I've thought of another idea. Take a simple compass, the needle always points north no matter what the compass housing does. You can rotate it around all you want and the needle will still go back pointing north. You could say it locks in pointing to the north. The housing, on the other hand, that supports the needle is physically on the earth and it will rotate along with the earth and the needle will always stay locked in pointing north. I would think that, if the earth does rotate, the housing will rotate too and the needle will still point north.
In my opinion, this is a better test then the hanging hammer because there is no bearing to add friction, wind or air has no effect on it because it is in a sealed housing and the needle can not rotate with the earth because it always goes back pointing north.
I've done this with my compass. I set a reference point on the housing and lined the needle up to it. The compass has been setting on my desk for over 30 minutes and the needle is still pointing at the reference point. it has not moved at all.
Do you think this is a legitimate test and does it prove anything?