Top Prop Spinner Problem

[scottfromiowa]

That operational restriction on a "Top Prop" for the M20E would be a deal killer for me.  I am a 25 squared ( or what I can get with ram air open at altitude) and lean guy in cruise.  I run LOP almost always without Gami's.  I have NEVER had cylinder temp issues with this setting.  Why buy a Mooney to give up speed in cruise for a couple of gallens of fuel and then spend thousands on mods to make it go a couple knots faster...doesn't make sense to me...same as these prop limitations don't make sense.

 

[Stefanovm]

I run at 2600 or 2550+ unles I am flying slowly on purpose. This results in more power, more speed, and no MP limitation. There is nothing magic about 2500.

[skyking]

Steph. Thanks for posting all the info.

I have just had this prop installed about 100 hours ago and i am leaving on a cross country tomorrow morning.

I will be putting about 60 hours on in the next few weeks.

I will need to take a good long look at mine tonight.

Russ

[scottfromiowa]

O.K. Got it...

Ephiphany for me as I could never understand the 24 squared guys...and was doing the same thing at 25 squared based on Bob Kromer's MAPA article that made sense to me.  Just "bad" harmonics or whatever at this RPM for Top Prop, but fine for 2600rpm or greater...I will check this out when I get my EI fuel flow installed...

I guess we just get "set" in our ways when the engine and prop don't fail at a certain power level...Maybe I will become a 2600 RPM guy since engines are supposed to make TBO at max rated power.

Do you notice much more noise at 2600?  I have a Bose, but still notice a significant reduction in noise/harmonics when I reduce from 2700rpm (climb) to 2500 in cruise.

On another note I recently felt very sheepish as I was going into lean find and pulling mixture to the point of rough run...and enriching 50 degrees...engine monitor (GEM) wouldn't find peak...then I learned that I was always lean of peak when a cylinder peaked (forgot to take off of lean find) when I enriched for decent...Big Homer Simpson DOH!...but I was seeing good ground speed so didn't worry about it...and good fuel flows at my LOP...by accident setting.  I was always wondering why I had solid bar accross the top for exhaust gas...and was NOT finding peak EGT, SIGH...result is I am now burning a little more fuel and going faster with 50 degrees rich of peak instead of flying max LOP.  Engine seems to perform well at both mixture settings.

[Stefanovm]

Scott,

I do not notice much noise reduction until 2300. I normally use 2550+ or 2600 and I can converse with passengers. My intercom can take 6 positions, but only has two run at the present time. With passengers I only wear one headphone and run speaker for all to hear.

Russ,

Should be no problem as correction to spinner attachment was made about 2/09. Yours sounds newer. Mine missed  as it sat in a hanger for over a year not being flown and was purchased relatively soon after the Mooney STC approval.

[Stefanovm]

I had to take today off from work for a medical procedure. When I got home there was a new spinner on the front porch. If I get the energy, I will take off the old and photo the support difference. Doc said take it easy, no work or driving for next 24 hours. Is changing a spinner considered work? Many thanks to Harztzell!

[MooneyMitch]

Quote: Stefanovm

I had to take today off from work for a medical procedure. When I got home there was a new spinner on the front porch. If I get the energy, I will take off the old and photo the support difference. Doc said take it easy, no work or driving for next 24 hours. Is changing a spinner considered work? Many thanks to Harztzell!

[Stefanovm]

My Mooney's hanger is in my backyard at 07TS, a residential airpark. I can walk 20' to the "fun". That is my opinion also.

[Stefanovm]

The concern starts now.  The parts look identical, except for damage on exisiting spinner. What caused the failure? Will send all photos to Hartzell. A little grease or something on mount hub and inside the spinner, and several very tight screws in the lock nutplates. The front fit looks okay from reading the manual, no chafing, and feel upon removal.

[carusoam]

Stefan,

For your consideration.....

From the original installed photos...

Firstly, Follow whatever the manual says.  Let me know if the following makes sense...

[1] It looks like there is no spacer under the screw where the crack is.   It looks like that screw is holding the spinner dome against the backing plate (somewhate against it's will), the curled edge where the blade comes through is trying to stay off the backing plate.

[2] When you mount the new one,  The curled edge will be in the same place.  The screw will pull the spinner dome metal toward the backing plate.  The tighter the screw, the more bend in the metal.  This bend will stress the metal at the screw hole.  Stresses lead to cracks.

Two things come to mind,  the curl on the blade hole adds strength to the un-screwed blade hole, so it can't be removed.  A spacer will allow for tightening without bending under this adjacent screw.

Since the crack on the old spinner occurs in the exact same place, twice.  You got two experiments for the price of one.  Without the spacer you got cracks.  New dome is identical to old dome.  I would be thinking the proper spacer in the proper location will keep the dome from bending when tightening.  No bending will lead to no cracking.

Keep in mind the method used to manufacture the spinner dome leaves the aluminum in a relatively thin and brittle state.  Minimizing the stress put on it during installation will keep a crack from initiating.

On the old spinners, there were two filler pieces that fit in that area.  The dome wouldn't crack, but the filler pieces would.  There are many stop drilled spacers on old spinners.

Overall:

Forces from spinning are tremendous.  Avoid any additional stress applied to the metal when tightening it in place.

Best regards,

-a-

[Stefanovm]

Makes sense, but spacers (washers?) are not shown or detailed in installation manual as far as I can tell. I might try them to relieve the obvious stress.

[carusoam]

In the first drawing you have posted above...

I am intrigued by the inset drawing indicating Spacer "A".

If it is the proper drawing, it indicates a stack of hardware: Screw head, Spinner, SPACER "A", wave washer "B", washer "C", bulkhead, washer "D", nut "E".

The second drawing you have posted is the original, short "bullet" shaped, spinner that does not have the internal support that fits snugly around the front of the hub.  (This cannot possibly be for your new spinner, it does not match).

I think Hartzell owes you the information on exactly what hardware is involved.  There should be part numbers and the number of each set of hardware required.  I would think that spacers are only required in two or possibly four places for the reasons stated above, not in all places.  Again this should not be a guess.  I don't think that spacers are standard practice either.  Meaning, a trained A&P is not going to see this as an obvious and proper way to mount the spinner.  (at least not without the instructions from the manufacturer).

Too much risk of new cracks to try something without having the proper knowledge from the manufacturer.

Best regards,

-a-

[721lp]

This topic makes me feel better about my decision to put the original style prop back on my C model back when Hartzell had them on "sale". I didn't think mine would make it through another overhaul, so I just replaced it with a new original prop. No probs. so far......

[carusoam]

721lp,

Do you still have the small filler pieces that cross behind the blades?  Are they whole?

It seems prop hubs and blades are still an area of trial and error, on top of a great deal of science and engineering...

[721lp]

Carosuam.....Yes I have the cross pieces. I replaced the spinner when I got the airplane, because it was cracked in 2 places and had been stop drilled also. I just didn't want pieces flying off the nose.

Agreed, prop engineering, like everything else in GA flying, is worlds behind the engineering advances of today.......mostly because of the insane costs due to FAA certification.

[Stefanovm]

Quote: carusoam

I think Hartzell owes you the information on exactly what hardware is involved.  There should be part numbers and the number of each set of hardware required. ........Meaning, a trained A&P is not going to see this as an obvious and proper way to mount the spinner.  (at least not without the instructions from the manufacturer).

Too much risk of new cracks to try something without having the proper knowledge from the manufacturer.

[tony]

just wondering .......what was the final outcome?

[Kevin]

Here's how it ended . . .

http://www.mooneyspace.com/index.cfm?mainaction=posts&forumid=1&threadid=2202#post24115

[jamesm]

Question: Regarding  the new top prop for a  '67 M20C. I noticed that newer top prop spinner doesn't have the filler plates ( I am not sure what technical term /name is) but it the plates goes behind trailing edge of the prop blade  and is ahead spinner bulkhead for a tighter aerodynamic seal or at one would think so . Plus I would think that the filler plate  would give the spinner more strength as well. The older  Hartzell has the filler plates. Is there a reason for  removing them on the newer top prop?

 

[carusoam]

The older hartzell filler plates cracked at the screw holes too.

Best regards,

-a-

[Lionudakis]

My first spinner had the filler plates, along with instructions not to use it, just install hardware in the holes. My replacement spinner had no holes drilled at all for the filler, the new spinner did have a bulkhead in the forward part of nose that slips over the front of the prop hub, the first one didn't. less than 20 hrs on first, over 100 on current with no cracks. 

I don't fly enough !

 

[carusoam]

I saw a modified P51 today with a pair of counter rotating props.  The filler plates were cracked and stop drilled.

 

Best regards,

-a-

[jamesm]