Popular Science Monthly 



balanced. They begin to revolve on their 

 pins, toward the low-pressure side. The 

 high-pressure side of them no longer carries 

 its wheelshaft pinion around unyieldingly. 

 It lags till pressures are equalized, the 

 wheelshaft with the higher resistance turn- 

 ing more slowly and the other wheelshaft 

 more rapidly in the same proportion. The 

 total of power utilized remains unchanged, 

 except that a portion of it is spent in over- 

 coming the friction of the revolving pinions. 



As friction adds tooth 

 pressure on both sides, it 

 may be purposely increased 



Links and 



eccentric5 

 An eccentric can drive 

 a link in and out but 

 cannot be rotated by- 

 turning the link around 



31 



turned on. Suppose, further, that one 

 wheelshaft resists very little and does not 

 equalize tooth pressures until it is revolved 

 eight times as fast as the other. Then the 

 differential works four times as much as 

 before and the value of the friction rises 

 rapidly, perhaps from 2 to 8. The power is 

 consumed. By arranging the friction on a 

 less drastic scale, however, one can have a 

 shaft which offers a rather small resistance 

 under small differential action, yet equals 

 the resistance of the other shaft 

 as soon as its rotary velocity 

 becomes only two or three 

 times as high, after which 

 no greater difference in 

 shaft speed can be pro- 

 duced. The power is 

 then divided somewhat 

 on this plan: 2 for the 

 slow shaft, 1 for the 

 small friction identified 

 with its side of the dif- 

 ferential action, 4 for 

 the friction of the rapid 

 shaft and I for driving 

 it. If the wheel of the 

 rapid shaft has no trac- 



It is built strong enough to resist the 

 stresses that arise in its operation 



tion, there is still a net 

 power of 2 for driving. 



to modify the action of the differential. 

 For example, if the power delivered to the 

 casing has a numerical value of 8 and the 

 resistance of each shaft against rotation at 

 a certain velocity is 4, no friction in the 

 differential arises. But when road contact 

 interferes and one of the shafts produces in- 

 creased resistance at this velocity but only 

 4 at a velocity 33^ per cent higher, while 

 the other shaft produces 4 at a 

 velocity 33^ per cent lower, 

 such as may be the case when 

 a vehicle is made to turn or 

 a fairly sharp curve, one shaft 

 is turned twice as fast as the 

 other and a certain friction is 

 produced. In the ordinary 

 differential this friction i 

 negligible; but suppose it i 

 made to have a value of 2 

 then there is only a 

 power of 6 available 

 and there is less 

 than 4 for each 

 wheelshaft. The < 

 vehicle speed is 

 reduced or more 

 power must be 



A L 



The refrigerator-basket is the picnic party's 

 ice-box. In it all perishable food is preserved 



A Refrigerator Basket for the 

 Picnic Outing 



LL the luxuries of home are now at 

 the disposal of the vacationist starting 

 off for a picnic at the beach or in the 

 woods. The increasing vogue of automo- 

 bile touring trips has also created a demand 

 for portable creature comforts. A refriger- 

 ator basket is a refrigerator in minia- 

 ture, which keeps the butter hard, 

 the meat fresh and the 

 milk sweet. It consists 

 of a rust-proof metal 

 food container with a 

 smaller ice compartment 

 partitioned off at one 

 end. Around this shell 

 is a layer of insulating 

 material to keep the 

 cold air in and the warm 

 air out. Externally the 

 carrier is a reed basket 

 with convenient handles 

 and straps to bind the 

 lids down. Separate lids 

 are provided for the 

 two compartments. 



