for solid tires. No dependable figures indicating the relative cost per mile of the two types are available, but from such information as can be obtained, it is my belief that it will cost from two to three times more per mile to run on pneumatics than solids.
 Let us see how pneumatic tires may effect the time factors If the oper- ator is engaged in long-distance haul ing with relatively few stops, pneu- matic tires will almost invariably save running time, due to the fact that they absorb the road shocks so much more easily than solids. It should also be noted that the drivers fatigue in such cases is far less on pneumatics than on solids.
 Up to the present, however, compar atively few trucks are engaged in long-distance hauling. The great majority of trucks operate in cities where they canot possibly obtain speed of over ten miles an hour. For such speeds there can be no possible saving in time which would offset the extra cost of running on pneumatic tires.
 The condition of road surface has very important bearing on the time element, as it has a direct effect on the speed of the truck. In fact, un- der certain circumstances the increas- ed traction afforded by the heavy duty pneumatic makes it possible to oper- ate the truck while if it is equipped with solids it canot be driven at all. This is particularly noticeable in rural districts where there are no hard-sur- faced roads.
 One of the advantages frequently mentioned is the greater number of trips per day which may be obtained from a truck equipped with pneuma- tics. So far as this factor by itself is concerned, there is no doubt that the advantage is in favor of the penu- matic.
 There is one more important fac tor to be considered as affecting the time element, and that is the number of hours the truck is laid up for re- pair. Barring occasional lay-ups caused by defective material or work manship, solid tires can be depended upon to give uninterrupted service from the time they are applied until worn down to the point. They can then be replaced without serious loss of time.
 Owing to the comparative vulner- ability of pneumatic tires, they are far more likely to require time out for repairs and replacements.
 Punctures do not seem to be so,fre- quent or so costly in point of time as blowouts due to cutting and chaff- ing of side walls from ruts, as well IS to under-inflation and overlooking.
 When we come to campare the time 'ut for causes other than tire trouble, We find variety of conflicting claims, ;hough it seems to ma the evidence avors the use of pneumatics.
 It is claimed by some that the use # pneumatic tires accelerates the year on certain parts, such as bear ngs, bushings and steering knuckles, nd that A eorrespondingly greater