RE: Piston Damage

RE: Piston Damage
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RE: Piston Damage - 4/5/2008 11:40:30 PM

summerwind

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From: fresno, CA, USA
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Dar makes some good points here........other than the bearings which i enhanced with my CS2 program, there may be some other bit/s that have become unlodged and ventured through the engine.

this enhanced photo shows little evidence, but then again it is only one side of the bearings

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(in reply to DarZeelon)

Post #: 26

RE: Piston Damage - 4/5/2008 11:56:09 PM

Super Splatter

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From: , MN, USA
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nope, nope, nope. once a bearing gets like that the actual ball bearing begins to flake apart. It starts chemically, and finshes phyiscally.

Take your dremel wheel and cut the outer ring in two and you'll find some balls that aren't round anymore. The flakes from the balls is what does it.

Flew a new Viper today with my AX & a Sportster with a 56a FS today. Brought'em home in one piece. that 56a drops in where a 46AX fits.

(in reply to estradajae)

Post #: 27

RE: Piston Damage - 4/6/2008 12:35:41 AM

PlaneKrazee

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I wonder if using a little more castor in the fuel would have helped prevent the destruction of this engine. Looks like it was ridden hard and lean with little to no castor then put away wet.

What type of fuel/oil were you using? Did you run the engine dry at the end of every day? Those bearings looked bad.

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(in reply to Super Splatter)

Post #: 28

RE: Piston Damage - 4/6/2008 3:24:50 AM

Bad Tooth

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From: Lawton, OK, USA
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The fuel used in the engine has varied over the past couple of years: S&W, powermaster, coolpower, etc. Not sure about the castor oil content in these fuels that were used. And to be honest I didn't always run the engine dry at the end of each trip. But I can say that it was never run for any extended period of time very lean. I always tried to keep it pretty rich.

No doubt though, a little more maintenance would have prolonged the life of the engine. I am learning that now. I also think I should have checked these bearings at some point. The problem has just never popped up until now with any of my engines. Guess I've got some bearings to check........

(in reply to PlaneKrazee)

Post #: 29

RE: Piston Damage - 4/6/2008 5:32:27 AM

somegeek

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My rear bearing was the same... no visible material missing from the cage but the center race wobbled enough to know there was significant material missing from the ball bearings.

somegeek

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Post #: 30

RE: Piston Damage - 4/6/2008 6:06:14 AM

Checklst

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Joined: 12/19/2002
From: Alpharetta, GA, USA
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Your photos are great....that engine should go into the abused Hall of fame............Looks like a mixture of ...Lean run.....Lack of proper lube, and foreign object strikes. The chunks that is missing from your piston in the photo could have caused most all of the hard foreign strikes on the piston top. How that material got down to the con rod(while she is still running) for the hard crank/con rod strikes is a one in a million or higher.

Usually we only see odds that high in a Lotto ticket. sheeeese!!

< Message edited by Checklst -- 4/6/2008 6:07:35 AM >

(in reply to somegeek)

Post #: 31

RE: Piston Damage - 4/6/2008 9:31:55 AM

DarZeelon

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quote:

ORIGINAL: Checklst

...The chunks that are missing from your piston in the photo could have caused most all of the hard foreign strikes on the piston top. How that material got down to the con rod (while she is still running) for the hard crank/con rod strikes is a one in a million or higher.

Checklst,

Missing chunks!?

Those are indentations caused by a piece(s) of a material much harder than aluminium, finding its way into the combustion chamber and being repeatedly 'pressed' between the piston and the head, deeply denting both surfaces.

The piston has not 'exploded'... Detonation, or lean-run damage would have manifested itself as a deep hole in the middle of the piston-crown (there isn't one); not many shallow ones in the squish-band area of both the head and the piston...

What you are seeing is definitely FOD. The only question is where this rather large piece of shrapnel came from.

This doesn't look like rock damage and I am under the impression that a close inventory of the rear bearing will find the source; be it a piece of the cage, or a 'sliver' off one of the balls, or a race.

< Message edited by DarZeelon -- 4/6/2008 9:37:46 AM >

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(in reply to Checklst)

Post #: 32

RE: Piston Damage - 4/6/2008 12:34:37 PM

Ed Cregger

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Joined: 1/31/2002
From: Ringgold, GA, USA
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quote:

ORIGINAL: Bad Tooth

I just got done reading SomeGeek's experience with his .46ax. Although I haven't taken my bearings out they don't look much better than his bad bearing. The rear bearing also seems to have a little slop in it. Today was a really windy day and going downwind it was really winding up. Probably too much eh?

--------------

Going down wind, the model's relative speed to you was faster, which caused the Doppler Shift of the sound to be greater than normal. The engine ran the same speed it always did, minus any rpm loss due to damage.

Ed Cregger

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(in reply to Bad Tooth)

Post #: 33

RE: Piston Damage - 4/6/2008 12:36:42 PM

Ed Cregger

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From: Ringgold, GA, USA
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quote:

ORIGINAL: rcdude7

Time to replace that engine. I would bet my paycheck that the sleeve is damaged also. OS is very proud of their engines, and the price of spares reflects that thinking.
The only other cost effective option would be to get a crashed OS .50 cheap and strip the parts needed to get this engine running again.
I did this to get a MOKI 1.35 running again after it ingested a wrist pin retaining clip and sustained severe piston/sleeve damage. I bought up a crashed MOKI 1.35 for $40 and combined the good parts I had to get a excellent engine. I got lucky. The price of new parts would have been around $200, give or take a few.................

Post a ad in the RCU engine wanted section and wait. Maybe you'll get lucky.

Mike

----------

It sounds like you have the game figured out well, rcdude7. That's really about the only way to economically rebuild our small glow engines, with spare parts prices being so high, unavailable, or both.

Ed Cregger

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(in reply to rcdude7)

Post #: 34

RE: Piston Damage - 4/6/2008 12:42:02 PM

Ed Cregger

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From: Ringgold, GA, USA
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quote:

ORIGINAL: Gizmo-RCU

As gross as the bearings look and the rod damage, if it's not the bearings it must be gremlins.

--------------

There was a kid about an 1/8th of a mile away that shot his BB gun into the air, slightly towards the club field. Guess where the BB went?

Before we start lambasting OS much more, just think of the rpm these engines are expected to turn each and every time we take them flying. It is a wonder to me that they stay together as long as they do.

Has anyone that is using the plastic caged bearings had to replace one of them as yet? How long did it last when compared to the traditional metal cage ball bearing it replaced? How did you know the bearing needed replacing? Radial play? Cage failure?

Ed Cregger

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Artisan

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(in reply to Gizmo-RCU)

Post #: 35

RE: Piston Damage - 4/6/2008 1:16:00 PM

pe reivers

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Might be even a split ball from the bearing. This is not obvious on first sight.

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Post #: 36

RE: Piston Damage - 4/6/2008 3:54:21 PM

Sport_Pilot

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The "corrosion" looks like burned castor and synthetic oil to me. Likely the engine was run lean for prolonged periods with low percentage oil and the bearings were hot, that and maybe a bit of sand caused the bearings to part with a hunk of metal. Just a guess. You will have to replace all of the parts, but it may be cheaper to replace the engine. Use the old one for spares.

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(in reply to pe reivers)

Post #: 37

RE: Piston Damage - 4/6/2008 4:20:35 PM

Bad Tooth

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Well, it looks like I found the problem. I took SuperSplatter's advice and sectioned the outer ring of the rear bearing and look what I found. One of the balls was still together with a clearly visible fracture line right through the center of the ball. This ball separated as soon as I touched it. It was also missing a piece of metal, I'm sure I didn't lose it when I took it apart. The cage appears to be intact. If you go back and look at the outline of some of the 'strikes' from previous pictures the missing piece of that ball looks to match the shape of the stamps.

I did my best to put the ball back together for the picture (what a pain!

) Those little balls don't want to pose for the camera. There were also 2 balls in the bearing that show signs of wear. The picture shows the separated ball, 2 balls with visible wear and a "good" ball.

So what's the consensus? This is definitely what happens when rust/corrosion sets in on a bearing?

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(in reply to Sport_Pilot)

Post #: 38

RE: Piston Damage - 4/6/2008 4:29:22 PM

summerwind

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this is a good learning top