CHAPTER XV.

THE SIDE-SLIP OF THE SAFETY.

The question of side-slip is not entirely new; it was first mooted in connection with the Safety of the Kangaroo type, which had a driver of from thirty-six to forty inches in front of a rear wheel of eighteen or twenty inches, as will be noticed in the cut of this machine given hereinafter. Now, to come to the specific features supposed to account for the side-slip, note that, in order to make room for the sprocket-wheels, the cranks had to be unusually wide apart and, by the necessary construction of the machine, also very low down; in other words, the machine had a very wide tread, swinging very close to the ground. The slip of this wheel was something fearful to behold, and its cause was supposed to be fully explained by the peculiarities of construction just noted, in accordance with a theory which, though religiously believed in at the time, has of late been somewhat shaken, and which we now proceed to develop.

In order to compare the different machines in respect to this theory, suppose we take, first, the Ordinary with a fifty-inch wheel and cranks, say, eight inches apart, or four inches from the centre of the wheel to either crank. Now, if the pedalb(Fig. 1) is four inches long, the distance from the centre of the pedal to the centre of the axle of the drive-wheel is six inches, and the diameter of the wheel fifty inches; then, when the crank is extended horizontally out in front, this being the position when it is supposed to be subjected to the greatest strain, we have the following conditions (seeFig. 2):

Fig. 1.

Fig. 2.

Side-slip diagrams.

Leta brepresent the distance of the centre of thewheel from the centre of the pedal,a cthe vertical height of the pedal from the ground, andWthe weight of the man. ThenWapplied vertically downward atbwill create a horizontal side-slip pressure,Ratc, in the direction of the arrow, such thatR=Wabac. If, then,W= 150 pounds anda banda c= 6 and 25 inches respectively, we haveR= 150 ×625= 36 pounds. Supposing the theory to be correct, the above may be said to represent the side-slip resultant in the fifty-inch Ordinary. In the Kangaroo the cranks, being belowthe centre of the wheel, average about twelve inches from the ground when power is applied. The pedals are about a foot apart, so thatab= 8,ac= 12, andW= 150, whenceRby the same formula equals one hundred pounds. The above, though perhaps slightly exaggerated in its application to some of the Kangaroo patterns, is substantially correct, showing the difference to be sixty pounds against it. According to this theory, then, the greater the tread and the less the distance of the pedals from the ground, the greater should be the side-slip.

Appertaining to this matter, I have used a machine with the same sizes of wheels as those found in the Kangaroo, but in which the power devices were very close together, and I have found it comparatively free from slip; and I am also informed by riders of the machine called the Facile, in which the pedals are closer together, that it is remarkably free from the same difficulty. But these facts cannot be taken as a proof of the theory under consideration, for the reason that the application of the formulaR=Wabacto the two machines just spoken of, at best, still gives, as a result, a large amount of side pressure, which in actual practice does not exist. What difference it may make in the Facile or other treadle machines that the point of application of power is in the rear of the driving axle, I cannot say, or what difference a lever motion would show as compared with the simple crank is also not apparent; in fact, there is very little of established data from which to draw a conclusion, and a good reason which would now deter any cautious man from offering much experience or any theory in the matter will be readily surmised after reading the following extracts from theCycliston the subject.

“SIDE-SLIPPING ON SAFETIES.“One of the principal causes of the falling out of favor of the ‘Kangaroo’ type of Safety was the great proneness it had to side-slipping upon greasy roads, and it was confidently and freely asserted when the rear-driver was introduced that this defect was, in its construction, overcome. That this is not the case every one who has had any extensive experience with this class of machine will admit; indeed, the side-slipping of the Safety is its one great fault. As our readers know, the forks of a Safety of this type are considerably sloped,—some more so than others. It matters not whether the forks are straight or curved, so far as the point we are dealing with now is concerned. The sloping of the fork places the wheel, unless travelling in an absolutely straight line, more or less on its side. The result is manifest. There is a strong force behind pushing it forward. So long as the ground gives enough frictional resistance to the wheel, well and good; but so soon as the surface is lubricated, as it is, by the slippery mud, then the tendency is at once to push the machine over. This tendency is increased, as with the side-slipping upon other forms of machines, by a sloping road surface, the side of a rut, or the cant of the machine in turning a corner; and, moreover, the harder the rider pushes the more chance there is of the machine slipping. Having, then, pointed out the cause of side-slipping, it remains for those who devote their time and talents to invention to overcome it. So far as we can see, a vertical steering-fork should do that which is needed.”[7]“[1113].—Your leader in last week’s issuerethe side-slipping of rear-driving Safety bicycles is, in my opinion, somewhat calculated to mislead. I cannot for one moment think you are right in stating that the cause of side-slipping in this class of machine is the sloping fork of the steering-wheel. You conclude with the following remark: ‘So far as we can see, a vertical steering-fork should do that which is needed.’ Here again I must say I emphatically disagree with you.Had you tried one of the old ‘B.S.A.’Safeties, you would not say this. These machines were far worse than any sloping-forked machine.I gave one an extensive trial, and found that the side-slipping was one of its worst features. Further, you have only to take one of the old ‘Humber’ Safeties, for example, with the perpendicular fork. Was side-slipping impossible on these?“In my humble opinion, sir, you have entirely overlooked the real cause of side-slipping on rear-driving Safeties, which isthe absence of sufficient weight on the driving-wheel. My argument is still further proved by the fact that the ‘Scout’ Safety (two-chain rear-driver), on which machine the weight of the rider is thrown as near as possible over the centre of the axle, will not slip sideways on the most greasy surface; and again, the American ‘Star,’ I am told by experienced riders of this machine, possesses a like good quality. Here, again, the weight is almost entirely on the driver.“The subject of side-slipping on the most popular machine of the day—viz., the rear-driving Safety—is so serious a one that I am sure you will see your way to open your columns to a discussion on the same.Sydney Lee.”[“The position of the weight doubtless forms an important factor in the question of side-slipping, and the thanks of the community are due to Mr. Lee for his experiments in that direction. We are bound to say, however, that our experience, so far as the question as to which wheel slips first, and also as to the stability of the tandem Safety on greasy roads, and on the point of safety at high speed, is exactly the reverse of that found by Mr. Lee.—Ed.”]“[1114].—I have read with great interest your article on side-slipping in Safeties, and, being a Safety rider myself, should be indeed thankful to see this very serious fault overcome. I am very much inclined to your opinion as to the cause,—viz., the canting over of the steering-wheel in turning,—which can only be obviated, as you suggest, by having a vertical steering-post.“Side-slip.”“[1131].—The ‘side-slip’ of the Safety seems to be the argument of to-day, and probably it is the great and all-important question to winter riders, as well as the members of clubs, near large towns, who attend the Saturday runs, and have to endure the double dose from our friend the ‘water-cart.’ Undoubtedly, the argument ofThe Cyclistis correct.J. Nicholson.”“[1132],—I have been trying experiments on the greasy wood and asphalt roads these last few days, and I have come to the conclusionthat the nearer the rider can getto a vertical position over the centre of the driving-wheel the less liability to side-slip.C. Leni.”

“SIDE-SLIPPING ON SAFETIES.

“One of the principal causes of the falling out of favor of the ‘Kangaroo’ type of Safety was the great proneness it had to side-slipping upon greasy roads, and it was confidently and freely asserted when the rear-driver was introduced that this defect was, in its construction, overcome. That this is not the case every one who has had any extensive experience with this class of machine will admit; indeed, the side-slipping of the Safety is its one great fault. As our readers know, the forks of a Safety of this type are considerably sloped,—some more so than others. It matters not whether the forks are straight or curved, so far as the point we are dealing with now is concerned. The sloping of the fork places the wheel, unless travelling in an absolutely straight line, more or less on its side. The result is manifest. There is a strong force behind pushing it forward. So long as the ground gives enough frictional resistance to the wheel, well and good; but so soon as the surface is lubricated, as it is, by the slippery mud, then the tendency is at once to push the machine over. This tendency is increased, as with the side-slipping upon other forms of machines, by a sloping road surface, the side of a rut, or the cant of the machine in turning a corner; and, moreover, the harder the rider pushes the more chance there is of the machine slipping. Having, then, pointed out the cause of side-slipping, it remains for those who devote their time and talents to invention to overcome it. So far as we can see, a vertical steering-fork should do that which is needed.”[7]

“[1113].—Your leader in last week’s issuerethe side-slipping of rear-driving Safety bicycles is, in my opinion, somewhat calculated to mislead. I cannot for one moment think you are right in stating that the cause of side-slipping in this class of machine is the sloping fork of the steering-wheel. You conclude with the following remark: ‘So far as we can see, a vertical steering-fork should do that which is needed.’ Here again I must say I emphatically disagree with you.Had you tried one of the old ‘B.S.A.’Safeties, you would not say this. These machines were far worse than any sloping-forked machine.I gave one an extensive trial, and found that the side-slipping was one of its worst features. Further, you have only to take one of the old ‘Humber’ Safeties, for example, with the perpendicular fork. Was side-slipping impossible on these?

“In my humble opinion, sir, you have entirely overlooked the real cause of side-slipping on rear-driving Safeties, which isthe absence of sufficient weight on the driving-wheel. My argument is still further proved by the fact that the ‘Scout’ Safety (two-chain rear-driver), on which machine the weight of the rider is thrown as near as possible over the centre of the axle, will not slip sideways on the most greasy surface; and again, the American ‘Star,’ I am told by experienced riders of this machine, possesses a like good quality. Here, again, the weight is almost entirely on the driver.

“The subject of side-slipping on the most popular machine of the day—viz., the rear-driving Safety—is so serious a one that I am sure you will see your way to open your columns to a discussion on the same.

Sydney Lee.”

[“The position of the weight doubtless forms an important factor in the question of side-slipping, and the thanks of the community are due to Mr. Lee for his experiments in that direction. We are bound to say, however, that our experience, so far as the question as to which wheel slips first, and also as to the stability of the tandem Safety on greasy roads, and on the point of safety at high speed, is exactly the reverse of that found by Mr. Lee.—Ed.”]

“[1114].—I have read with great interest your article on side-slipping in Safeties, and, being a Safety rider myself, should be indeed thankful to see this very serious fault overcome. I am very much inclined to your opinion as to the cause,—viz., the canting over of the steering-wheel in turning,—which can only be obviated, as you suggest, by having a vertical steering-post.

“Side-slip.”

“[1131].—The ‘side-slip’ of the Safety seems to be the argument of to-day, and probably it is the great and all-important question to winter riders, as well as the members of clubs, near large towns, who attend the Saturday runs, and have to endure the double dose from our friend the ‘water-cart.’ Undoubtedly, the argument ofThe Cyclistis correct.

J. Nicholson.”

“[1132],—I have been trying experiments on the greasy wood and asphalt roads these last few days, and I have come to the conclusionthat the nearer the rider can getto a vertical position over the centre of the driving-wheel the less liability to side-slip.

C. Leni.”

The above quotations explain themselves, and many other such, “from experience” (sic), might be given. TheCyclisteditor and Mr. Lee are justly considered to be authorities in such matters. It is beyond all question that all of these writers are strictly honest and speak the truth so far as they know it, but we may well ask, under these circumstances, what is any individual experience worth? Certainly nothing, until it becomes verified and definitely settled by the generalverdict of all sides. For such reasons the writer is loath to offer his own observations on this subject as of much value. It is a peculiar fact, and one worthy of notice by all who desire to form an accurate opinion in the matter of cycling or of any other art, that the experience of an interested party is generally as one-sided as his desires. A machine will do an enormous amount in the mind of the user, if he wants it to; and this is not said in a spirit of criticism or deprecation, for the writer has found himself just as liable to the same error as others. In being interested, I do not mean that it is necessary to be financially interested; all a man has to do is totake a side, and he is deeply enough interested for all practical purposes: let him set up an opinion and ten to one his experience will bear him out, not in the way of villanous, premeditated misrepresentation, but results will honestly appear to justify him. It does not appear that we must contend with this vicious tendency to any greater extent in connection with the cycle than in any other art. Almost every rider is prone to consider himself an expert in our pet subject, and it very often happens that he is; yet he may not be an observer capable of defending himself against himself in the delusions of experience.

Having probably confused the reader’s mind sufficiently by this time to go on with the subject, I may say that another fact why the reasoning and formula in regard to the side-slip are not correct is that the same rule applied to the Rover does not in any way justify the results we find by experience. The slipping of the Rover is much more than it should be, in the light of any conclusion based on our formula; in fact, I believe the entire theory is, and always has been, an unmitigated blunder. A well-known correspondent, Mr. Gerald Stoney, has thrown a little light on the subject by an article in theIrish Cyclist, which, though death to one theory, sets up another still of dubious tenability.

“SIDE-SLIPPING OF BICYCLES.“Mr. Gerald Stoney, in last week’sIrish Cyclist, adds the following to this interesting and important discussion. It will be noticed his deductions differ both from those of Mr. Lee and ourselves.“In a leader inThe Cyclistof November 28, the reason that low machines of the Kangaroo type slip more than the high Ordinary is referred to the pressure of the foot being low down, pushing the bottom of the wheel to one side more than in a high machine when it is high up. We should wish to point out that no such effect can take place so long as the pressure of the foot does not cause the machine to wabble; since, so long as there is no change in the velocity or direction of motion of the machine, the position, direction, or amount of internal forces, such as the pressure of the foot, do not affect the position, direction, or amount of external forces, such as the pressure of the wheel on the ground. This is one of the first great elementary principles of mechanics. The reason why a small bicycle has, in general, more tendency to slip sideways than one in which the rider is seated high up is, that if the wheel slips off a stone or down the side of a rut, the distance sideways to which the wheel will slip is independent of the size of the wheel, and depends on the size of the stone or rut, the state of the road, the speed the machine is going at, etc. But the amount by which the machine is inclined to the vertical from a given side-slip will depend on how high the centre of gravity is, and, therefore, on how high the rider is seated, and accordingly it will be less the higher the saddle is. Now, it is a theorem in mechanics, which we will ask the reader to assume, that the greater this inclination the greater the tendency of the wheel to go on slipping, when it has hopped off the rut, stone, etc., and, therefore, the higher the saddle the less side-slipping there will be insimilar machines.’”

“SIDE-SLIPPING OF BICYCLES.

“Mr. Gerald Stoney, in last week’sIrish Cyclist, adds the following to this interesting and important discussion. It will be noticed his deductions differ both from those of Mr. Lee and ourselves.

“In a leader inThe Cyclistof November 28, the reason that low machines of the Kangaroo type slip more than the high Ordinary is referred to the pressure of the foot being low down, pushing the bottom of the wheel to one side more than in a high machine when it is high up. We should wish to point out that no such effect can take place so long as the pressure of the foot does not cause the machine to wabble; since, so long as there is no change in the velocity or direction of motion of the machine, the position, direction, or amount of internal forces, such as the pressure of the foot, do not affect the position, direction, or amount of external forces, such as the pressure of the wheel on the ground. This is one of the first great elementary principles of mechanics. The reason why a small bicycle has, in general, more tendency to slip sideways than one in which the rider is seated high up is, that if the wheel slips off a stone or down the side of a rut, the distance sideways to which the wheel will slip is independent of the size of the wheel, and depends on the size of the stone or rut, the state of the road, the speed the machine is going at, etc. But the amount by which the machine is inclined to the vertical from a given side-slip will depend on how high the centre of gravity is, and, therefore, on how high the rider is seated, and accordingly it will be less the higher the saddle is. Now, it is a theorem in mechanics, which we will ask the reader to assume, that the greater this inclination the greater the tendency of the wheel to go on slipping, when it has hopped off the rut, stone, etc., and, therefore, the higher the saddle the less side-slipping there will be insimilar machines.’”

I think the above sufficiently exposes the sophistry of the wide-tread theory, but lest some of the old adherents to the idea should not be willing to accept Mr. Stoney’s mechanical reasoning, I have had made a device to test the matter in this way (seeFig. 3).

Fig. 3.Roller experiment.

Fig. 3.

Roller experiment.

We have an upright frame provided with two cross pieces,b cande f, a saddle ata, rests for the feet atbandc, and a roller,d, placed undere f. Sitting upon the saddlea, I was totally unable to move the rollerdby any pressure upon either pedalborc. The above I consider conclusive proof and the result unbiased by prejudice in trying the experiment, because I tested the matter before looking carefully into Mr. Stoney’s article and becoming convinced that in this he is right. The laws applying to internal forces or forces within a system are very often disregarded, and especially are internal confounded with external forces, as in this case. In any machine where the rider throws his weight on and vertically over the pedal, the formula given for the side-slip does represent a force acting to swing the machine out of perpendicular and to cause it to “wabble,” as Mr. Stoney calls it, but not to slip it on the surface of the roadway, as many would suppose. The rider rarely, however, throws his weight directly over the pedal sideways, as he does in raising upon it in a forward direction in order to get over the work. The lateral or wabbling strain in a cycle of the foot-pressure in one direction is balanced by the pull on the handle-bars and pressure of the leg against the saddle. The only feasible connection the formula theory can possibly have in this matter is that the thrust on the pedal is so sharp and violent that the inertia of the man and other heavy parts of the system are not perceptibly affected sideways; hence we might get an action against the slight weight in the lower part of the wheel. I cannot, however, detect any slipping action of this or any other kind in the roller experiment.

The futility of an effort to slip the machine sideways by a force upon the crank might be illustrated in this manner: Suppose the drive-wheel of an Ordinary ismade rigidly fast to the front fork. Now, it would be impossible for the rider to slip the tire on the road-bed by pressure on the crank, as he can when the wheel is free to revolve in its bearings, no matter how long the crank may be; if the rider leans out over it, the machine could be rolled forward, but not slipped on the surface. Loosen the wheel so that it can revolve as usual, then it can be slipped, as every good rider well knows. Suppose now that the drive-wheel is rigidly fixed in the frame of the bicycle so far as any lateral motion is concerned, and the wheel cannot revolve within the system about any horizontal line at right angles to the axle of the wheel, as it would have to do in order to make it slip in the manner it would in the other case, then it is easy to see that the machine and rider might be rolled over sideways by throwing the weight on one crank; but it cannot be slipped: the only slipping that can occur is when the machine is allowed to get out of perpendicular, but the angle at which it would begin to slip would be the same regardless of width of tread. If the wide tread does affect the slipping, it is the result of other forces than those generally supposed.

I do not believe that the extra weight on the drive-wheel will relieve the trouble. I have a Rover pattern machine in which the weight is almost entirely in the rear, and I can conscientiously aver that it is the worst slipper I was ever on. Now, this is in spite of the fact that there was every reason to believe, and to desire, that it should not slip at all.

One of theCyclistcorrespondents mentions the American Star, and justly says that it does not slip; yet that fact could be explained by our formula, since it is a tall machine with narrow tread. I cannot see, after all, that any theory of wide or narrow tread could be applied to the Rover type, even if it were found to be valid in other cases, because there seems to be complaint, and I have found it so in practice, that the machine will slip more than the old Ordinary, even whennot pushing on the cranks at all. It seems to slip worse than any other in making a curve or in descending hills and upon cobble-stones, whether there is any pressure on the crank or not. This will apply against theCyclistidea that the slanting fork breeds the mischief, since, if it slips in running a straight line, the slant of the fork could not possibly have anything to do with it.

In answer to the idea advanced that the fault is due to the mere size of the wheel,—that a large one has more surface exposed to contact, etc., and will hold better,—the writer has noticed very little difference in his thirty-eight-inch narrow-tread front-driving pattern as compared with a fifty-two-inch Ordinary; if there is any difference caused by the size of the wheel, this fourteen inches ought to have shown itself more than it did.

If the small wheel in a bicycle is a cause for slipping, we could naturally ask why it does not show itself more in the rear wheel of the Ordinary. It may be said, in answer to this, that there is but little weight on it, and that, not being a driver, whatever capers it might choose to cut are ignored by its regal, imperturbable leader; hence, if the rear wheel slips, it is immediately drawn up in line again. Another plea is that the lack of weight on the front wheel of the Safety makes it slip, and then it carries the rear wheel with it. To the last I can simply reply, as I would to theCyclist’snotion of the slanting fork, that it is the rear wheel which slips first, last, and all the time, or else a large majority of riders are very much misled, and really can’t tell what is going on under them. Certainly we must say that if appearances and sensations of the riders are worth anything, the doctrine of the front wheel slipping first must go to the wall and carry several ingenious solutions with it. Still another bright speculation is, that the unusual bumping of the front wheel holds it back, and the rear pushing on, for the nonce, cannot go forward, hence it must go sideways.

If we admit that the American Star does not slip, then the theories of small weight on the front wheel, the slanting fork, and front bumper must all go for naught. There are some other qualifications, however, which would modify or exclude the Star as a reference. The fork is slanting to a greater extent than in any other machine, but the small front steerer is swung from a point directly above the centre, which, it is said, gives the wheel a better chance to caster. To our ingenious front-bumper friend, I would also suggest the trial of a first-class anti-vibrator to the fork, which will let it spring back a good way.

And again, it has been stated, in regard to the Rover slip, that the large rear wheel swings from side to side, or wabbles, humorously likened by some to the wagging of a duck’s tail. This feeling of disturbance in the rear part of the machine is felt in the Ordinary when supplied with the large rear wheel advocated by some, and it may have something to do with the slip, though it is hardly possible that it would in the well-built, steady machines of the present time.

As to the high-up saddle or centre of gravity, true, an inch side-slip at the ground, of a machine with a low-down centre of gravity, will cause it to assume a greater slant or angle from the vertical than a higher; hence our friend could well say that when the Safety starts to slip it will be more certain to go on down. It is to be noted, however, as against this idea, that other machines with low-down saddles do not slip.

Taking all the theories and experiences,proandcon, into consideration, I am inclined to believe that no one cause can account for the entire difficulty; it is probably a combination of smaller elements partly belonging to several of the theories advanced. The elements which have been most strongly urged are, first, the driver being small; second, the driver being in the rear; third, the weight being in the rear; fourth, the work being done between the wheels. All these seem towork to the same end. Again, any drive-wheel will slip worse than a non-driver, since a sliding force in any direction will tend to loosen the hold of the rubber tire from the surface of the road more than any rolling action. A short slide from a stone is felt more when the weight is upon the wheel, and the drop in rolling off so distinctly felt in connection with the small wheel is much sharper than a similar action of a large one. A rider can certainly manage himself better and more surely when he drives, steers, and leads with the same wheel and has his weight upon it. This is what hedoeson the Ordinary and just what hedoes notdo on the rear-driver.

The deepest and most profound explanation of all side-slip was recently proposed to the writer by a mathematician of great ability; but it is so complex that he has not worked it out himself yet, though expecting daily to hand in the solution. He says it is all from the relation of the points, first, of the centre of gravity, second, of the centre of oscillation, and third, of the transmission of power, to each other. Just where and how they ought to be is, as yet, not fully determined.

To remedy the evil of the side-slip in the most obvious ways would be to make the rear-driving Safety no longer the same machine; it would ruin, to a great extent, the very qualities for which it is prized, and therefore, if any such theories as before enumerated should prove tenable, the only clear way out of the difficulty would be in the use of non-slipping tires, if such can be produced.

In regard to the angle at which any machine will slip in rounding a corner, some, who have advanced the idea that the Safety slipped because it had to lean more, do not appear to be aware of, or take into account, the fact that the angle at which the cycle, or any other machine, must lean under such circumstances is entirely independent of the height of the centre of gravity. The angle is a function of the speed and radius of curvature only.

[7]Mr. Sturmey should have broached this subject in its relation to castering.

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