Practical Carriage Building
Compiled by M.T. Richardson, Vol.1. 1891
Repairing wheels with Criticisms and Suggestions
The one troublesome part of the carriage is the wheel. It is difficult to make, and when made is subjected to innumerable conditions which impair its durability, and when broken it must be repaired by putting new wood to old in a manner that will insure solidity, and at the same time not weaken the old part by unduly strengthening the portion where the break occurred.
The prevailing idea is that the great point in building a wheel is to insure strength at the hub, as it is popularly supposed that the most breaks occur at that point. This is a mistake. Close observation, extending over a period of several years, resulted in establishing the fact that the breakage of wheels at the hubs and at the rims was as five at the hubs to seven at the rims. The breakage at the hub was due in most cases to the hub being damaged by grease, or rather the hold of the spokes in the hub was loosened by the grease. The breakage at the rim, on the other hand, was due almost entirely to the rotting of the tenon at the rim.
The difficulty of repairing, so as to make a good job, is much more marked at the hub than at the rim, because of the grease, which prevents the spoke tenon getting a grip. The first step to be taken therefore by the repairer is to remove as much of the grease from the mortise as possible if a new spoke is to be inserted, and from the mortise and tenon if the old spoke is to be put in. This can be done by strong acids, such as vinegar or beer. These will eat the grease without doing any harm to the fiber of the wood. Alkalies will cut the grease to a saponaceous substance equally injurious as the grease. After as much of the grease has been absorbed as possible, the timber should be allowed to dry before the spoke is driven into the hub. If the old spoke is to be returned, the chances are that the mortise and tenon will both be bruised a little. In that case glue a strip on the back edge of the tenon, leaving enough of the new wood to fill the mortise, but not to the same extent as if the hub and spoke were new.
It seldom happens that the sides are bruised to an extent that will render it necessary to enlarge the tenon on the sides. But when this is the case, it is best to use a new spoke even if the old one is good. But in using the new spoke it must not be larger than the old, even if the tenon has to be enlarged both ways. One way of fitting the old tenon into the old hub is to surround it with wet canvas and then drive the spoke as tightly as possible. This is a botch job, one that no man claiming to be a mechanic should allow. It fills the mortise, it is true, but it also helps to batter the tenon and the edges of the mortise, and as it is a substance that can be compressed, it works away quickly, and the second condition is worse than the first.
Old spokes have been wedged in by removing the axle box and inserting an iron that fills the hole in the hub. The tenon is then split midway between the face and back, and a thin, slender wedge is inserted. The spoke and mortise are then thoroughly coated with white lead, as thick as it will work. As the spoke is driven in, the wedge comes in contact with the iron case, and as the spoke is driven home, it is forced up, and the lower end of the tenon is expanded. This insures a firm hold, but I doubt if the advantage is not more than counterbalanced by the disadvantage arising from removing the box. I prefer working entirely from the top, and where the space must be filled to make the spoke hold, to fill it with wood, and when driving the spoke, to use as much pure white lead as I can got into the opening without interfering with the driving. The white lead will soon harden, and it will hold all parts better than any other material. It will also resist water longer. Where new spokes are required because of the breaking of the spoke at the felloe or elsewhere, without injury to the hub mortise, care must be taken to clean out the mortise, but not to enlarge it. Fit the spoke snugly and drive in glue the same as with a now wheel.
"It is good enough for repairing," is a common expression when condemning spokes for now wheels. To a certain ox-tent this may be correct, but not to the extent it is too often carried. A straight grained spoke of second or third quality as to timber, will often be the article wanted for repairing an old wheel. But if the wheel is comparatively new, the spoke used for repairs should be as near in quality as possible to the one removed. If the wheel is weakened throughout by wear, a second or third grade spoke should be used, as a first grade will be so much firmer and more rigid than the old spokes as to contribute to their destruction by not yielding in common with the others.
Spokes that have become crooked from any cause are unfit for use, no matter how prime their quality. They can be straightened so as to appear all right, but they will go back to the original bend in a short time, and except for the filling of a gap, they might as well be out of the wheel. The springing of a spoke, unless by pressure, is due to the contraction of the grain on the concave side. If straightened, this grain is simply relaxed and weakened, while the grain on the convex side is as rigid as ever, and it will in a short time assume its former bend.
It is sometimes necessary to replace a broken spoke without removing the tireóa bad practice, but one that is excusable under certain circumstances. To do this, mortise out the broken tenon in the hub to the depth of half an inch, and about the same in the felloe tenon. In both cases the tenons on the spoke should bear upon the old tenon, otherwise the shoulders will crush in and the spoke will loosen. Fit the spoke carefully between the shoulders, and insert the felloe tenon. Protect the hub by a piece of thin band iron. Set the wheel upright and secure it in position with the face to the wall, or, what is better, in a position where one work-man can work on each side of the wheel. Construct a lever with an opening in the end to admit the spoke, and round the top a little, so that the lever will not bruise the felloe. Nick the underside of the lever, and make the fulcrum with a top end slightly wedge-shape, and the bottom end hollowed out, to bear upon the hub at the front band.
For carriage wheels the purchase need not be severe, but for heavy wheels a long lever is necessary. In all cases set the fulcrum nearly upright. When the weight is applied to the lever, the tire should be struck with a heavy hammer on each side, covering a space of two or three feet. This will assist in equalizing the strain, and will enable the workman to get one-half to three-quarters of an inch spring over the spoke. This amount of spring will admit the spoke, which the workman should enter from the back without bruising the hub. As soon as the spoke is in its place, release the lever, and set down the rim by quick, sharp but light blows upon the tire, over the entire half of the wheel where the new spoke was inserted. I do not favor this springing in of spokes, but it is much better to do this as a temporary expedient when the tire is firm and where the facilities for setting a tire properly are lacking, than to cut the tire and have it reset badly.óBy W. N. F.