July 8, 1897] 



NATURE 



219 



occupied in stopping the rise and starting a fall of the 

 body. Thus the rider is able to store up the effect of 

 gravity at the less useful, and employ it at the more useful 

 periods, and so relieve his arms from the holding-down 

 strain, which is so tiring. 



After dealing with other points in connection with 

 stability, the author comes on to steering in general, and 

 to the difficult subject of steering and balancing upon the 

 "Rover" type of safety without using the hands. Five 

 pages of somewhat difficult reasoning are devoted to this 

 point, and after the establishment of all the forces and 

 couples which come into play, a theory is elaborated 

 which should apply even to the case when the steering 

 axis cuts the ground at the point of contact of the front 

 wheel. It is often stated that riding without hands under 

 these conditions is impossible ; difficult it is certain to 

 be, for this feat, as it used to be considered, is certainly 

 easier when the castor action is moderately increased. 

 It would be interesting if expert cyclists who have the 

 means would see if they can succeed. 



The writer noticed, when first practising to ride without 

 hands, that the lateral hinging of the body about a joint 

 in the neighbourhood of the saddle seemed to have a 

 definite influence. This motion is evidently under the 

 control of the rider, and so an actual variation of inclina- 

 tion can be forced upon the machine, the amount rela- 

 tively to that in the upper part of the rider's body depend- 

 ing upon the moments of inertia of the two systems about 

 their independent horizontal fore and aft axes. By this 

 means it is certainly possible to make a rapid and tem- 

 porary inclination of the frame, which, combined with the 

 gyroscopic action of the front wheel, is all that is needed 

 to control the steering. No doubt the forces calculated 

 by Mr. Sharp act as he has explained, but to what extent 

 they, or the temporary dynamical action just described, 

 are those which are depended upon in practice, whether 

 consciously or not, the writer is not prepared to say. 



The chapter on resistance of cycles is very instructive. 

 The conclusions are represented graphically, so that any 

 one non-algebraically-minded can grasp the enormous 

 importance of air resistance at high speeds. Extra- 

 polating from these curves, it is seen that a man who can 

 drive his machine under present conditions through 

 the air at, say, 30 miles an hour, would, if road and 

 machine resistance only had to be met, be able to drive 

 at 330 miles an hour, or if he can actually go 20 miles 

 an hour, he would be able to drive his machine 100 miles 

 an hour. This shows the very essential part that pace- 

 making plays in the cycle race. Whether Dr. Turner's 

 theory on the fatigue caused by brain work in constantly 

 determining the most suitable speed, plays any part or 

 not, it is evident that a long machine with half a dozen 

 riders upon it, or an autocar just in front of the racer, 

 will make such a draught as materially to reduce the 

 enormous resistance he would meet with if the air were 

 still. The writer would like to propose a method to 

 enable great speeds to be attained, which, however, is of 

 spurious interest, since in real cycling the wind resistance 

 must be overcome. All that is necessary is that a large 

 box or small house with glass sides big enough to 

 entirely surround the rider, but with a safe margin, 

 should be dragged by steam or other power along at 

 gradually increasing speeds until the rider shows that he 

 NO. 1445, VOL. 56] 



is beginning to lag. Of course, there would be no floor 

 or bottom to the box, and it should be made so that it 

 would clear the ground by any predetermined amount. 

 It might be safer if the house had no back. 



Another suggestion offered more seriously where 

 record-breaking without pace-making is the object, is 

 that a day should be chosen when the barometer is very 

 low, for a fall of an inch, if it reduced the air resistance 

 by one-thirtieth, might mean a gain of a second in a 

 minute, or a minute in an hour, i.e. if the corresponding 

 diminution of oxygen in the rider's lungs did not com- 

 pensate for the reduced resistance. 



The chapter on gearing is one that cycle inventors 

 would do well to study. It is interesting here to find the 

 Simpson lever chain under the heading " Perpetual 

 Motion." Mr. Sharp very clearly and forcibly points out 

 the fallacy that renders auxiliary hand-power mechanism 

 a practical failure. 



Part iii. opens with two chapters upon the frame, 

 which will probably be found to designers the most 

 useful in the whole book. Graphic methods, explained 

 in the first part, are employed to show how the stresses in 

 a link- work frame can be calculated. It is clearly im- 

 portant that the design should be such in a cycle frame, 

 that the members of the frame may be mostly in tension 

 or compression, as they would be if they were pivoted 

 and not brazed together. The difficulty of dealing with 

 the actual case in practice in which they are brazed, and 

 stresses other than tension and compression are certainly 

 met with, is only referred to, but, perhaps wisely, the 

 an.Kious engineer is not shown how to reduce these to 

 figures. 



It is a question whether too much stress has not been 

 laid upon the necessity of straight members in a cycle 

 frame, for in order to meet the racking and other stresses 

 which must be met with in practice, a gauge of tube is 

 necessarily employed, which, considering the frame as a 

 mere girder carrying a dead weight, is quite absurdly 

 strong, so that a moderate bending moment, due to the 

 design, need not be feared when some distinct gain is 

 effected in consequence. 



This is more especially the case in the dropped frame 

 which, unfortunately for themselves, ladies in this country 

 think they prefer. Great abuse is often heaped upon the 

 makers of machines with curved frames. Now, provided 

 that the top and bottom members are kept apart, and the 

 more so the better, and are effectively stayed at a few 

 points, the bending stresses introduced by the curvature 

 are quite moderate, and space is obtained where it is 

 required, so that mounting and dismounting is more easy 

 A further point is the extra steepness of the frame in 

 front, which allows the skirt to hang more easily. 



Mr. Sharp accepts the situation with regard to ladies' 

 machines as he finds it at the present day in this country. 

 Again, perhaps, he is wise. He assumes a drop frame to 

 be a necessity. Now, if any person will depend upon 

 reasoning alone, and pay no attention to the vagaries of 

 fashion, he will see first, as is evident from Mr. Sharp's 

 diagram, that the stresses in a so-called lady's "Safety" 

 are greater than in one of proper design, so that in order to 

 make it strong and stiff enough the machine has to be 

 heavier than any that a man would ride, and is even then 

 without that wonderful rigidity of the diamond frame. 



