Tool_maker, that reminds me of that old Michael J. Fox movie - Doc Hollywood. He crashes his Porsche in a small rural town. When the home grown mechanics give him back his car after completing repairs, they hand him a little white box. Michael's character asks what is it for? The mechanic shrugs and says "I don't know, but I always have some parts left over..."
Fred, not only a torque wrench, but a proper tightening sequence can make a huge difference. One shop where I worked made oil pans for a number of vehicles, including a large earth mover. We had to pressure check for leaks and our customer sent a chart illustrating the proper sequence and torque. If you just started at one bolt and went around the pan torquing screws down, it would leak. But loosening the screws and retightening in the proper sequence would usually produce a good seal. I say usually because occasionally improper sequencing would so wrack the pan that they would have to be returned to production and be restruck in the die.
Nancy, that is a great point. At the shop where I apprenticed every toolmaker made it a habit to put all parts in a box as they disassembled a die for maintenance. After the work was done having a screw or dowel left in the box was cause for disassembly until correct assembly was verified. We had a clown in the shop who thought it was clever to throw an extra part in the box of parts when a tool was being worked on. One old journeyman did not find the humor and a threat to meet the guy on the parking lot after work ended that behavior.
I thought this was a fascinating story. In regards to part verification - I think it should be a part of any "kit" endeavor as a built in cost. Even something as mundane as student kits for an electronics course. I have a friend that teaches online and apparently the company they use to send parts to the students does not think part verification is important. Unfortunately it has really hurt the students who are taking a time-compressed course to have to wait on part replacements because they received an AC input voltage PLC instead of the DC one which is used in the course and they can't conduct the labs according to the course timeline.
Nice point bdcst! After several years on those big earth stations I moved on and only went back to them later as a consultant for refits to extend their working life another ten years or so. By then for every 30m dish there were a dozen smaller dishes with ambient LNAs and so much simpler and cheaper to build and run. Many of the early generation of big dishes were scrapped by the end of the 1990s. Of course, it was the advent of more sophisticated satellites that drove those changes, with localised footprints (hence much greater EIRP) and higher frequencies (hence smaller dishes). But it was all good experience and I got the chance to work on everything from LNAs and TWT transmitters to digital encoders and servo tracking systems, all of which stood me in good stead later on.
Back to the point of the tale, earth stations were a very competitive field so we always struggled to balance the commercial pressure to get the station on air and earning revenue, and getting the job done right. The station in the Gulf was only our second big dish and it was the very first entirely to our own design so we learnt a lot of very hard lessons in a few hectic months. Nevertheless, the local Sheikh was very pleased because we got ours on traffic before any other station in the Gulf. Subsequent stations evolved to a more or less standardised design and those projects went much more smoothly. I believe a few are still working 40 years on.
Just as an aside, early LNA's cost between $40k-$200k. Today 15degree K noise performance can be had for several hundred dollars and is a fist size device bolted to a flange, no cooling is required! Progress!
I have found that many times the liberal application of a torque wrench or a little but of alignment can solve a wide variety of problems. Oft times we search for solution to an apparently difficult problem before we make sure the system under consideration is at it's "should" state.
This expresses, also, the danger in JIT planning. One mishap and you are burned! But how many times have we put something together only to find extra parts that were either put in by mistake or added to be sure we had extras if something went wrong? Extra screws are wonderful, unless we left the screw off the brake on the bicycle we just put together. Was the waveguide not put together properly because someone assumed there were extra parts? Did someone think close was good enough? These things can cost a lot of time and money. Proper training and supervision could have prevented so many heartaches in our field.
In aerospace applications, the cost of part controls is not part of the safety culture, but rather the lesser of two cost factors. It costs less to verify each part is installed, down to the fastener level, because the cost of not doing it and losing the satellite is higher. This is true regardless of manned or unmanned missions.
Linear guides are one of the most important components required for the design of automated or computer-controlled equipment. Aluminum profile extrusions, used for these guides, can enable designed-in functional features.
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