Spinner Bulkhead Replacement

[Ratso]

It seems my spinner has developed a "wobble". Putting slight pressure on the spinner causes a small amount of movement in the back plate. I removed the spinner and there is no visual evidence of a crack in the exposed areas of the backing plate. My assumption is a crack(s) have developed under the prop. I located a replacement at Univair (p/n u0550162-3) for $296.51. I also searched the archives and noticed that price is significantly higher than what was discussed in forum topics in 2003, although 100LL is significantly higher than in 2003.

Questions: Will my existing spinner attach directly to a replacement bulkhead? Anything else I should look at while the prop is removed? Any source for a quality bulkhead at a lower price?

Thanks for any advice.

Steve
1953 170B
N3244A sn 25888
Home field D25

[flyguy]

You need to make certain that the inside diameter of your spinner dome is within .010" of the outside diameter of the replacement back plate you intend purchasing. There are domes and backing plates manufactured by various sources that are .062" difference. After you dismount the propeller you may find a radial crack through the bolt circle. I doubt that a condition like that would produce a wobble as you have described. Check the integrity of the rivets holding the bulkhead in the forward end of the dome - - the one with the big plug that rides in the center of the prop. good luck - - -I will pm you

[GAHorn]

Fitment of the spinner to the dome in any postion other than exactly-centered is what produces "wobble" as the prop turns.
Careful fitment/centering is required to prevent "wobble".
Accurate placement of the dome upon the backplate prior to final torquing of the mounting screws is not easy. To accomplish that requires patience during the installaton. I use a crayon to make a mark/dot on the very tip of the dome. I mount the dome onto the backplate, leaving the screws only finger-tight. I use a stiff board or simiar, stood vertically in front of the prop and make a corresponding mark on the board exactly opposite the crayon-dot. (This marks the exact height of the dot above the hangar-floor.) Next, I rotate the prop by hand one-half rotation (using appropriate caution re: hot mags) and observe if the dot moves away, up/down from the index-mark on the board. I readjust the dome upon the backplate repeatedly, turning the prop repeatedly, until the dot no longer shifts away from the board index-mark. Now I have certainty the spinner dome is actually centered upon the backplate, and tighten the mounting screws. A re-check after tightening the screws confirms the dome will not have "wobble". Now the problem remaining is to ascertain that the plug fits tightly to the prop hub to avoid future shifting of the dome. (Not to mention that a loose dome will contribute to backplate cracking as it continuously flexes the backplate.)
Most folks use some sort of common tape. I found that the common method of "shimming" the dome's interior plug to the prop-hub, that of using tape...wrapping it about the plug, was unsatisfactory. Not only did that method require tedious trial-and-error to find the "right" amount of tape to provide exact thickness to take of the space between plug and hub....
.. I found at each inspection that the tape either deteriorated or slipped out-of-position, which allowed the dome to loosen and "wobble". I felt I needed something that would allow me to fit the dome easily, but which would "adjust" to the exact thickness required.... stay in-place.... and not absorb moisture or contribute to corrosion of the prop-hub or spinner.
The product I use in my fix might be unique. While building my hangar, the metal-supply company provided rolls of "expandable rubber-foam weatherstripping". This is a type of adhesive-backed tape which is made up of compressed, quite firm, black-rubber-foam, which after it is applied, slowly expands or relaxes to fill any space into which it's been inserted. It is 1" wide and a length of it only 1" long will expand into a 1" cube as it relaxes subsequent to being compressed. It can be re-compressed many times and it will re-expand over a short period of time. Being designed for weatherstripping metal, it does not absorb or hold water.
I cut 4 short 1" strips of it, squeezed it flat/thin with my fingers, and stuck it to the spinner-dome plug sides, then installed the dome inserting the plug into the hollow prop-hub as intended. The short foam-tape strips expanded to fit the hub, and the nature of the foam holds the spinner properly. No more trial-and-error of fitment, and no more wobble. (And less chance of future cracks developing in the backplate because of a loose dome.)
It comes in 25' rolls... enough to supply a squadron. I have a roll of this stuff remaining, and can share it. It only requires about 4" of tape cut into short pieces. (Let's avoid filling up this thread with requests, however. Send me any request by email only.)

[Ratso]

Sounds like backing plate cracks are not an uncommon occurrence--either from incorrect mounting or victims of hangar rash. It appears the prop will come off this weekend. I'll post with the results.
Thanks!
Steve
N3244A

[FredMa]

I guess we should have asked first if you have a spinner with the front plug or front plate. The problem is most likely one of these. If it is the plug type it probably can be fixed as George described. If you have the front plate you may have cracking of the plate that follows the circumference of the prop bolt heads. This is what happened to mine.

[Ratso]

Update on spinner "wobble" problem. After a pleasant conversation with Ole Gar, he recommended before I remove the prop I should first-off verify a tight fit exists between the spinner boss and prop hub. After removing the spinner close inspection revealed the material used to make a tight boss-to-hub fit was black ATV sealant. Some of this had worn away and the fitment was loose. Also, some of the ATV material had pooled and dried in the spinner itself causing an out of balance condition.

After removing all offensive material and cleaning all parts, I used a material recommended by ole gar to create a good tight fit between the spinner boss and propeller hub. Reinstalled and trued spinner using George's technique. Flew myself (and wife) to brunch yesterday and spinner turned straight and true.

Thanks for all the advice.

Steve
N3244A

[wingnut]

" I used a material recommended by ole gar to create a good tight fit"


It didn't involve alum did it?

[buzzlatka]

I had this same problem with the old spinner and just switched to the skull cap type spinner. Looks nice, easier, and a lot more simple. It makes the lower cowling removal easier too.

http://www.aircraftspruce.com/catalog/a ... ullcap.php

[redneck]

Buzzlatka, you wouldn't happen to have a picture of your skullcap spinner wouldya? I'm trying to imagine how your spinner is different enough to make removing the lower cowl (ugh!) easier, but that sounds interesting.

[n2582d]

Buzzlatka, you wouldn't happen to have a picture of your skullcap spinner wouldya? I'm trying to imagine how your spinner is different enough to make removing the lower cowl (ugh!) easier, but that sounds interesting.

http://www.aircraftspruce.com/catalog/a ... ullcap.php

05-21600w.jpg (28.92 KiB) Viewed 6527 times

[Bruce Fenstermacher]

Redneck, in 52 and prior cowls SOME but not ALL spinners with back plates make is nearly impossible to remove a few of the screws behind the back plate in order to remove the cowl. My own spinner on m first plane was not much of a problem with some special Phillips screw driver bent at a 90° angle or a low profile ratcheting type. Reverting to the skull cap type spinner eliminates any spinner back plate and these screws are easily removed with common Phillips.

[redneck]

Bruce, showing my ignorance here. How does the skullcap spinner attach without a backplate? Those 2 lower cowl screws are hex head screws on mine, so I can get a small wrench on them, but it's awkward. The curvature of the top of this lower cowl makes it (for me) impossible to remove it (with the prop and backplate installed) without roughing it up a bit. Would the skullcap spinner make that easier also? And, does it look goofy or ok? Roger.

[n2582d]

Roger,
The skullcap spinner doesn't fit over the prop, it fits on top of the front of it. The mount shown below fits under two of the bolts as seen in the IPC.

[flyguy]

" I used a material recommended by ole gar to create a good tight fit"


It didn't involve alum did it?

HAY JUARKIE ALUMY DOANT WURK LESSN U GOTS SUM LUBERKASHUN. NO SWEAT NO SWELLIN. ER SHRINKIN TU

[flyguy]

Redneck, in 52 and prior cowls SOME but not ALL spinners with back plates make is nearly impossible to remove a few of the screws behind the back plate in order to remove the cowl. My own spinner on m first plane was not much of a problem with some special Phillips screw driver bent at a 90° angle or a low profile ratcheting type. Reverting to the skull cap type spinner eliminates any spinner back plate and these screws are easily removed with common Phillips.

IFFN JU LOOK AT THE BAK PLATE THERE IS A HOLE THAT WILL LINE UP FOR URE SCREWDRIVER JEW ROTATE THE HOLE TO LINE UP WIT DA SCREW! ! ~@~@~ !