JZ I have been watching your excellent videos for several years. I’m a retired avionics/aircraft instrument technician. I worked on a lot of gyros for many years. The air driven ones used buckets cut in about a 1.5 inch brass rotor. The rotor turned normally around 17,000 rpm with 5 PSI of air pressure. Others were electric and turned more like 26,000 rpm. We overspeeded some of the air driven ones in excess of 300,000 rpm and they never exploded unless we put cracks in them with a chisel. Interesting stuff. Keep up the great teaching my friend.
I think it is very convenient for the engineers that those small structures reach speeds needed to function long before they ever get to speeds where the forces might cause damage. I want a small air powered gyro mechanism that I can turn into a desk toy. What would you like in trade?
When damage or wear is beyond limits: for sure. Sometimes it is more economical to replace instead of repair if the owner has surplus blades. Usually it's less expensive to repair if the damage is within acceptable limits.
Yeah , I was just thinking quite how much time and effort goes into finishing each of those blades and how many blades there are in one engine, that's a LOT of polishing!
My Dad would come home every p.m. telling how many (or few) compressor blades he had hand FILED and balanced (by intuition) that shift. Son of J-79 Mechanic ( F &S Grade ) Bob Duda
It is nice to see what polishing and some filing can do for an entire engine! However, seeing that whole thing wobbling while you are polishing it gives me goosebumps all over the body. As usual, thank you for a great video!
Tolerance for blade weight is quite high.. they vary a lot. But the final assembly is balanced... so it's balanced. Dimensional tolerances are within a smaller range, but for aerodynamic reasons, not for weight.
Your comment reminded me of the argument about lift as being a reaction as opposed to a pull due to low pressure. There is a book that is titled "Lift Doesn't Suck". I've never read it, but I intend to at some point and add it to my reference library. Looks like good reading. I just figured I'd pass that on if you were interested.
AgentJayZ said there is no such thing as thing as suction, he directed me to the NASA website to see the physics of what and why, I was confused by, but now understand
I do an awful lot of tool and die polishing at this point in my life. I use small stones instead of emery cloth, but this process you're doing is similar. I have to feel for imperfections, blend them in, and put a mirror finish on them. I use 320 and 400 stones of various compositions. Your fingers do get really sore, dirty, and sometimes cut up. I appreciate the commentary about power tools. The primates I work with screw up precision tooling with die grinders and send it to the customers.
They are very tough. Designed to run at 8000rpm. If you drop one, some minor damage will occur, which you have to inspect for, find, and repair. Plus you live with the shame of being a ham-fisted dumbass.
I work next door to a Titanium forge in the UK (Wyman and Gordon) that makes the shafts. Sounds like a Dinosaur is walking when they are forging. The vibrations makes the floor bounce. They have to stop at night because the houses nearby shake.
The balance machine is a two-plane computerized deal, that makes it easier, but not easy, to determine where to put the weights. Balancing a rotor like this can take a day or two.
The contamination is reducing the aerodynamic performance of the blades, so you need to burn more fuel in order to get the same amount of compressed air from the compressor. This means a higher than expected EGT for a given power output, and the max power, being limited by EGT, will be less than expected. If the deposits won't come off by manual scrubbing, the blades ( and stators ) will need to be removed for chemical or media blasting treatment. We work on Saturns.
I have often worked out the vectors required to find the "angle of attack" of the the blade with the axis of the engine, but I never worked it out for a series of compressor disc following each other as the pressure/ temp rises. Looking at these compressors with multi stage at the same time, I see that the angle of attack of the set of blades on the compressor stages is almost the same. Presumably it is the stator blades that are critical in feeding the vector of the air in the oncoming blades, I suppose that is the reason they make some stator blades variable so that they would adjust the relative direction to suit the leaving trailing edges and the entry into the next set to increase efficiency. Would love to see thise effect through a glass pane and a stroboscope. The hidden beauty in a jet engine is brought forward so nicely by this gentleman presenter of this series, he is an expert in every way.
Carmel Pule' You are a very smart observer to have worked that out on your own. Most introductory gas turbine books go into some detail about airflow direction and vectors, and also discuss stator function.
AgentJayZ Thank you, I teach engineering but when I was young I worked at Chatham Dockyard on the first Turbine Ship HMS Exmouth which had an Olympus at the centre and two Proteus modifies for Naval work. I have never gone into the details that you cover, I have a lot to learn from you Thank you for these videos, Brilliant in every way, You will make a great University Lecturer at the manner in which you present these complex machines. You know every nook and cranny and al detail about their function. Your clients are in good hands, congratulations.
AgentJayZ, got a question about reworking compressor blade. I'm a flight line guy and our books give a limits as to what we can repair before its an engine change, "nicks and dents" What I am curious about is just how much can be removed from the leading edge before the blade is scrapped. Is there a minimum blade width that must be retained as with propeller blade? Sorry if its too vague of a question.
The engine overhaul manual gives a great deal of very specific information on repair limits, shapes, locations and dimensions for both compressor and turbine blades.
Thanks. That's what I figured. Our back shop doesn't do compressor tear down/over haul. They just remove and replace the module if it bad. It was just out of curiosity.
There's no room, and if you ram against a corner, a rag would not stop the cut. Leather would, but there's no room for cushioning. Plus as we've discussed before, even adding a few seconds of setup to each blade's rework adds up to hours or days when multiplied by the many hundreds of total blades. What is required is skill.
Interesting video. Reminds me of Surfboards. Surfboard shapers, fiber glassers, and finishers try to make surfboards as smooth as possible, similar to automobile body and fender repair people. For a while, Surfboard shapers were intentionally putting golf ball type dimples in the bottoms of surfboards. I don't think it worked well, so they stopped. Also reminds me of Sailboards. Sailboard shapers, fiber glassers and finishers try to make the bottoms of sailboards as smooth as possible. My thoughts always were, when you are pushing a sailboard through choppy water at 15-25 mph, it doesn't make a difference if the bottom is smooth, has a few dents or dimpled. There is so much chop and water running under the board, I would think a smooth bottom or dimpled bottom wouldn't make a difference. But some people are fussy about smooth surfaces. Another example of smooth or rough, the finish of an Unlimited Reno Air Racer Mustang like Dago Red, Voodoo etc. They paint and polish all the surfaces to be smooth. Compare that to an F-16 Falcon Military Fighter Aircraft which has a rough surface. Which one has more or less drag due to the surface or does it matter?
Just did a interview / test for a company that rebuilds tubine engines and gave me a welded blade to grind down. I think the min / max was 0.0740 - 0.0840 I came from a line of bodyshops This stuff is all new to me But looks like fun to learn Hardest part was the inner angle of the blade and the weld on it
Your videos are just great! Can't stop watching them.. Is there anyway I could get a rejected turbine or compressor blade? Thanks and keep on with your videos ;-)
Each blade has a leading edge covered with thousands of defects. We are removing all of them. Blending is filing and sanding, so it is removing material.
There are so many variables, a short and definite answer is not possible. It looks like the dents on the edge of thse blades may have been caused by ice, because the second stage showed none. If they were from rocks of a certain size, they would also mark up blades all the way through. Sand does scar up the blades of all stages, but this did not happen in this compressor.
File cost 6 bucks, and is quite a bit tougher than the titanium. Restored Orenda 14 for youur jetfighter will run you half a million, sir. ..Plus a file, so add six bucks.
I would guess the reason that the "underside" is not normally called the "working face" is that, just like with airplane wings, the upper (convex) side actually does about two thirds of the work. Obviously the "pressure face" still suffers more impacts. I guess more recent designs have more advanced airfoils, and yes, lower blade drag per "lift" (i. e. per air-shoving capacity) will require less power to move the same amount of air, making the engine more efficient.
Thanks to you! I wonder how many times a single blade can be polished? And how often this work done need to be balanced?This took me back when working jewerley, the rough file and later finer and finer sand paper.Later to the wheels for finer work.One of viewers said the work done with files, he states the file should work one way only.And I learned that a long time ago, I was about 20 tears old when working at a jewelry shop. Thanks and appreciate your vieos,great work!!!
These are not golf balls, and their job is not to travel anywhere with minimum drag. A huge amount of aerodynamic drag is produced when these blades do their job. They accelerate vast amounts of air (100 lbs/sec) rearwards and shove it into the second stage of compression. This compressor rotor requires 20 thousand Hp to keep turning at 8000 rpm.
Now I just want to know how the computer works that out as well. I have a feeling this rabbit hole goes a long, long way down... I'm actually kind of amazed it only takes a day or two.
My dream job... doing camera/lighting/sound for your videos... they are amazing already but imagine how sweet they would be if you didn't have to worry about all that stuff on top of whatever's going on. I'm cheap! You can give me a closet to sleep in or whatnot. I might have to bring some cats depending on how mad my wife gets tho
I won't comment on Bernoulli-vs-deflection lift... but the last part of your comment is not correct. Although modern compressors achieve the same compression with fewer stages, they are not more efficient in terms of compressed air delivered per W consumed. Modern engines are more fuel efficient (TSFC in lbs of fuel used /hour, per pound of thrust) due to three things: better air seals allowing greater compression, higher firing temp, and better match of exhaust velocity and aircraft speed.
There are many good training centers all over your country and mine. I do believe you will be a much better tech if you have the knowledge that distinguishes the professional from the OTJ-trained individual, who does not know what he missed by not learning it.
Your a unique individual I can tell. LOL I' just started living in SD . I became a regular guy-- almost. In Arkansas I could have hooked you up. How are they for a knife? Are the titanium? Or what.
Do you get paid the scrap value for damaged or defective blades? I would SERIOUSLY love to buy an old compressor blade of any type from you. Love your videos btw!
When I went to west Vancouver secondary school we had an old DC8 jet engine in the power mechanics shop (back when they actually taught such things)I think every kid who took the class had a blade kicking around in a junk drawer at home.....
Enjoyed the vid as always. I acutally had the same thought as Films4you about the dimples. but i think the dimples were not there to reduce drag but to give a more laminar flow. Of course that statement is probably completly wrong and its entirly possible that I just made it up! I was wondering if a blade that had been worked on like this would still be allowed to be fitted to a commercial plane? By the way I love that your videos dont treat the viewer like they are completly thick!
Hi Jay, Once you're done working these blades, I presume you'll have to balance the rotor. If so, do you have to disassemble and do it a stage at a time, or can you spin up the whole rotor assembly and balance as one piece? If that is again the case, how does one determine where to add or remove weight along the length of the assembly? I imagine easy enough to figure out where it belongs radially, but is axial (?) position important too? Thanks again for all these videos. They're awesome.
Like most things in physics it probably isn't much more than some linear algebra and/or some differential equations. Linear algebra is more like a pot hole than a rabbit hole, but the differential equations?
kimberly clark makes cut resistant polyurathane coated ( oil proof) reusable work glove that might work well to prevent a gouged thumb. can't say it wont hurt like a dickens but might save money on bandages. :) think the're called g60 level three cut resistant
up to which stage of the compressor usually there are heavy dents on the blades' leading edge? does the centrifugal force push the debris out of the way of the blades of the deepest compressor stages?
I really appreciate your videos and have a variety of gas turbine projects. One of my Solar Saturn gas turbines had a higher than normal exaust gas temperature when it was operating. On inspection of the intlet section, the airfoil side the 410 SST first stage compressor blades felt rough and look crusty and I was wondering how I could clean them. My other two Saturn turbines have much smoother compressor blades. Could compressor airfoil surface roughness be a cause of this higher EGT?
AgentJayZ at 24:01 every microsecond....the mental stress of the high risk of using a machine tool for extended periods on fine surfaces makes it a miserable work experience....better to do it slow manually like you said
I have to ask....Why do the blades have to be able to move? A stress countermeasure, or a thermal / compensatory / expansion measure? Or am I missing the point? Extremely interesting stuff.
If they are rigid in their mounts, they can resonate like a tuning fork, Without the damping of a loose mount, the vibration can lead to cracking and failure.
You mentioned that the blades on this model are irreplaceable - no spares left. This is a 6 yearold video. With today's seemingly magical manufacturing techniques, is it now possible for a company somewhere to scan a healthy blade and duplicate it? Probably not by 3-D printing, but maybe some version of CNC?
This might not be the place to ask this question but I do appreciate your input . I work at an airport, and sometimes when the jets are sitting on the ramp hooked up to the jet bridges at night and it's windy out, the blades on the jet engines "windmill" and I can hear what sounds like the tips of the turbine blade tips hitting or scraping the turbine housing. Sometimes it's a tic tic tic as its spinning , and sometimes it's multiple tics at the same time. Can you please tell me what that sound might be? Thank you for your vids, I do enjoy them immensely 😊
It may be exactly what you said, or it could be compressor blades. The tip clearances in modern engines is very tight, and there are mechanisms in place, like GEs Active Clearance Control, to maintain a tip clearance in the HP comprerssor at as close to zero as possible...
I thought (was hoping) that the clicking was due to the looseness of the 'spruce' anchors which enable the blades to wiggle a bit. Wouldn't the blades scrape around the inside perimeter if there was less than zero clearance?
How tight tolerances do you have for physical dimensions and weight of those blades? Vibrations are always a big problem on high revolutions in any machine.
why you are working on the whole span of LE not only the area with defect? are you using any requrements from manual? how about root fillet, are you removing there some material as well during blending?
Titanium blades on a compressor with no replacement possible?! An archeological relic in 2 ways. For sure never let power tools near these. Question: do you use power tools at any stage of engine disassembly / reassembly?
If a blade breaks, which is very unlikely, there would be a lot of damage in the stages behind it. With this particular engine, we would try to find a donor engine. If not... no you would not run an engine with compressor or turbine blades missing in an attempt to achieve balance.
To which point one refurbishes a compressor blades?, as in, the process reduces sayd blade surface area , to which a compressor with the most part of compressor blade's which are refurbished would yield noticeable thrust readings for given rpm if it can start and then idle, all this being obvious. My question is to which point diminishing returns "appear", "point" at compressor would have to spin faster as a new bladed one. PS: Your compressor stall vajeyo is epic, if it were me ,I am not sure I could decently match yours.
Compressors are not used by the engine to produce thrust. Compressors are designed with a bit of "margin" to allow for the minor losses cause by blending blades. Minor is the word. The overhaul manuals have very strict limits and dimensions for repairing compressor and turbine blades. At a maximum, a repaired blade which is deemed serviceable might have lost 2 or 3 percent of its performance. A compressor made up of 100% blended blades will have no noticeable loss in efficiency compared to one made of all new blades. That's what the limits are for...
I did a quick calculation on the force that would exist on a half-pound blade rotating at 10000 RPM with a radius of 3 feet. It calculates to about 50000 pounds of force pulling on it, if I did it right.
You are right, except the radius should be about 12 inches of so ( from the center of rotation to about halfway along the length of the blade), and the speed would be about 7500 rpm. Also, for compressor blades, the weight is less, but your estimate is close for the turbine blades in this engine.
Very interesting topic. Ok here comes the silly question, could not you make a special tool to work with the blades without hurting your fingers and go faster? It shouldn't be necessary an electric tool, only one that makes the job easier. Have seen in other videos that you can make your own tools... Regards and thank you for sharing all this knowledge.
The tool you are referring to is a piece of scotch brite or sandpaper on a stick. At the time of making this video, I had to endure working with a blowhard who actually claims to have invented the stick. Classic self-obsessed braggart. Thankfully those days are in the past.
The assembly weighs about 200 Kg. The weight removed by the filing is in the milligrams. So... in the parts per million. Blending a couple of blades is allowed by the procedures in the overhaul manual.
Those are compressor blades, so no. The amount of blending done on an assembled rotor is miniscule. Any serious repairs or replacements would require another balancing procedure to be undertaken.
Perhaps you've covered this previously, but: do you have an opinion re. Rolls Royce's titanium fan blades vs. General Electric's ceramic matrix composite blades? Thanks.
Dang! You got me. I realized after making this video that the first couple of stages in the Orenda compressor are stainless steel. I never remade the video. I think I made this same public admission quite a few years ago...
Thanks for the reply , just an fyi for you the rotor blades stg 123 are material spec AMS 5613, i am wondering the Hawk one jet that you started up ,was the engine ser # 2919 ??
+Brian Graves Golf balls are golf balls... as far as I know, they are not components of jet engines. My interest in golf balls is over now. If you want to know more about golf balls, maybe you should check the golf ball channel. Or maybe the ball channel. Balls in general... I guess.
The dimples on a golf ball reduce the vortexing on the trailing side of the ball and therefore reduce ball drag. That was my guess on why they don't bother putting a polish on the turbine blades. Especially given the immense lengths and costs they put into making every single one of these blades. It would seem silly.
A less condescending answer would be "Well, the skin friction caused by the dimpling on the turbine blades would cause more drag than than that caused by of any vortexing on the trailing edge and outer trips of the turbine blade. While reducing this effect is helpful on low speed and more bluntly shaped objects such as cars, wind turbine blades, passenger jets, and golf balls, it only adds more drag than is reduced on sharply shaped and high speed objects as turbine blades" It took me modeling up these shapes and using flow modeling in solidworks to answer this question for myself. Thanks anyways. Keep making videos. Been watching them for years.
Solidworks fluid modelling is very coarse, and it cannot be accurate for complex flows(compressible, turbulent flows and rotating reference frames). You must use simulation softwares designed to simulate compressor flows.
Hi Jay. I am looked your videos. I am envy because of you can work with turbine blades. Actually I doing slurry mixer and my propeller is almost quality of jet engine :D it is amazing how bad version of propellers are agricultural sector. Please check my home page www.tikkasenpaja.fi/l4 It is by English language. When I looked you work with smooth leading edge and whole blades. I can see that is nice work just like make for me :) Do you need worker who have eager work with blades?Last year I was in exhibition AgriTechnica in Germany, there was spraying machine were a big fan making airflow to sprayed chemicals . The fan was made aluminium and leading edge was spoiled by bad grinding work. the worker was grind leading edges after mold work. My heart bleeding when I saw the fan, it was made in USA. but never figure out where or what company.
Your videos are just great! Can't stop watching them.. Is there anyway I could get a rejected turbine or compressor blade? Thanks and keep on with your videos ;-)
Thank you for your time, effort and patience in producing these videos, it is very much appreciated.
JZ I have been watching your excellent videos for several years. I’m a retired avionics/aircraft instrument technician. I worked on a lot of gyros for many years. The air driven ones used buckets cut in about a 1.5 inch brass rotor. The rotor turned normally around 17,000 rpm with 5 PSI of air pressure. Others were electric and turned more like 26,000 rpm. We overspeeded some of the air driven ones in excess of 300,000 rpm and they never exploded unless we put cracks in them with a chisel. Interesting stuff. Keep up the great teaching my friend.
I think it is very convenient for the engineers that those small structures reach speeds needed to function long before they ever get to speeds where the forces might cause damage. I want a small air powered gyro mechanism that I can turn into a desk toy. What would you like in trade?
still love your series! amt's everywhere appreciate u good sir! 💯
Your patience amazes me Jay.
Well, I could be better, but I am always improving... I hope, anyway!
When damage or wear is beyond limits: for sure.
Sometimes it is more economical to replace instead of repair if the owner has surplus blades.
Usually it's less expensive to repair if the damage is within acceptable limits.
Liked, favourited, subscribed!
It is *amazing* you are showing *HOW much work and attention* goes into maintaining engines/aircraft!
Yeah , I was just thinking quite how much time and effort goes into finishing each of those blades and how many blades there are in one engine, that's a LOT of polishing!
My Dad would come home every p.m. telling how many (or few) compressor blades he had hand FILED and balanced (by intuition) that shift.
Son of J-79 Mechanic ( F &S Grade )
Bob Duda
It is nice to see what polishing and some filing can do for an entire engine! However, seeing that whole thing wobbling while you are polishing it gives me goosebumps all over the body. As usual, thank you for a great video!
You sir, have the patience of Jobe. Thank you for the very clear reasoning why it is done by the way you demonstrated
Excellent demonstration of blending and finishing the blades.
Tolerance for blade weight is quite high.. they vary a lot. But the final assembly is balanced... so it's balanced.
Dimensional tolerances are within a smaller range, but for aerodynamic reasons, not for weight.
these are very valuable videos with good information
Your comment reminded me of the argument about lift as being a reaction as opposed to a pull due to low pressure. There is a book that is titled "Lift Doesn't Suck". I've never read it, but I intend to at some point and add it to my reference library. Looks like good reading. I just figured I'd pass that on if you were interested.
AgentJayZ said there is no such thing as thing as suction, he directed me to the NASA website to see the physics of what and why, I was confused by, but now understand
You have found the time for all of you videos, this is very difficult! thank you for you job!
Another outstanding post. There's nothing like human touch.
I do an awful lot of tool and die polishing at this point in my life. I use small stones instead of emery cloth, but this process you're doing is similar. I have to feel for imperfections, blend them in, and put a mirror finish on them. I use 320 and 400 stones of various compositions. Your fingers do get really sore, dirty, and sometimes cut up. I appreciate the commentary about power tools. The primates I work with screw up precision tooling with die grinders and send it to the customers.
They are very tough. Designed to run at 8000rpm. If you drop one, some minor damage will occur, which you have to inspect for, find, and repair. Plus you live with the shame of being a ham-fisted dumbass.
I work next door to a Titanium forge in the UK (Wyman and Gordon) that makes the shafts. Sounds like a Dinosaur is walking when they are forging. The vibrations makes the floor bounce. They have to stop at night because the houses nearby shake.
Me: watches and thinks "interesting"
my brain: "all those blades go SPIN SPIN"
The balance machine is a two-plane computerized deal, that makes it easier, but not easy, to determine where to put the weights. Balancing a rotor like this can take a day or two.
The balancing process and equipment are off-limits, for fear of the large and vocal population of "experts" out there deluging me with their "advice".
The contamination is reducing the aerodynamic performance of the blades, so you need to burn more fuel in order to get the same amount of compressed air from the compressor.
This means a higher than expected EGT for a given power output, and the max power, being limited by EGT, will be less than expected.
If the deposits won't come off by manual scrubbing, the blades ( and stators ) will need to be removed for chemical or media blasting treatment.
We work on Saturns.
only AgentJayZ can make watching sanding interesting
I have often worked out the vectors required to find the "angle of attack" of the the blade with the axis of the engine, but I never worked it out for a series of compressor disc following each other as the pressure/ temp rises. Looking at these compressors with multi stage at the same time, I see that the angle of attack of the set of blades on the compressor stages is almost the same. Presumably it is the stator blades that are critical in feeding the vector of the air in the oncoming blades, I suppose that is the reason they make some stator blades variable so that they would adjust the relative direction to suit the leaving trailing edges and the entry into the next set to increase efficiency.
Would love to see thise effect through a glass pane and a stroboscope. The hidden beauty in a jet engine is brought forward so nicely by this gentleman presenter of this series, he is an expert in every way.
Carmel Pule' You are a very smart observer to have worked that out on your own. Most introductory gas turbine books go into some detail about airflow direction and vectors, and also discuss stator function.
AgentJayZ Thank you, I teach engineering but when I was young I worked at Chatham Dockyard on the first Turbine Ship HMS Exmouth which had an Olympus at the centre and two Proteus modifies for Naval work. I have never gone into the details that you cover, I have a lot to learn from you Thank you for these videos, Brilliant in every way, You will make a great University Lecturer at the manner in which you present these complex machines. You know every nook and cranny and al detail about their function. Your clients are in good hands, congratulations.
that aerokroil is some good stuff. works great on seized bolts
AgentJayZ, got a question about reworking compressor blade. I'm a flight line guy and our books give a limits as to what we can repair before its an engine change, "nicks and dents" What I am curious about is just how much can be removed from the leading edge before the blade is scrapped. Is there a minimum blade width that must be retained as with propeller blade? Sorry if its too vague of a question.
The engine overhaul manual gives a great deal of very specific information on repair limits, shapes, locations and dimensions for both compressor and turbine blades.
Thanks. That's what I figured. Our back shop doesn't do compressor tear down/over haul. They just remove and replace the module if it bad. It was just out of curiosity.
Good explain nice understanding english and good job
There's no room, and if you ram against a corner, a rag would not stop the cut. Leather would, but there's no room for cushioning. Plus as we've discussed before, even adding a few seconds of setup to each blade's rework adds up to hours or days when multiplied by the many hundreds of total blades.
What is required is skill.
i worked on airfoils for 15 years we had a polish dept and airfoils were polish with 10 micron and called convex and concave
Interesting video. Reminds me of Surfboards. Surfboard shapers, fiber glassers, and finishers try to make surfboards as smooth as possible, similar to automobile body and fender repair people. For a while, Surfboard shapers were intentionally putting golf ball type dimples in the bottoms of surfboards. I don't think it worked well, so they stopped. Also reminds me of Sailboards. Sailboard shapers, fiber glassers and finishers try to make the bottoms of sailboards as smooth as possible. My thoughts always were, when you are pushing a sailboard through choppy water at 15-25 mph, it doesn't make a difference if the bottom is smooth, has a few dents or dimpled. There is so much chop and water running under the board, I would think a smooth bottom or dimpled bottom wouldn't make a difference. But some people are fussy about smooth surfaces.
Another example of smooth or rough, the finish of an Unlimited Reno Air Racer Mustang like Dago Red, Voodoo etc. They paint and polish all the surfaces to be smooth. Compare that to an F-16 Falcon Military Fighter Aircraft which has a rough surface. Which one has more or less drag due to the surface or does it matter?
Just did a interview / test for a company that rebuilds tubine engines and gave me a welded blade to grind down. I think the min / max was 0.0740 - 0.0840 I came from a line of bodyshops This stuff is all new to me But looks like fun to learn Hardest part was the inner angle of the blade and the weld on it
Enjoyed the video! Thanks again!
Darren
Very interesting as always.
Thanks
Thanks for sharing...Nice vid and skill sharing
Your videos are just great! Can't stop watching them.. Is there anyway I could get a rejected turbine or compressor blade? Thanks and keep on with your videos ;-)
I have managed to find a mounted compressor blade from a 757-200 RR RB-211 engine from Ebay to reach me soon, maybe look there.
Each blade has a leading edge covered with thousands of defects. We are removing all of them.
Blending is filing and sanding, so it is removing material.
Awsome, I'm not a jet engine mechanic but I was just curious about that sound.
Mostly on Boeing 757 engines but hardly on Boeing 737's
Thanks again
There are so many variables, a short and definite answer is not possible. It looks like the dents on the edge of thse blades may have been caused by ice, because the second stage showed none.
If they were from rocks of a certain size, they would also mark up blades all the way through.
Sand does scar up the blades of all stages, but this did not happen in this compressor.
File cost 6 bucks, and is quite a bit tougher than the titanium. Restored Orenda 14 for youur jetfighter will run you half a million, sir. ..Plus a file, so add six bucks.
I would guess the reason that the "underside" is not normally called the "working face" is that, just like with airplane wings, the upper (convex) side actually does about two thirds of the work. Obviously the "pressure face" still suffers more impacts. I guess more recent designs have more advanced airfoils, and yes, lower blade drag per "lift" (i. e. per air-shoving capacity) will require less power to move the same amount of air, making the engine more efficient.
Thanks to you! I wonder how many times a single blade can be polished? And how often this work done need to be balanced?This took me back when working jewerley, the rough file and later finer and finer sand paper.Later to the wheels for finer work.One of viewers said the work done with files, he states the file should work one way only.And I learned that a long time ago, I was about 20 tears old when working at a jewelry shop. Thanks and appreciate your vieos,great work!!!
These are not golf balls, and their job is not to travel anywhere with minimum drag.
A huge amount of aerodynamic drag is produced when these blades do their job.
They accelerate vast amounts of air (100 lbs/sec) rearwards and shove it into the second stage of compression.
This compressor rotor requires 20 thousand Hp to keep turning at 8000 rpm.
Thanks Jay
Now I just want to know how the computer works that out as well.
I have a feeling this rabbit hole goes a long, long way down...
I'm actually kind of amazed it only takes a day or two.
My dream job... doing camera/lighting/sound for your videos... they are amazing already but imagine how sweet they would be if you didn't have to worry about all that stuff on top of whatever's going on. I'm cheap! You can give me a closet to sleep in or whatnot. I might have to bring some cats depending on how mad my wife gets tho
I won't comment on Bernoulli-vs-deflection lift... but the last part of your comment is not correct. Although modern compressors achieve the same compression with fewer stages, they are not more efficient in terms of compressed air delivered per W consumed.
Modern engines are more fuel efficient (TSFC in lbs of fuel used /hour, per pound of thrust) due to three things: better air seals allowing greater compression, higher firing temp, and better match of exhaust velocity and aircraft speed.
There are many good training centers all over your country and mine.
I do believe you will be a much better tech if you have the knowledge that distinguishes the professional from the OTJ-trained individual, who does not know what he missed by not learning it.
Your a unique individual I can tell. LOL I' just started living in SD . I became a regular guy-- almost. In Arkansas I could have hooked you up. How are they for a knife? Are the titanium? Or what.
Do you get paid the scrap value for damaged or defective blades? I would SERIOUSLY love to buy an old compressor blade of any type from you. Love your videos btw!
When I went to west Vancouver secondary school we had an old DC8 jet engine in the power mechanics shop (back when they actually taught such things)I think every kid who took the class had a blade kicking around in a junk drawer at home.....
Enjoyed the vid as always.
I acutally had the same thought as Films4you about the dimples. but i think the dimples were not there to reduce drag but to give a more laminar flow.
Of course that statement is probably completly wrong and its entirly possible that I just made it up!
I was wondering if a blade that had been worked on like this would still be allowed to be fitted to a commercial plane?
By the way I love that your videos dont treat the viewer like they are completly thick!
Man I want a blade 😍
+ripfletching No sell. Trade. Cool stuff only.
Hi Jay,
Once you're done working these blades, I presume you'll have to balance the rotor. If so, do you have to disassemble and do it a stage at a time, or can you spin up the whole rotor assembly and balance as one piece?
If that is again the case, how does one determine where to add or remove weight along the length of the assembly? I imagine easy enough to figure out where it belongs radially, but is axial (?) position important too?
Thanks again for all these videos. They're awesome.
Love these videos.
Do you throw all of your oily rags away or do you have a washing machine in the back of the shop, perhaps by the kettle?
I assume that when your done you balance it and the blade positions will change.
Like most things in physics it probably isn't much more than some linear algebra and/or some differential equations. Linear algebra is more like a pot hole than a rabbit hole, but the differential equations?
kimberly clark makes cut resistant polyurathane coated ( oil proof) reusable work glove that might work well to prevent a gouged thumb. can't say it wont hurt like a dickens but might save money on bandages. :) think the're called g60 level three cut resistant
AgentJayZ the surface roughness at
16:09 might be a deliberate omission by
engine designers, to facilitate micro turbulence
up to which stage of the compressor usually there are heavy dents on the blades' leading edge? does the centrifugal force push the debris out of the way of the blades of the deepest compressor stages?
I really appreciate your videos and have a variety of gas turbine projects.
One of my Solar Saturn gas turbines had a higher than normal exaust gas temperature when it was operating.
On inspection of the intlet section, the airfoil side the 410 SST first stage compressor blades felt rough and look crusty and I was wondering how I could clean them. My other two Saturn turbines have much smoother compressor blades.
Could compressor airfoil surface roughness be a cause of this higher EGT?
AgentJayZ at 24:01 every microsecond....the mental stress of the high risk of using a machine tool for extended periods on fine surfaces makes it a miserable work experience....better to do it slow manually like you said
when does a blade have to be replaced? Different evaluations for aircraft and ground engines ?
how delicate are the blades? if a blade falls from your hands on the floor when working on it do you expect damage or are they sturdy enough?
I have to ask....Why do the blades have to be able to move? A stress countermeasure, or a thermal / compensatory / expansion measure? Or am I missing the point? Extremely interesting stuff.
If they are rigid in their mounts, they can resonate like a tuning fork, Without the damping of a loose mount, the vibration can lead to cracking and failure.
Thank you kindly....
always start with hand tools first get good then you can work on getting fast
You mentioned that the blades on this model are irreplaceable - no spares left.
This is a 6 yearold video. With today's seemingly magical manufacturing techniques, is it now possible for a company somewhere to scan a healthy blade and duplicate it? Probably not by 3-D printing, but maybe some version of CNC?
3D printing is amazing. Now, cool old stuff can live forever.
@@AgentJayZ Awesome... so now you can get replacement blades again?
This might not be the place to ask this question but I do appreciate your input
.
I work at an airport, and sometimes when the jets are sitting on the ramp hooked up to the jet bridges at night and it's windy out, the blades on the jet engines "windmill" and I can hear what sounds like the tips of the turbine blade tips hitting or scraping the turbine housing.
Sometimes it's a tic tic tic as its spinning , and sometimes it's multiple tics at the same time.
Can you please tell me what that sound might be?
Thank you for your vids, I do enjoy them immensely 😊
It may be exactly what you said, or it could be compressor blades. The tip clearances in modern engines is very tight, and there are mechanisms in place, like GEs Active Clearance Control, to maintain a tip clearance in the HP comprerssor at as close to zero as possible...
I thought (was hoping) that the clicking was due to the looseness of the 'spruce' anchors which enable the blades to wiggle a bit. Wouldn't the blades scrape around the inside perimeter if there was less than zero clearance?
How tight tolerances do you have for physical dimensions and weight of those blades? Vibrations are always a big problem on high revolutions in any machine.
why you are working on the whole span of LE not only the area with defect? are you using any requrements from manual? how about root fillet, are you removing there some material as well during blending?
Why not use a buffing wheel with a rubbing compound?
Titanium blades on a compressor with no replacement possible?! An archeological relic in 2 ways. For sure never let power tools near these. Question: do you use power tools at any stage of engine disassembly / reassembly?
Cripes! How do you have time for anything else if you have 1,000 of those to do!?
So where would you recommend someone going to school to become a jet engine tech.
The weight removed during refurbishing isn't critical?
IF a blade -would- break for whatever the reason the only way to get "away" from that would be to remove the direct opposite side blade as well?
If a blade breaks, which is very unlikely, there would be a lot of damage in the stages behind it.
With this particular engine, we would try to find a donor engine. If not... no you would not run an engine with compressor or turbine blades missing in an attempt to achieve balance.
AgentJayZ Yea of course a donor engine, didn´t thought about that could be an option. Ok thanks!
you're doing this for 8 hours a day for 7 days?
To which point one refurbishes a compressor blades?, as in, the process reduces sayd blade surface area , to which a compressor with the most part of compressor blade's which are refurbished would yield noticeable thrust readings for given rpm if it can start and then idle, all this being obvious.
My question is to which point diminishing returns "appear", "point" at compressor would have to spin faster as a new bladed one.
PS: Your compressor stall vajeyo is epic, if it were me ,I am not sure I could decently match yours.
Compressors are not used by the engine to produce thrust. Compressors are designed with a bit of "margin" to allow for the minor losses cause by blending blades. Minor is the word. The overhaul manuals have very strict limits and dimensions for repairing compressor and turbine blades. At a maximum, a repaired blade which is deemed serviceable might have lost 2 or 3 percent of its performance.
A compressor made up of 100% blended blades will have no noticeable loss in efficiency compared to one made of all new blades. That's what the limits are for...
I did a quick calculation on the force that would exist on a half-pound blade rotating at 10000 RPM with a radius of 3 feet. It calculates to about 50000 pounds of force pulling on it, if I did it right.
You are right, except the radius should be about 12 inches of so ( from the center of rotation to about halfway along the length of the blade), and the speed would be about 7500 rpm. Also, for compressor blades, the weight is less, but your estimate is close for the turbine blades in this engine.
Very interesting topic. Ok here comes the silly question, could not you make a special tool to work with the blades without hurting your fingers and go faster? It shouldn't be necessary an electric tool, only one that makes the job easier. Have seen in other videos that you can make your own tools... Regards and thank you for sharing all this knowledge.
The tool you are referring to is a piece of scotch brite or sandpaper on a stick. At the time of making this video, I had to endure working with a blowhard who actually claims to have invented the stick. Classic self-obsessed braggart.
Thankfully those days are in the past.
you seem to work on weekends a lot ... so much work to do ?
Noob question here! How can you do this without rebalance of the specific rotor assembly? Especially if your doing two or three together.
The assembly weighs about 200 Kg. The weight removed by the filing is in the milligrams. So... in the parts per million.
Blending a couple of blades is allowed by the procedures in the overhaul manual.
Does filing away at the blades have an effect on the balance of the turbine?
Those are compressor blades, so no. The amount of blending done on an assembled rotor is miniscule. Any serious repairs or replacements would require another balancing procedure to be undertaken.
Do you polish the new blades, or do you install them as they come to you , i.e. a little bit rough?
New ones we use as they arrive. These ones we polished a bit, because it seemed like the right thing.
@@AgentJayZ I really appreciate you taking the time to reply, thank you for producing these informative and fascinating videos.
Has anyone any idea how much a titanium blade (as the one he works at) costs? Ruffuly.
Thanks.
he explains why in the video...
where does al the dust go?
Perhaps you've covered this previously, but: do you have an opinion re. Rolls Royce's titanium fan blades vs. General Electric's ceramic matrix composite blades?
Thanks.
GE does not use ceramic matrix composite fan blades. So empty set.
Ah yes, that was careless of me. I meant carbon composite, as on the GE90.
Hi, you sure they are titanium blades, for i think the orenda OT-F-3 engine never used them, stg 1-2-3-9-10 where all steel.
Dang! You got me. I realized after making this video that the first couple of stages in the Orenda compressor are stainless steel. I never remade the video.
I think I made this same public admission quite a few years ago...
Thanks for the reply , just an fyi for you the rotor blades stg 123 are material spec AMS 5613, i am wondering the Hawk one jet that you started up ,was the engine ser # 2919 ??
That poor file. A file is only supposed to be drawn one way. Running it back and forth while in contact will shorten the files life.
Did you delete my comments?
16:28 What about golf balls?
+Brian Graves Golf balls are golf balls... as far as I know, they are not components of jet engines. My interest in golf balls is over now. If you want to know more about golf balls, maybe you should check the golf ball channel. Or maybe the ball channel. Balls in general... I guess.
The dimples on a golf ball reduce the vortexing on the trailing side of the ball and therefore reduce ball drag. That was my guess on why they don't bother putting a polish on the turbine blades. Especially given the immense lengths and costs they put into making every single one of these blades. It would seem silly.
+Brian Graves Excellent. They are still golf balls, and no relevance here.
A less condescending answer would be "Well, the skin friction caused by the dimpling on the turbine blades would cause more drag than than that caused by of any vortexing on the trailing edge and outer trips of the turbine blade. While reducing this effect is helpful on low speed and more bluntly shaped objects such as cars, wind turbine blades, passenger jets, and golf balls, it only adds more drag than is reduced on sharply shaped and high speed objects as turbine blades" It took me modeling up these shapes and using flow modeling in solidworks to answer this question for myself. Thanks anyways. Keep making videos. Been watching them for years.
Solidworks fluid modelling is very coarse, and it cannot be accurate for complex flows(compressible, turbulent flows and rotating reference frames).
You must use simulation softwares designed to simulate compressor flows.
ebay. google. you're welcome. ;)
Hi Jay. I am looked your videos. I am envy because of you can work with turbine blades. Actually I doing slurry mixer and my propeller is almost quality of jet engine :D it is amazing how bad version of propellers are agricultural sector. Please check my home page www.tikkasenpaja.fi/l4 It is by English language. When I looked you work with smooth leading edge and whole blades. I can see that is nice work just like make for me :) Do you need worker who have eager work with blades?Last year I was in exhibition AgriTechnica in Germany, there was spraying machine were a big fan making airflow to sprayed chemicals . The fan was made aluminium and leading edge was spoiled by bad grinding work. the worker was grind leading edges after mold work. My heart bleeding when I saw the fan, it was made in USA. but never figure out where or what company.
Your videos are just great! Can't stop watching them.. Is there anyway I could get a rejected turbine or compressor blade? Thanks and keep on with your videos ;-)