His Topic, "Motor Bicycles," attracted Record-breaking Attendance.
At the last session of that admirable institution, the Cycle Engineers Institute,- of which America might profitably have a counterpart, - "Motor Bicycles " was the topic, G. Douglass Leechman, M. C. E. I., being the lecturer. The subject was of such interest that it served to attract a record-breaking attendance, nearly three hundred members being present.
After remarking its uses and economies, Mr. Leechman asserted that the motor bicycle cannot be regarded as a single entity, but as consisting of two separate and distinct parts - the bicycle and the motor. In nearly all cases it is a bicycle to which a motor has been supplied, and the people who bought and used motor bicycles were those who had already become expert in riding the ordinary safety bicycle. The motor can be placed in almost any position on the machine that the designer pleases,- in the front, the middle or the rear, - and the bicycle will go and keep upon its keel.
The two points to decide were (1) which wheel to drive and (2) where to place the motor so as to drive the bicycle easily and avoid sideslip. Some people supposed it was an advantage to have the center of gravity low, but from a purely balancing point of view on a bicycle, it is desirable to have the center of gravity as high as possible, in order to avoid sideslip.
There are two causes of sideslip. First, from riding over uneven, greasy surfaces; and in this case, if the center of gravity is low, the rider will not have a chance to recover himself. The higher the center of gravity, the slower the oscillation and the more chance there is of correcting any disturbance. The second cause of sideslip is the endeavor to overcome centrifugal force when turning a corner. Take the case of a rider coming fast around a corner; the rider wants to go one way, but the machine would much rather go off at a tangent; but in this case the position of the center of gravity makes no difference, and need not enter into the calculations.
As regards the durability and successful working of the motor, as a rule it will be found that the higher it is from the ground, the less likely it is to be influenced by mud, dust, etc. This is a small point, but a practical one. Another point in favor of keeping the motor high is that when it is placed low it does not allow of much clearance from the pedal cranks, and things have to be cut very fine to get a proper length of crank-shaft, bearings, and sufficiently large fly-wheels, etc. Thus it is not advisable to get any part of the motor within the line of the chain wheel. A good deal of attention has been paid in recent years to the width of tread, but this is not a point that should worry the designer of a motor bicyle. If the motor is a good one it will not need much pedaling, and so far as sitting still is concerned, it is quite as comfortable to sit with feet a little wider apart than is the case upon the pedal-propelled safety. It is also necessary to get the motor in a position where it will secure a draft of cool air, but not so as to cook the rider.
Another point requiring careful consideration is the inclination of the cylinder. It is much better for the motor to be run vertical, and it is certainly much preferable for the valves to be in an upright position, since in that position they are much more reliable in their action. When the inclination is great, it is possible that the motor will run all right for a time, but it cannot be expected to give continued satisfaction. There is certainly some scope for ingenuity in the arrangements of the various taps and levers, etc., and all electrical apparatus should be worked from the handle, since it is often very awkward for one to loose the grip of the handle in order to attend to taps arranged along the top rail or elsewhere. After some remarks upon the necessity of good brakes, Mr. Leechman spoke of the tendency in some quarters to substitute chain driving for belt, and when one remembers the high pitch to which the art of chain-making has been brought, it is easy to see that good results are possible. Upon an ordinary cycle the chain is good, but upon the driving gear of the motor there is no dependence upon muscular energy, so that if the belt is quieter it is preferable.
- The Bicycling World.