Mounting HB in a horizontal beam? Need advice

[aoktav]

Hi, I just got my RPTC hangboard and so excited to install it in my garage. The garage has horizontal wooden beams. Some beams have 3 inches thickness and other beams have 1.5 inch thickness. The height from the top part of the beam to the ground is 8 feet. I want the hangboard to be adjustable so other people can use it. Anyway, I have no experience in installing a hangboard nor knowledges in basic wood construction. I think this is the best place to ask. What's your thought? What materials I need to get? Excited to go to Home Depot soon! Thanks!


The beams I plan to mount the hangboard
 

Overall structure