Nice job! I have a similar timing bag but I got bored and experimented around with various universal and pivot joints that I had lying about to try to mimic the synovial joints of the body. More specifically, I experimented with a parallel angled offset to the cobra neck (the parallel offset is achieved with two pvc angle joints connected by a short length of pvc pipe a universal joint can be attached to this. The net effect is to create a timing bag that mimics the erratic head, arm and kick movements of an opponent. This rotating offset can be placed above or below the spring to produce different effects. It can be flipped upside down. All are useful for training. In my case, I have it set up so that I can swap out straight and offset sections to get different motion from the same basic cobra. You seem like a curious and capable guy. I’m sure that if you gave this idea a try, you could perfect it into something really useful.

Buenas mi profe soy un amante del boxeo, y me gustaría adquirir ese producto para mi gimnacion de boxeo en Venezuela , estado Sucre, en Carúpano

awesome video very informative

How can you make the spring higher?