IO360 slight give when pushing/pulling on prop

[TYK]

I normally use the tow bar to move my 14-A, but after doing some maintenance I took hold of the prop roots to move it around and noticed the prop has back and forth give to it. It feels like a thrust washer on the crank is missing or worn. it's a polished, close-tolerance oiled shaft feel, not like loose bolts.
It felt a bit excessive. Maybe an 1/8 inch? Maybe less.
I'm not an engineer or a NASA scientist, I'm a farmer accustomed to TLAR so I regrettably didn't think to measure the travel.

The forward/aft give in the crank doesn't seem right.
Is this normal?

About a year into this flying thing, so really appreciate what I've been able to learn from this community!

 

[bjdecker]

I don't think pulling on the prop is an acceptable method to measure end-play, at least not with any accuracy The tolerances are in the .002" to .007" range - you'll be able to feel something, but without a feeler gauge strategically placed, you won't know for sure.

If you were missing the thrust washer, or the tolerances were excessive, the engine would be making ALOT of aluminum.

See attached from the IO-360-N1 Overhaul manual (probably not your engine, but close enough for gov't work.)

 

[PCHunt]

Sounds normal to me. My O-360-A1A does the same thing.

I understand that there should be some fore-and-aft play, and if there is Zero play, it is cause for concern.

 

[Richard RG]

My Mooney M20e had the I0-360 A1A and most often I dragged it out of the hanger pulling at the base of the propeller blades. I too noticed a very slight fore/aft movement when giving a pull or push.
It did the same thing 300+ hours before overhaul and 200 hours after overhaul. I mentioned to my AME (mechanic) and he said not to worry, carry on.

 

[mahlon_r]

totally normal! It's not even unusual for it to go thunk, thunk when you push and pull.
Merry Christmas,
Mahlon

 

[PCHunt]

totally normal! It's not even unusual for it to go thunk, thunk when you push and pull.
Merry Christmas,
Mahlon

From the Guru's mouth to your ears.......

 

[TYK]

Thanks all! Greatly appreciated.
Tim

 

[BillL]

Epilog

It always "feels like" more than measured. BITD I would check VW's by grabbing the crank pulley and pulling back/forth - - .010" can feel large, but .040" will feel massive, like 1/4"!!

 

[PCHunt]

It always "feels like" more than measured. BITD I would check VW's by grabbing the crank pulley and pulling back/forth - - .010" can feel large, but .040" will feel massive, like 1/4"!!

Trying to follow this..... pardon my ignorance of your abbreviations.....
What is BITD?
What are VW's?
How do you pull back/forth on the crank pulley without removing the cowl?

And I agree with you when you say that the "clunking" will feel much larger than the actual clearance dimension.

If VW's means Volkswagen engines, I fail to see the relevance.

 

[Full Throttle]

BITD=Back in the day

 

[lr172]

I don't think pulling on the prop is an acceptable method to measure end-play, at least not with any accuracy The tolerances are in the .002" to .007" range - you'll be able to feel something, but without a feeler gauge strategically placed, you won't know for sure.

If you were missing the thrust washer, or the tolerances were excessive, the engine would be making ALOT of aluminum.

See attached from the IO-360-N1 Overhaul manual (probably not your engine, but close enough for gov't work.)

end play clearance (i.e. total axial travel) on a lyc crank is ~.025" That doc is a bit confusing, as they also have a min clearance fron the slinger at full forward position and the slinger only acts as the rearward facing thrust surface (while running, all force is fwd). This clearance erodes as the primary thrust surface wears. If this clearance drops to 0, the slinger can start taking some of the fwd thrust load and it is way too small to handle that load. Also, the slinger needs some clearance to actual sling oil.

There is no thrust washer and unlike most auto applications, there is no bearing flange acting as a thrust surface, it is just the face of the offsets riding against a flat surface of the case. If you truly have .125" of play you need an expert to tell you how serious of a problem you have, as at some point the radii on the crank surfaces are going to start eating into your main journal bosses and bearings across the crank. The radii on the crank are critical areas and need to be polished and any wear is serious. Most crankshaft cranking seems to always start in this area, so wear or scratching is not allowed there.

I do agree with Bill that it probably just feels like 1/8", but if it really is you need to do something about it.