I think i pick up on the tedious nature of these information sessions and you grinding your way answering various questions. As a novice fascinated by high level engineering, these are pearls of wisdom for me, I truly appreciate you slogging through Jet Engines 101. What you know as unremarkable given knowledge, are absolutely fascinating for those of us who have no experience whatsoever. Your efforts are appreciated !
JayZ I notice the OV-10 on your shirt. Great airplane. I have over 600 hours in combat in this beautiful aircraft. I really enjoy your videos. I use them in my class.
So the moral is kids, spelling mistakes are a perfect example of poor attention to detail. There will be no tolerance in the aviation industry or any other profession..... Mediocrity loves company.
I will try to answer some of the questions regarding bearing specifications and bearing selection. The first part of the study is the shaft itself. The type and measure of loading is calculated for each loading point, and afterwards the minimum diameter of the shaft is chosen for each segment depending on the material and a shock loading factor based on the application (turbines have quite low shock loading). The minimum diameter is then rounded to the next higher standardized shaft diameter (e.g. if the minimum diameter was 97,5 mm the chose diameter would be 100 mm), in order to accept standard features like bearings, key ways, retaining rings of standardized diameters too. Then the bearings are selected depending on the loading of each mounting point, the speed of rotation and the life expectancy. The most important is the life expectancy which should be high enough to meet the service intervals required but not higher in order to avoid the extra weight and cost of a bigger bearing. Finally the equivalent safety factor is calculated. The final part must be able to withstand 1,8 to 2,0 times the dynamic loading at the operating conditions. In general applications equivalent safety factors between 1,5 and 2,5 may have been accepted but they are evidence of a design either too light to withstand prolonged operation (in the case of 1,5) or one that's heavier and more expensive than required (if it gets to 2,5). In aviation it must never exceed 2 as this would make the part too heavy.
The most unusual bearings I ever encountered were in the Hamilton-Standard ACM. They were gas lubricated. As you might guess, the real problem is getting the machine up to speed so that a hydrodynamic film of air is developed.
Hi Jay, do you get to do diagnostics on the engines in the field at all? Or do you mainly just do overhaul? Also when you get these engines in what is the most common damage? Would it be foreign debris contact on the compressor leading edge or something else? Thanks Jay
(the flaps on the back of the jet that open when the afterburner is activated) is it powered bye servos or is it held by tension. and if i were to make a turboprop, or a jet engine (out of bean cans) what would be a good hi-temp resistent bearing.
Hellor Sir, I would like to know if any other types of technology is used, besides bearings, to guide in rotation the main shaft of a jet engine? Thanks for your response !
I know this is an older video, but you are the type of teacher I wish I would have had years ago. Took me a while to smarten up and fly right. (Hopefully no spelling mistakes).
I'm super late to the party here, but I need to comment on the "thrust bearing load" question/response. Rotor thrust (which is the load that the thrust bearing must resist) is actually one of the more complicated points in gas turbine design. Contrary to intuition, it has nothing to do with the thrust of the engine. Rotor thrust is simply the sum of all of the pressure forces on all of the airfoils and cavities on the shaft. The cavity loads are always much greater than the airfoil loads. We're talking areas in the order of hundreds of square inches and pressure differences of hundreds of PSI on a large turbofan. The challenging part is that these loads on the order of 100,000 lbf have to balance out to something less than about 7,000 lbf for the bearing. LP rotor thrust is usually pretty easy, it's the HP system that gets problematic as the pressures are higher and the secondary airflows are more complex. When the components of net rotor thrust are so much larger than the resultant, even the tiniest changes in the secondary airflow system can have huge, potentially catastrophic implications for the thrust bearing. A seal with the improper clearance means that the pressure inside the adjacent cavities is incorrect. A pressure deviation of even a few percent can change net rotor thrust by several times. One more thing, while the net rotor thrust must be kept comparatively small, it also can't to *too* small, or the thrust bearing will skid.
Yes. With our industrial engines, the seal cavity pressures are adjusted to get the rotor thrust to a value that reduces stress on the main bearing, but as you said, not too low, to avoid the rolling elements skidding in the races, which would cause greatly accelerated wear.
AgentJayZ, this video reminded me of one of my many examples of mechanics vs engineers: The T700-GE-401C engine had a Power Plant Change (engineering change) to the oil nozzles in the power turbine oil sump. The oil nozzle that spray the number 6 bearing was relocated from 7:30 o'clock to 12 o'clock, utilizing a tube that runs from the oil supply inlet to the new nozzle location and mounted on the original stud. This new design now requires a 1/4 inch 12 point wrench to be shaved to fit over the locknut. Additionally, the new tube restricts access to a coupling nut, that now has precisely enough room to rotate the coupling nut one flat with a wrench. Have you encountered anything on the engines that you work on with similar scenarios?
Hello part about control loop in the afterburner with the thermocouples made me think about combustion stability. Problems with combustion stability in the afterburners is that a big issue in old engines ? Were they solved by some guestimation like the baffles on the injector plate in Rockedyne F1 combustion chamber that damp part of frequencies and is the afterburner liner designed in some way that helps with damping the instabilities in certain frequency regimes by passive systems or are there modern active systems that have an active control over that kind of problems?
+Shlomo2 Rocket chamber design, and afterburner liner design are not what I do, and I have no knowledge of the process the engineers went through to arrive at the successes I get to work with.
Hi JayZ. I could be wrong, but I believe on the first question they were asking about testing procedures, or perhaps tolerances, of used bearings that are being put back into a rebuilt engine. That was the way I would interpret the question. Off the top of my head, I would assume that the answer is that the bearings are carefully measured to ensure that the wear they have incurred during operation has not worn them beyond the tolerance that is specified in the manual. I don't know if this procedure is simple or complex, or if you even perform such measurements in your own shop, but I can think of about 6 different ways to measure the wear-tolerance of a bearing+race to ensure that they are still within operational tolerance. ;)
Is there ever an application for floating bearings, the type used in turbo chargers, ever applied in aviation or industrial gas turbines? I've noticed that even small RC gas turbines use ball bearings. Thanks AgentJayZ. I love your videos. You've taken a lot of the mystery out of gas turbine engines for me.
Hi Jay, Hope you survived the Jet City parties and got some nice turbine stuff for Christmas. I think you said that some (or most) T engines have vibration detectors which i assume are either inertial or piezoelectric devices. Can they detect the difference between a new bearing and used ones with say 30,000 hours? Also do you know the testing procedures that sort out aerospace, AN, Milspec , industrial and other classes of bearings? Thx, Bob.
This may be a better replacement for question #1; is there a visual inspection process for bearings during an overhaul, or do you just scrap them all and replace? :P The main turbine oils I've worked with are MIL-PRF-23699 and MIL-PRF-7808. I'm sure each has about a half dozen different designations depending on what hemisphere/continent/country/organization you live in.
Is that just background workshop harmonics or can I actually hear the eye watering tones of bagpipes towards the end? This question is being asked from bonnie Scotland!
PC (Suncor) seems committed to selling fuel in BC so thought that location could still be a PC stn. While other majors seem to be getting out of province. Chevron sold out and Esso seems scarce now.
Hello JayZ.May I ask please, do bearing replacement depend solely on number of hours in service, or is there a set tolerance level. I'am no engeneer, just do some general maintenance on my bike, but very much interested in aeronautics.
If you had to pick one component on any of the engines you've worked on to call your favorite, which would it be? I realize this is a silly question, but I'm not letting it stop me.
I have watched GE industrial gas turbine engine promo video, it had tilted pad journal thrust bearing and all other bearings were of journal type. It left me with few questions though. 1. Before the engine start and shaft movement are journal bearings lubricated using independent oil pump or it starts moving on residual oil left from previous run? If it moves from residual oil than isn't it damaging to the bearing surfaces? 2. Are journal type bearings used in aviation gas turbine engine main shaft or shafts bearing role? (are tilted pad journal bearings ever used in aviation gas turbine engines in main shaft or shafts thrust bearing role?)
1) We only work on aeroderivative gas turbines, so I have no experience with the large frame industrial engines. 2) I have never seen any type of main shaft bearing in any aviation or aeroderivative engine except for rolling element.
I believe that the heavyweight industrial gas turbines with plain bearings do require pressurised oil to their journal bearings before being turned over. My recollection is that this principle was used in R-R's industrial and marine power turbines, which had plain journals and tilting pad thrust bearings. I have never come across the use of a tilting pad thrust bearing, or a plain journal bearing being used as a primary bearing on a mainshaft, in an aero application. However, I believe that, if AgentJayZ gets round to stripping a certain marine engine change unit in his (or S&S's?) possession, he might find that there is a plain journal 'steady' bearing on the LP shaft - but my memory could be at fault.
Could you please talk across the fixed bearing and floating bearing in the engine shaft. What happens to bearings when the shaft and parts expands in high operating temperature.
+jim5870 The shop does not go anywhere. And there are no new replacement parts for those engines. We have several sources of serviceable parts, and always are able to obtain what is needed.
You said there is no selection of bearings for each location and that the manufacturer specifies a certain bearing for that location and only that is used during assembly, I am assuming that means when there is a damaged bearing that spins the race on the shaft it can not be salvaged by having the shaft turned down and use a smaller inside diameter race?
+spoolinaround That is correct, sir. But the inner race is installed on the shaft, and is part of the bearing assembly. If the bearing inner race mounting diameter on the shaft is damaged, then the shaft must be replaced, but this is an extremely unlikely occurence.
Please tell me the T-58 compressor blades are on a stand/support of some type and it just looks like they are resting on the blades. It would look like the aft compressor blades are too brittle to support the weight of the entire compressor section (minus the compressor housing). Or is it lite enough that it can handle being laid down on the tips of the blades.
what prevents the flame from going to the compressor or to the front of the engine? The engine of the car has the intake valves that make the seal for example .. Tanks for all!!
In my series of Jet engine diagram videos, we talk about the pressure of the gas flow as it moves through the engine. Pressure does not rise due to the heat of combustion. You read that right. These are not piston engines.
I checked a few manuals and could not get a figure for oil consumption. Any oil "consumed" would be in the form of leaking seals, and no leakage is the normal expectation. Unlike a piston engine, the oil never comes in contact with the combustion gases. I would expect a J79 to need a litre of oil added to the reservoir every hundred hours or so of operation.
Hi AjentJayZ what was the worst condition engine you had to restore ? and what was wrong with that ? was it a runable engine ? I'd be interested to hear. I know one of your engines had melted turbine blades, was this the worst one ?
I love your low tolerance for poor spelling and "stupid" questions. As a computer/electronics tech, I have to constantly remind myself that the majority of people cannot seem to grasp what I consider common sense.
Around 90% of the worlds ppl doesnt have common sense or any sort of logic what so ever. When you look on youtube movies you sometimes start to think its even close to 95%+
I have a question. Whereas helicopters have a tail rotor to counter the torque applied to/by the main rotor on the body of the aircraft, do single engined jet aircraft (F-16, F35 etc) have a similar issue? By that I mean does the force required to spin the turbine induce a noticable counter torque on the body of the aircraft? If so, what mechanisms are in place to stop the plane from rolling?
+AgentJayZ I understand that the turbine/compressor and it's shaft only contact the airframe via bearings and that (by design) little torque it actually transmitted through these but in my mind I feel like Newton's 3rd law is being violated if there are unbalanced torques. I get that the turbine is spun by the exhaust gasses but do the gasses traversing the engine apply no torque to the airframe as well? Not even at the stators?
+Stuperfluous I am sure you understand that the torque generated by the turbine rotor blades is absorbed by the compressor blades in compressing the air and that this is not transmitted to the static structure of the engine. There is, as you appear to understand, also a torque generated by the turbine nozzle guide vanes in turning the gas flow into the rotor blades. However, what you appear not to have appreciated, is that there is also a torque generated by the compressor stator vanes. This is substantially equal and opposite in direction to that of the turbine NGVs.
Thank you for this reply! My brain made an audible click as it finally sank in and I understood. I feel like an idiot because it seems so simple and elegant now. Thanks again.
Lobby The rotor blades produce a torque which is balanced by stator vanes. Any torque produced by the engine would result in an angular rotation distribution of the exhaust stream Conservation of angular momentum. That is why behind the fan there are stator vanes , usually smaller and more numerous. On a propeller there aren't, so there is a torque, compensated by the ailerons (actively) and the tail surfaces (passively). Some energy is lost, counter rotating propellers recover some but not all .
+AgentJayZ I'm sitting here watching several bearing-specific videos of yours as I clean and inspect a pair of tapered-roller bearings in a new (to me) GA nose wheel - and I can't help but wonder why turbojet engine thrust bearings all seem to be ball bearings? Based on my admittedly limited knowledge, I would expect a tapered-roller bearing to transmit the same thrust with smaller (and therefore lighter) elements. Granted, as you say yourself in this video, the design aspect of these engines is very far removed from your interactions with them, but do you have any knowledge of why ball bearings are selected over tapered-roller bearings? Are you aware of any engine which use tapered-rollers instead of balls for the rolling element of the main thrust bearing?
Since thrust on the shaft of a Turbojet happens in either direction, depending on running conditions, two tapered roller bearings would be required to do the job of one deep groove ball bearing. I think the main reason might have to do more with the sustained high speeds of rotation. Tapered roller bearings seem more suited to very heavy loads at relatively low speeds, compared to ball bearings.
Hey Jay, Love the vids you've made me a Jethead!! Anyway surfing around youtube i came across a video of a MD83 (AA2224) taking off and then the left engine made a sort of banging sound and then following with sounds like a car with a flat tire? The video was shot by a passenger and he captions the video as it being a compressor stall? With your interpretation of the reverse flow of air and loss of the correct angle of attack on compressor blades being really at the core of a stall, this aircraft was able to make a very safe emergency landing and continued to climb even after the event in the engine. My question is, does an engine that is in a "Stall" condition does it still make power? If so how much? And since this aircraft made a quick emergency landing was that just for safety reasons or does an engine have to be shut down and restarted after it encounters a stall? I know you are planning on explaining this more in the future, but as i watch your vids and get a better understanding of how engine systems "do what they do" in such harmony, this question starts to become very relevant because to understand how it stalls will in context also better illustrate what the "correct airflow" pattern is, and how it contributes to the engine and how it makes power? Thanks in advance.. Drew
+drewbin101 I've come in on this topic in the past and questioned the use of the term 'stall' when the correct term should really be 'surge'. A compressor can experience various stall conditions, without the engine actually surging. A real surge is a nasty experience, when the flow through the compressor(s) breaks down and reverses, with flames coming out of the intake. This can happen repeatedly, with the engine surging, recovering and surging again. From memory, elsewhere on RU-vid, there is a clip of a twin-engined airliner (I've checked: it was a B.757) on take-off at Manchester Airport, UK, suffering an engine bird ingestion event and the affected engine going into repeated surge before being shut down. The compressor(s) of that engine were obviously damaged and it wouldn't have been producing much useful thrust.
+drewbin101 The engine of that MD83 (or whatever it was) apparently suffered an event not dissimilar to that of the B.757 mentioned in my previous comment, as it went into repeated surge. I assume from your description that the engine was shut down as, if not, it could well have destroyed itself. Following such an event the aircraft would obviously have to make a precautionary single-engine landing and, in all probability, the suspect engine would be rejected for inspection and repair. The root cause of the problem could have been foreign (or domestic) object damage or possibly malfunctioning of any airflow control system (eg, compressor bleed valves). In an engine with compressor variable stator vanes, it could be down to malscheduling of the vanes: however, I believe that the JT8D series does not have variable vanes. An intermittent surge problem can occur in an otherwise 'good' engine, which is getting a little 'tired'. This can happen as a result, for example, of some erosion/contamination of the compressor aerofoils (airfoils, if you prefer), or worn tip clearances, which would degrade the compressor's surge margin.
Thanks Graham.. So what you are saying in effect is that this event is common in a Axial type compressor engine? So from your description of variable vanes and other countermeasure systems that are installed on aircraft, a "stall" is a failure of the these systems failing to prevent the condition and not the condition itself?
+drewbin101 The effect isn't at all common, provided an engine is well-maintained, its gas paths are in good condition and any airflow control devices operate to their programmed schedules. Anything that degrades any of these will tend to reduce the engine's surge margin and increase the risk of a surge occurring. Nevertheless, it would be entirely possible to induce even a brand-new engine to surge, if it was accelerated too rapidly: however a modern FADEC (full authority digital engine control) system would prevent this happening. All compressors have the potential to surge, but normally do not, because they are operated along a working line that is sufficiently displaced from their surge line to give an adequate surge margin. Can I suggest that you find a graph called a 'compressor characteristic' via Google? It is essentially a map of pressure ratio against speed, with a surge line plotted and, below it, a working line, the distance between the two being the surge margin. Incidentally, centrifugal compressors can surge, too.
Jay, I recall on a bump test you did on a larger engine the clearance on thrust bearing was a bit loose but within acceptable tolerance. You said the owner decided to reuse the bearing. Was that due to high cost of a new bearing? Thanks. Bob.
Within acceptable range means just that. To replace it with new is an optional call made by the owner. It is not necessary according to the manufacturers specs, and adds cost to the job.
OK i'll take that to mean they did not think it was worth buying one of those overpriced bearings. Which i totally understand. Also IIRC it was still under spec limit by about 0.006". Which prob. means it would still operate with another 0.010 clearance due to engineering margin.
Good video. You have definitely earned your confidence in bearings. It's not hard to whip up 50 pounds of crab cakes or make 6 dozen home made creme brulees following a good recipe and having a little confidence. Must know your tools and what you are trying to achieve.
How 'bout I take the comment section i different direction. The questions about catastrophic failures make me wonder. Is it safe to say the those very carefully made bearings will not fail except for a lubrication problem? It seems that parts that are so carefully engineered would not ever fail, except for lubrication/cooling failure. Or to put it in different words. Do those fancy huge main bearings fail on their own? Or do they only fail because of a no oil situation? Thanks Jay, for this and all your videos. And letting us into your world.
I have a question about jet engine lubrication. Your excellent output suggests that the systems are largely sealed recirculating loops. I always understood that the oils were organophosphate derived and mist distributed and that the systems were not very well sealed and so at least the older military jet powered craft, whilst being air to air refuel capable, were limited as to ultimate range by their onboard oil tank capacity. This understanding, I admit, is only based on anecdotal reports from the last cohort of the Vulcan pilots who were very sniffy about the replacement MRC (multi role combat) planes which they unkindly referred to as Much Reworked Canberras! They bragged that whilst they had been able to fly return from Ascension Island to the Falklands with inflight refuelling, the replacements could not make it nonstop to the Mediterranean from the UK before running out of oil. Is there any validity to this belief of mine or was it just a good story!
You are talking about different engines at different times, and there is really no answer. Some aircraft jet engines had mist oil systems, but not anymore. Some "disposable" jet engines have total loss mist, or total loss pressure lube systems, and they are used in missiles. Also, you have made a very grave error by listening to a pilot talk about the engines in his aircraft. ( The Canberra was an earlier aircraft than the Vulcan, so we need to know if, where, when, and why they would have been a replacement. ) The Avons in the first Canberras would leak oil on startup, but not in flight. The Olympus engines in the Vulcan were less leaky, but much larger, and were a full generation newer than the Avon. So I have no answer except 42.
Thanks AgentJayZ. I can see that you have given it deep thought! If 42 is the ultimate answer then I must work harder on the ultimate question! . Vulcan Pilots may be unreliable sources as they considered themselves the last of the "heavies" of the old bomber command and resented their replacement by the ?MRC Jaguar? (Can't remember what actually replaced them) which was a jack of all trades in their view.
Some interesting things related to bearings that I've found on my quest in building high rpm reliability; bearings have a wide gamut of price in the extremes on sizes. Below 15mm and above 3 inches on bore ID, things get very expensive! If you happen to want to build your own one day from scratch, aim for .5"/12.7mm to 5-8th inch/15mm ID bearings as you can get them from anywhere to $10-45 each, depending on if you want 20k reliability with SS balls or 100K with ceramics and PEEK carriers. One inch NOS can occasionally be had on ebay, but they tend to pop up as NOS and are in fact scrap salvage, so find someone reliable that actually has NOS parts. That list is quite small comparatively.
Hi Jay, Is there still a Service stn across from an RCMP shop at top of the hill on E. (i think) side of town there? Used to be Pacific so maybe PetroCan. I worked there getting frozen cars running for a short time many years ago. Merry Christmas, Bob.
Jay, have you any idea what model NG turbines are in the Shepard EC on E side of CGY? Power output is 860 MW between 2 NG and 1 steam turbine. Steam turbine runs on exhaust heat from NGT's. So really 860 MW power is coming from 2 NGT's. Enmax does not tell public NGT details on their video. Who would be vendor and do service on those? Bob.
There is an Enmax facility east of Calgary that I have been to. It's in the middle of nowhere and very quiet, due to a very large silencer (looks like a five storey apt building). When I was visiting, they had two LM6000s running. Those are roughly rated at 50MW each, so maybe not the same place?
Hi Jay, HNY. Ok this is at Shepard, a small town just E of CGY limits. Old community hall on the main corner last time i was there. But NGT's likely outside town somewhere. Maybe they expanded the site you were at by adding 2 very large NGT's. What are the largest made? LM9000? I like the power rates in CGY but fixed charges are high. They have likely been getting NG for almost free in recent years due to lack of pipe and markets. So this project looks brilliant. I will try to go on tour and see NGT's myself next time in in CGY. Bob.
So this facility is about 3 km NE of village of Shepard. South of Glenmore Trail on 100 St. Prob. where you were when smaller units were there. Not sure of what the NGT's are but have to be big. Bob.
After seeing that last shot, How often do you or others get their hands cut by compressor blades? Those look like they could do some damage if you're not careful.
+bob345 I got caught in an oil tank mounting strap on Thursday... had to steady myself against the compressor rotor. Cut my fingers in three places on my left hand. Good thing I have a spare! Happens about every couple years....
So is the engine's thrust, those 50 tons, transmitted through the bearing? That would mean that the rotating parts, and specifically the compressor creates the thrust, because the turbine doesn't. But we know that it's the expansion in the combustion chamber that matters, right? So the biggest part of those 50 tons should actually work against the forward walls of the combustor cans I guess, somewhere near the fuel sprayers, the diffuser etc?
You're on the right track. The thrust bearing does not transmit "engine thrust" to the outer cases and then to the aircraft. It only handles internal thrust created by the tug of war between the turbine and the compressor ( the turbine wins). The overall thrust of the engine, which pushes the aircraft forward, is as you said, caused by the expansion and acceleration of the heated exhaust gases, which push on the combustors, the jet pipe and the combustor outer casing in a mystrious, black magic kind of way... Check my playlist "your questions answered" for thrust. Also have a laugh at my video called Thrust.
+smlbstcbr Aerospace bearings are made just like any other bearings, but with smaller tolerances. They usually have a bearing manufacturer's part number on them, as well as the engine manufacturer's part number.
I'm not any kind of engineer, but from what I know of delegation the engineer designing the engine tells a tech that this bearing has to handle this much load and the tech skims through a catalog of bearings with listed tolerances and then picks one. Either that or another department gets a work order for a bearing with a specific size and tolerances.
+Societal Pillage That's the way it works when designing something new. When working on an existing product like an engine, there is a part number for everything. Replace a worn part with the same part number. No other option.
I have a question about those bearings. Let's say you have a fully loaded airliner, with a take off weight of 300 tons. While the engine spools up to it's take off thrust power, and the aircraft is accelerating down the runway and then taking off, doing it's flying thing, is the bearings inside the engine taking all the horizontal force from the thrust (except for the engine mounts)? You said in the video that the biggest ones has a capacity of withstanding 50 tones of force. Then I interpreters that the sidewalls of the bearings (that keeps the balls inside the bearing) just as well must withstand more than 50 tonnes of pulling force, as I take it that you mean each ball can handle a load of 50 tonnes of thrust force. Isn't part of that force being spread out on the engine mounts and the pylons (if any) or the airframe? And apart from the pulling force, is the whole weight of the aircraft also transmitted through the bearings, as the aircraft takes off? Because I though the bearings had one job to do: Act like a friction limiter only. Thank you for great and interesting videos!
The thrust bearing in a turbojet handles internal loads placed on the shaft of the engine, which might be a few tons, and rotating at high speed. The thrust output of the engine is a different thing. It acts through all the parts of the engine, and the outer cases, and is transferred to the air frame though the engine mounts. For the bearing on the fan of an airliner engine, it is handling almost all the thrust output of the engine, which is why it is over ten times the size and capacity of the bearings shown in this video. Yes, the aircraft is essentially hanging on those bearings, and the requirements for it to pass inspection for serviceability are so high that the differences between a good one and a bad one are not detectable to the eye. Even ones that fail inspection look perfect. Seems to work. I have not heard of a fan bearing that has ever failed in service.
+Beach&BoardFan The bigger brother/sister to the T58. That's out of a TF34, the engine(s) in an A-10. It takes ten thousand horsepower to turn that cute little thing...
I amn an engunearing stident. Today I learned that if I am a bearing and I fail I am catashtropy. So I must never fale. Must work harder to be the best baring I can be.
Hi Jay. Regarding to I think question nr. 6 or seven: How hot is the oil in the return line, let´s say at full military RPM, before it reaches the scavenge pump or the oil cooler... Please in °C ;-) As I think that will be the temperature of the bearing... Simon
+Kleinstwasserkraft Klopp Each engine has its own operating temps, and each bearing has its own nominal operating temp range. One source of heat is conduction from hot parts of the engine. Another is bearing loading. Ball thrust bearings are more heavily worked than roller bearings. Thrust bearings often have rotor thrust balance chambers which use compressor discharge air pushing against an area to help carry the load placed upon the thrust bearing. Varying this pressure will change the load, and the temperature of the bearing. This is the long way of saying that it depends on a lot of things, so there is no one answer.
+Chainspike101 We deal with Mobil Jet II, and 2380. I'm not an oil expert enough to tell you anything about the differences. Even the text books I have just describe them as hi temp lo viscosity synthetic oil.
Hi j, if a brand name, let's say SKF, bearing kit in a box has several bearings made in various countries would that concern you? Let's say Canada, Mexico, Japan. Or do you accept the brand name on all containers as a sign of quality control by the brand name? Bob.
Every part, whether new or green tagged, gets a cursory visual inspection as the technician has it in hand or unpacks it. A new part from an internationally reputable manufacturer would be expected to be up to the job regardless of where it was made.
I liked the part about the temperature control negative feedback loop. Whoever was picking the background soundtrack did a good job. I'll have to make an effort to spell more gooder and have more better grammer before I post this coment :-)
Keep those students in line! Spelling was a big thing to many of my teachers in grades 1 thru 12, which is becoming a lost art. Even with 'spell check', you see misspelled words far too often. We're starting to sound 'old', Jay, however correct we may be. And let us not get 'grahamj9101' started on proper grammer, a subject on which he is master. My Indiana upbringing will still cause me to occasionally end a sentence with a preposition. Thanks for sharing & 'bearing' with us!! ; ) DD
+Darren Duncan I'm of the post-war generation in the UK that had regular spelling tests and learned grammar quite formally, reinforced by learning French and Latin at a traditional 'Grammar School'. However, I do try to be lighthearted, if not entertaining, about grammar and the differences between US and UK English. Nevertheless, I can be pedantic (as you will have seen elsewhere). One of my pet hates is a road sign near the city of Bath: from memory, it reads, "Possible peak hour queues ahead." So do I need to explain the UK English usage of the word 'queue' for 'waiting in line'? I did, years ago, at Disneyland Anaheim.
+Darren Duncan So why should your (or should this be 'you'?) being a Hoosier cause you speak any worse a form of English than your compatriots? Er ..... dare I mention the split infinitive?
+grahamj9101 Well, nothing against my fellow Hoosiers but there is a fair amount of 'rural' & 'country' influence here in Indiana, which includes 'slang' & bad grammer. My grandmother was from Kentucky, which has a notable 'Southern" accent & she had some good sayings. I am in the middle somewhere, as I found out being in the A.F., where others could peg me as being from the 'Midwest". I enjoy listening to Brits & Australians speak, probably most of all. Love the expressions. PS: I learned about the British use of queue via Monty Python!
Most complicated bearing arrangements by far you can find in a helicopter gearboxes. I reccomend you to find some x-sect. of one of these and study it.
+Michał Wielek Those are not part of the engine, and outside the realm of gas turbine engine work, so I have no experience with them, and I'm not able to comment on them.
Pressure really depends on which model the engine is. I would say the largest static pressure of the working fluid would be at the end of the last compressor stage. After that the combustion is isobaric and in turbine stages the pressure drops until it reaches ambient pressure at the nozzle.
7:49 This may be too EE-specific for Jay (no offence, I just don’t want to waste your time), so all responses welcome: does the amplification of the AB fuel control signal use an OpAmp (Operational Amplifier)? FWIW, my speciality is Mathematics (to PhD & further research level) - all this aeronautical and other types of engineering is purely a personal interest and lifelong fascination with how things work. Thanks in advance. Particular thanks to AJayZ for his infinite f**king patience and trait which sadly, I confess, I do not share.
The temp amp does indeed contain op-amp (s). The first op-amps were available before the J79 was introduced, and they used tubes like the 12AX-7, which I think is in tube preamps for guitars. I asked our J79 guy, and the earlier temperature amplifiers do contain tubes. Their enclosures are solder-sealed, and we don't usually open them up.
I get the feeling that if you started "selecting/deciding" which bearings to use, you could possibly end up litigated out of business or worse... I'd also guess it never happens in your shop.😀
It's standard industry practice, accepted and endorsed by the OEMs, to do exactly as you fear. Inspection to specified standards and deciding whether parts are serviceable, repairable, or scrap is how it has been done since the time when aircraft braced their wings with cables and their pilots wore silk scarves.
When I was learning, our lecturer could be harsh. The difference was he prefaced it - not explained retrospectively - with an explanation of WHY he was being tough: Because we were about to go out in a world and make decisions that could affect projects, costs and lives. It was because we needed to subject our thinking to the kind of scrutiny that will help us avoid making those mistakes. Students liked and respected him, even if his words could be harsh. We learned more from him. The other guy? Who just behaved like that with no explanation? Everyone thought he was a jerk and lost respect for him. We learned less because most of the time we were too busy thinking how we could get a little revenge (which some did). Please at least preface your videos with this explanation - otherwise it comes across as pointlessly overbearing (no pun intended) and the videos where you are friendly seem less genuine.
AgentJayZ No, I asked if you'd preface harshness on students with a reason for your harshness, because that way students learn better. Harshness without reason produces a student who continually doubts themselves, rather than an engineer who makes confident and informed decisions. Help them understand why its so important.
+Matthew Smith In my work, I don't deal with the prices of parts very much. If new parts are required, I receive them from our parts dept. and install them. I did destroy a bearing race out of a matched set ( meaning the whole assembly had to be tossed), that I was pleasantly informed cost over 20 thousand. It was a ball bearing about 4 inches in ID.
:) catastrophic bearing fault due to engineer/designer ignorance: en.m.wikipedia.org/wiki/LOT_Flight_5055. It is really worth to find out, what exactly was the russian engine designer tragic mistake.
- because of supply problems, shipping engines with 13 rollers instead of the designed 26. WTF !?! It is not a bicycle !!! - delivering shafts with heat treatment only fit for water pipes, instead of aviation standards. Not a design, but a manufacturing issue. And the USSR used to spew rhetoric about 'capitalist greed'. The political pressure to fulfill the 5 year plan led to even worse decisions. Like 'Kursk' and 'Chernobyl'. This is well within the realm of 'Ford Pinto', 'Enron' or the spare parts trade with forged certificates.
love your slightly disparaging attitude toward some of the questions and associated spellings :) put the shoddy spelling and down to dyslexia, and weak grammar down to the possibility that english may not be everyone's first language. as for idiot level questions, that's mostly just simple psychology. awesome as always.
Oh, by the way. Just for fun, I searched for "half million horsepower gas generator" and the first hit was a test of the Saturn V - F-1 "gas generator" here in my hometown of Huntsville, AL. I suppose they don't call it a "rocket" until they install the nozzle, but I thought of you when I saw this test video and thought I would share it with you. ;) (Honestly, it looks like it's just the biggest fuel pump in the world... but I'm not a rocket surgeon, so I'm sure it's much more complex than it looks like in the video.) ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-1AD-DbC3e68.html
= translated into entry level aerospace engineering geeksteerisum : 1. inspect bearing box certification seal , manufacture's authentication inspection codes on batch ( often done in shipping & receiving department's @ the parts distributor's depo before shipment to authorized dealer " parts jobber " outlet and box , ditto on installers end ) and shipping damage on box or parts ; covering " ass-sets all along the watchtower " ( parts flow pathways ) as Dr. Gaius Baltar often use to meme ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Y9j7tkSnk3g.html&feature=em-uploademail in capitulation or something ?
+docatomics = try not too get overly caught up on " spilling mowstakes " , as some of us are still getting that transmission scrambling in data transfer hacks U.N.der Bill C-51 and that previous OMNI bill the now disposed off criminal government of Canada has applied illegally threw off shore criminal servers contracted threw the civil contractor CESC's criminal sub-contract , contrary to the bidding rules and regulations long established by Crown Asset's doings ons in Canadian Law and Procurement Policy , as best I can recollect ( no point in looking anything up on line in this chindogu state of non-communication , really )
+Nicholas Washburn That has indeed been established. Anyone aspiring to the occupation of engineer should be ready for the responsibility of being held to the highest possible standards of technical literacy and accuracy.
Couldn't have said it better, I one hundred percent agree. I love your videos by the way, thanks for the hard work, I think people tend to take it for granted but it takes a lot of time to video everything you're doing. So many times I have told myself I'm going to document a project until I realize how much it actually slows you down.
Nice troll. No spelling mistakes were made in this video, because no spelling took place. Engineers are subject to zero tolerance for spelling mistakes. You will learn that once you step in to the working world. Good luck in the future.
my god...I am so surprised at the level of spelling and general lack of basic common sense knowledge in those who were asking questions...wow! it seems as if each generation is getting less and less connected to the basic experiences of being an inquiring mind at a young age...before I even hit my teens I had been given books on science, engineering, chemistry, biology all of those types of things by my parents and grandparents too...kids books that explained the basics of how everything works and I know that it was this that made me carry on to learn more just out of pure interest...I think parents these days do not realise what their job is with kids !.....
Fuck. It's this kind of attitude that really pisses me off. You should never be afraid to ask questions, no matter what age you are how stupid you think it may be. THERE IS NO SUCH THING AS A STUPID QUESTION.
of course there is...I suppose if you were a teacher ALL your students would be winners..right?..young minds need to hammered and forced into proper shape,if you baby them, ie, don't treat them realistically, you end up with some twit with a pH.D who can't tie his shoe laces...professionals need to be ready for the real world, because the real world is competitive, just like nature itself...
+psycronizer the problem with that attitude is that people _will_ fall behind and nobody notices until it's too late. All your students are winners until the rest results are in. I don't like it when people assume that the centrist point of view is the correct one either, but you're so against letting everyone be winners that you're willing to pretend they're winners. If you're a teacher and someone makes a "stupid question", and I mean a really stupid question, you realize that one person fell behind - that's a warning sign because probably 3 or 4 people fell behind as well but didn't want to admit it. At that point you will have to make the choice between wasting class time or telling the students you'll explain it again outside class hours. But you don't move on and pretend that your hammer forges things into shape in one strike. Your vision is the equivalent of mass producing cast parts, not bothering to check for voids and get people killed by a faulty product that went out the door. If it's a stupid business move, why would it be a smart way to approach education?
I do not believe any engineering students are falling behind due to lack of understanding. It's lack of effort, and that's what I'm commenting on in this video. If you don't bother to do the basic background reading, and then ask simplistic questions over and over again, because you refuse to believe the answers that don't make sense to your unprepared mind, those are stupid questions, and they waste everybody's time.
AgentJayZ This was not about what was on the video, the person I tagged on my comment took a generalist approach and started it from the "young minds" which seems a little late for someone already enrolled in an engineering degree. I made a generalist response that also takes into account _children_, not adults. Engineering students mostly just study the theoretical Brayton cycle, so trust me, they're not falling behind by being ignorant about turbines.
