That is because it is known as intellectual property. it's out there, you just have to buy it. as far as supporting the old engines there is plenty of data already in circulation.Originally Posted by Aaron Novak
Tom,
I hope you dont mean using the internet when you say "research"Honestly about 1% of what is known in the field of engine design is published "online".
Eh I beg to differ on the point of being able to buy information. Typically the experts dont publish anything. Do you work in engine design for a living?
design,,, no,, repair yes.
Ok. Well honestly there is a large information gap between the design world and the "outside" world, just like in any industry. We try to bridge it when we can especially with fun stuff like old engines. So I think "anyone" could reverse engineer a part, no, not at all. You can reverse engineer dimensions, and basic material specs, however material processing is one of those details that borders on impossible to reverse engineer. The devil is in the details. Give the old engine part to a group well versed in engine design and materials, and thats a different story. Or look at it this way, if it was easy to reverse engineer, the engines coming from china might actually be decent.
With the type clubs we have today and the ability to contact many different people/organizations involved in restoration and repair of old aircraft and engines we are now able to do in a couple days what took years in days gone by.
With links to the FAA and the ability to converse with your FAA engineering staff at several FSDOs at the same time, we have been able to get a 337 authorized in less than a day by passing data by e-mail, and FAX.
MY point in this thread was we have the ability these day to gain authority and pass data that we were never able to do in days long ago. Finding the blue prints and other data to gain authorization to manufacture parts is easier than many believe, and the kids entering this occupation know how to do this better than most older A&P-IAs.
We in the repair part of the industry have no need to design any thing, all we must do is duplicate. and prove it is as good as OEM that is not difficult with a blue print.
For a good example the Fairchild Club has a CD they produced that has over 5000 blue prints on it, that gives the details of all the parts of the F-22 and the F-24. When I need to prove any thing to my PMI at FSDO all I need to do is take the CD to Office Max and have the blue print cleaned up printed. The Warner engine has a parts supplier that has all the prints for the Warner series and the Jacobs engines and several others.
All we need to know any more is Who's got What, and we can get it in a couple days
Http://www.whidbey.com/fairchild-nc19143/
Last edited by Tom Downey; 11-16-2011 at 11:52 AM.
Ok I see where you are coming from. My point is that you cant just hand an old factory drawing to a supplier and expect the same part as was made 60 years ago. All the information needed to make the part is NOT on the drawing, never has been and never will be. So thats why I am saying that not just anyone can take a drawing and have a part made, and expect it to be OK. Now of course its also dependent on the type of part, material, etc. A simple bushing from a copper based alloy should be straightforward. A ground bearing race for a roller type bearing, much more difficult to reverse engineer if it was even possible. A drawing for an exhaust valve may indicate the materials and dimensions, and if it were a multi piece valve may say "spin weld" or "flash weld" or just "weld". The details of the welding such as rpm, inertial loading and force ( if spun welded ) are not on the drawing usually. Since every supplier has its own ways of welding, if you just handed over the 60 year old drawing, they might make a part that while technicly meeting the drawing, might be unsatisfactory for use. Thats what I mean when I say that all the process engineering is missing, and so having someone experienced in the design field of the same components can be very helpful when it comes to reverse engineering it.
I believe you are off on a tangent to the subject at hand, " the continued airworthiness of old engines". Under the FAA's advice in several ACs they require the new part to be equal to, or better than, the OEM part. "better than" is a qualifying statement in which many A&P-IAs see as a modification, That's a different issue. during Restoration or rebuilding an old aircraft or engine we seldom if any time need to do a complete reverse engineering of any part. So when we do need a complete reverse engineering, and the part can't be made in the same fashion, the field approval system is used to gain authorization to use the part being made, properly documenting the new process used is important to gaining approval.
Many times the original manufacturer used off the shelf parts also used elsewhere in the industry. If you remember the Franklin engine club used tractor bearings in the rebuilding of the Franklin 165, these engine were in service many hours until the FAA found out they used a dead A&P-IA signature to return to service, that got us an AD for any engine built by these folks, point being, these parts do work, and can be used when properly documented.
many times the Illustrated parts breakdown can be used as approved data to return to service with only a maintenance record entry, such as the skins on an early Cessna 100/200 series, the IPB gives the part number, but says "made from (old designation for the aluminum)" and we know that converts to the "new designation", so we manufacturer the new skin from the aluminum called out in the IPB. and record the replacement of the skin as a repair of a larger unit.
Getting back to subject, many new processes can and are used as excepted shop practices now that were never heard of in the days these old engines were manufactured, but as pointed out these processes are not cheap.
Hey Tom,
I guess maybe where I was going was not clear, its been known to happen. My basic point is that just because an engine component gets approved by any one of XXX methods by the FAA, does not mean that the part is as good as the original for the application. Thats not to say it CANT be as good or better than the original. So really there are 2 issues, coming up the the replacement part and the associated engineering, and getting FAA approval. The Approval is the easy part as typically the person doing to engineering qualification work should know more about the component and its application than the FAA representitive.
That's why we have DERs
We now have materials and machining process far superior than they did prior to WWII, I don't see any problem making parts now that will be better than New old Stock.
welding in a worn bearing bore and remachining a new surface is pretty easy with the robot welders and CNC machines we have today. In fact Chuck Ney will still do Franklin cases, It will cost you the tear down and set up time, but he will do them. It will be a very strange occasion when you find any thing exotic in these old engines, It usually the cost, not the ability that shuts us down.
Last edited by Tom Downey; 11-18-2011 at 10:30 AM.
Tom,
I wouldnt expect a DER to know about the inteaction of valve tip and rocker materials, would you? And the difficulty is also relative to the type of engine. An A-65 or Franklin should be a lot more straigntforward than a TC Wright engine. Dont get me wrong, I love making parts for old engines, however I have seen a lot of poorly made parts that were due to the individuals lack of understanding and knowledge about the part they were trying to duplicate. Take a crankshaft for instance. Sure you can measure it for dimensions, thats simple, materials can be scanned with a GS or an SEM ( both is better ), thermal metal treatments can be estimated. However what about mechanical treatments like shot peening? What size was the shot? What pressure? What angle? How long? How many times? This is where you would make multiple parts, and try various types of shot peening, cut up the cranks and compare them to a cut up original. Under the eye of an expert metalurgist this would still only give you a "best guess". This project undertaken by a group of people experienced in crankshaft design would at least have a decent chance of working. Done by anyone else would be a risky business. So what does this come down to? It aint gonna be cheap!
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