17 August, 1831.
middle of the Engine, do more injury to the roads than the propelling wheels.
Have you been engaged in running Stage Coaches?—I was engaged in running a Stage Coach with horses four years ago, and since this Committee commenced their examination. I have been making some calculations as to the comparative wear and tear of the road by horses' feet and coach wheels; and I consider that the tear and wear of the horses' shoes is very much greater than that of the tires of the wheels. I know it to be so. A set of tires will run 3,000 miles in good weather, or on the average 2,700 miles, while a set of horses' shoes will travel only 200 miles. Take the square inches of the rubbing surface: I think the rubbing surface of the wheel, on an ordinary road, to be somewhere about sixteen square inches; I am taking a gravelly road.
Do you mean to say that if a coach was standing still, there would be a segment of the wheel of eight inches touching the ground?—On a gravelly road, with a dished wheel, it is about that; and I take the average of sixteen square inches, because all tires are not limited to two inches width: some of them are a little more; I take sixteen inches as the standard on the average quality of roads.
You state that eight inches of the wheel are imbedded in the road, in ordinary cases?—That is the fact. I took the whole together at the average.—With the front wheels it would not be so much, on all occasions, as on the hind wheels. I take the average, allowing for this variation.
Do you give this answer from actual experiments?—From observation.
Having measured that part of the wheel which touches the road?—I cannot say that I have put my rule to it; but I mean to say a segment of eight inches is pretty accurate. If it is on a perfectly hard road, in dry weather the road will almost be a mere tangent to the circle; but on a soft road, in damp weather, the wheel will make more or less of a rut, and the average depth of the rut will give the average for the segment.
