THE INDIA RUBBER WORLD 



565 



inliation pressure, hand pumping is out of the question and a 

 power-driven pump on the truck or close at hand becomes a 

 necessity. In many cases this is not practicable. 



TRUCK MANUFACTURERS' OPINION IMPORTANT. 



While these mechanical considerations apiily particularly to 

 using pneumatics on trucks now in operation on solid tires. 

 most of the same problems are involved in changing the equip- 

 ment on trucks manufactured but unsold. The truck buyer 

 should satisfy himself that his agent's counsel on the equipment 

 is based on jwsitive facts and endorsed by the manufacturer. 

 Otherwise he may expect more or less disappointment and dis- 

 satisfaction over the performance of his truck if he orders the 

 equipment changed lo pneumatics before delivery. 



To sum up. since so many important technical features are in- 

 volved, the operator or prospective buyer would do well to seek 

 the advice of the manufacturer of his truck before changing the 

 equipment. No one else knows so well the probable effect on 

 various parts nor can advise more intelligently as to the probable 

 loss or saving such a move would entail on the mechanism of his 

 truck. 

 TRUCK EFFICIENCY DEPENDS ON SAVING TIME AND MONEY. 



Let us now look at the practical operating features that must lie 

 considered in determining which type of tire will make the truck 

 most efficient in service. Broadly speaking, the efficiency of a 

 truck in performing its function depends upon the amount oi 

 time or money, or both, that is saved for the shipper, as com- 

 pared with any other means of haulage. While it is difficult to 

 separate all the factors bearing on these two items, they may be 

 roughlvclas,ilicri ns fnllrnvs : 



The factors affecting time are: Distance of hauls; traffic con- 

 gestion; speed of delivery; regularity of delivery; condition of 

 roads (effect on speed of truck); numlier of trips per day; and 

 time out for repairs, etc. 



The factors affecting money are ; .Xmount of pay load and 

 overload; condition of roads (effect on t:res anl truck) ; number 

 of trips per day; cost of operation; cost of up keep, and cost of 

 substitute equipment. 



In what way docs the tire equipment bear on ihest- i,i--or>? 

 THE EFFECT OF PNEUMATICS ON TIME FACTORS. 



Let us see how pneumatic tires may affect the time factors. If 

 the operator is engaged in long-distance hauling with relatively 

 few stops, pneumatic tires will almost invariably save n-nning 

 tiiTie, due to the fact that they absorb the road shocks so much 

 more easily than solids. It should also be noted that the driver's 

 fatigue in such cases is far less on pneumatics than on solids. 

 Up to the present, however, comparatively few tru-ks are engaged 



in long-distance hauling. The great majority of trucks operate 

 in cities where they cannot possibly obtain a speed of over ten 

 miles an hour. For such speeds there can be no possible saving 

 in lime which would offset the extra cost of running on pneu- 

 matic tires. 



The condition of road surface has a very important bearing on 

 the time element, as it has a direct effect on the speed of the 

 truck. In fact, under certain circumstances the increased traction 

 afforded by the heavy duty pneumatic makes it possible to operate 

 the truck while if it is equipped with solids it cannot be driven at 

 all. This is particularly noticeable in rural districts where there 

 are no hard-surfaced roads. One of the advantages frequently 

 mentioned is the greater number of trips per day which may be 

 oljtained from a truck equipped with pneumatics. So far as this 

 factor by itself is concerned, there is no doubt that the advantage 

 is in favor of pneumatics. 



There is one more important factor to be considered as affecting 

 the time element, and that is the number of hours the truck is laid 

 up for repair. Barring occasional lay-ups caused by defective 

 material or workmanship, 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 vulnerability 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 blow-outs due to cutting 

 and chafing of side walls from ruts, as well as to under-inflation 

 and overloading. 



\\'hen we come to compare the time out for causes other than 

 tire trouble, we find a variety of conflicting claims, though it 

 seems to me the evidence favors the use of pneumatics. It is 

 claimed by some that the use of pneumatic tires accelerates the 

 wear on certain parts, such as bearings, bushings and steering 

 knuckles, and that a correspondingly greater amount of time is 

 required for the adjustment and renewal. Moreover, many own- 

 ers state that the use of pneumatics on trucks causes their drivers 

 to overspeed and take more dangerous chances that result in acci- 

 dents and time out for otherwise unnecessary repairs than is the 

 rase on solids. 



THE QUESTION OF PAY LOAD. 



The amount of work a truck can perform and hence the saving 

 • T profit it will show depends largely upon the amount it can 

 rarry ; in other words, its pay load. There is a well-nigh universal 

 tendency to overload trucks beyond their rated capacity and it is 

 not uncommon to find trucks carrying twice iheir rated capacity. 

 When it comes to standing up under this usage, there seems to 

 lie no doubt that solid tires will not only carry heavier overloads, 

 but will last longer in such service. This seems to me the most 

 iinportant and least understood factor in the entire list. Apparent 

 savings may be offset or overbalanced by the additional trips that 

 become necessary when an overload cannot be carried. 



Closely allied to the cost of overloading pneumatic tires is that 

 of underinflation. The constant and extreme flexing caused by 

 overloading has a tendency to weaken the side wall, making it 

 much more likely to fail in service. While solid tires are not 

 invulnerable they can stand more abuse and are less expensive to 

 maintain in working condition. In addition to the likelihood of 

 incurring expense from overloading and underinflation. there is 

 the danger of ruining pneuinatic tires from running them after 

 being punctured or blown out. It is not uncommon for practically 

 new tires to be ruined by drivers who do not stop their trucks as 

 soon as they begin to suspect tire trouble. 



In attempting to collect data as to mileage on pneumatics, I 

 found many varying claims, ranging from 200 miles under adverse 

 conditions to 2S.(K)0 miles on lighter trucks, over good roads with 

 proper care. With rare exceptions the mileage delivered by solid 

 lires is considerably greater than that from pneumatics in the 

 same class of service. When the earning capacity of the truck 



