How to make this locomotive driver?

I'm thinking of a way to make radial triangular cuts…

ok, mount a round piece of plywood inside a u-shaped
cradle so it can turn from the middle. Your router will
have a square base installed and run in a rabbet on each
top end of the "U". Make a second round piece and cut
notches into the edge you can use to index a moving
stop mounted to the bottom of the cradle. Screw the
template to the part that turns. Tape your workpiece
to the notched template. Screw stops to the top of
the cradle to limit the router travel. The set your
stop in the first notch, plunge and cut. Turn to the
next notch and repeat. This will get a lot of the
material out and the "spoke" lines will be pretty straight.

It also avoids a fragile template with a lot of cutouts.

what is the diameter of the cutter you expect to use? looks like about 3/16. pretty small for cutting through 11/16 in one shot. make a template that the base of your router will fit into and properly cut the open section of the wheel. this will be fastened to a base with a 11/16 spacer between. use a hole saw or whatever you have to drill a nesting hole in the spacer. the spacer will stabilize the router since the opening in the jig will likely expose the whole completed wheel. precut the outside of the wheels. mark the divisions on the outside of the wheel. mount the wheel at the center with a screw to the base of the jig. appropriately locate the top (template) of the jig and fasten thru the spacer into the base. mark the nesting hole at any one of the division marks. cut the hole. loosen the wheel fastening screw. index the wheel. refasten. cut and so on. if you need more grip use a couple screws from the back side of the base that just break the surface of the base where the rim will contact.

Here is a jig I came up with.The circular piece sits inside a square piece of plywood with a circular hole cut in the middle. The square piece has index marks set at 20° spacing. I can bolt the driver blank to the square piece and use the template to route the opening; then rotate the template to the next index mark and repeat. I will probably drill away as much of the wedge opening as possible before routing. What do you think? BTW, I have no problem working in thousands of an inch. The router bit is 1/4". The round template will be hard board or aluminum. I may use a flush trim bit in a router table.

Wont this work

my router has a 6" diameter base so I drew it for that base. the spokes are about .226 wide then. wow thin!

OK! This is the jig I finally came up with. I have to build another jig in order to make this jig. I also have to build another jig to route the flange and other features of the driver. It's a lot of work, but so much faster and accurate than cutting drivers by hand. I have 8 drivers to make and maybe more later. Thanks for all the help. Good thing I enjoy what I'm doing and I have the time. BTW, I will use double stick tape to secure the driver blank to the bottom of the jig and although the dimensions are in decimals, I will be only working to 1/64" (eyeball settings). I always work in decimals because fractions take up too much drawing room.