My question is what is the average ball speed for a strike. I have been taught 13 - 15 is good, I have seen PBA bowlers ball 18+. My ball is 13lbs, I am completely double jointed that turns my shoulder, my elbow, my hand and my fingers opposite of a right handed bowler. I have been trained to bowl right handed but I have more consistency bowling back up with an average of 150 back up to 102 right handed. I am not giving up on bowling right handed. I continue to practice that. My ball is the Aura by Brunswick and the Natural by Storm.
Note: I have been bowling fall league for four years.
There is no average ball speed for a strike. You can strike rolling a ball slowly or throwing hard (as many Pros average more than 18 mph.) The speed used tied to a players rev rate and tilt and rotation help make them successful. Striking is about angle of entry and continuation. If for a right hander, you can hit the 1 and 3 pins, push past and hit the 5, then roll through and split the 8 and 9, you've rolled a perfect strike.
As you only hit 4 pins (usually), and they hit the other 6, a strike is about how you hit pins not how hard. Thank for the question.
Not sure why you mentioned the double jointed stuff. If you do well enough to be satisfied, continue. But I would mention, no where in the history of this sport has there been any back-up bowlers that have been successful at a high level, consistently achieving high scores. There is enough physical manipulation going on that the technique is inherently flawed and difficult to sustain. The limitations to rolling the ball as a backup and being consistent are many.