Stanislav Hadri

I have trouble making circle with arrays

Hello, I am currently trying to solve the wheel exercise in modeling with modifiers but when I try to make it into circular shape like rotate the array I cannot find the right angle or shape, I can either connect the outer part of the wheel or the inner part. I dont know what is the proper angle to use or how many array count should I use. The picture is the closest I got 

Since I want to solve the exercise myself first some tips would be nice. 

Thanks and have a nice day