That looks like a worthwhile project to do with your son
I hope this gives you some ideas!
I used a centerpoint arc slot.. I've never actually used one before, but it's pretty straight forward.
I didn't know how to dimension it, but thought maybe you could take the measurement across the width as shown by the tangent construction lines.
You can just delete any dimensions you don't like and recreate them.
I took the assumption that the radial lines DO point directly to the central axis.
Again you will have to mess about with it to get it right.
A couple of extra things I did you might like to look into are
adding a sketch picture
using a revolve
Any questions, do not hesitate to ask.
Part1.SLDPRT.zip 899.5 KB
@Rob - Thank you very much! I was able to modify the part and get the arc to match as close I could to the original part. I had to make about 6 iterations of it (half a mm makes a difference on this thing), but finally the new printed part works great! Only bad thing is it's made from plastic and not metal, but at least I know I can keep working on improvements if needed.. Thank you again for your time and assistance!