2. The speed at which the transmitting machinery must move.
3. The course or direction of transmission, whether in straight lines or at angles.
4. The cost of construction and durability.
5. The loss of power during transmission.
6. Danger, noise, vibration, and jar.
In every case where there can be a question as to whether gearing shafts or belts will be the best means of transmitting power, the several conditions named will furnish a solution if they are properly investigated and understood. Speed, noise, or angles may become determinative conditions, and are such in a large number of cases; first cost and loss of power are generally secondary conditions. Applying these tests to cases where belts, shafts, or wheels may be employed, a learner will soon find himself in possession of knowledge to guide him in his own schemes, and enable him to judge of the correctness of examples that come under his notice.
It is never enough to know that any piece of work is commonly constructed in some particular manner, or that a proposition is generally accepted as being correct; a reason should be sought for. Nothing is learned, in the true sense, until the reasons for it are understood, and it is by no means sufficient to know from observation alone that belts are best for high speeds, that gearing is the best means of forming angles in transmitting power, or that gearing consumes more power, and that belts produce less jar and noise; the principles which lie at the bottom must be reached before it can be assumed that the matter is fairly understood.
(1.) Why have belts been found better than shafts for transmitting power through long distances?—(2.) What are the conditions which limit the speed of belts?—(3.) Why cannot belts be employed to communicate positive movement?—(4.) Would a common belt transmit motion positively, if there were no slip on the pulleys?—(5.) Name some of the circumstances to be considered in comparing belts with gearing or shafts as a means of transmitting power.