874 EEPORT— 1903. 



On January 21, over the same kilometre, hardened by the frost and 

 very smooth, on the third speed the ti'ack was covered in 3 minutes 

 28 seconds with a current of 20 amperes at SO volts. This speed would 

 be equivalent to lO'SO miles per hour or 15-80 feet per second, with a 

 total tractive effort of 75 lb., or 42"7 lb. per ton. 



Thus the tractive effort was •12-3 per cent, less on the hard road than 

 on the muddy road at the third speed. On the fuurth spted M. Jeantaud 

 found that this difference increased to 50 per cent. 



These experiments conlirm those of General INIorin and show tlie 

 accuracy with which that ingenious man carried out his work. But they 

 have to bo made at speeds near to those used by JMoriii, and it is not at 

 all certain that other experiments, at much higher speeds, under the new 

 conditions of automobilism, so different from those of the iron-tyred 

 vehicles, would give corresponding results. 



When pneumatic tyres are used, it must not be tliought that springs 

 can be dispensed with, as the duty performed by the tyre is quite 

 different from that of the springs. The pneumatic tyre does away with 

 the sliglit vibration caused by the wheel encountering gravel, stones, and 

 small obstacles generally, but the height of the axle from the ground 

 scarcely varies, as the tyre absorbs within itself these small objects. 



Experience has proved that these small vibi'ations, if not absorbed by 

 the tyre, would be transmitted through the springs to the body of the car 

 to the great disct)mfort of its occupants, and would tend to reduce the life 

 of the motor, owing to the crystallisation of tlie parts subjected to strain. 



But the pneumatic tyre will not yield much more than 1 inch, and 

 is in consequence unable to save the car from vibration when passing 

 over a large obstacle or a deep rut ; whereas the springs, with a resilience 

 of, say, 4 inches, would be well adapted for this purpose. 



Spiral springs have been tried with unsatisfactory results, and they 

 can practically only be used where heavy weights <ire carried. Plate 

 springs must necessarily be employed when ease and comfort are desired. 



It may be pointed out here that the method of attaching plate springs 

 to the frame is a matter of considerable importance. M. Caillardet 

 believes that the usual method is not at all satisfactory. The ordinary 

 practice is to use clips which are jiivoted to a bracket depending from 

 the frame, these clips being outside of and lower than the normal plane 

 of the spring. From the bracket they rise at an angle of about 45° and 

 meet the ends of the sjsring to which their upper ends are pivoted. The 

 residt is, when the wheel passes over an obstruction of any appreciable 

 size, the axle rises under the centre of the spring, the plates of which 

 lengthen (theoretically) and tend to form a straight line, and at once the 

 load aboN'e is thrown upward in the same proportion. 



On the other hand, where the clips are S(^ connected with the spring 

 as to work within its length and under its ends, instead of beyond them, 

 any shock given to the wheel causes the load to fall, and the loss of 

 mechanical energy is less. 



M. Gaillardet is of opinion that the springs should be so arranged 

 that each wheel is free to rise or fall independently of the others. When 

 this is done, an obstacle under one wheel will raise that wheel only, and 

 the centre of gravity of the whole car is raised a smaller distance than 

 would otherwise be the case. To attain this result he ^^roposes to mount 



