I like to make tapered spoke flywheels for my engines because I think they look rather elegant. Since most of my engine models are small, I machine the flywheels from solid stock rather than fabricating them from separate pieces.
Starting with a cylindrical blank on the lathe, I machine a reduced thickness web that separates the central hub from the rim. Then I mount this blank on the rotary table and define the corners of the cutouts with holes drilled through the web. After these holes are drilled, I use a milling cutter to machine away the material defined by the holes in the web - what remains are the tapered spokes.
The included .jpg image [copied into picture below] should make clear how this process works and what the associated calculations are.
The calculations are tricky and error-prone - especially those for offsetting the rotary table to cut along the spoke edge. I wrote a program to do all the calculations and produce an output file to print and take to the shop. Note that the important angle, phi, is found by solving a transcendental equation by iteration - something to try one's patience if done by hand but a piece of cake for a computer.
For an arbitrary choice of spoke dimensions, the angles for drilling the outer holes in the web can get to be messy as the first part of the solution obtained with the defaults will show. Since the exact spoke dimensions are seldom critical, the program also generates a solution in which the angles for the outer holes are integer values and adjusts the other dimensions to suit this choice. Just ignore this solution and live with the messy angles if you're finicky about the spoke proportions.
The spoke tapering can be defined in two ways. Either the offset of the outer hole from the spoke centerline (d2 in the diagram) or the angle of the outer hole relative to the spoke centerline (Θ2 in the diagram) can be specified. The program allows you to use either method.
Although the diagram shows the inner and outer holes as different diameters, this is not required. The defaults are set up for the case where the inner and outer holes are the same diameter and the tapering is accomplished by angling the outer holes seven degrees away from the spoke centerline.
As with most of my programs, no attempt is made to check for unreasonable inputs. Your construction sketch should be examined for problems such as overlapping holes, etc. If you find real errors in the program, contact me at mklotz@alum.mit.edu.