Crankshaft Rust

[Flywheel]

A&P says (In connection with a Continental O200 top overhaul) the crankshaft has too much rust between engine housing and propeller (outside engine).
I'm thinking the crankshaft diameter reduction and strength reduction from rust is less than 1% and irregular distributed over the length and diameter.
The design strength of the crankshaft has likely a 50 % safety factor. So there should be no problem.

Here are the photos:
http://hc-research.com/Continental.html

What do you think?

[n2582d]

SB09-14, Crankshaft Corrosion Treatment

From the Continental Standard Practice Maintenance Manual Chapter 6-4.6 § 9:

Inspect the exposed area of the crankshaft between the crankshaft nose oil seal and the propeller flange for evidence of corrosion. If corrosion is detected, use a Scotch- Brite® pad and a no-corrosive soap solution to remove surface corrosion.
CAUTION: Adequately mask the prop flange bolt holes and the forward prop contact surface to prevent paint damage to nut/washer bearing surfaces.
a. If the cleaning process eliminated the corrosion and no evidence of pitting exists, apply a single coat of high performance rust preventive acrylic enamel (designed for steel), minimal thickness required for coverage, not on load bearing surfaces according to the paint manufacturer’s instructions to the exposed portion of the crankshaft to prevent further corrosion.
b. If cleaning is unsuccessful (suspected corrosion has advanced to pitting), disassemble the engine and replace the crankshaft.

[GAHorn]

shss-shss-shss-shss-shss (nationwide sound of rustling-feet toward hangars)

Steve Grimsley dropped a crankshaft off at my hangar last year for my use as a “teaching tool”. It had failed this very inspection process. (I just don’t care to fly that much dead weight all the way to convention….and back… and Jamie wanted to bring her hair-brush instead.) Anyone need a $7K boat anchor..??

[c170b53]

Crocus cloth, to remove the surface rust, then you will be able to see what you have in terms of real pitting. Doesn’t look real good from the pics, clean it up and maybe you can post. I have a 8 bolt crank for an 0-300 and although it looks good, (no corrosion, dials good) I fear it will fail due to a wear groove from the front crankcase oil seal. Stuff you really don’t think about, but that 25 years since overhaul can turn pliable rubber hard, add some dust and it turns into a cutter.

[sfarringer]

A&P says (In connection with a Continental O200 top overhaul) the crankshaft has too much rust between engine housing and propeller (outside engine).
I'm thinking the crankshaft diameter reduction and strength reduction from rust is less than 1% and irregular distributed over the length and diameter.
The design strength of the crankshaft has likely a 50 % safety factor. So there should be no problem.

Here are the photos:
http://hc-research.com/Continental.html

What do you think?

It would be a mistake to ignore the possibility of stress-risers on highly stressed parts such as crankshafts.

[c170b53]

Maybe I should walk back what I thought I had and maybe listen to myself So thought I’d post a pic, initially the groove could be felt by a fingernail but after giving it a scrub with scotchbright (green) it looks better.
o.

A close up does show a few pits on the inside side of the oil seal but I believe they can be polished out or at least I hope so

[GAHorn]

Since we often machine undersize crankshafts .010-.020 without penalty….. I wonder why this area of the crank cannot be similarly..??

[Flywheel]

I'll try to use Scotch- Brite® pad and see if I can clear it up.

I feel the torque load is not as high as in a car (unless you have a prop strike).
In a car, if you hit the brakes at full power, there would be much more torque.

[sfarringer]

I feel the torque load is not as high as in a car (unless you have a prop strike).

Perhaps.
But the gyroscopic loads are much higher.