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  #1  
Old 07-09-2018, 10:15 AM
jacksel jacksel is offline
 
Join Date: Jul 2005
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Default Difficulty fitting spinner after prop repair

I have a Hartzell C/S on my RV-6. After 14 years and 800 hours it started seeping grease out a small section of the hub split. I sent it in for inspection and repair, and when I put it back on the airplane the front plate holes didn't line up with the corresponding holes in the spinner (~1/4" off). Is this a normal potential consequence of disassembly and reassembly of the prop? A mechanic friend of mine told me the 4 holes attaching the front plate to the prop are usually elongated (more like curved slots), allowing some rotation of the front plate before it is tightened in.
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Old 07-09-2018, 10:37 AM
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Ironflight Ironflight is offline
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Yes, this is normal. The front cylinder doesn’t always end up at exactly the same spot when the prop is re-assembled. I have never slotted the bolt holes - have either made a new bulkhead or if the offset is far enough, mounted new nutplates.

Paul
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  #3  
Old 07-09-2018, 10:44 AM
jacksel jacksel is offline
 
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Thank you Paul.

John Walsh
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Old 07-09-2018, 10:44 AM
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Dale D Dale D is offline
 
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Default Elongate the Front Plate Holes

Jacksel,
I just went through this same experience with my RV-9a and Hartzell C/S prop a couple of months ago.
My prop was resealed by a reputable prop shop. When they reassembled the front hub to the specified torque, the front spinner plate holes no longer matched the spinner's holes. They were off by 1/4" - 3/8".

As a side note, the prop shop told me that those 4 threaded prop hub holes were originally intended for assembly/disassembly. Vans conveniently uses them for the front spinner plate.

The solution was to create a template with curved, slightly elongated holes where the 4 bolts mount through the front plate. Remember, if you are off by 1/4" on the perimeter of the front plate, it won't take much near the mounting holes to achieve this.

I actually drew up my template in AutoCAD to make an accurate template of the elongated holes. I then taped the template to the front plate. Then, I took a Dremel tool and appropriate bits to slowly and carefully elongate each of the 4 holes, according to my template. I finished the the holes by lightly filing them smooth with round files.

If you would like any help developing an accurate pattern with CAD, just PM me. I would be glad to help.

Dale
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  #5  
Old 07-09-2018, 08:05 PM
jacksel jacksel is offline
 
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Thank you Dale. I actually hadn't thought of that geometric relationship between the screw holes and the plate attach bolts. Makes sense. If the holes are off by ~3/8" then the elongation required at the bolt holes is considerably less.

John
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Old 07-09-2018, 08:25 PM
Ralph Inkster Ralph Inkster is offline
 
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Much easier to mount front plate 90 degrees from original position and remark new hole positions thru the spinner screw holes, followed with drilling & mounting new nutplates. This will insure that plate and spinner stay true.

I'd worry about maintaining true centerline if elongated holes were used.
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Old 07-09-2018, 08:48 PM
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JonJay JonJay is offline
 
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I just drew three large circles on the bulkhead, center line bisecting the existing holes, inner line, outer line, drilled my new holes and used a rat tail file and filed to the lines to make an arc between the holes.
My spinner remained true. Not sure how it could get out of true at the front bulkhead. The backplate is pretty stiff and there are a lot of screws holding the spinner to it. You would have to force something, not even sure you could.

Mine where out about 1/4" final slot length.
It took no time at all to do this.
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Last edited by JonJay : 07-09-2018 at 09:01 PM.
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Old 10-09-2019, 07:23 PM
jliltd jliltd is offline
 
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Quote:
Originally Posted by Ralph Inkster View Post
Much easier to mount front plate 90 degrees from original position and remark new hole positions thru the spinner screw holes, followed with drilling & mounting new nutplates. This will insure that plate and spinner stay true.

I'd worry about maintaining true centerline if elongated holes were used.
Since the 4 mounting holes are 90 degrees apart I can't for the life of me figure out how this works.
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  #9  
Old 10-10-2019, 04:45 AM
cajunwings cajunwings is online now
 
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Default Forward Spinner Bulkhead.

If the prop dome is removed and reinstalled its almost certain that the bolt holes will be in a different location. The fix is easy. You can install a new bulkhead or just relocate the nutplates. If it?s a small amount just slot the holes. If it?s more move the nutplates. The bolt holes are 90 degrees apart and the 6 nutplates are 60 degrees apart so by installing the bulkhead in a different position you should be able to find a spot where the nutplates can be installed away from any of the previous holes. It?s very important to use bolts that are short enough in the dome. The threaded holes are not very deep and if a bolt is bottomed out and tightened its possible to break the dome.


Don Broussard
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  #10  
Old 10-10-2019, 08:11 AM
jliltd jliltd is offline
 
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Don,

Aha! My front bulkhead has 4 nutplates. Not 6. So the re-clocking of the bulkhead around the 4 prop dome bolts won't result in any nutplate clearance. Hence my frame of reference with respect to my question of how that works.

And you are right about the four 1/4" AN4 bolts that attach the bulkhead to the dome. My bolts are very short and still have 3 washers stacked up under the heads.

In my case I wanted to paint my Hartzell black while my engine was at Barret Precision getting 4 new Superior cylinders. My original ECI Titan cylinders slung their nickle coating at 260 hours since new.

I almost painted the blades myself but decided to send it to a certified prop shop and let them do it. They did a reseal and flush so the dome came off and was retorqued resulting in the front bulkhead position issue.

Thanks for the information.

Jim
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