Cracked Spinner Bulkhead now AOG

[jabodine]

This weekend while doing the annual on my 1968 M20e I found that the spinner bulkhead is cracked. This is the piece behind the prop, bolted to the flywheel to which the spinner is attached. I believe it is part # D3338. Any thoughts or good ideas as to where I might source this part? I am AOG until I find a suitable replacement.

Thanks in advance for your help.

Best regards,

Jonathan Bodine

[MB65E]

What spinner do you have? I might have a ring. I had the short original spinner. We changed to the larger cone spinner with the forward bulkhead.

Shoot me a picture of the spinner ring and spinner!

-Matt 

[jabodine]

Hello Matt:

Plan to be at hangar today, will try to get photo when there. Thanks.

Best regards,

Jonathan Bodine

[Wildhorsesracing]

How does one get cracked? Can you post some pictures of the crack and where it is?

[carusoam]

Two part answer to Jim's question...

Stress and strain.  The spinner's bulkhead is made by bending and drilling.  The strain (stretching caused by bending ,and stress magnifiers left by drilling).  A crack can start with these trouble spots and propagate due to the additional stresses under the force of spinning and vibrations.

waiting for the pics to see where the cracks start and run to...

If they start at a hole, it may be possible to remove this type of stress magnifier using a file and emery cloth to eliminate microscopic cuts.  Or stop drilling holes to stop the propagation of a crack that has already been initiated.

The fact that it is happening on the spinner adds to the challenges of balance and other rules to follow.

This is when we go to Cody for professional prop insight...

Best regards,

-a-

[N201MKTurbo]

Don't push on the spinner when moving the plane.

Make sure the spinner is mounted straight. Install all the screws loose, give the spinner a good solid push to get it bottomed, then tighten the screws in sequence. I do the center screws between the blades first then move back and forth towards the blades. Do the little ears last working towards the nose.

Make sure the spinner is clean. When parking outside crud can build up inside the spinner making it unbalanced.

Sometimes bad things happen to good people.... (i.e., $h#^ happens)

[RobertGary1]

If the prop has some hours on it I'd go ahead and send it to the prop shop to look over if you're removing it anyway. They can do misc repairs without having to do a full overhaul. Nothing on your plane experiences as much stress as the prop.

 

-Robert

[jetdriven]

39 minutes ago, RobertGary1 said:

If the prop has some hours on it I'd go ahead and send it to the prop shop to look over if you're removing it anyway. They can do misc repairs without having to do a full overhaul. Nothing on your plane experiences as much stress as the prop.

 

-Robert

the vast majority of prop shops say that  but once they get it, it never comes out without ending up scrapped or completely rebuilt for a ton of cash. be very careful here. 

[mike_elliott]

On ‎3‎/‎20‎/‎2016 at 3:03 PM, N201MKTurbo said:

Don't push on the spinner when moving the plane.

Make sure the spinner is mounted straight. Install all the screws loose, give the spinner a good solid push to get it bottomed, then tighten the screws in sequence. I do the center screws between the blades first then move back and forth towards the blades. Do the little ears last working towards the nose.

Make sure the spinner is clean. When parking outside crud can build up inside the spinner making it unbalanced.

Sometimes bad things happen to good people.... (i.e., $h#^ happens)

Knowing how to install the spinner is key as pointed out by N201MK. Make sure also on the forward centering ring, this is a proper fit on the prop hub. If it is a loose fit, it will be short lived as will the bulkhead and ears.

[FloridaMan]

There are a fair number of used E/F spinners on the market. HOWEVER, if you have a J style spinner, the cheapest solution is to suck it up, contact LASAR and BUY A NEW SPINNER ASSEMBLY. They have the absolute best prices on them. I cannot stress this enough. I have THREE cracked bulkheads sitting on my shelf from the years. If you are lucky enough to find a used bulkhead for a J style spinner for a Hartzell propeller, it will likely have a fair amount of time on it AND WILL EVENTUALLY FAIL. The new design mounts directly to the hub and not the flywheel and does not use the cheek plates. There is fairly tight clearance (~1/16") between the trailing edge of the prop blades and the openings in the spinner dome. This is normal. 

One of my cracked bulkheads was one that had been repaired and failed within 10 hours. The other two I believe cracked after around 400 hours each because of a combination of age and fatigue, and improper mounting and vibration. It is important that the spinner be tight on the hub, especially with the older style spinners that have the bulkhead that is mounted to the flywheel. Both times when pulling the spinners after the "non-repaired" bulkheads cracked, they were clearly not on very tight. The mechanics who mount them tightly that I've seen place a ring of tape (teflon, copper, et cetera) around the hub where the ring on the spinner attaches. Those little "cheek plates" that are inserted under the spinners fail also and tend to run $300-$500 IIRC. 

Edited March 26, 2016 by Antares

[BubbaDoc]

There are numerous spinners on the market, but the easiest and cheapest is to have it FAA welded and heat treated. Most of these cracks form from the spinner moving over the inner bulkhead mount. I had the same problem, talked to all the experts only to find out that tightening the inner bulkhead fixes the problem. If the crack is not fixed quickly you will have a bulkhead blowout. After being looked after by A&P's, the blowout took out the left quarter of the upper and lower cowling. If you need the gentleman in Wisconsin contact let me know. I have 250 hrs in 1 year on the fix.

[carusoam]

Welcome aboard, Bubbadoc.

Best regards,

-a-

[1524J]

Checking the spinner bulkhead is part of my pre-flight now.

[Cyril Gibb]

Two part question related to AOG:

1) is it legal to fly without the spinner?

2) is there any risk (legalities aside) associated with flying without a spinner?

[Guest]

Here are 2 bulletins relating to J model spinner bulkheads.

http://www.mooney.com/en/sb/M20-219.pdf

http://www.mooney.com/en/sb/M20-201.pdf

Clarence

[1524J]

40 minutes ago, M20Doc said:

Here are 2 bulletins relating to J model spinner bulkheads.

http://www.mooney.com/en/sb/M20-219.pdf

http://www.mooney.com/en/sb/M20-201.pdf

Clarence

Thanks Clarence! I'm not sure if we complied with the service bulletin when we replaced the bulkhead but I'll check now. Part of the challenge of having parts from two different Mooney models. 

[carusoam]

Something to consider...

It is apparently an AW issue to not have the small sheet metal plates that fit behind the prop in the spinner of the C.

Not having the spinner would follow the same logic. Apparently all the test flights supporting the airplane's AW had a full healthy spinner on it at the time.  Any changes from that become an AW issue.  Paper / legal issue, not so much spinning balance or WnB issue.

I am not a mechanic. Just been here a while...

Best regards,

-a-

[sreid]

On 3/25/2016 at 4:55 PM, jetdriven said:

the vast majority of prop shops say that  but once they get it, it never comes out without ending up scrapped or completely rebuilt for a ton of cash. be very careful here. 

That may be true, but there are exceptions. Cody Stallings runs Stallings Aircraft Propeller in Arkansas. He has IRAN'd my propeller and done a fantastic job, with quick turn-around, and charged reasonable prices.

[FloridaMan]

I have some of those doublers.