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.
Although performing a system recovery will erase your primary disk, you'll have the option to back up your files during the recovery process and quickly place the computer back into service. 1  1. Turn off the HP computer and disconnect non-essential cables and devices such as printers, fax machines and flash drives.