Archive for the ‘TALES FROM THE FIRST EIGHT DECADES OF A LIFE.’ Category

WHISTLE VALVE REPAIR IN THE OERM SHOP


One of the members of OERM is an avid collector of steam whistles and one day he brought some of the whistles from his collection to OREM and showed them to us. I made the comment that one of the whistles seemed too large for use on a steam locomotive. I was told the whistle used to be the  “noon” whistle at the SPRR Taylor yard shop. The whistle’s owner told me the whistle was not in working condition and asked me if I would make a new valve stem and renew the seat for the whistle. I said I would give it a try if we could figure out how to do it. The major uncertainty was about the method we could use to refinish the valve seat. I knew we had the equipment in the OERM shop that we would need and the job did look interesting. I also was sure we did not have any bar stock large enough to make the new valve stem, but I knew where to purchase bar stock of the size required. It was a done deal, or so I thought.

  What I did not know at the time I made the original agreement was that I would become unable to complete the job personally. I have Parkinson’s disease and the symptoms have progressed to the point that I no longer am able to operate machinery in a safe and responsible way. Also, I recently voluntarily stopped driving because I am not sure my reflexes are up to the driving challenges. Brian kindly offered to come to my Lakewood home and drive me to OERM for an occasional work session. There I would instruct him on what has to be done to complete this and future jobs. We decided to try the plan and see how it went. 

We have done this twice and it seems to be working out for us. I arrive back at home in the early evening tired but pleased that I am able to remain a working member of OERM. It is all to easy for a person with a chronic debilitating disease to become homebound. I am very fortunate to have a supportive family and friends like Brian in my life. What more could a person want.

Later, Brian began the work by setting the valve body up in the lathe. Because the seat is located deep inside the cast bronze valve body and hard to reach with a lathe cutting tool, I decided to have Brian chuck the body up in the Axelson’s four jaw independent chuck to maintain a secure grip on the casting and use a boring bar arrangement to extend the cutting tool to the valve face so we could make the cuts. The process worked perfectly.

I previously had purchased a piece of brass stock for the valve stem and, after settling the account, I found myself with a renewed commitment to saving brass cuttings.* After a little bit of preliminary lathe work, Brian setup the brass stock in a dividing head mounted in the Bridgeport milling machine. He machined the three flutes of the stem and we moved to the the  Axelson lathe for the remainder of the work. We reviewed the dimensions of the new valve stem to make sure we understood them, Brian finished the lathe work.

The lever that was used to blow the whistle is attached to the valve body by a bolt that had seen better days so we replaced it with a new one. For the whistle to work properly, it is necessary to lap the new valve stem face to the valve seat in the valve body. To do this properly, we had to make a tool to keep the valve stem straight while  lapping the seat. A piece of scrap aluminum was found that met our needs and the tool was made.

The lapping operation went without a hitch. After rough lapping, the valve seat was finished with 320 grit lapping compound. An air driven hand grinder head and a carbide burr was used to deburr the valve stem. The valve was assembled.

All that remains to  be done is deliver the refurbished valve assembly to the collector.

I wonder if we will get to hear this very large whistle.

 

*I have been saving copper alloy waste (chips) in a container for a considerable time and it has become to heavy to move easily.  Waste not and thus want not are words to live by.

 

THE CRISPY CRITTER AFFAIR


For about ten years I was what was called “The Senior Responsible Engineer For The G9 Gyro”. The engineer working in that capacity was responsible for all engineering work that was pertinent to that gyro. His approval was required for literally every thing. It was a position of great responsibility and it required an in depth knowledge of the G9 gyro design. I was never bored in the years I held that position. Prior to becoming the Senior Responsible Engineer, I was the Senior Test engineer for the G9 gyro and had held that position since the first G9 gyros were powered up. Several hundreds of G9 gyros were produced for the N16 Inertial Navigation System (INS), used on the FB-111 strategic bomber, and the N16 Minisins INS used on the USS Los Angeles class submarines. The performance requirements for the two applications of the gyro were fundamentally different. The aircraft INS was required to be ready to navigate eight minutes after power was applied and the length of the mission was less than ten hours. The submarine INS on the other hand was used in a much more permissive environment and the length of the mission was measured in weeks. The gyro was first produced for the aircraft INS and later for the submarine INS. As a consequence of being the first INS produced, all of the hard won experience we had accrued during the production of the G9 was biased toward the short term requirements of the aircraft mission. We began the production of the G9 gyro for the Minisins with little practical knowledge of what problems would arise as a result of the lengthy submarine mission. It turned out we had some interesting challenges that increased running time brought us.

I remember that I was somewhat confused by the phone call I received from someone in the the project office. The caller was trying to describe to me what had happened when a Minisins N16 failed during an acceptance test. I was told of a strong burned smell that was noticed after the INS system was opened up. I remember wondering why they were calling me. I could not recall any gyro failure that had produced smoke. The caller finally told me that he could see what appeared to be heat damage at the module end of the gyro. I agreed to the removal of the gyro and its return so that we could look at it. When we looked at the gyro we saw what could only be described as damage due to overheating. I remember trying to make sense of what I saw and coming up blank. The only possible source of the energy, required to produce that much damage, was the power source for the rotor spin motor. How could a short circuit in the motor circuit have resulted in the damage we plainly were seeing. Someone, during one of our gatherings to discuss the problem, used the term “crispy critter” with reference to the damaged gyro. The name stuck! We now had to solve the mystery of the crispy critter affair.

We were astounded at the severity of the damage we found when we disassembled the gyro. It looked like an explosion had occurred within the electronic module. The question in our minds was: what had exploded and how? The G9 gyro is a smaller version of the G6 gyro and it uses case rotation to improve gyro performance. Sliprings are an essential part of the G9 gyro due to the case rotation.  The gyro is designed such that all of the power and signal circuits, except the torquer coil circuits, pass through the  electronics module. The slipring is part of the electronics module. We were at a loss as to what was the root cause of the explosive damage to the electronic module. We did speculate the causal event was a short circuit in the spin motor circuit as only that power supply seemed robust enough to delivery the burst of energy needed for an explosion. Meanwhile, we had more crispy critter type failures. We were on our way to a serious problem.

All programs fall behind schedule sooner or later. The Minisins program was already behind schedule when we had our first crispy critter failure. Dr. Pickrell, our VP & Gen. Mgr., believed that any large program that fell behind schedule could only benefit from his personal attention. We, all the responsible engineers and their support staff , project office staff, and factory managers, were required to meet with Dr. Pickrell at 0700 hrs every day and report to him verbally about any problems that were delaying the program. I had to make a report on our crispy critter problem and we were flat on our ass. Not good! Dr. Pickrell was a person who did not suffer fools well. As long as he felt you were working the problem and not feeding him a line of B.S., you were treated OK. But, if he ever thought you were feeding him B.S., he could be harsh towards you. I survived the encounter, but he made it plain he was not happy.

We examined the damaged modules carefully. We noticed what appeared to be some kind of metallic debris on the slipring rotors. It looked as if it was wear debris from the sliprings. We were uncertain of this as the slipring was a disaster zone. The slipring wipers in many places had been melted back to their base. We began think along the lines of a short between wipers caused by slipring wear debris. It seemed far fetched, but this was our only theory. We disassembled a module removed from a gyro that had accumulated more than a few hours of running time and inspected the slipring rotor, looking for wear debris. We found what we were looking for. The sliprings were wearing out and the debris was piling up on the lands between the rings. We decided to propose a slipring design change to the slipring vendor. The proposed change would be to add a raised barrier between each ring which would keep the wear debris from building up and possibly shorting to the adjacent ring. The vendor agreed to make the change as soon as possible. This change in slipring design did not not provide a solution to or explanation of our crispy critter problem. We, however, thought we were on the right track towards an explanation and a solution for the problem.

I do not remember who reminded me that the photography dept. had the capability to do highspeed photography. It did not take long for me to arrange to have high a speed movie made of an exploding slipring. But I did not know how to cause a slipring to explode. We gradually made a plan that seemed to make sense. We made a precise mockup of the gyro’s module interface and that had provision  for camera access. All the module circuits were energized and loaded such that the current in each circuit was  the same as during gyro operation. We tried to make the test parameters as close to the operation of a gyro as possible. We setup the test, readied the high speed camera, and did several dry runs. When we felt we had done all we could do to make the test a success, we went for it. We energized the circuits, turned case rotation on, started the camera and immediately introduced a piece of debris harvested from a slipring using a pair of tweezers. The slipring exploded! 

We had to wait for the film to be developed. When the film came back we viewed it at normal projection speed. What we saw on the screen was amazing. One saw the debris being introduced at very slow motion speed and soon as it made contact with the wipers, the wipers melted and the molten metal sprayed onto the adjacent wipers which promptly melted and the damage spread to the whole of the slipring. We had replicated a crispy critter failure under controlled conditions. The fix for the problem was already in work with the the addition of a raised barrier between the rings of the slipring rotor to keep wear debris from shorting over to adjacent rings.

I do not recall how long it took fully implement the new design sliprings but it must have been quick as I do not recall the problem being a discussion item at the 0700 hrs meeting. If it were otherwise I would have the scars left by DR. Pickrell’s bite.

   

WHAT PROMPTED ME TO BECOME A MACHINIST?


My Mother and Father were somewhat different from a lot of people you might have met in the 1930s and 1940s. I am eternally grateful to them that they taught me through the example of how they lived their day-to-day lives. My Mother and Father, knowingly or unknowingly, gave me the gift of not indoctrinating me with explicit “rules” on how I must live my life. I was not burdened with religious beliefs or the tenants of racism, rather I was shown, by example, and sometimes by verbal admonitions, the way to live my life according to the golden rule. I was never told what I was to do to earn my living, but it was always clear to me that I was expected to sustain myself by honest labor. My Father was a an auto mechanic, starting at the age of sixteen when he left High School and knew well what honest labor meant. He did not like working for others and did so only when necessary in his younger years. He started his auto repair shop in 1946 and the shop remained open until the retirement of my Brother over fifty years later. My Mother and Father were “people” persons and were active in the civic affairs of the small California town we lived in. They were well liked and respected by members of our community. We ever had much money but we were never poor.

My Grandmother was very vocal in her belief that I was capable of becoming whatever I wanted. Like most teenagers, I did not listen and my academic record at Excelsior high school is dismal. I was expected to work part time in my Father’s shop and I did so grudgingly. Changing mufflers on hot summer day was not my idea of a great way to spend  your time. However, I was was an “A” student in my aeronautics shop classes. I married Patty a year after graduation and never looked back from that time on. 

After graduation  from High School, I went to work in a large, brand new, factory in East Los Angeles. I was the second person hired into that factory and that placed me second from the top on the seniority list. After a short stint as a punch press operator, I became the tool crib attendant for the machine shop that made the factory’s tools. The experience of being a punch press operator, after the novelty wore off, showed me that repetitive production work was not for me and I wanted something better. After I had worked in the tool shop for a short while, I talked my Boss into letting me operate the machines and make simple tools. I demonstrated my willingness to learn and I became the shop’s unofficial apprentice. That is how I learned my trade. I owe a large debt of gratitude to my boss and to the toolmakers for taking an interest in an impatient teenager. After several years had passed, I began to make noises that I felt I was ready to work as a machinist. One of my mentors was a friend of the shop foreman at Revere Copper & Brass, which was nearby to the factory where I worked. Revere was a large operation that manufactured copper and brass tubing. It was a classic foundry. My mentor told me that his friend’s shop had an opening for a lathe machinist. I went over to the shop and was promptly hired. I strongly believe that it was a recommendation by my mentor, Jack, that paved the way for me to get my first machinist job. I stayed at Revere for several years. By that time I had been promoted to machinist and was earning the maximum wage. I left only because I wanted to work in a more modern shop, not a old fashioned foundry shop. Some of the machines appeared to date back to the pre-1900 era. At about that time, my wife and I had decided that it was necessary that I should go back to school and get a college education. That, and my desire to work in a modern shop, led me to look for work elsewhere. I accepted an offer of work in the NAA Research Laboratory machine shop located in Downey, California. I left Revere and went to work at NAA on the swing shift as a research machinist. That is how I became machinist at NAA. 

BEING “SQUARE WITH THE WORLD” CAN BE COSTLY


The North American Aviation (NAA) machine shop in Downey, in which I worked when I first hired in as a Research Machinist, was located a long walk inside the old, WW II era aircraft manufacturing type buildings. Adding to the walk time was the requirement that I had to pass though three check points, each of which marked the outer boundary of areas of increasing security levels. Until I received my security clearance I was escorted in and out of the plant. I got my green “football” shaped sticker on my badge quickly because I was too young to have a lengthy record. The shop was located within a group of rooms which were clearly not designed to be used as a machine shop. The shop was doing work in support of some of the most sensitive projects of the Defense Dept. so we were at the “cutting edge” of new technology. But you would never have guessed this based on seeing the old style machines in the shop. My first assignment was to make several small shafts using an old 9″ ,,flat belt driven, South Bend lathe. Not exactly the machine I was expecting but it did the job.

In a few months the shop was relocated to a building located on the North side of Imperial Hwy. We were treated to a shop full of new machine tools that were more in keeping with the loftiness of our mission. I was unfamiliar with some of the machines in the new shop. I had no idea why the shop had several “jig boring” mills. I resorted to my custom of asking lots of questions. I learned the purpose of the “jig borers” was to machine the “inertial instrument” mounting surfaces located on the “stable platform” of the “inertial measuring unit” to as close to being orthogonal as possible. Full understanding of this would have to await the answers to more of my questions. As learned more about the capabilities of the machines, I began to understand why these machines had special operators and were not used for ordinary shopwork. I was allowed to look but not touch! I do not know what circumstance prompted the summoning of a technician from Switzerland, the country in which the machines were made, to rescrape the ways of these machines but he did just that. I cannot help but speculate it had something to do with some engineer trying to push the boundaries of what was then possible towards “better”. It took a long time to complete the work but it must have been successful because he never came back. As time went on, I began to understand more fully why the “jig borers” were necessary.

In the NAA inertial navigation world I lived in, the “stable element” referred to the innermost structure of the gimbal set. The gimbal set decoupled vehicle motion from a local level, North pointing, frame of reference. In other words, the vehicle could do a loop maneuver and the stable platform would remain North pointing and level throughout. The “inertial instruments” were the three gyros and three accelerometers necessary for navigation purposes. These instruments were mounted on the stable element such that the control and/or measuring axes of the instruments were mutually orthogonal. The function of a gyro was to provide the means by which a navigation reference axis could be defined. Three gyros and you get three reference axes. If the three gyros are mounted such that their control axes are mutually orthogonal, the control axes can become the basis for the three mutually orthogonal axes assumed in the navigation equation solutions. The function of an accelerometer is to provide a signal proportional to the acceleration of the instrument. If each of the three accelerometers are mounted on the stable element such that the sensitive axis of each accelerometer is coincident with a gyro control axis, then a frame of reference in which vehicle position can be computed from the vehicle’s accelerations is formed. An assumption implicit in the statement that “the computer solves the navigation equations and thus knows where it is” is that the frame of reference used in the computations is orthogonal. The computing capacity of “computers” was very limited in those days and it was not possible to perform the complicated calibration procedures that came later. This fact of life made it necessary that the gimbals and stable element be machined to as close to perfect as possible. It seems reasonable that the best possible machines be used for this work. This is my simple explanation for the presence of the jig boring machines in our shop. 

As the computing power increased over the years, the complexity of the IMU calibration procedures became more complex but this increased complexity enabled a great relaxation in gyro test requirements. By the time of the  N16 IMU only nominal tolerances governed the placement of the G9 gyro on the stable element. Perhaps the greatest level of complexity came into play with the advent of the “strap down” system. The “strap down” system replaced the actual gimbals of the 1950s inertial navigation system with virtual gimbals that existed only as mathematical equations in the computer. The Autonetics N73 was a pioneer strap down system and the strap down mechanization worked flawlessly. I wonder what became of the shop’s jig boring machines?

  

 

MORE ON THE AUTONETICS G5B GYRO


Yesterday I went to lunch with my fellow Autonetics retirees, at least those who are left. I sat next to a fellow retiree, an old friend of mine. We spoke briefly of his experiences when he was working on the design of the test equipment used in the production of the “Houndog” missile’s G5B gyros. He also told me that the work done in the development of the G5B was done using Navy money. This leads me to speculate the Navy may have had need for the N5 IMU. At about this time the Navy was procuring carrier based bombers from NAA. I wonder if there was any connection?  This information may explain the Navy depot stamp seen in the photo. He told me of the G5B gyro float balance weight adjustment procedure and described to how it was done. The gyro was operated in four different positions with respect to the gravity vector and at each of these positions, the rotor was spun in both the positive and negative sense. At each position, the magnitude of the torquer current necessary to precess the rotor while keeping the pickoff nulled was recorded. The change in float balance weights necessary to bring the float into balance was calculated from the eight values of torquer current recorded. He remembered the hectic pace of the production work for the G5B gyro and the pressure he felt whenever the production 0f the gyros slowed down. I know well what he means.

He told me the pump power frequency was 10 Hz. He doubted the float was subjected to any further machining after final assembly.

It was good to see my fellow Autonetics retires again. We made plans to meet again next year.

A TAPE RECORDER AND BORED TECHNICIANS


It will be no surprise to anyone that night workers in the Instrument lab sometimes became bored. Monitoring the drift test of SINS gyro is not like doing aerobic exercises; its more like trying to outrun a sloth. The technician assigned to monitor a drift test was required to periodically measure the magnitude of the current flowing through the torquer coils of the test gyro. As part of the ritual performed during the startup of a drift test, this current was caused to flow thru the test gyro’s torquer coils such that the gyro was observed to be stationary with respect to the room. The technician was trying to determine the torque that would be necessary to keep the gyro precession rate as close as possible to the rate at which the room was turning. The accumulated angular difference that resulted from the inevitable small difference in the two rates was recorded using a Bristol strip chart recorder.  It was important that the torquer current magnitude be measured periodically to provide proof it did not vary during the drift test. The current magnitude was measured using equipment that today would be considered as museum pieces. They consisted of a large potentiometer, a galvanometer, a bridge circuit using high precision resistors, and a dust cloth. The dust cloth was necessary to enable the technician to keep the shiny black surfaces of the galvanometer clean. (Dr. Pickrell, the Vice President and General Manager of the Marine System Division, had a habit of writing his initials in the dust and there was hell to pay if they were still there the next time he came by.) The measured value was was entered into a logbook. This left plenty of time for other “projects”.

I had just transferred into the lab from the machine shop. I remember one night being asked if I knew about the tape recorder test. I indicated that I did not. I was taken to an old reel to reel tape recorder that had a set of ancient earphones attached and a microphone. I put on the earphones as I was asked to do. I was handed something to read out loud and the tape recorder was started. I started to read out loud using the microphone and almost instantly found I could not continue. I tried several more times with the same result. During the ensuing discussion with the onlookers, I was informed that they had found nobody who was able to read out loud. I examined the setup and discovered, with the help of the onlookers, that the tape recorder was rigged so that a small time delay was introduced between the microphone input and the output to the earphones. I have never been informed of the reason for this apparent disabling of the brain circuits by this time delay. I still wonder what happened to my brain.

POLHODE – A NEW WORD


If an ESG ball were made without the Tantalum inclusions and such a ball was spun up to the normal rotor speed and the ball was maintained at the normal operating temperature, the spinning ball would be round and homogeneous. It would show no evidence of a MUM signal as the surface of the rotating ball would be running “true”.( To use a word taken from the machinist’s lexicon.) The ball would be symmetric around any axis of the ball; the moments of inertia, measured around any axis of the spinning ball ball, would be the same. It would be a very uninteresting spinning ball. If, on the other hand, the Tantalum inclusions were magically inserted into the spinning ball such that the ball spins around what is now the axis of the greatest of the ball’s moments of inertia, and the other conditions under which it is spinning were the same, the surface of the spinning ball would be found to be”running out” by 40 microinches (if my memory is correct) when measured in the plane normal to the spin axis of the ball. If an observer had the patience to monitor the spinning ball for a long time, he, or she, would find the ball appeared to not move relative to an inertial frame of reference. In particular, the “run out” of the surface of the ball would remain at 40 microinches. The observer would be justified in concluding the spinning ball’s position in inertial space is stable, ie, not changing with time. Now spin the ball down until it has stopped spinning. Go to lunch and relax.

After lunch, spin the ball up to the normal speed and bring the temperature of the ball up to the normal temperature. As before, measure the runout of the ball’s surface in the plane normal to the spin axis of the ball. To the great consternation of the observer, the”run out” is less than 40 microinches and, worse, it is slowly changing with time. As time goes on, the observer finds that the runout is slowly increasing and after more time realizes the “runout” has moved up to 40 microinches and is no longer changing. Just to be  sure, the observer waits for more time to pass and, finally, concludes the ball is back to normal, ie, spinning as before the spin down of the ball.

The observer concludes that a pretty fair gyroscope can be made using the asymmetric spinning ball, if some way can be found to shorten up the time it takes the ball to come a stable equilibrium condition. The time to reach this equilibrium “naturally” is not acceptable for any practical navigation system. After some time spent reviewing the relevant theories of the rotation of asymmetric balls, the observer concludes that the observed behavior of the spinning ball can be attributed to these factors:

1.) The asymmetric ball described above has three moments of inertia, each greater in magnitude than the one before it. The three moments of inertia of lie on mutually orthogonal axes. (inertia means “resistance to change”)

2.) The ball, when spinning such that the spin axis lies along the axis of the maximum moment of inertia, is in a stable spin state that will not change over time.

3.) The ball, when spun up to the normal speed, will not, in general, be spinning such that the spin axis lies along the axis of the greatest moment of inertia. It is spinning in an unstable state. Over time the position of the ball will drift toward the stable condition described in 2.).

4.) The path, or motion, of the ball above is called the polhode.

What is needed is an “artificial” scheme to cause the drift of the ball toward the stable position to happen in a much shorter time. This in effect requires that information within the ball “run out” signal must be decoded to determine the magnitude of the difference between where the ball is now and where the ball should be when it is stable, ie, where are we relative to where we want to go. To achieve this, a solid theoretical understanding of the polhodes must be gained and the means by which to move to ball with respect to the spin axis, without moving the spin axis in inertial space, must be developed. The scheme must differentiate between the two possible final orientations of the spin axis with respect to the axis of maximum moment of inertia to enable the control of the polarity of the mass unbalance along the spin axis.

I hope the reader of this has gained a feeling for the process known as “polhode damping”. The process is required to be performed each and every time an ESG rotor is spun up prior to use as a gyroscope. The time allowed to perform polhode damping ranges from “take all the time you need” for test equipment to the astounding 45 second requirement of the N73 system. (the N73 average time was 22 seconds.). I had to learn how to perform polhode damping on test ESGs by what is called “the manual method”. It required the use of old fashioned knobs to control the motor voltage and the recognition of the polhode you were moving on using MUM signals displayed on Bristol Chart Recorders. I was hopelessly lost in the beginning, but with the patient help of Gerry Hardesty, I finally developed a knack for the process.

The development of the N73 polhode damping software was done by Dr. John Wauer. I was very impressed with the software. John was never able to find simple enough explanations of how the software did its thing in such a way as to bring me to a high level of understanding. To this day I still wonder how the motor used for rotor spinup was used to move the rotor without any effect on the rotor spin axis. It must be magic!

I do not recall much discussion on the part of laboratory people about polhode damping and I attribute that to the complex nature of the process. It was not possible to concoct short and sweet answers to questions about polhode damping. As a group, the engineers and technicians of the test laboratories were very proficient in carrying out their assigned tasks and I was, and still am, proud to be counted with them. The labs I worked in all have been leveled but we all have lasting memories of the work we did – at least those of us that are still alive still have memories of those times – when “cost plus” reigned.

 

 

%d bloggers like this: