in reducing the bearing loads). The bearings would all require cleaning and lubrication in-house, but this  just provided more “opportunities for learning”. The lesson learned was simply, order bearings early! Obtaining the Damper fluid took equal patience and luck. While readily available, it could only be  purchased in 55-gallon  drums, shipped from Euro pe. Needing only a quart of two different viscosities, this  was difficult to justify. One liter samples were free, but certs were out of the question. Samples were  requested anyway, under a plan to certify the material in-house through chemical analysis and viscosity testing. As fortune would have it, the samples arrived with lot codes. A quick call to a different department  at the manufacturer was all it took to obtain the certs corresponding to those lot codes. Lesson learned:  sometimes it’s better to be lucky than good. Assembly  The Spring/Dampers were the first items assembled. At this time, a number of design problems were  encountered. The heritage wave spring that preloaded the bearings did not fit in the heritage bore. When  a suitable off-the-shelf replacement could not be identified, the heritage wave spring was “filed to fit”. Its  preload force would be reduced, but such was the lesser of many evils. Even worse, the outer bearing  race it was preloading should have had a sliding slip fit to the housing, yet when machined correctly per  the heritage drawings, there was substantial interference. The only solution was to re-machine the  Damper Housing. Adding insult to injury, the Heater Resistors had been modeled mirror-image, resulting  in a reversed bolt pattern. While mounting the Resistors upside-down was considered, the proper solution was to disassemble the Damper yet again for re-machining. There were also repeated problems with  pinched o-rings, though luckily all were immediately obvious from the incomplete seating of the parts.  This had historically been a problem, and unfortunately wasn’t solved despite paying special attention to the design of the o-ring glands. Subsequently, the Dampers underwent a helium sniff test to check for  leaks prior to filling. The lesson learned was that heritage designs need to be completely analyzed and  understood, or else they may surprise you. Also, always dry-fit assemblies to discover problems early,  and recognize that o-rings can be finicky. As mentioned earlier, installing the deployment Spring Lamination Stack was tricky due to the bolting of  the Stack to the Spring Arbor. This was made more difficult by having to thread the bolt into the stationary  barrel nut, during which operation the hard Springs wore on the fully-threaded bolt causing damage and  generating debris. In addition, the Hi-Torq recess of the heritage fastener continually stripped. Drilling out  the threads to make a barrel washer  allowed the bolt to remain stationary, and a standard, locking nut to  be installed from the back (Fig. 7). The bolt was also changed to one with a grip and hex wrenching, making assembly a snap. Here, the lesson learned was that tricky assembly procedures should be  practiced ahead of time. As with the heritage devices, the Spring Motor developed a heritage problem. As the actuator deployed,  each spring lamination coiled at a slightly different rate than the one next to it due to the difference in  rolling diameter. This required the laminations to slide over each other. The inner laminations were also heavily pinched against the Roller Pin due to the force of all the laminations above. The resulting  interlaminar sliding friction and the Roller Pin drag generated enough resistance to the coiling of the inner  laminations that they would instead “bunch up” ahead of the Roller Pin in a runaway buckling fashion (Fig. 10). This was the case for nearly the inner third of the laminations, at which point the force from those  above was low enough to allow the necessary slippage. The earlier decision to not lubricate the Springs  increased the problem, and a few spare (coated) Springs from Galileo were used in the innermost two positions. This helped, but didn’t solve the problem  completely (which is pro bably why it had been  deemed ineffective). The Vespel SP-3 (MoS 2) Roller Pin Sleeves were wet lubricated with Braycote, and  the OD of the Sleeves was increased to give greater mechanical advantage over the rolling friction (though this wasn’t implemented), each with further improvement. The ultimate solution wound up being  the heritage solution, which was to band the laminations  together with lacing cord. While not graceful, this  was the only approach that offered any sense of reliability. The lesson learned was that while heritage  should be appropriately scrutinized, don’t be too  eager to change a design. 244