SPOKES AND FELLOES

By Cedric Lewis

(Editors note: Cedric Lewis is one of our most accomplished members who is also a volunteer wheelwright who practices at the Worcester County Museum in Hartlebury refurbishing wheels and vehicles)

One of the questions most frequently asked is: “how many spokes should there be in a wheel?” and, oddly enough, this is not as vague a question as it may at first seem. The answer is really self-governing, not by the number of spokes, in fact, but by the number of felloes.

The weakest part of any felloe is at the outer ends where it comes face to face with its neighbouring felloes. This is because, having been cut from a straight-grained board, due to the curvature of the felloe the grain begins to run at an angle rather along the length as it will be at the centre.

Obviously, if the number of felloes remains constant, then the bigger the wheel, the longer the felloes will become and the effect of the ‘short grain’ will become increasingly worse, seriously weakening the wheel structure.

The answer to this problem is to shorten the felloe length so that it does not wrap around so far and across the grain. This is achieved by increasing the number of felloes and, therefore, the number of spokes, to maintain the normal rule of two spokes to a felloe.

So there would appear to be a rough ‘rule of thumb’ which seems to apply to most wheels up to around four feet in diameter and that is a felloe for every six inches of wheel diameter.

Thus a thirty inch diameter wheel would have 5 felloes (10 spokes); a thirty-six inch diameter – 6 felloes (12 spokes) and so on. There is obviously some overlap on these parameters but as a general rule that seems to be the way it works.

For example, a heavy-duty wheel may have more spokes than a lighter duty wheel of the same diameter to enable it to carry a greater load. Alternatively it may be more heavily constructed and so there will be deviations from the general rule.

The ‘short grain’ problem does not arise on wheels with steam-bent felloes, usually two-piece as in, for example Governess Cart wheels. Being bent, the grain will naturally follow whatever curve is induced into the felloe. However, the number of spokes would still seem to relate to the size of the wheel as guided by the general above rule.

Whilst on the subject of spokes, those who build wheels, model or otherwise, have learnt to appreciate the “two spokes to a felloe” custom and the fact that, because the spokes have to be sprung into the felloe due to the angle between them, the overall effect is to hold the whole wheel together, even before the tyre is shrunk on.

Another aspect relates to the shaping of spokes. A suggestion was once made that the almost aerofoil section “was to make the wheel go faster!” However, although the section is aesthetically pleasing, the truth is weight reduction with very little loss of strength, a round or ovaloid section being almost as strong as the rectangular section. This also applies to the chamfering on wagon bodies which became an art form but could reduce overall weight by 5%.

Occasionally the exception to the rule appears as, for example, on one of the bow-topped caravans at Hartlebury. This has small wheels, less than thirty-inch diameter, which have 14 or 16 spokes in them with three spokes in some felloes and two in others. This was almost certainly done to reduce the number of felloes which with two spokes/felloe all round would have been ridiculously short, creating lots of joints. Three into 14 or 16 does not go, so for example, on the 14 spoke wheel there are 4 - 3 spoke felloes and 1 - 2 spoke felloe.

Why, you may ask, have so many spokes on this vehicle in the first place? Good question but the wheels were probably made up from old (or stolen) carriage or gig wheels. They certainly have Warner hubs and were probably cut down from a much bigger size which had possibly rotted at the felloe ends whilst the hubs had remained sound along with the lower ends of the spokes.