160 



Popular Science Monthly 



to two other larger sprockets, one bolted 

 to each of the rear wheels of the truck. 

 The motor power is thus transmitted to 

 the jackshaft, to 



^,^S-r-.-- 



the jackshaft 

 sprockets and 

 thence through the 

 chains to the rear 

 wheel sprockets. 



The internal-gear 

 drive method 

 shown in No. 4 also 

 employs a jackshaft 

 but this, instead of 

 being mounted on 

 the truck frame, is 

 made into a unit 

 with a stationary 

 axle carrying the 

 rear wheels. The 

 wheels are revolved 

 through small 

 pinions positioned on the ends of the 

 jackshaft which mesh with large internal 

 gears bolted to the rear wheel spokes. 



The bevel drive is used mostly on 

 trucks of one-ton capacity and under. 

 It is not used on 

 larger trucks because ;,— - . 



the greater gear reduc- 

 tion necessary due to 

 the greater weight of 

 the truck and its load 

 would make the bevel- 

 pinion too small or 

 the bevel - wheel too 

 large for practical 

 purposes. This neces- 

 sarily larger gear re- 

 duction is secured by 

 means of the tloublc- 

 chain dri\e b>' making 

 the driving-wheel 

 sprockets much larger 

 than those on the 

 jackshaft. 



On the other hand, 

 the necessary gear reduction for larger 

 than one-ton trucks can be secured 

 by means of the worm and worm- 

 wheel due to the design of the worm- 

 teeth and its rubbing instead of roll- 

 ing action on the worm-wheel. It is 

 also more efficient than the bevel or 

 double-chain methods and delivers more 

 power to the rear wlieels becauso of llu- 

 elimination of niucli of the fric-tion of tlic 



bevel-pinions and chains. It also has the 

 advantage o\'er the double-chain method 

 in being an enclosed dri\-e, like the in- 

 ternal-gear type, 



Fig. 3. Double-chain drive. The motor-shaft 



ends in a jaclcshaft which transmits the power 



to sprockets cormected by chains 



Fig. 4. Internal-gear drive. A jackshaft 



pinions with two large meshed wheels on 



the back axle 



thus preventing 

 dirt and grit getting 

 on to the driving 

 members, and 

 causing loss of 

 power and excessive 

 wear. 



Another advan- 

 tage of the worm 

 drive over both the 

 chain and internal- 

 gear types is that 

 the aggregate parts 

 weigh less than 

 either. This light- 

 ens the truck, 

 permitting more of 

 the motor power to 

 be used for hauling the load to be 

 carried instead of moving the heaN'j' 

 \'ehicle itself. 



Measuring Rainfall on the Farm 



AN excellent 

 equipment for 

 collecting and meas- 

 uring either rain or 

 snow consists of a 

 simple pail or bucket. 

 The location selected 

 for setting out the 

 pail should be in some 

 open lot or field un- 

 obstructed by large 

 trees or buildings. If 

 the diameter of the 

 pail is just 10}^ ins. at 

 the upper edge, each 

 ounce of water collec- 

 ted represents 0.02 in. 

 of rainfall. The pail 

 should hold twelve 

 quarts, in fact, most 

 twel\e-(iuart pails are exactU- io32 '-is. 

 at their ui)per edge. The depth of the 

 rainfall, as shown by the water caught, 

 may be found by w^eighing the contents 

 of the pail. An ordinary small balance 

 which reads in ounces and half-ounces is 

 suitable for the purpose. In hot weather, 

 when water ex-aporatos quickly, the rec- 

 ord should be made as soon as the rain 

 has stoi)ped, if possililc. 



--/,' 



- INTERNAL GEAR 

 90LTfO TO acAD wwfrt 



