Cowling hinge pin "stuck"

[Steve Brown]

Hi guys,
This is a flying RV9A with over 400 hours on it. These pins have always been a little tight, but nothing alarming. So this was an annoying surprise
Yesterday after an oil change, I could not get the hinge pin in on the pilot side hinge joining the top and bottom cowling.
I have narrowed the problem to some misaligned and/or partially crushed eyelets (teeth, knuckles, or?) On the top hinge.
Not sure how they got so bent, but they are.
I managed to get them aligned and opened enough to get the pin into that hinge half, but barely.
Pin easily goes in the other half. The copilot side is fine. A little tight as usual, but no problem.
Wondering what tools and techniques others have used to align and open these eyelets.
Help appreciated!

[thinkn9a]

Do a search with. ?Grinding compound hinge?..... it should return one item with title above.

Lots of good info in the thread including,... check alignment of each eyelet by pushing pin in (and looking at entry to each eyelet)...


Good luck

[Scott Hersha]

Tips and tricks - first place, when you remove your cowls try to sit them on a piece of carpet, towel or something else so you damage the hinge eyelets on the floor. Now that you have maybe flattened a couple of them, try to get them round again manually one at a time, which sounds like you?ve already done. Now here?s the trick - get a length of stainless hinge pin material the same size as what you have. You may be able to find it locally. Next flatten one end of the pin with a hammer on a piece of hard steel, like on your bench vice, making it look a little like a duck bill - but not too flat because your going to be using it as an auger to run through your hinge and the goal isn?t to make it all hogged out and huge - just easier to insert your pins. Put a tapered point on the flattened end with a file or scotchbrite wheel, not sharp, just talered so it can guide itself through. Finally, chuck the not flattened end of the modified pin into your drill, lube it up with some grease or boelube, and with the cowling in place on the airplane, work that modified hinge pin through the hinge while spinning it with the drill. It?s a good idea to have a helper to hold the cowl halves together for alignment, and to steady the flexible hinge pin with their hand while you do the spinning while applying some force with the drill. You might want to do that to both sides if the other one is too tight.

[RV Jerry]

If you are unable to get hinge to align satisfactory .078 Bowden cable can be used instead of the .090 standard pin.

[Steve Brown]

Thanks Guys!
For the good advice and links.
I ended up reading & absorbing all of it and doing a similar variant possible with what I could get my hands on today. I couldn't find a hing with appropriate size pin to make a reamer so:
To open the eyelets I bent a couple of nails into an "L", with the bottom leg slightly less than the half inch pitch of the hinge. The one I used on every eyelet is about 98 mils. The other I used on a few problem eyelets is about 113 mils.
The big one seemed to open the eyelet seam excessively so I only used it on a few.
Once they were opened, trial and error trying to put the upper & lower cowling together on the hangar floor. Marking misalignment, taking it apart and bending the offending eyelets into position. I used the small nail to keep the eyelet open while bending.
Eventually I could get the rod into the problem hinge without pliers, and finally get both halves together with minimal use of pliers.
It went on the airplane with only slightly more difficulty.
After the nail treatment, the good side went on easier than ever.
For follow up I'm going to:
Replace at least the one rod because it is a little tweaked and rough after all this manhandling. I'll get the standard size and something a little smaller and then make the choice next time I put it together. Whether rod from Mcmaster or Bowden center wire TBD.
I also want to polish the inside of the eyelets a bit using a standard rod and some grinding compound. I just need to get the rod.

Thanks again!

[Scott Hersha]

You can buy extra pins from Vans Aircraft. They are rolled into a circle about 24? in diameter for packaging. I found them locally at a metal supplier. The reamer idea works - every time, and it?s a quick fix. A smaller diameter pin won?t be as strong and hinge fit will be a little sloppy.

[Steve Brown]

I guess one big advantage of the reamer is that it comprehends the departure angle from the previous eyelet.

I'll order the pins to make one.

[Ron B.]

You probably flew your RV before changing the oil heating things up. I always have difficulty reinstalling the cowl on both the RV's I built if the cowls were hot. But they always slide right in if removed cold or, are only installed after things have cooled down. Try it next time. They probably had cooled down by the time you got them installed?

[thinkn9a]

In fact, if you can find lapping compound you might use that.

[Berchmans]

Another alternative is check the McMaster Carr catalog for steel pins of slightly smaller diameter. As the eyelets wear over time you can increase the size of the pin for a tighter fit. Working so far for me.