The U.S. Armys hummer vehicle was not meant to be a combat vehicle, or a power generator, but that's what it is turning into during the continued Iraq operations. Of the 10,000 hummers in Iraq, over 40 percent of them will be armored. Moreover, it has become more common for troops to run numerous electronic devices off the hummers power supply. As a result, a growing number of the vehicles are breaking down. The engines are being worn out prematurely, and the extra weight of armor, and additional weapons, is doing more damage to suspensions and tires. Nearly ten percent of the hummers in Iraq are out of action waiting for repairs. Getting sufficient spare parts to Iraq is also a problem. Moreover, the hummer was not designed to be quickly repaired, especially for things like engine replacement. It takes 62 man hours to replace the engine. The M-1 tank, which was designed for ease of repair, can have its engine replace much more quickly. As a result of this experience, the first time hummers have been used in a sustained combat operation, design changes for the vehicle are being made for the future models.