This picture shows, from left to right, how to shape the wooden spokes. The exact dimensions and cross-sections can be modified to suit your own tastes. I found it easier to make the spokes in pairs like this because the flat pads at either end helped to keep the piece steady for machining.
Pine wood worked fine for me, but I would recommend something harder. Starting with a flat rectangular piece of wood, cut the initial spoke contour. Be sure to leave the flat ends large enough to provide a good surface for mounting the hub flange. The spokes can then be shaped by hand, but it goes much quicker if you use a router with a curved bit. For eight spokes per wheel, the arrowhead angle at the ends is cut at 22-1/2 degrees. The final product will look better if the angle is cut accurately. But, it's not the end of the world if you're off by a bit because the joint will eventually be covered by the hub flange. To provide clearance for the axle, cut the pointed tips off the arrowheads. Finally, cut the piece in half and you have two spokes. If you are supremely confident you can immediately cut the spokes to the correct length. But if you're like me, you should leave lots of extra length in each spoke until you are ready to commit yourself later. I would also strongly recommend that you take the time to cut several spare spokes now as insurance against future accidents.
This picture shows how to assemble the spokes to the hub. There are several potential problem areas here. The metal hub flanges only come with 4 predrilled holes set at 90-degrees to each other (at least mine did). Unless you have a well equipped machine shop, you're probably going to drill the extra 4 holes at the 45-degree positions using a hand-held drill (like I did). It is fairly critical that all the holes line up with each other. So before you start drilling holes which you will later regret (like I did), it is a really good idea to mark each spoke and hub flange with a unique number so you will always be able to fit everything back together in the same configuration.
Before drilling any holes, fit the spokes together and temporarily clamp the hub flanges in place. When you've got everything lined up to your satisfaction, drill through the four wooden spokes at the positions for which there are already holes in the metal hub flanges. Then you can securely bolt at least those four spokes through the metal flanges.
Now you can decide whether you really want to drill the other four holes. In theory, the spokes at the 45-degree position shouldn't need to be bolted into place. They will be held clamped between the two hub flanges. And once the whole assembly is mounted inside the wheel rim, the loose spokes shouldn't be able to fall out. But for added strength and appearance, you will want to drill and bolt these spokes too. With the spokes all assembled into place, it should be relatively easy to drill straight through the one metal flange, through the wood spoke, and out through the opposite flange all in one straight line.
This picture shows how the wheel rim is attached to the spoke assembly. Hopefully, as recommended, you will have cut the spokes slightly longer than required to fit snugly within the rim. You can temporarily mount the hub on the axle shaft and spin the hub assembly. Holding a pencil at the required radius from the hub, mark each spoke at the correct length. If done properly, this will ensure that, not only will each spoke be the right length, but the hub will actually end up near the centre of the wheel rim. After marking the spokes, checking, checking again, and re-checking, cut the spokes to the correct lengths. You will discover (like I did) that regardless of how often you checked before cutting, at least one spoke will end up too short. Of course that will not be quite as big a disaster as it could have been because you (unlike me) will have made several spare spokes in anticipation of just such an eventuality. Drill pilot holes through the rim into the end of each spoke and fasten with screws. If you don't drill pilot holes first, you risk splitting the spokes when you drive in the screws!
This picture shows how the hub of one wheel is fastened to the drive axle. Once the hub is finished (with brass insert, etc.) as per the plans, position the finished wheel on the drive axle. Mark its location on the shaft. For the next step, it's much easier to keep everything straight if you have a drill press. You may, or may not, want to disassemble the hub again. It's up to you. Of course you must have the hub positioned on the shaft as you drill through the hub and axle shaft simultaneously to ensure that the holes lines up properly. Try to get as tight a fit as you can between the small bolt and the hole through the axle shaft to limit any play between the two.
The rims, tires, and inner tubes were purchased from a local bicycle shop. For our application we used 16" rims and tires. The rim diameter, when checked with a tape measure is actually only 12", but the tires are labelled as 16".
The wheel hubs and other running gear were all exactly according to the plans from Stevenson Projects. The wheel hubs are simple floor flanges, available from any plumbing supply shop. They have a brass reduction fitting screwed into their centre, and drilled out to accept a 1/2" axle shaft. With a bit of grease in there, they last forever. Or you can simply screw in another reduction fitting if that one ever wears out.
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