A practical treatise on coach-building historical and descriptive

by James W. Burgess

Before cutting the mortises the stock should be fixed at some convenient angle, regulated by the amount of dish it is intended to give the wheel. This is particularly necessary, or when the felloes come to be fitted, if the mortise-cutting has been done in a slovenly way, the dish will not exist at all, or if it does it will be in the wrong direction.

Each alternate spoke is now driven in by the blows of a mallet to a perfectly close bearing of the shoulder of the tenon, the workman guiding it as best he can. But it is evident that the position that the spokes will take is by no means certain. Owing to the wedge-like form given to the tenon, the spokes are driven home very tight, and wood not being of a homogeneous texture will yield more in one part than in another; and the mortise, cut in the way that it is, must be to some extent uncertain. Every alternate spoke being driven, or those in the same plane, the remainder are driven in between them in the same manner.

Fig. 14.

In [Fig. 13], b, b, b, are the mortises for the face spoke, and c, c, c, the mortises for the back spoke. [Fig. 14] shows a section of an ordinary spoke, the hatched part showing the form of the greater part of its length, and the plain lines completing the rectangle show the extent of the swelling at the shoulder of the tenon at the nave.

Fig. 15.

[Fig. 15] shows a very handy adjunct to the wheelwright’s shop; it is called the “centring square.” It is found extremely useful in marking and setting out the mortises for the spokes. Its construction is very simple, being but a T square, whose stock is the segment of a circle. A is the blade, B the circular stock, the extremities of which should be protected by steel or brass, or, better still, have a steel edge round the whole of the inner surface of the stock, so that it will always keep true; for if it wears at all, of course its true circular form will be destroyed, and it will be rendered useless. And another important thing should be borne in mind, and that is to make the upper edge, C, of the blade in a line with the centre of the curve from which the circular head is struck; the reason of this will be apparent to the most obtuse, for unless the lines radiate from the given centre it is useless for the wheelwright’s purpose.

After the spokes have been driven in they are shaved off by the spokeshave to their proper form, [Fig. 14]; and the lengths being measured from the nave, the outer tenons are cut, sometimes square, sometimes cylindrical, but leaving the back shoulder square to abut on the felloe with greater firmness. In the manner of tonguing there is a great deal of difference of opinion amongst wheelwrights; that the tongues in size should be slightly in excess of the hole or mortise to receive them, is a generally received idea, but a difference of opinion exists as to the length. But certainly it seems more reasonable to cut the tongues a little shorter than the length of the hole in the felloe to receive them, because when the tyre is put on it shrinks in cooling and draws up all the joints. Now suppose the tongues are a little longer than the holes, the shrinking of the tire causes it to press on these; and as they are firmly fixed at the nave, there is no escape for them, and the result is that the spoke is seriously crippled. It is fair to say that there are many good practical men who work in this latter way, and with to all appearance good results, but it is evident that the principle is not a good one.

One of the difficulties in making light carriage wheels is to get the spoke tightly into the felloe without splitting it, and the manner of accomplishing this is more successfully done, not by making the tongue on the spoke so large that it will fill the hole in the felloe of itself, but by making the tongue rather smaller and slitting the edges after it has been driven in, and then wedging up with small wedges, just in the same manner that a joiner would wedge up the mortises and tenons of a door.