Practical Carriage Building
Compiled by M.T. Richardson, Vol.1. 1891
Carriage and Wagon Wheel Making in Country Shops Part 6
Now to proceed with the job of putting the tire on the wheel. To do this accurately, measure with the measuring wheel around the felloes before you bore the dowel pin holes. If the felloes are all of the same thickness and true to the circle, and all joints are tight except one, the wheel should measure one hundred and eighty-nine inches, inclusive of the open joint. In using a measuring wheel the periphery of which is exactly twenty-five inches, it will travel around its own center seven times and fourteen inches more. Of course wheels and tires can be measured with a wheel on which the inches are not marked, by making pencil or chalk marks where needed; but for calculating the diameter of a wheel, and, having found this, getting the proper length for spokes between the hub and felloes, a measuring wheel di¬vided into inches, halves and quarters, is far preferable to any other, because every measure can then be taken on geo¬metrical principles. Measures taken from old spokes and felloes lead often to mistakes, and in some cases only the hub and tire are at hand. If the wheel measures more than one hundred and eighty-nine inches, say an inch and a half, divide the surplus by six, and with the hollow auger take off from each spoke a quarter of an inch, leaving a hairbreadth on the mark. This reduces the height of the wheel, and con¬sequently the periphery. Then fit the felloes at the joints. But by being careful to take the exact measure of the tire, calculating from this, measuring the diameter of the wheel, and there from the proper length for the spokes, every wheel can be made to fit a tire perfectly.
To get the diameter of a wheel from a given tire, to the measure of a wheel around the felloes (or periphery) a half or three-quarters of an inch should always be added for 'draw.' From this sum calculate the diameter of the wheel, deducting the size of the hub and double the depth of the felloes, in order to get the length for spokes between the hub and felloes. To this sum add the full depth of the mortise in the hub, less a quarter of an inch, and the depth of the felloe, plus a quarter of an inch.
Example 1: A wheel is forty-four inches in diameter. To find the measure of the tire, forty-four multiplied by twenty-two equals nine hundred and sixty-eight; divided by seven equals one hundred and thirty-eight and two-sevenths. Take off one-quarter or three-eighths—for small carriage wheels require less dish—and take one hundred and thirty-eight inches for the measure of the tire. If the tire is made smaller it will draw more on the wheel, and spokes will be¬come crooked.
Example 2: To find the diameter of a wheel from a given tire. Tires are often not a true circle, and will give different measures, if measured across the center for the diameter. Therefore it is always better to find the exact diameter by measuring the periphery and calculating from this. Suppose a tire measures one hundred and fifty-seven and one-eighth inches. Add a quarter of an inch for draw, and say one hundred and fifty-seven and three-eighths. This, divided by twenty-two and multiplied by seven, gives fifty and an eighth inches as the diameter of the wheel. From this sum deduct the size of the hub and double the size of the rim, and we have got the length for the spokes between the hub and rim. For example, fifty and an eighth, less five, add two, equals forty-three and one-eighth; divided by two, equals twenty-two and nine-sixteenths. Now add one-sixteenth for pressure exerted by driving, we have twenty-two and five-eighths inches.
To find the proper distance of spokes from each other in the rim of a wheel of forty-four and fifty inches diameter: Take off double the size of the rim, multiply the remainder by twenty-two and divide the result by seven; then divide the sum by fourteen or sixteen, according to the number of spokes in the hubs. Example : Forty two multiplied by three and one-seventh equals one hundred and thirty-two; divided by fourteen equals nine and three-sevenths, or nine and three-eighths inches; or forty-eight multiplied by three and one-seventh equals one hundred and fifty-one; divided by sixteen equals nine and seven-sixteenths, or nine and three-eighths inches.
In conclusion let me say that these remarks of mine are not put forward as a perfect treatise on wheelmaking, and in some respects my views may be" open to criticism. At the same time my critics must remember my object has been simply to describe the methods of work best adapted to the average country shop. I have not attempted to lay down rules for large establishments in which machinery of every kind is at the service of the operator.