213 output distance required of the on-track axis. The profile  was conservative, and yielded a series of test  events to be repeated in cycles, each with a 2.3 Nm ( 20 in -lb) continuous applied output load being driven  at a speed of eight  degrees per second, with dither frequencies requiring direction changes every 1.5, 6.5,  or 16 seconds. The test would run for three times longer than one mechanical life, with a total runtime of  almost 700 hours, equating to approximately 13.5 million equivalent Wave Generator input revolutions.  

Additionally, since the updated MAIA Du plex motors were specified to have a minimum stall torque of  184 mNm ( 26 in- oz), and the HD gear ratio is 244:1, a risk to be addressed was that the actuator could  easily exceed the 5.1 Nm ( 45 in- lb) momentary peak (ratchet) torque rating of the size 10 HDs. Although  test records could not be located, the memory remained of the earlier completion of static, sustained noratchet verification testing up to a 11.3 Nm ( 100 in- lb) output load,  completed for the MISR  program. Thus,  passing this test before, after , and throughout the three times life program  would also be a success criteria  for the Endurance Test campaign at large.  

The element of the MDDA most susceptible to wear due to fatigue is the HD output gearing.  One of the two  redundant drive output subass emblies served as the test article, shown in Figure 2. The HD was to be  grease plated using Braycote 601EF and the duplex bearings with Braycote 600EF, both using Brayco  815Z  oil, reflecting the heritage grease plating and packing method. The unit was mounted into a simple  dynamometer fixture, driven by a brushed test  motor, loaded with a brake, along with an input torque  transducer and output transducer measuring torque and speed. The simplicity of the setup was intended to  allow for continuous operation, to be monitored by a chart recorder, and checked on periodically by  engineering.  

Figure 2. Endurance Test Article, the MDDA Drive Output Subassembly  

The HDs, and a spare lot of the necessary 440C duplex output bearings, were pulled from flight storage  and taken to the cleanroom for cleaning and inspection. The Wave Generator subassemblies had been  delivered with their AISI 52100 bearings and 304 CRES spacers bonded onto the Wave Generators hubs,  and, per the original source control drawing, a black oxide coating had been applied to the ductile iron  circular splines and the AISI 1144 Stressproof Steel® Wave Generators per MIL- DTL-13924. Everything  was heavily coated with a layer of a lightweight water -displacing hydrocarbon oil. Similar to the HDs, the  Timken duplex bearings were still sealed in their original packaging, also covered in hydrocarbon oil.  

The HDs were partly disassembled, leaving the bonded Wave Generator subassemblies intact, and  ultrasonically cleaned using acetone, followed by Vertrel XF , and a final oven bake. They were inspected  under 15x magnification by engineering and quality and, after receiving passing inspection results, the units  were immediately grease plated using Braycote 601EF (10% by mass) and Vertrel (90% by mass), reinspected, and sealed in moisture barrier bags under dry nitrogen gas purge. The same process was  followed for inspecting and processing the duplex bearings, using Braycote 600EF, and all of the packages  were stored in the cleanroom to await further assembly st eps. When the Drive Output subassembly was  completed, a layer of Braycote 601EF was applied to each of the Wave Generator bearings as required to  obtain 100% ball coverage, which was manually run- in while also adding 12 drops of Brayco 815Z Oil to