Strobe Lights and Fly Wheels

Space, Space Programs, Manned and Unmanned Missions
blackirishkarma
Joined: 09 Aug 2013, 03:20

29 Jul 2016, 18:34 #1

One of the responsibilities with my job refurbishing the test area involved checking out and getting operational the control system for the pump house. The pump house was a large building containing 13 locomotive diesel engines that we used for pumping coolant water to the test stand during an engine test. The test stand had originally been built to test the Saturn V engines that flew on Apollo. It was a huge structure that was being refurbished when I hired in to test shuttle engine components. We weren't the main test stand for testing the shuttle engine performance but would instead test different component configurations on the shuttle engines. 

Below the deck where the shuttle engine would mount, which was on the 12th floor of the test stand, was a huge flame bucket. The flame bucket was some 130 feet high and about 80 feet wide. It was actually a dual walled steel structure that was fed by a lot of 36 inch water lines tied it at different locations. The interior of the walls was filled with water which flowed out of hundreds of 1/'2" holes on the top of the flame bucket. The flame bucket was fed from the pumphouse where the diesels were used at pressure pumps. A 96 inch water line flowed the 300 yards down the hill to the test stand where it split off into a lot of 36" lines that fed the flame bucket and a system of 12 inch firex lines that could be turned on in case of a fire on the test stand. 

At peak capacity each diesel pump could flow 2400 gallons a minute at 150 PSIG. Each pump had a 36 inch feed line and a 30 inch outlet line that tied into the 96 inch header underground. The diesels themselves were sixteen cylinder Alco diesels. The pistons were the size of a small garbage can and there was a large turbopump on top of each engine to facilitate getting enough air to them to create the massive horsepower required to pump all that water. A few minutes before the engine was fired we would ramp up all the diesels while they opened all the 36 inch valves feeding the flame bucket. 

The diesels were made to peak out at 1000 rpm which for a flywheel that fed the pumps that was 8 feet across was plenty enough speed for anyone in the vicinity. When we ramped those engines up the whole building was shake. The huge concrete platforms they were mounted to strained to hold them down and you could see the whole frame of the engine try to torque over as you ramped it up. They were impressive engines and the facility that housed them was an engineering marvel at the time it was built in the sixties. 

During peak flow through the flame bucket we would flow 155,000 to 165,000 gallons of water a minute up out of the flame bucket. It looked like Niagara Falls opened up when we were at full flow. The water was used to keep the test stand steel from melting as we fired the engine down into it. Most of it would instantly turn to steam when the engine began firing but there was a large lagoon behind the test stand that caught the excess. If we opened all the firex's up along with the flame bucket we were flowing over 200,000 gallons a minute through the 96" feed line at 160 PSIG. 

The pump house and associated systems had been mothballed for many years previous to our efforts to refurbish the area in the late 1980's. It was quite a job to get the whole thing operational again. Almost all of the people who had originally ran the test area were long since gone so we were reading manuals and digging through drawings to figure out how everything was supposed to work. We were also refurbishing the Hydrogen and LOX storage areas at that same time but they were not as complicated to get running again as the pump house. 

A lot of the lines had rusted considerably, especially in areas where they hadn't been properly drained. We wound up replacing all the main bypass lines off of the water pumps as you could take a welding hammer and punch a hole right through most of them. There was also a lot of corrosion that affected the heat exchangers that were used to provide oil and water coolant for the engines. We wound up taking all of them apart and painstakingly running wire gun barrel cleaning rods through them to push out all the rust. Once we got the piping system operational we found that the 96 inch line feeding the test stand was heavily corroded as well with a couple of inches of loose scale rust on the inside of the pipe. To clean these out we removed the main shutoff valve and took a high pressure sand blaster to the inner walls of the pipe all the way down to the test stand. Working underground in a 96" inch line and a sand blaster wasn't too fun but at least we could stand up in there even though we had to use scuba tanks to breathe. The rust and sand waste was hauled out in wheel barrows after we filled them with shovels. 

The EPA gave stirred up a pretty good stink when they found evidence of lead in the waste products we pulled out. We all wound up being tested for lead poisoning for years afterwards but thankfully no one showed any abnormal signs of lead poisoning. We had even more trouble getting some of the electric powered 30" and 36" gate valves functional, both those inside the pumphouse and the bigger 54" inch valves that fed different parts of the test area. Someone had cannibalized many of the control parts of those on the outside. Most of these were in large underground manholes where they were exposed to the elements. For quite a while afterwards we were jumping out controls with jumper wires and physcially reversing phasing to get the valves to go back the closed whenever we needed to operate them. 

more later....
The increase of misery in the present state of society is parallel and equal to the increase of wealth..... Unknown member of Parliament 1840's
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blackirishkarma
Joined: 09 Aug 2013, 03:20

05 Aug 2016, 21:56 #2

Eventually, we got the pumphouse up and running. It was a pretty long and drawn out business but we managed to get everything working and proudly supported the first few test firings Shuttle engines on the test stand. It was an impressive sight to see, the roar and perfectly diamond shaped plume of the engine itself shooting down into the flame bucket and the massive clouds of steam that resulted, often drifting out over the swamp and lagoon behind the test stand for quite a long distance. 

As time went on, we began having more issues with the diesels themselves. We had some older Waukeshaw diesels that were much smaller and less efficient that we ran for another test area to the east of the shuttle stand and we began having a lot of engine failures with them as well. The Alco diesels in our pump house were pretty hardy and they were a lot newer and bigger than the east area diesels but it soon became obvious that we needed more expertise on the Waukeshaws. The company was long since out of business and we were having to make parts that we didn't have in stock. After casting about for a locomotive diesel mechanic we finally hired one that had worked on tugboats pushing barges up and down the Mississippi. 

His name was Keith, and he was one of the best, if not the best mechanic I ever had the pleasure to work with. The nature of the tugboat business was that you had to push barges to make money. If an engine went out, you fixed it wherever you were. This takes a lot of ingenuity. It is one thing to have access to unlimited supplies and tooling but when you break down miles from the nearest small town and have to get going again, it takes a whole different level of understanding of mechanics and engines.

Keith was in his late twenties when we hired him. He came by being a mechanic the old fashioned way; his dad had taught him. His dad was a mechanic on tugboats his whole life and Keith eventually followed him into the business. Being on a tug for 4 weeks at a time was not his favorite part of the job however, so when a job offer that would let him spend every night at home came along, he jumped on the opportunity. 

It was soon obvious to everyone that his knowledge and expertise was far more detailed than ours when it came to the mechanical workings of the engines themselves. He could almost instantly diagnose problems with just a few minor checks or tests and his knowledge of how to physically get to and change the faulty parts was just as good. I liked him immediately. With his mechanical knowledge and my understanding of controls and instrumentation we made a formidable team when it came to diagnostics and repairs on many different systems, but his special area of genius was the diesels themselves. 

It didn't hurt that we had the same kind of sense of humor and work ethics. Every work project was a combination of serious concentration and constant needling between the two of us. His favorite description of me was "that red headed, left handed, color blind electrician," which he said with great disgust and aplomb dripping with nasty sarcasm at every opportunity. There was rarely a dull moment when we got together, whether it was at work or after. 

At one point, we had a tachometer failure on one of the diesels. It was one of the few times I saw him nervous because the tachometer pickup was in the hydraulic governor on the Alcos. The governor was a hydraulic over electric setup combined with an air driven throttle. It was a complicated piece of equipment. It was also the only thing on the engine that could override the fuel rack and cause a runaway condition on the diesel. Keith had witnessed that one one occasion and it had made quite an impression. 

The fuel rack on the Alco engines had a manual override below the governor. In case the electrical kill solenoid failed and the air throttle didn't work, you could take a large crescent wrench and physically pull the fuel rack cog down until you starved the engine for fuel and shut it off. I had done this on a couple of occasions but it was a struggle and took a lot of force as the governor would hydraulically try to override this process. If something went wrong in the governor it would simply overpower the manual override so that you could not shut the engine down. The thoughts of that huge flywheel spinning right next to you while the engine ramped up RPM's until it slung a piston out of the side of the block was not something I wanted to witness. Keith said the only time he had seen it happen was when another mechanic was trying to adjust the balance on a governor. 

Once we figured out we had to diassemble the top part of the governor to put in the pickup for the new tachometer we were both a little nervous about making sure everything was put back in the exact same way it came out. It took most of an afternoon and we were very careful. After we got it put back together we started talking about how to calibrate the tachometer. The Alco maxed out at 1000 RPM but we had know manual tachometers or speed sensors to check the calibration on the new tachometer. I had a couple of cabinets in the back of our instrumentation room filled with old pieces of test equipment so we started digging through it for a solution. 

I soon found an old Strobotac light with a large potentiometer drive dial on the front of it. A strobe works like a timing light on a car by turning the light on and off to match the frequency of the drive shaft mark with the firing of a spark plug. The Strobotac used the same principle only instead of triggering off of the firing of a spark plug you simply set the frequency pot until it was timed correctly with a bolt or nut on the shaft or flywheel. The massive flywheels on the Alcos were bolted on with 1 1/2" stud bolts so I knew we could simply adjust the dial until the bolt was "still" in space and that would tell us the true RPM. We could then compare this with the tachometer reading to see if it needed adjusting. Following this process we would adjust and check until they agreed, at which point the tachometer would be calibrated. 

When we drove back to the pumphouse and put our plan in order we soon found a couple of issues. The Strobotac light wasn't as bright as we needed so we were going to have to kill all the lights on the pumphouse to properly see the nuts on the flywheel. This made it impossible to see the adjustment dial on the Strobotac so we were going to have to use a flashlight after we got it adjusted correctly to see where we were in RPMs. The large grating platform on that end of the engine was not very wide so it was pretty crowded with both of us crammed into that area. 

We were already nervous about cranking the engine after working on the governor so we first checked that the electrical kill solenoid was functional. We also made sure to have a large crescent and cheater bar on the manual cog just in case as we started the diesel up. The diesel used a 2" supply large volume air drive to turn them over. It was an ear splitting sound and we were going to be standing right next to it on the first startup. 

When we had everything in place we cranked the diesel. We were both relieved to find that it responded well to the throttle and gave no sign of ramping up in speed on its own. We checked both the manual and the automatic shutdown and everything seemed to work fine. Now that it was time to use the Strobotac we shut off all the lights in the pumphouse and cranked the diesel again. 

True to plan, the Strobotac showed the flywheel nuts three at a time when we started. As I cranked the adjustment dial on the strobe up in frequency the light flashed faster and we soon were seeing just one nut. As it got closer to matching the strobe to the RPM the nut slowed its seemingly clockwise motion and soon slowly reversed direction. Realizing I had overshot the frequency I began slowly dialing it back and soon had the nut almost perfectly still in space, which meant that I had matched the frequency to the speed of the engine. 

We were both smiling and a little proud of ourselves that our plan was working as I went to the fine adjustment to get the nut perfectly still in space. That's when the flaw in our thinking came to the forefront. As the nut became clear and motionless we could see it slowly start to back off of the stud. We looked for just a second in disbelief but it was definitely spinning counterclockwise very slowly, effectively backing itself off of the flywheel while the engine was running. The thought of that massive flywheel spinning off the end of the engine panicked both of us and we immediately jammed the manual override down as hard as we could to kill the engine. 

As the engine died the engineer we had stationed at the electrical shutoff asked what had happened. We explained that one of the nuts on the flywheel was backing itself off. 

"How did that happen," he asked rather incredulously. 

We were all asking ourselves that question but none of us had an answer. 

Anybody care to guess what the flaw in our thinking was?

 
The increase of misery in the present state of society is parallel and equal to the increase of wealth..... Unknown member of Parliament 1840's
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blackirishkarma
Joined: 09 Aug 2013, 03:20

18 Aug 2016, 23:43 #3

We all figuratively scratched our heads for a while trying to figure out what had just happened. The best thing we came up with at first was that we were dealing with two seperate issues. Obviously, one of the flywheel nuts must have been loose before we started working on the governor and we just didn't notice it. Still, something about this just didn't ring true in my mind. Why hadn't it just fallen off over a period of time if it was backing itself off as the engine ran? It seemed too coincidental that we just happened to be using the Strobatac when we noticed it. 

As we took the overhead crane and lifted the protective cage over the flywheel after we had taken the mounting bolts loose I kept puzzling over it in my mind but didn't come up with an answer. Besides, maybe it was a coincidence. At least that was possible. It didn't take long after we got the cover off to discover that none of the nuts were loose. This puzzled me even more. We both knew we had seen it backing itself off the stud. Or had we? 

After a little while of thinking about it as we replaced the fly wheel cover I absentmindedly counted the bolts on the flywheel. There were exactly 16; evenly and seemingly concentrically spaced around the flywheel. As the word concentric went through my mind a tiny idea began to take shape. I looked at the dial of the Strobatac to see the full range of it. It was marked in increments up to 5000 RPM. In other words, we were operating in the bottom end of the range as the diesel tachometer was up to 1000 RPM. 

Since the bolts were concentric that meant there were two bolts directly opposing on opposite sides of the bolt pattern. What would happen if I had effectively doubled the Strobatac speed as compared to the diesel's speed? I would see two seperate bolts, one on each side, instead of just the one I was looking to suspend in space to calculate speed. If the nuts were in different relative positions and tight, which they almost certainly would be, then it would appear to move every time I went from one to the other. As a matter of fact it would appear to back off and then float back which is exactly what we had seen when I thought about it a little bit. 

That is exactly what had happened. We didn't see what we thought we did. It was like a clever magician's sleight of hand; it only really made sense when we realized we weren't seeing what we thought we were. Since the dial on the Strobatac was meant for much higher RPM's we had effectively skipped right through the correct reading and hit it's exact double as we fine tuned it. It didn't help that we were doing it in the dark and couldn't see the markings on the dial but it was still a pretty stupid mistake. Keith told me that only a color blind, left handed electrician would make that kind of mistake but he instantly saw that was what we had done. 

When we cranked the diesel back up and actually used the flashlight to get the Strobatac in the right range our plan worked perfectly and we were able to calibrate the new tachometer to the known frequency on the Strobatac with very little trouble. There is an old saying about believing nothing that you hear and being skeptical of what you see. I can attest that even two direct simultaneous eyewitnesses can be completely wrong about what they see if they aren't completely sure of all the variables first. 
The increase of misery in the present state of society is parallel and equal to the increase of wealth..... Unknown member of Parliament 1840's
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