Our experience with locust is that is is unstable as timber. It tends to be very "shakey" and will often split quite severely and delaminate during drying. In small diameters it's good for fence or deck posts, and it makes great pegs, although finding straight grained stock can be next to impossible. We have also used it with success for naturally shaped braces and struts in outdoor work like rails and gates.
I tend to stick with species I find in old timber frames and black locust isn't one of them.
Good luck with your project!
Rudy
