I have a friend let’s call him A who is an aircraft enginner working in a company partly owned by the Rolls Royce. His job is to repair jet engines. I haven’t told him anything about bias wheel except that roulette wheel can be beaten. It was amazing that he can tell me the defect which i have mapped out! He also can tell me that the way dealer throw throw the ball can have an impact on the dominant angle of the ball hitting the rotor and that strike to final test can tell which pocket has bias, whether the whole section of the wheel is bias due to wheel head wobble! He was also shocked that how roulette wheels are made so badly comparing to aircraft engine parts!
He then told me that even we can spot defect, it is impossible to just know the bias or 100% confirm the bias otherwise aicraft engines repairing company would not need machines to perform test on parts which has defects! Using visual and sound method to determine bias is just not enough!
Using his knowledge in aircraft engine and quality check for parts, he concluded that every wheel is different, and need to perform statistical test to find out what bias to play for even the same batch of wheel can have different signatures.