TG-8000 gyro: reduced cost and new features The TG-8000 gyro is known as one of the most inexpensive gyro compasses available. The main reason for this is that there is no need to change any fluids during overhauls. So, no additional costs for support fluid, mercury, insulating and gasket sets. In contrast to the Sperry NAVIGAT 100/200 and Raytheon Standard 22, the Tokyo Keiki TG-8000/8500 doesn’t have a gyro sphere container so this doesn’t need to be replaced periodically. Additionally, it includes a feature that significantly reduces overhaul time as the gyro motor can be braked electronically. This makes a typical overhaul of the TG-8000/8500 no more than 5 hours and cuts down on the number of spare parts needed.