For making your own flywheel steel should do fine. You're probably not aiming for an 80,000+RPM flywheel that rides on magnetic bearings. So composites shouldn't be needed. The best material, eventually, for flywheels should be carbon nanotubes. They have huge tensional strength, but lousy compression strength. Tensile loads is what a flywheel has, so they'd work great.
It is important to note that not all batteries associated with these computer models are affected. The company is directing all users to its HP Battery Recall website to go through the online validation and replacement process.
Imagine my surprise when, on September 16th, a window I had never seen before opened up. It was an HP program that apparently was supposed to let me know important news regarding my system. To my delight, I saw that there was a recall on my graphics card because of known issues with the cooling fan. Imagine my greater surprised when I saw that all claims must be made by July 15th, 2010.