For shaft linings steel rings of H or channel section supported by intermediate struts are also used, and cross-bearers or buntons of steel joists and rail guides are now generally substituted for wood.
When the coal has been under-cut for a sufficient length, the struts are withdrawn, and the overhanging mass is allowed to fall during the time that the workmen are out of the pit, or it may be brought down by driving wedges, or if it be of a compact character a blast in a borehole near the roof may be required.
The fan has eight arms, framed together of wrought iron bars, with diagonal struts, so as to obtain rigidity with comparative lightness, carrying flat close-boarded blades at their extremities.
The Howe truss had timber chords and a lattice of timber struts, with vertical iron ties.
In the Pratt truss the struts were vertical and the ties inclined.
Warren type in which the bracing bars form equilateral triangles, the Whipple Murphy in which the struts are vertical and the ties inclined, and the lattice in which both struts and ties are inclined at equal angles, usually 45° with the horizontal.
The top flange consisted of cast iron hollow castings butted end to end, and the struts were of cast iron.
In compression boom, 7 o tons in tension boom, 5 o tons in vertical struts, 6.5 tons in diagonal ties, 8 o tons in wind bracing, and 6.5 tons in cross and rail girders.
- A frame is a rigid structure composed of straight struts and ties.
The struts and ties are called bracing bars.
The compression members are of timber, except the struts and bottom chord panels next the river piers, which are of steel.
The moulds for the face of a wall consist generally of wooden shutters, leaning against upright timbers which are secured by horizontal or raking struts to firm ground, or to anything that will bear the weight.
Struts starting from main c, c', Wing propellers driven by spar.