Pics are here: https://photos.app.goo.gl/7HUvLUvYpqeR2kBD7 Parts and pieces off to the appropriate shops on Monday. Forgot to get a pic of the camshaft. It is already .010 under and has some scoring so we'll see. Lobes looked good. Should get the bad/not so bad news by the end of the week.
I may be projecting because I one day dream of having a Luscombe with an O-200, but this would be a great time to put an O-200 in it.
I agree. We'll see what the shop says about the crank and cam. I also need to find the STC and an engine I trust. The Luscombe groups will know. I that an AA-1 in your avatar? I have many hours in them. Quite enjoyed it. BOS - BUF - ACK - BUF - BOS in one day.
Without actually seeing the parts, nobody is going to be able to provide a definitive answer. That said, if the crank is already .010 under you might need to start looking for a replacement.
#1. Continentals are numbered back to front. Lycomings opposite. That oil pump needs to come apart to see what the bore looks like. Bearing trash goes through it and rips it up.
Crank might be toast. Unless you have wing tanks on your 8A you are stuck with the A65 unless you spend the money to add them. Pretty sure even upgrading it to an A75 requires at least one wing tank.
It's still a valid statement. Those cranks are so old and so soft that many of them are at .010" and there is no further undersizing.
There are no bearings because Continental never authorized anything beyond .010". Automotive cranks and are often taken down as far as .040". Removing metal weakens the crank, hence the conservative .010" limit for a lot of aircraft engines. In the 1980s I ran a crankshaft grinder like this one:
You probably could have just stopped at “that oil pump needs to come apart.” Anyone who would put an engine back together without looking at it, much less one that lost oil pressure and had metal go through it is a fool.
I think Aircraft Specialties has an STC to go to .020 but I’m too lazy to look. Regardless, judging by the pictures that crank is going to be iffy. Especially if it has been ground a few times already. Ive had automotive cranks welded and reground but haven’t ever heard of a shop offering similar services on aircraft cranks. Do you know if anyone does it?
Never on an aircraft crank. Some done many years ago, with spectacular failures, then outlawed. Never seen it mentioned as being approved in any overhaul manual. Some WWII cranks get welded just because there's no option and those airplanes run in exhibition categories that type-certified airplanes can't. Welding introduces stresses that cause warping and can cause cracking, neither of which are acceptable. Very difficult to do and still achieve safety. Aircraft engines are run at high power levels most of the time and also have to deal with gyroscopic precession from the prop.
This process is cool, but my concern is that the bearing surface is now made of the powder substrate. I would need more information about how the substrate reacts to different environments. How does it fail? If the bearing seizes, will it get hot enough to warp? (If I understood him correctly) It is applied at 600 degrees F, is that hot enough to for the shaft to fail with the substrate, or will the substrate fail and separate from the original part? Last, how will the substrate corrode? The engine on my plane has flown just over 1000 hours in 22 years. If that happens, will the substrate corrode and pit before the rest of the shaft? Like I said, this process is cool, but I would need far more information before I took that risk.
Looks $$$ to me. As mentioned; Oil Pump cavity may be damaged or worn. That requires Accessory Case replacement.
I'm pretty sure there is a repair available for that. IIRC, they open up the cavity and then fit/machine a bushing. But that area is one of the weak points in the A series engines.
As far as I know, this is one of the methods that gets used to restore journals. The ones I’ve had welded weren’t done this way but I believe this process was used by a friend of mine to restore some cranks and cams for some exotic cars with parts made of unobtanium.
Flame spray really only has a mechanical bond to the substrate material. It is still porous so its ability to support bearing loads on an oil-journal bearing would be very poor, and would do nothing to restore the mechanical properties of an undersized crankshaft. My experience with it is with hydraulic actuator piston rods where it failed almost immediately.
Unlike a crank or cam ,the area repaired will not have a moving part running on it. The build up is for a stationary fit. As mentioned not sure how with a moving part , how it would stand erosion .
no bushings should be used.. weld the case close and re-drill Problem is, cases of these old cases can't be welded.
The last one I was involved in the folks that had the approval for repair had stopped doing them for some reason. Since a serviceable item could not be located a new Acc Case was ordered from TCM. After waiting for a Production Run the aircraft returned to flight SIX Months later. And this was for an O-200!!! btw - Old Case was Magnesium & New Case is Aluminum.
That oil pump has a snowman-shaped cavity and the walls are rather thin. Very difficult to do much of anything with it. Pics in this thread https://www.pilotsofamerica.com/community/threads/o-200-loses-oil-prime.88189/
Those spray-welded cranks have failed when the welded layer comes loose. Some VW flyers have had such failures.
