To the group: Having monitored some of the discussion on this thread, I thought that I would weigh in with some of my experience with this test. The purpose of the test is to subject the E.U.T. to a specific force of impact from a hard steel impactor (ball) of known radius. The surface should be smooth to avoid subjecting the E.U.T. to additional point stress (the "center punch" effect). Anything else is frosting on the cake. It does not matter whether the ball is dropped or swung, as long as the force is consistent and the E.U.T. is firmly mounted.
A ball bearing is perfect for the job. A typical chrome steel ball is more than hard enough to meet the specification. If the weight is a little off just raise or lower the drop height to compensate. An eyebolt is nice but not really needed. The reason the "official" balls cost so much is the difficulty of machining the ball for the bolt, and the fact that these are very low volume items. A trailer hitch ball will also work without modification. Just weigh it, calculate the drop height, hold it by the threaded bit and "bombs away". A tube is nice but not needed if you can drop the weight accurately. The idea of standing on a chair is excellent as a 1kg ball can make a serious bruise! I would also recommend padding the floor (except under the E.U.T.) with cardboard or carpeting scraps so the ball won't get all scratched up. If you really must have an eyebolt and don't want to spend the money thread a flanged nut onto an eyebolt and epoxy it onto the ball with a steel-filled epoxy (common at auto parts stores). It may break off occasionally but you can just re-epoxy it. Just degrease all the parts before gluing and it works surprisingly well. Have Fun Scott Lacey
