Continental TSIO-360-MB1 Cam corrosion

[nationwide]

1 hour ago, OR75 said:

Nice pictures ..... just wondering why you opened engine in the first place. Or were these taken with a borescope ? if they were what kin of borescope was it. I want one. 

He found rubber and steel fragments in the oil screen which they believed was from a mag cushion drive and mounting cone (mag woes, and what seems like some A&P buffoonery concerning same, are one of the issues I've dealt with since owning the plane).  He pulled the mags and accessory case to make sure there was nothing else.

I don't even know what that entails. I've been wondering myself what the engine looks like now. I want to ask him "Hey, can you take some more zoomed WAY OUT?"

[jetdriven]

4 hours ago, Mooney_Mike said:

Preoilers, roller cams, Ney nozzles, oil additives (additives help some) do not stop cam corrosion. Let an engine sit long enough and the oil will drip off the cam and expose it to moist air and rust will start. The only true solution is to fly it frequently (weekly), change oil every 3 or 4 months / 25 hours, and ground runups do not count. It needs to be flown to get the oil hot to get the moisture out of the oil.

I am now also using an engine dryer system as an added measure to the above.

http://www.aircraftspruce.com/catalog/eppages/engsaver.php

 

 

 You are right none of these things prevent corrosion. But a roller camshaft will mostly recover from this because it is rolling friction and It'll polish the rust off of the cam and keep on running, where the flat  lifter engine starts to spall and make metal and progressively get worse until it forces an an overhaul. Of thousands of roller engines out there in the field in the past 12 years, I've never heard of one taking the engine out.

It's important to consider the extra cost to gets roller camshaft engine and compare that the the near certainty of the bottom end making TBO.  

[jackn]

1 hour ago, nationwide said:

He pulled the mags and accessory case to make sure there was nothing else.

If the accessory case was removed, a lot of the hard work to remove the engine has been done. My advice would be to finish removal, overhaul & replace. 

[aviatoreb]

3 hours ago, carusoam said:

NatWide,

Take a look at the second picture that MooneyMike posted...

there is a lot of detail.  What stands out is the lunar surface of the cam follower that is pointed towards the camera.

the cam followers pointed away from the camera aren't very helpful...

 

See if you can get a picture of your cam follower's surfaces.

If they are lunar like, it would be good to know.

 

material selection is a science that requires matching the hardness of two materials so that one wears at a very slow pace compared to the other.   Too much of a difference, is bad.  Too little of a difference is worse.

selecting the materials to match the chemical environment also adds another level of challenge.  The engine builders haven't designed for sitting long periods of time to their environment for design..?

any of the 'guesses' for coating or metals like titanium, have to match the stiffness, hardness, strength, economics,  and chemical  resistance required for the cam.

There are not a lot of  Continental cams suffering from this type of sitting challenge.  They engine has a significant design difference where the cam is located in the engine.  It can sit a little longer than a Lycoming, but not a lot longer....

PP thoughts only. Not a mechanic.

Best regards,

-a-

Could an engine theoretically be made entirely out of titanium?  If so it seems like it would be mostly immune to corrosion.

I wish my whole airplane was made entirely out of titanium.

I have several bicycles made out of titanium, and the stuff is so corrosion resistant it is not even necessary to paint them, so they remain the raw titanium battleship gray color.  They stand up to decades if riding on summer and winter (salty) roads, and salty sweat (which is very very corrosive since its a lot more than just NaCl) without a hint of corrosion, or stress.  An all Ti Mooney would be cool....  Tubular structure, wing spars, skins, engine....everything.

[75_M20F]

5 hours ago, jetdriven said:

 You are right none of these things prevent corrosion. But a roller camshaft will mostly recover from this because it is rolling friction and It'll polish the rust off of the cam and keep on running, where the flat  lifter engine starts to spall and make metal and progressively get worse until it forces an an overhaul. Of thousands of roller engines out there in the field in the past 12 years, I've never heard of one taking the engine out.

It's important to consider the extra cost to gets roller camshaft engine and compare that the the near certainty of the bottom end making TBO.  

Or one could just fly it weekly?

[jetdriven]

That doesn't prevent it either. @aaronk25 flew his weekly and put a lot of hours on it in a year and it spalled out again. 

[carusoam]

Need to look into the possibility of a Ti cam with roller tappets...

1) Flex modulus... wouldn't want it to flex differently than steal.

2) Hardness... wouldn't want it to be softer than steal.  For best wear, it would need to match what is there. Bearing wear is a consideration, too.  Or, a new material for the bearing surfaces would need to be considered..

3) A Ti cam would be crazy expensive, Raw material and machining costs...

4) pulling an engine because it ate a rusty cam is pretty expensive.  Now we have something to compare to economically...

 

Thoughts that come to mind...

 

Best regards,

-a-

[aviatoreb]

There are various ti alloys.  I hear the so called 6.4 alloy is quite hard.

if they can make bicycles - why not a cam at a reasonable cost?  Even high end bicycles are cheap stuff compared to airplane stuff.

i understand what you say about matching hardness...

[carusoam]

This is where the experimental category has an edge...

Best regards,

-a-

[jetdriven]

I don't think we know totally what causes cam and lifter spalling and we certainly don't know how to prevent it except equip the engine with roller tappets. 

[nationwide]

20 hours ago, jackn said:

If the accessory case was removed, a lot of the hard work to remove the engine has been done. My advice would be to finish removal, overhaul & replace. 

That's good info to know, thanks

[nationwide]

12 hours ago, aviatoreb said:

There are various ti alloys.  I hear the so called 6.4 alloy is quite hard.

if they can make bicycles - why not a cam at a reasonable cost?  Even high end bicycles are cheap stuff compared to airplane stuff.

i understand what you say about matching hardness...

[Maybe more than] A bit off topic now...it is hard but brittle (poorer elongation), especially in the 6% Aluminum/4% Vanadium alloy, although it is "stronger" (higher tensile, yield, and fatigue strength) than 3 Al/2.5 V Ti alloy.

Not a metallurgist, but I'm assuming if Ti were a better choice it would've been done by now.  Ti is expensive but that's likely not the driving factor.

[Yetti]

Ti is hard to machine... so the process is different  Especially if you are machining and then hardening like a fair amount of rotating parts are created.

 

On that note the OP pictures did not just happen last year.   It's been running like that for a good while....  how much longer it will survive is anyone's guess.

[75_M20F]

Saw this on another forum. Lycoming roller cam 1 1/2 years old w 300 hours on it w 50 hour oil changes found during teardown for a propstrike according to the poster.

 

Edited August 6, 2017 by Mooney_Mike

[INA201]

Semi off topic question.  Would you guys assume that corrosion in the original post pictures would eventually cause failure of the cam with some certainty?  A lot of owners have planes that have sat for periods of time and probably have some level of corrosion.  Does all cam corrosion at a pitted level eventually cause failure of the cam or do they quite often still make TBO?  Definitely a tricky topic but it's obvious that you should run your engine a lot.

Before I bought my Mooney I looked at one from an older gentleman who would stuff a towel tightly into the exhaust pipe after flight.  He said that when the engine cools it will pull drier air through the towel into the engine and help prevent corrosion.  The hot air is expanded and when the engine cools It must draw air in.  I've never seen it before or since but kinda makes sense.

[jetdriven]

A towel won't block moisture. All that does is make him feeel better. The hot air holds more water grains than cool air, so when it cools it condenses on all the internal parts.   A rubber glove over the tailpipe will seal that moisture in there real good. But what really takes it out is a plug in dehydrator.  No moisture no corrosion.  

Edited August 6, 2017 by jetdriven

[ArtVandelay]

FWIW, I do remove the dip stick which allows water vapor to escape.

[aviatoreb]

On 8/4/2017 at 9:44 AM, Mooney_Mike said:

 

I had the engine removed and sent to Penn Yan Aero for overhaul. They did a spectacular job and it is the smoothest running IO360 I have ever flown behind.

 

I had an overhaul on my IO360 by Penn Yan when I had a DA40 - they did an amazing job I agree.

[aviatoreb]

29 minutes ago, teejayevans said:

FWIW, I do remove the dip stick which allows water vapor to escape.

I just open my oil stick, and lift it up slightly but otherwise leave it in place so I don't loose it - anyway that seems to do the same thing as far as letting vapor escape.

[jackn]

2 hours ago, INA201 said:

Does all cam corrosion at a pitted level eventually cause failure of the cam or do they quite often still make TBO?  

The answer is no, but it will start shedding metal bits. As mentioned previously, Those metal bits will find their way into bad places ( oil galleys, bearings). You may get lucky, but it's risky. 

[Pissed'Ole-Pete]

On 8/4/2017 at 2:06 PM, aviatoreb said:

Could an engine theoretically be made entirely out of titanium?  If so it seems like it would be mostly immune to corrosion.

I wish my whole airplane was made entirely out of titanium.

I have several bicycles made out of titanium, and the stuff is so corrosion resistant it is not even necessary to paint them, so they remain the raw titanium battleship gray color.  They stand up to decades if riding on summer and winter (salty) roads, and salty sweat (which is very very corrosive since its a lot more than just NaCl) without a hint of corrosion, or stress.  An all Ti Mooney would be cool....  Tubular structure, wing spars, skins, engine....everything.

A slightly off topic reply... I was in the Air Force (1st TFTS) when the F15 (all Ti) became operational. It seems Titanium reacts with Cadmium. We had to have ALL our tools certified "Cadmium Free" before we could go near the flight-line. Apparently there is a nasty corrosive reaction occurs on the Titanium when marred with Cadmium. Would all mechanics wish to replace all cadmium coated/containing tools in their shops?

Edited August 6, 2017 by Pissed'Ole-Pete
typo

[ArtVandelay]

Titanium is already used in jet engines and aircraft bodies (maybe only military). I believe the cadmium restriction was referring to bolts, rivets, and other long term exposure. Casual contact from tools was not a problem, it had to be at higher than room temperature. Oh yea, and silver is a problem too, so all you mechanics with silver plated tools, watch it

 

[aviatoreb]

36 minutes ago, teejayevans said:

Titanium is already used in jet engines and aircraft bodies (maybe only military). I believe the cadmium restriction was referring to bolts, rivets, and other long term exposure. Casual contact from tools was not a problem, it had to be at higher than room temperature. Oh yea, and silver is a problem too, so all you mechanics with silver plated tools, watch it

 

Better to use gold plated tools then.

is titanium common in domestic jet engines or just military stuff?

Edited August 6, 2017 by aviatoreb

[ArtVandelay]

Better to use gold plated tools then.
is titanium common in domestic jet engines or just military stuff?

Yes, domestic engines. I saw some program on how they build jet engines, they mentioned use of titanium. I believe they were new engines for an Airbus. The intense heat required titanium.

[aviatoreb]

32 minutes ago, teejayevans said:

Yes, domestic engines. I saw some program on how they build jet engines, they mentioned use of titanium. I believe they were new engines for an Airbus. The intense heat required titanium.

Cool.