Page:Report from the Select Committee on Steam Carriages.pdf/42



Mr. G. Garney. 3 August, 1831. On a very rough road, full of ruts?—If you start the Carriage from a rut, it takes more power; but when the Carriage is in motion, the momentum takes it over all the inequalities with the usual force.

Do you find that when the propelling wheel gets into a rut, the first power it exerts is in sliding?—Frequently; and sometimes it will be necessary to attach the two wheels, for one wheel will not be sufficient to get it out of that difficulty; the engineer in such case attaches a second wheel by the bolt, and I have never known a situation yet, in which a carriage with both wheels attached will not get out; I have seen it in a clay pit eight inches deep propel itself through, having sunk through the upper surface of gravel in a yard.

When you attach the second wheel, is the increased power owing to the more favourable situation of the cranks?—The power of the Engine remains the same, but the application of it is doubled by friction.

Suppose that both wheels were in the rut?—I have seen both wheels in a rut; in the case I have just spoken of they were both in the rut; in a different state of weather, the effect, hold or bite on the wheels is very different; if the state of the road is between half wet and half dry, it is more apt to slide; and in some instances with a heavy weight attached, we are obliged to go with both wheels locked, when the same weight would have been taken by one wheel only in very wet or dry weather.

Is it only in starting that that difficulty occurs?—Only in starting on a level or slight incline; but up hills we have sometimes been obliged to attach both wheels, the bite only from the one wheel being not sufficient to propel a load behind it.

What is the operation of the propelling wheel when it meets with the obstruction of a large stone on the road?—If the difficulty is so great that the Carriage cannot advance, it slips on the stone; but I have blocked up the wheels of the Carriage with square pieces of wood four inches diameter, and started it when so blocked up.