Practical Carriage Building
Compiled by M.T. Richardson, Vol.1. 1891
Carriage and Wagon Wheel Making in Country Shops Part 5
Having now finished the practical part of my remarks, I will devote a few words to the theory of wheel making. Wheels are a certain number of levers, all inserted in a common center, the ground being the fulcrum and the axle the power to move the lever, as boys use a stick for jumping. The rim of the wheel is for holding the spokes or levers in the hub or common center and at an equal distance apart. Now, look at a boy jumping on a stick. If he inserts the stick in the ground in a slanting direction and jumps, the stick will throw him sideways; but if it is put on the ground in a plumb line, when he jumps he will be thrown a greater distance and in a straight lino. It therefore follows that a wheel should stand on a plumb spoke, on the face or front, because if taken plumb from the back, the spokes would be standing in a little slant, on account of the taper in them. The axle pulls or pushes in the wheel from one direction— from behind—and therefore spokes should be braced against this strain of pull or push. In a wheelbarrow wheel the spokes taper from both sides, because the strain comes from both; but in a wagon wheel the strain comes from one side only. The spokes are therefore tapered on one side and braced against this taper by dishing the wheel on the front.
In carriage wheels this bracing is affected partially by stepping out every other spoke; and such wheels require less dish. In order that the wheels shall be thrown forward by every spoke with the same leverage and for the same distance, the spokes should be all of the same length and same distance apart in the hub and rim.
To make a dished wheel stand on plumb spoke, the arms of the axles are made tapering, and the under side at the taper is thrown a little on a point below the level. This is done by setting the axles to provide for the taper in the box. By this means every spoke touching ground will be plumb, and the other spokes will slant by degrees to the rim. The proper amount of set in axles and dish in wheels depends on the taper and length of the axle arm and spokes.
A few rules for measuring wheels will not be amiss here, as I have often found workmen who were not acquainted with them. A circle is, around the periphery, related to its diameter as twenty-two to seven. This assumption will at any rate suit all practical purposes. Therefore, if we know the diam¬eter of a circle we can find its periphery or circumference by multiplying the former by twenty-two and dividing the result by seven, or multiplying the diameter by three and one-seventh; or we can find the diameter by dividing the periphery by twenty-two and multiplying the product by seven, or by dividing the periphery by three and one-seventh.
I have already alluded to the matter of boring dowel holes, and, to make this point still clearer, would call attention to Fig. 134, showing a felloe with a cross marked on the proper spot for boring the dowel hole. It is, I suppose, unnecessary for me to explain even to the youngest apprentice that the hole is made where it is shown in the engraving, in order to best meet the peculiar strain to which the rim is subject.
Fig. 135 of the engravings represents the Little Giant Hub Borer, a machine so well known to the trade that I need not expend further words upon it.