Decision time! Since we're making our own "custom" wheels, why not design the rim to fit our hands perfectly? Also, do we want a larger overall diameter (or smaller)? With all those things in mind we got out our compass and a stiff piece of paper (manila folders work well). We also selected the base wood we'd use to make the wheels, in this case cherry. Why cherry? Well, it's a very stable wood in varying temperatures, it's easy to shape and sand, has a nice grain pattern and takes a stain evenly. These are all very important attributes.
We laid the bare wheel assembly onto the large piece of craft paper, then traced the wheel's spokes and both the outer and inner circumferences of the metal rim on the paper (this creates the actual location of the channel where the steel will rest in the wood). We then carefully marked the center point of the traced wheel circle. Using it as the pivot point for our compass, we drew one circle 3/8ths inch smaller than the two traced circles and another 3/8ths larger. These two circles then formed the rough dimensions of our wood wheel. We then drew some "transitions" from the inner circle to the spokes, as shown in the finished photos (the transitions are the shaped wood fixtures that form the connection between the wood rim and the wheel's spokes. This is an area where you can be creative by designing your own curvature and thickness).
Theory (sort of): All wood wheels are a sandwich of two layers, whether or not a fancy mid-layer of different wood is used. The top of the wheel will be 2/3's of the total and the bottom 1/3rd. Have your wood boards planed to the proper thicknesses and glue them edge-to-edge to slightly exceed the finished size of the wheel, as follows...
We bought a piece of cherry 6 inches wide, 3/4 inch thick and 6 feet long, then cut it into several lengths of 20-24 inches. We also bought some additional cherry and planed it to 3/8ths thickness for later. We glued (wood glue) and clamped enough of the original pieces, edge-to-edge, to form a wide board large enough to trace the drawn wheel onto. When the glue had set up overnight we cut out the paper wheel, complete with spokes, and lightly glued it onto the wood block. We did this to make cutting out the rough wood wheel easier than following pencil lines, thus avoiding mistakes. We cut the outer wheel diameter with a jig (or band) saw (slowly and carefully) and then stopped to admire our work.
Top (outer) wood circle is cut. Looking carefully, you can see layout lines for center channel and inner ring.
Then we laid out the "transitions" to the spokes. We positioned our wood wheel circle on the bench and laid the old wheel on it. On most wheels, the transitions curve from the wood rim to the spokes in the same plane, as in the Jaguar wheel. In the case of the Falcon, those transitions curve downward to the dished spokes, so we created the proper shapes on to our wood piece. No rules here, just something that looks pleasing.
On the left, the cut-out Falcon outer wood rim, with transitions, and the Jaguar's wood blank, with routed-out channel that will house steel rim.
Speaking of the routed-out channel, it's time to perform that rather nasty chore. Here's a neat tip: we found a large piece of the discarded wood circles trimmings. Then, we measured the distance from the outer diameter of our wood circle to the center of the two inside "core" tracings and clamped the scrap piece to the router tabel to act as a jig — a curved fence, really — to correctly guide the wood circle. Putting a 1/2 inch wide mortising bit (or other suitable one) into the router, we set its cutting depth to about 1/8 inch. We then held the rough wood rim against our guide and routed out a full 360 degree slot, checking to make sure it was centered in our rim. We then kept increasing the depth, in small increments, until we created a 1/2 inch deep channel (the channel is deeper and wider than the steel rim it will encase so that bonding glue can fill the voids).
That done, we routed out channels in our transitions. Why? The spokes occupy space in the wood. You must cut out a channel in the transitions for the spokes and this can be done with your router or a chisel. This is a free-hand operation, so take your time. Just mark in pencil where the channels have to go, set the tool in a comfortable position and cut away. Keep your patience and watch what you're doing.