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Wisdom does indeed come with age. I'm 43, and have been successfully using advanced simulation for the last 20 years, so hardly an inexperienced engineer in this realm.
Your airplane rivet failure example is interesting; a literal game of telephone. You got that story from a professor who got that story over the phone from their buddy, who likely got that story from the engineer responsible. So who knows how accurate that is? I would be surprised if they actually preformed fatigue simulation on the rivets themselves; the structure as a whole with representative rivets, sure, but not the actual rivets. So if the rivets failed, was the simulation really wrong? Or was an assumption wrong? Did they blindly trust simulation which lead to the rivet failure, or did they fail to validate the simulation? And if we're supposed to throw out theory per your earlier comments, why was the Boeing guy calling your engineering professor, the one who teaches theory?
Based on your comments, you seem to think I just run simulations, blindly trust them, and never validate them? That couldn't be further from the truth. Engineering simulations are a tool to arrive at a final design quickly and in an optimal manner. The "guess and check" method can lead to better designs, but at significant expense, far longer lead times, and the resulting design won't preform nearly as well as the simulation based design. The "guess and feel" method you've applied in your polishing doesn't work at all.
Regardless, I'm not sure how simulation crept into this thread. None of my comments about surface finish were based on simulation, just well accepted fluid dynamics principles that have been experimentally proven many times over.
Anyway, enough of the thread derailment from my side, I've got some real engineering to do!
enjoy the metaverse Billy.
It's much more likely the gains came from smoothing square edge and improving minor transitions than an actual polished surface. 😉
You cannot ignore Fluid Dynamic principles. Tested and very relevant. It doesn't matter what you feel. So much research has been done about boundary layer principles.
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In my opinion ceramic bearings offer less patristic drag and offer an advantage. however, that could be is offset by several external factors.
Interesting. Where do you stand on porting of cylinders to get more effect? Or just see it as a way to make it run cleaner/better?
I'm a high school drop out who's been building engines for engineers for three decades, I take everything they say with a grain of salt. To the topics at hand, PW 50s respond to fancy bearings well and polishing is supposed to reflect heat. Also, when match porting cylinders and cases its best to take a break and sleep on it, and look what you've done the next morning.
To be clear, all the talk above was around the surface finish, not the actual geometry. Altering flow geometry can certainly change things, and altering port heights changes the power curve, both for better or for worse depending on what was changed and what the goals are.
You're on to something! Take all the BS with a grain of salt.
Billy - try a 10 mg fluid dynamic based gummy inside the metaverse.
So airplanes never had structural failures before computer simulations? Interesting take
Huh? Is this directed at me? If so... it doesn't make any sense. Enlighten me on your point.
Here you go Billy... A real world Seminar around testing parts in the real world... and how they perform in the real world. Not the computer world.
You going to attend or live in the metaverse?
https://www.crystalinstruments.com/seminar-registration
It's interesting that @PTshox's example of FEA was a plane crash from 1988, when FEA was in it's infancy, and the fastest supercomputer, the Cray Y-MP who's 8 processors, had a combined processing power of 2.6GFLOPS. wow!
Any desktop computer from the last 10 years has more computing power, the latest Intel i9 has processing power of 1,228GFLOPS, the fastest supercomputer is now over 1,200,000GFLOPS.
Computing power in the late 80s would have only allowed rudimentary FEA, I doubt Boeing even used it to model rivet joints.
Back to the OP's question, ceramic bearing will make negligible difference, there are larger power losses between the crank and the rear wheel, the largest is the final drive.
It is directed at you. If you want to keep bashing sticks with rocks, I’m not going to try and convince you otherwise.
The thing about fluid modeling is it can be back checked with real fluid and is not some theoretical estimate of how many stress cycles an airplane rivet can endure. If folks want to fly in the face of hard facts, well this is Vmx.
There has been a lot of research validating computer models against tested rivet joint fatigue life, it is well understood, it's not the 1980s anymore.
I am sure it is. The problem is there is no way to replicate RW load cycle so it remains theory.
Funny the aerospace/plane topic should come up. One of my classmates did his graduate work for one of the aerospace companies and the topic title was something like "A study of crack propogation in thin aluminum sheeting".
Ah, the geeky things you remember from almost 40 years ago.😄
Pit Row
Strain gauges can be used to measure real world loads cycles, this data can be used to validate the computer modeling and fatigue testing.
This has been common practice in high volume consumer products and safety critical products for many years.
In the late 80s, I remember my math lecturer telling the class, matrices could be used to calculate fluid dynamics and model stresses in materials, while I was thinking, not with my 8088!
Did you actually read the FAA summary you linked or the NSTB findings?
It was a multitude of problems that lead to that situation. One being the inspection program was prescribed solely by flight hours, not flight cycles. That AC was doing almost double the flight cycles as anticipated for the flight hours between checks. A 737 has a Design Service Objective of 75k cycles but Aloha 243 had done 89,680.
Additionally, there were human factors involved with questionable inspection procedures, manufacturing issues (poor bonding), and corrosion issues. This was much more than “FEA says rivet is good for X cycles, rivet was not good for X cycles“.
I agree with what you have written above..Those planes got a lot of cycles / day. Short flights.
And I never said FEA was used in that example. Just that it was modeled on a computer. And the model was relied upon (including all assumptions used). And computer modeling is just that. Modeling. The real world is where it matters. Does it work? Also I never said anything about no plane failures before xyz... You are just making up stuff. You work for the media?
Bottom line is the polishing of the cases - as someone did in the example of the cases they showed - which is why it was brought up..works on a 2 stroke. It makes a difference. Especially case reed 125's. Saying it doesn't - as various arm chair folks have said - because of a "theory" is not accurate.
Further, and exactly my point, not one of those people bashing it with fluid dynamic theory of whatever has tried it. Not one. And bashing someone - or stating something doesn't work because of a theory - with out actually trying it.. Really? I did it. And it works. Also there are other things going on that the models and theory don't take into account too. That is not understood. There are not perfect models. No perfect simulations. And if you don't want to try it I could care less. But don't bash the idea or me because of something you believe (theory - fluid dynamics... text book .. simulation) without trying it.
I m done with this ..... waste of my time.
Bottom line is you are out of your depth and can’t circle talk your way out of it. Have a great day and I hope you enjoy watching the race as much as I do.
Your living in a simulation. And making things up. You work for CNN? NBC?
Here is your quote. Show me in my example where I stated "Airplanes never had structural failures before computer simulations".
You're making things up to feed your ego. Sad.
You’re right, I am living in a simulation.
Why don't you show me where I wrote what you claim in your statement above.... Show me.
Nah, this is more fun
So you got caught making things up. You'll do well in the media!
Dang, you caught me, the jig is up
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