Trundles and Pin-Wheels.If a wheel or trundle have cylindrical pins or staves for teeth, the faces of the teeth of a wheel suitable for driving it are described by first tracing external epicycloids, by rolling the pitch-circle of the pin-wheel or trundle on the pitch-circle of the driving-wheel, with the centre of a stave for a tracing-point, and then drawing curves parallel to, and within the epicycloids, at a distance from them equal to the radius of a stave.
Common throughout the northern and middle states and Canada, the red oak attains a large size only on good soils; the wood is of little value, being coarse and porous, but it is largely used for cask-staves; the bark is a valuable tanning material.
The barrels employed in the transport of petroleum products are made of well-seasoned white-oak staves bound by six or eight iron hoops.
They are coated internally with glue, and painted in the well-known colours, blue staves and white heads.
These measures were largely successful, but in 1902 the export of oak staves was discontinued owing to a shortage of supply.