November 1, 1920 



THE INDIA RUBBER WORLD 



85 



a heavy-duty type, different from the ordinary valve insides in 

 construction, but the two are interchangeable in any valve stem. 

 On the 10 and 12-inch sizes, which inflate to 130 and 140 pounds 



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 for Valve. 



The Journal of the S. A. E. 



Fig. 1. Slotted Rim 



Offset Valve 



per square inch respectively, even the heavy-duty type is unsatis- 

 factory when used alone; so, a combination is used in the form 

 of a heavy-duty valve insides and a needle-valve operated by a 

 hand screw. 



As to the relation of the valve to easy tire changing, it is cus- 

 tomary in applying the small-size tires to insert the valve in the 

 hole in the rim and tip the tire on the rim. This necessitates 

 considerable clearance in diameter of the tire beads over the rim 



rim and then fish the valve through the valve hole. To avoid 

 this difficulty some steel wheels are made with a U-shaped slot 

 from the edge to the center of the rim, which permits the tire to 

 go on the rim with no difficulty at the valve. (See Fig. 1.) We 

 believe an oflFset valve with two right-angle bends in it, will even- 

 tually be used. The offset valve requires only a depression in 

 the rim from the edge to the center, and not a slot. The wheel 

 is stronger than if slotted, and besides making application just 

 as easy, the valve comes out at the edge of the rim and is more 

 accessible to inflate. 



DUAL PNEUMATIC TIRES 



The arrangement of tires on the trucks presents three possibili- 

 ties ; the ordinary truck with giant tires on four wheels, dual 

 pneumatics on the rear, and trucks with six or more wheels. 

 We look unfavorably only on the dual pneumatics, that is, two 

 tires on the same wheel. Dual tires do not share the load 

 equally because the inflation is seldom kept alike in both tires. 

 Because of crowned roads, and more particularly rough roads, 

 one tire takes more than its share of the load temporarily and 

 this will injure the tire. An exaggeration of this condition is 

 when one tire goes flat and the other takes all the load without 



a^*ts 



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The Journal of the S. A. E. 



Fig. 2. Examples of the Application of Pneumatic Tires to Motor Trucks : 



From Left to Right Are Shown a Demountable Rim, a Demountable Rim and a Steel Wheel, a Detachable Rim on a Wood Wheel and *BE 



Pneumatic Tire Applied to a Cast Steel Wheel ( 



and, in 7-inch sizes and above, such design is impractical because 

 the rims are wide and would necessitate too much clearance in 

 bead diameter. 



It is therefore necessary if a straight valve and the usual valve 

 hole is used, to push the valve up into the tire, fit the tire on the 



the knowledge of the driver. The tire which still holds air is 

 so badly overloaded that it is sure to be injured, if not ruined. 

 Changing an inside tire, in the case of dual tires, necessitates re- 

 moving both. Dual tires are too easily abused and prove more 

 expensive than either of the other possibilities. 



What Motor Trucks Need to Supplement Pneumatic-Tire Equipment' 



By E. W. TempHn= 



T 



he introduction of the pneumatic tire for motor trucks 



would have a material bearing upon the design of the truck 



itself, to get the most good from the use of such a tire. 



Table I. Road Speeds 



.\verage Pneumatic 



Present Solid Tire Oear Governed Capacity, Tire Speed 



Ratios Speed, m. p. h. Tons m. p. h. 



7 to 8 17 1 to IJ^i 30 



9 to 10 15 2 to 2/, 30 



11 to 12 ,„ 13 3J4 25 



12 to 13 10 to 12 5 ^ 



14 to 16 9 7 20 



Tire Size, In. 



36 to 38 

 40 to 42 



38 to 44 

 40 to 48 

 42 to 44 



Rear Wheel 

 r. p. m, 



280.0 to 265.4 



252.1 to 240.1 

 221.1 to 191.0 

 210.1 to 175.0 

 160.1 to 152.8 



Drive 

 r. p. m. 

 1,450 

 1,325 

 1,200 

 1,200 

 1,200 



Pneumatic-Tire 

 Rear-Axle 



Gear Reductions 

 5.18 to 4.47 

 5.26 to 5.52 

 5.43 to 6.28 

 5.72 to 6.86 

 7.50 to 7.85 



The main factors bearing upon the problem of truck design for 

 pneumatic tires are as follows: (1) speed, including road and 



'Abstracted from Cleveland-Detroit Sections paper. The Journal of the 

 Society of Automotive Ensinecrs, October. 1920. 

 » Motor-truck engineer. The Goodyear Tire & Rubber Co., Akron, Onic 



