Propeller Flange Bushing Replacement

[0TreeLemur]

In late summer I took my old Hartzell prop in for overhaul, and the blade roots were found barely out of spec.  Rather than wait for parts or buy used, we decided to upgrade to a Top Prop.   After 20 hours flight time, the paint started coming off the new prop.  Last week I returned it to my favorite local prop shop where they applied a new paint job.   So far so good.

Saturday while reinstalling it with my favorite A&P IA, one of the prop flange bushings would not achieve the specified 60-70 ft lb of torque.  So I need to replace that bushing.  Looking at Lycoming SI 1098Q, I see that it is one of three unique part numbers.  It's not one of the four long ones that all have the same part number and protrude from the flange face.  It's one of the two short ones that do not protrude.  Replacements are about $150 each so I am not going to order two and use the one that matches what we remove.   According to the SI, if I can identify the No. 1 crank pin, then I can identify the p/n.  See figure.

Help: How do I identify the No. 1 crank pin on the flange?  The prop is still on the aircraft.  With reference to the figure from the Lycoming SI, it is one of either F or C.  How can I tell Which without removing the prop?   Yes, I know it is easy if the prop is off, but it isn't yet.

Guess, is the No. 1 crankpin the one that is vertical when cyl #1 is at TDC?  Is there a marking on the back of the flange that I might see with a scope?

Thanks.

-Fred

[PT20J]

With the crank pin positioned as shown, the piston would be half way between TDC and BDC. I would rotate the crankshaft to #1 TDC -- there's a mark on the back of the ring gear for that -- and then rotate the drawing 90 degrees CCW for reference.

Skip

[jamesm]

Hi,

Several years ago I had to replace two or three of the bushings because messed up threads when taking the prop off myself (not a  smart move on my part).The index pin was either longer or short than the rest I don't remember which is which. An IA told me the if the bushing are in there correct positions. you should get no Prop rock against the crankshaft flange then that is the correct position if the prop hub  rocks against the the crankshaft hub  then you are 180 degrees out.

Hopefully that makes sense  good luck on you project.

James '67C

[0TreeLemur]

A data point from my trip to the aircraft this afternoon.   I pulled the spark plug on cyl #1, and turned the prop to TDC.  The prop was oriented 1:30 to 7:30, with the offending bushing being at the 7:30 position.    I saw the mark on the ring gear you mention but it had what looked like a 25 next to it, so I wasn't sure if that was a BTDC indicator.  Based on what you wrote Skip,

2 hours ago, PT20J said:

With the crank pin positioned as shown, the piston would be half way between TDC and BDC. I would rotate the crankshaft to #1 TDC -- there's a mark on the back of the ring gear for that -- and then rotate the drawing 90 degrees CCW for reference.

this suggests that the bad bushing is in position F.   Conversely if I hold up a figure showing the orientation of my propeller from roughly 1:30-7:30 and rotate it 90-degrees CW, as opposed to rotating the above figure 90-degrees CCW, it seems to confirm F.  Do you agree? 

Thanks a bunch for your help.

-Fred

[PT20J]

1 hour ago, 0TreeLemur said:

A data point from my trip to the aircraft this afternoon.   I pulled the spark plug on cyl #1, and turned the prop to TDC.  The prop was oriented 1:00 to 7:00, with the offending bushing being at the 7:00 position.    I saw the mark on the ring gear you mention but it had what looked like a 25 next to it, so I wasn't sure if that was a BTDC indicator.  Based on what you wrote Skip,

this suggests that the bad bushing is in position F.   Conversely if I hold up a figure showing the orientation of my propeller from roughly 2:00-7:00 and rotate it 90-degrees CW, as opposed to rotating the above figure 90-degrees CCW, it seems to confirm F.  Do you agree? 

Thanks a bunch for your help.

-Fred

That sounds right. There should be timing marks on the back of the ring gear at TDC, 20 BTDC and 25 BTDC. To set the crank angle, align the appropriate mark with a straight edge placed along the crankcase parting seam.

[0TreeLemur]

Thanks @PT20J. 

Question No. 2: after doing some research about how to extract propeller flange bushings, there seem to be two methods.  (1) an expensive tool that is made solely for this purpose, and (2) an approach using two sockets and a threaded rod/bolt to exert force on the bushing and force it out of its hole.

Does anyone have an expensive tool they would be willing to share or lease?  My A&P IA doesn't have one.

Any thoughts on the likelihood of a good outcome using sockets?  Risk of damage to the flange?  Anyone done this?   How hard are the bushings to extract?

As always, any input appreciated.  I love the power of the MS community.

-Fred

[Andy95W]

I’ve never done it on a prop flange bushing, but I’ve used the socket method often on other areas.  I’ve never had a problem and it’s worked very well every time.

Go slow, watch every part carefully as you apply torque to the bolt.  When it’s going right, it’ll surprise you how little effort it actually takes to remove bushings.

If it were me, I’d try the socket method first.  If at any moment I didn’t have a warm, fuzzy feeling about the process, I’d stop and buy the tool.

To install the new bushing, you can use the same method.  If you freeze the bushing first, it’ll likely pop in with very little effort.

[PT20J]

That ST-115 tool is $1419.00.

I might consult with a nearby engine shop.

Also, if the problem is that the bushing is turning in the flange hole, maybe you need an oversize bushing. 

Skip

[0TreeLemur]

2 hours ago, PT20J said:

That ST-115 tool is $1419.00.

I might consult with a nearby engine shop.

Also, if the problem is that the bushing is turning in the flange hole, maybe you need an oversize bushing. 

Skip

Skip, you are on the same page as my A&P.  He said the same thing.   That can be tested with a 1/2x20 bolt in that bushing and turning it with a torque wrench?  Should see the rotation if that is the problem.   It probably is turning given that the threads appear mostly intact.  Not smooth at all in appearance, which would indicate stripped threads

BTW- I removed the prop today.  The prop shop where I bought it is going to replace all six studs.  After removing it, I measured the bushing dimensions, and it is definitely the "F" bushing, because it is about 0.03" larger diameter at the flange face than the "C" bushing.

-Fred

[0TreeLemur]

17 hours ago, Andy95W said:

I’ve never done it on a prop flange bushing, but I’ve used the socket method often on other areas.  I’ve never had a problem and it’s worked very well every time.

Go slow, watch every part carefully as you apply torque to the bolt.  When it’s going right, it’ll surprise you how little effort it actually takes to remove bushings.

If it were me, I’d try the socket method first.  If at any moment I didn’t have a warm, fuzzy feeling about the process, I’d stop and buy the tool.

To install the new bushing, you can use the same method.  If you freeze the bushing first, it’ll likely pop in with very little effort.

Thanks.   I'll definitely try the freezer idea.   I wish I had a pint of that liquid nitrogen we wasted used at the end of the 2010 field season in Antarctica.   Looks really nifty when poured down stairs.  

[0TreeLemur]

In anticipation of removing the misbehaving prop flange bushing, I decided to do a test.   Suspecting that the 'F' bushing is slipping under torque, I did an experiment.  Using 2 ea. 1/2" x 20 bolts, one installed from the front into the suspect bushing, and the other screwed in from the back into the other short 'C' bushing, I attached a torque wrench set to 60 ft-lb to F, and held bushing C with a wrench as shown below.

It took 60 ft-lb of torque with no slip.  !?!  WTF?    Saturday my A&P couldn't get that prop bushing torqued much above 50 ft-lb.  This is a ridiculous mystery.

I also took a photo showing the threads in all bushings.  The offending one is shown with the black arrow.

Tomorrow I plan to talk to the prop shop and see if they noticed something wrong with that stud.   It seems that it must be the stud, or a gremlin.

I don't think there is anything wrong with that bushing.

[carusoam]

Fire and ice... can often help

Dry ice is often available near by...

Just use caution with the cold stuff when not familiar... it can be easy to sustain a burn if not careful...

Or did you finish already?

Best regards,

-a-

 

[0TreeLemur]

3 hours ago, carusoam said:

Or did you finish already?

At this point I'm not going to remove that bushing.  There doesn't seem to be anything wrong with it.   In my little experiment I tightened the bolt up to 60 ft-lb easily.   I'm suspecting that there was something wrong with the prop stud.  The prop shop is replacing all six.  My A&P didn't think to check and see whether or not that stud it contained a roll pin.   Maybe there wasn't a roll pin installed and the Loktite broke.   We'll see.

Mysterious.

[0TreeLemur]

Update- called the prop shop this morning.   Owner of shop confirmed to me that one stud was slipping.   Roll pin either sheared or was absent (don't know this detail yet), and insufficient thread lock was applied AT THE FACTORY.  I've been pretty casual about the paint coming off and need to repaint, but manufacturing defect with safety implications on a brand new propeller is entirely another thing.   I called Hartzell this morning and was told that all warranty claims must pass through the seller, so I'll do that.

[PT20J]

Smart move to test the bushing before replacing it!

[RobertGary1]

Curious how the threads looked. 
 

-Robert 

[0TreeLemur]

Received re-studded Hartzell "Top-Prop" Friday.   There was a manufacturing defect.  One stud did not have enough Loc-tite, and the roll pin failed.  Called Hartzell and was told that all warranty claims must be submitted through the vendor that sold it to me, so I'll be doing that.   Receiving a brand new prop with mis-applied paint and an incorrectly assembled stud is not super-duper.  I think Hartzell owes me for the A&P labor charge for twice installing/uninstalling this propeller.  We'll see if I get it.

Yesterday I helped my A&P install it.  Torqued right up to spec. no problem.  Test flown, and seems fine.  Prop stops at 10:30-4:30 position looking aft as before. 

 

[carusoam]

Kind of redefines the meaning of built on honor.... doesn’t it?

Go Hartzell!

https://hartzellprop.com/built-honor/

Best regards,

-a-

[0TreeLemur]

2 hours ago, carusoam said:

Kind of redefines the meaning of built on honor.... doesn’t it?

Go Hartzell!

https://hartzellprop.com/built-honor/

Best regards,

-a-

Nice vid.   The robot had a bad day when it painted my prop at the factory... 

I hope they honor the warranty. 

[Yetti]

Earlier in the thread I was wondering how in the heck a bushing goes bad.   I can see buggering one up.  But just sitting there going bad.

[carusoam]

The video is really good... American manufacturing at its finest...

Of course, some things get away...

It’s how they correct the problems that counts...

For that...

I had two contacts...

Mike Trudeau, and Krista Folkerth... (I believe Mike is pretty far up the food chain...)

I reviewed a few emails from 2012... including one from my favorite power and Prop STC writer Bob Minnis...   

Bob supplied some insight to what I was trying to buy for my O...

Best regards,

-a-

[0TreeLemur]

1 hour ago, Yetti said:

Earlier in the thread I was wondering how in the heck a bushing goes bad.   I can see buggering one up.  But just sitting there going bad.

I was afraid it had somehow started slipping, which it had not.  Apparently that sometimes happens.  They make oversized ones for that case.