Pulled the prop this A.M. to repaint it and found that my spinner backplate is severly cracked. The cracks are under the last rivet (small end) of the peice of aluminum that covers the prop hole. They run about 1.5" along the bend in the flange, with two crakcs radiating towards the the center on the face. There is a small triangle piece, about a quarter inch on a side, that is actually missing from the face.
Anyone know of a good place to get this repaired? A local IA suggested it should be welded, but by who?
Any sources for replacements that might be cheaper than the $173.95 advertised by Spruce? Anyone have one they are willing to part with?
Kind of in a rush as there is a YE rally this weekend I am committed to. As always, much thanks.
Bruce
Broken Spinner Backplate
Moderators: GAHorn, Karl Towle, Bruce Fenstermacher
-
4-Shipp
- Posts: 434
- Joined: Mon Apr 22, 2002 11:31 pm
Broken Spinner Backplate
Bruce Shipp
former owners of N49CP, '53 C170B
former owners of N49CP, '53 C170B
-
GAHorn
- Posts: 21302
- Joined: Fri Apr 12, 2002 8:45 pm
Welding is not an approved repair for spinners or backing plates. (I've seen it done tho'. I knew of a Baron with a very small welded crack in it's spinner, and it was doing just fine 5 years later when I last saw it. The mechanic who did it refused to sign anything. It's just a "mystery" repair.)
It's important to have a shim under the spinner bullet to take up any space between the prop-hub center and the front spinner bulkhead. Otherwise the bullet will vibrate until it cracks the backing plate.
It's also inportant to mount the spinner, and then before tightening down the screws, to mark the very tip of the bullet center, then pull the prop thru with a measuring rule or plumb-bob dropped to the pavement. As you rotate the spinner, make certain it's actually centered and doesn't "wobble", before tightening the screws. Check your work afterwards by placing the engine at idle speed, and standing off to the side, observe the spinner to confirm it doesn't "wobble".
(I can only say, that I hope you go ahead and bite the bullet and buy a new bulkhead. It'd take most of that kind of money to manufacture a new one, and welding really is taboo. The heat from welding places stesses that later lead to more cracking. When that thing lets go inflight, it usually doesn't do a lot, but sometimes it creates quite a vibration that's unhealthy for the crank and engine.)
Next time someone wants to have their picture taken with your airplane, tell 'em to keep their !@#$! arms off the spinner and quit leaning on it!
It's important to have a shim under the spinner bullet to take up any space between the prop-hub center and the front spinner bulkhead. Otherwise the bullet will vibrate until it cracks the backing plate.
It's also inportant to mount the spinner, and then before tightening down the screws, to mark the very tip of the bullet center, then pull the prop thru with a measuring rule or plumb-bob dropped to the pavement. As you rotate the spinner, make certain it's actually centered and doesn't "wobble", before tightening the screws. Check your work afterwards by placing the engine at idle speed, and standing off to the side, observe the spinner to confirm it doesn't "wobble".
(I can only say, that I hope you go ahead and bite the bullet and buy a new bulkhead. It'd take most of that kind of money to manufacture a new one, and welding really is taboo. The heat from welding places stesses that later lead to more cracking. When that thing lets go inflight, it usually doesn't do a lot, but sometimes it creates quite a vibration that's unhealthy for the crank and engine.)
Next time someone wants to have their picture taken with your airplane, tell 'em to keep their !@#$! arms off the spinner and quit leaning on it!
-
4-Shipp
- Posts: 434
- Joined: Mon Apr 22, 2002 11:31 pm
Thanks, Bruce and George. Sure enough, AC 43.13-1B, para 4-89.d specifically states 2024 and 7075 should not be welded. I found a backplate from a salvage yard for undet $100, but will most likely buy the new one. Probably cheaper in the long run.
BTW, George, not sure if AC 43.13 was on your list of recommended owner publications but it should be. Lots of good stuff. Only $20 from Spruce.
Bruce
Bruce
BTW, George, not sure if AC 43.13 was on your list of recommended owner publications but it should be. Lots of good stuff. Only $20 from Spruce.
Bruce
Bruce
Bruce Shipp
former owners of N49CP, '53 C170B
former owners of N49CP, '53 C170B
-
Harold Holiman
- Posts: 579
- Joined: Tue Apr 23, 2002 1:54 pm
Cracked Spinner
George,
When my pre buy inspection/annual was done on my 180, it was found to have a "mystery repair" on the spinner which had been done several or many years prior. The then owner bought me a new spinner which was installed before I flew to the Shelbyville convention and I have the old "Mystery repaired" spinner decorating the wall of my office.
Harold H
Mbr #893
When my pre buy inspection/annual was done on my 180, it was found to have a "mystery repair" on the spinner which had been done several or many years prior. The then owner bought me a new spinner which was installed before I flew to the Shelbyville convention and I have the old "Mystery repaired" spinner decorating the wall of my office.
Harold H
Mbr #893
-
JDH
- Posts: 119
- Joined: Mon Apr 22, 2002 5:16 pm
Bruce, when I bought my '52 it had no backplate or spinner. The old one had been cracked. I bouhgt new backplate and spinner from Spruce. 1st annual: Backplate (bulkhead) cracked again. Bought another new one from Spruce, made by Univair. Here is the problem: On the '52, you need a couple of holes drilled into the backplate to get to a couple of cowling screws; if those are not drilled properly or deburred and you get some grease monkey that is not too carefull in moving the prop and gently inserting a small enough screw driver, he forces the hole and cracks the backplate. So, I decided that I could for a temporary fix, get a skull cap, which is in the parts book. Turns out, that is what I kept on. I am told that the biggest difference besides looks is that it does not flow as much air into the cowl openings and could tend to cause overheating. I have not found this problem and it only cost:$30. Spruce page 168 part#10220
Good luck, JD
Good luck, JD
Cessna® is a registered trademark of Textron Aviation, Inc. The International Cessna® 170 Association is an independent owners/operators association dedicated to C170 aircraft and early O-300-powered C172s. We are not affiliated with Cessna® or Textron Aviation, Inc. in any way.