Scrap Value

[PTK]

1 hour ago, mooniac15u said:

...An object will only move as a result of pressure differential if the air pressure exerts a force on the object...

What then causes the wing to lift? Is it pushed up or is it pulled up by the introduction of curvature into the airflow which introduces pressure changes, lower on the upper surface and higher on the lower surface of the wing? I think the latter. In the case of the prop lower on front and higher behind it. Just as the wing lifts into the area of lowered pressure so does the propeller lifts the airplane forward into area of lower pressure. No air pressure is pushing it forward. It is the lowered pressure due to the airfoil that lifts it forward because air goes from higher to lower pressure. If you are sitting on the prop you feel pushed forward. If you are sitting in the low pressure area in front of the airplane you feel the airplane move forward towards you.

[Shadrach]

1 hour ago, PTK said:

I disagree with the notion that since the prop pulls the plane through the air makes it ok to handle the plane by the prop on the ground. Consider that the prop's role is to move air and the airplane in air has a lot less static friction than when on the ground. The prop moves air to the back of the plane and in doing so creates lower pressure in front of the plane. This relative low pressure in the front of the plane is what moves the plane forward. Moving air is a lot easier on the prop than overcoming the airplane's weight on the ground. Also in the air power is exerted evenly on the whole prop. I bet you a six pack that pushing on the prop on the ground exerts a lot more force than pushing air.

I don't think you're really thinking this through.  I respect that you want to follow the manufacturer's recommendations. Probably best to leave it there as I think your attempt to explain the physics behind why it's hazardous falls a bit flat.  In flight, everytime you change the aircrafts pitch or yaw axis, you are putting a great deal more stress on the hub then you ever could with wiht your hands on the ground...unless you used a 5 pound sledge to move your plane. 

I have to wonder if you ever had a gyroscope as a kid? If you did, think back to the surprising amount of force required to angle of the gyro's axis.

[mooniac15u]

43 minutes ago, PTK said:

What then causes the wing to lift? Is it pushed up or is it pulled up by the introduction of curvature into the airflow which introduces pressure changes, lower on the upper surface and higher on the lower surface of the wing? I think the latter. In the case of the prop lower on front and higher behind it. Just as the wing lifts into the area of lowered pressure so does the propeller lifts the airplane forward into area of lower pressure. No air pressure is pushing it forward. It is the lowered pressure due to the airfoil that lifts it forward. If you are sitting on the prop you feel pushed forward. If you are sitting in the low pressure area in front of the airplane you feel the airplane move forward towards you.

Air pressure is absolutely pushing it forward. Low pressure is not a force that acts on something. It is actually a reduction in force. Air pressure is caused by collisions between the gas molecules and a surface. When the pressure is even on both sides of an object the number of collisions is equivalent on all sides of the object and the forces are balanced. If you reduce pressure on one side of the object you have reduced the number of gas molecule collisions and therefore reduced the total force on that side of the object. The forces are now out of balance and the object feels a net force from the gas collisions on the high pressure side. If the gas exerts sufficient force the object will move. There is no magical force that pulls an object toward a vacuum. 

[PTK]

26 minutes ago, mooniac15u said:

Air pressure is absolutely pushing it forward. Low pressure is not a force that acts on something. It is actually a reduction in force. Air pressure is caused by collisions between the gas molecules and a surface. When the pressure is even on both sides of an object the number of collisions is equivalent on all sides of the object and the forces are balanced. If you reduce pressure on one side of the object you have reduced the number of gas molecule collisions and therefore reduced the total force on that side of the object. The forces are now out of balance and the object feels a net force from the gas collisions on the high pressure side. If the gas exerts sufficient force the object will move. There is no magical force that pulls an object toward a vacuum. 

We are saying the same thing.

[mooniac15u]

7 minutes ago, PTK said:

We are saying the same thing.

Perhaps. Except for the part where you said, "No air pressure is pushing it forward."  I see that you have edited your previous posts.

The air pushes on the back of the prop blade. The force is transferred through the blade to the hub. To produce a given amount of forward acceleration the same amount of forward force is applied to the root of the prop blade at the hub regardless of whether the air is pushing on it or your hand is pulling on it. 

[Smiles201]

When at standstill there is no fluid pressure from oil under pressure protecting the bearings and surfaces, hence pushing or pulling could create wear? When engine is running no danger of marring the bearings or surfaces?

[Shadrach]

25 minutes ago, Smiles201 said:

When at standstill there is no fluid pressure from oil under pressure protecting the bearings and surfaces, hence pushing or pulling could create wear? When engine is running no danger of marring the bearings or surfaces?

 That's not how the bearings in a prop work.  Neither Hartzell nor McCauley propellers are pressure (flow) lubricated.

[Hank]

37 minutes ago, Smiles201 said:

When at standstill there is no fluid pressure from oil under pressure protecting the bearings and surfaces, hence pushing or pulling could create wear? When engine is running no danger of marring the bearings or surfaces?

Why not invite a propellor guru to the discussion? @Cody Stallings should be able to explain it clearly and simply.

[carusoam]

I sent a link to Cody yesterday...

Interested in his thoughts on this.

Best regards,

-a-

[markejackson02]

Just curious.  Is it normal for our older planes to have a two month repair job every 3-4 years?  Seems like that often something needs to come off to be overhauled which takes 6-8 weeks.

 

[carusoam]

Not sure of the lead time... but...

It will always selects a time when you need it most...

New props can take several weeks.  A reman engine only takes two. R&R a week on either end...

Good luck determining the next steps.

Best regards,

-a-

Edited April 19, 2017 by carusoam

[Cody Stallings]

13 hours ago, markejackson02 said:

The prop is going off to be inspected/tested/repaired if possible.  The engine will be removed and the mounts tested and inspected.  No insurance on the prop.

According to the propeller guy, they see a failure like this every 3-4 years.  It is usually induced by someone pulling the plane by the tips of the blades.  It can produce enough leverage to pop all the retaining rings out of the hub.

I haven't ever hauled the damn thing by the tips so we will see what they say.

That is not caused by pulling the plane by the propeller.

That problem started in the propshop.

It is the worst sign you can get of a blade being shimmed to tight.

A big problem with a Threadless McCauley is blade tip shake, it drives Owners/pilots crazy.

When the shop shimmes them to tight to try an cut down on tip shake, this is the result.

Its all about fits an clearance. A little loose, the blade/Hub marriage works great.

To Tight, the snap ring binds into the carrier as the proptip moves forward under power, an the snapping comes out.

When this happens it will break the fonolic linkarm yeilding one blade uncontrollable.

 

It looks really nasty, but in reality more than likely it's not that bad.

The blade will NOT exit the hub by design.

I have seen this before, an it usually happens the 1st or 2nd time it's run after leaving the propshop.

How long ago was this prop in the shop?

[Cody Stallings]

This is a J prop(Fellow Mooniac on the site)

You can see the large step Machined into the blade, the 2 split Retainers fit in that step very tight.

Thats what hold them together, unless you have a catastrophic failure of some type, the Threadless McCauley will hang on to its blades.

These Photos aren't that great, I was trying to take pictures for my customer as it was coming apart, keeping him in the loop.

Propeller cleaned up really nice thought.

 

[carusoam]

Cody,

It is great to have you here!

what would be the potential next steps for MarkE?  Is it OH or fix what's broken?

Thanks for sharing the pictures of the Mooney prop.  These are parts we don't often see.

Best regards,

-a-

Edited April 19, 2017 by carusoam

[Cody Stallings]

17 minutes ago, carusoam said:

Cody,

It is great to have you here!

what would be the potential next steps for MarkE?  Is it OH or fix what's broken?

Thanks for sharing the pictures of the Mooney prop.  These are parts we don't often see.

Best regards,

-a-

It's going to need to be fully inspected( Eddy Current an Dye Penetrate) which are all part of an O/H.

Its going to need some new or yellow tagged parts on the inside. Nothing through the roof expensive.

 

But the big IF is going to be, weather or not the blade/hub relationship has been compromised.

What I mean by that, if the blade socket has to much damage to be removed, the socket will open up to large an go outside its minimum ID. Sometimes being right at minimums on the blade socket will make the sealing surface a little to loose for the -96 blade ORing, an it will streak some grease.

Thats normally only seen on big blade/big engine applications though. Banana's C-185 C-206 that type.

To answer your question, it's thought to say without laying my hands on it.

Start with a Inspect an Advise.

Edited April 19, 2017 by Cody Stallings

[Cody Stallings]

7 hours ago, PTK said:

I disagree with the notion that since the prop pulls the plane through the air makes it ok to handle the plane by the prop on the ground. Consider that the prop's role is to move air and the airplane in air has a lot less static friction than when on the ground. The prop moves air to the back of the plane and in doing so creates lower pressure in front of the plane. This relative low pressure in the front of the plane is what moves the plane forward. Moving air is a lot easier on the prop than overcoming the airplane's weight on the ground. Also in the air power is exerted evenly on the whole prop. I bet you a six pack that pushing on the prop on the ground exerts a lot more force than pushing air.

I'll take that Bet.

Be a 6 pack of Dr.Pepper

[markejackson02]

8 hours ago, Cody Stallings said:

How long ago was this prop in the shop?

The prop was overhauled about three years ago.  It was leaking grease so it went back to be resealed in Dec 16.  It was re-installed in Jan'17 and has flown about 30 hours before this happened.

Might well be what happened.  It was leaking grease.

[Cody Stallings]

I'm still convinced the blade was to tight.

you can see where the carrier was eating into the hub in your photo

[Mcstealth]

Sounds like a claim in the woks, to me. 

Of course the shop will feed you a line of crap like "we see this every three or four years" to deflect the uneducated.

good luck

[Shadrach]

18 hours ago, markejackson02 said:

Just curious.  Is it normal for our older planes to have a two month repair job every 3-4 years?  Seems like that often something needs to come off to be overhauled which takes 6-8 weeks.

 

My prop guy turned our prop overhaul in under two week including pick up and delivery to my hangar.  My last prop overhaul was 10 years ago.

[75_M20F]

You guys arguing about makes a prop work and an airplane fly have it all wrong.

I will tell you what makes an airplane fly, the answer is  $$$ MONEY $$$  pure and simple.

[Stephen]

On 4/19/2017 at 0:23 AM, Cody Stallings said:

I'll take that Bet.

Be a 6 pack of Dr.Pepper

You don't see your prop blade deflecting like that when moving by hand on the ground  . Yes they really do that. If you stand to the side of someone doing a TO power run-up you can see the prop disk profile bend fwd toward the tips. 

 

[Yetti]

On 4/24/2017 at 11:42 AM, Mooney_Mike said:

You guys arguing about makes a prop work and an airplane fly have it all wrong.

I will tell you what makes an airplane fly, the answer is  $$$ MONEY $$$  pure and simple.

I disagree.   It is pure magic and my pilot skills to harness that magic.   I have my wife respond to "Talk to me Goose" with "Show me some of that pilot stuff Mav"

[markejackson02]

Update - Prop was removed and went back.  The seals and bearings on the affected blade were replaced after the hub was inspected.  No damage other than a scratch on the old bearing races was found.  Cleaned and inspected the engine and the engine mounts.  Reinstalled the prop yesterday.  Drained and replaced all the oil, changed filter, cleaned the screens.  Nothing found.  Everything ran up okay.  Had to hit the road this weekend for family stuff.  First test flight will be Monday, see how it goes.

I did find a cracked piece of baffling.  Installed a doubler plate until I can get a replacement piece.

 

 

[75_M20F]

2 hours ago, Yetti said:

I disagree.   It is pure magic and my pilot skills to harness that magic.   I have my wife respond to "Talk to me Goose" with "Show me some of that pilot stuff Mav"

Without money there would be no magic machine to show off your magic skills.... ha ha ha

I stand by my observation that money is what makes an airplane fly. It simply can't happen without money. Even the Wright brothers would have never flown without money.