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Removing taper pin in tailwheel stinger bracket

Greg Arehart

Well Known Member
Years ago I replaced the bolt in the tailwheel stinger with a taper pin (fat end down, the only way to actually get it in place). Doing the annual, I've found that the nut on the pin, along with the threads, have broken off. I have tried popping it out using a punch from the top, but no joy. Considering cutting a slot or drilling a hole in the bottom to see if I could add some twist along with the punch. There is about a 1" diameter hole in the skin around the fat end of the pin; no easy way to get a decent grip on the pin.

Looking for any additional potential thoughts on how to remove this pin so it can be replaced.
 
possible idea

Drill a hole up from the bottom and use an easy out used for removing bolts and screws that lost there head or too buggered up to get a screw driver or wrench on it. Use Kroil or Mouse Milk to penetrate. Also twist the tail spring while trying to remove it.

Steve
 
I wish you luck, let us know if this works.

Well, Greg this is a real challenge. You probably know this but just so it is stated . . think of it this way, the taper is a wedge, and the contact stress is massively (how about that for a number) multiplied by the force generated by the nut.

I have one in my tail spring. In talking to two different guys at the paint shop, one said - i removed the tail spring to paint it. The taper pin came out fine. [that is because I torqued it to 10 in-lb] I asked what torque he used to reassemble. "Standard torque" 25 in lb is standard but based on all the others, it was likely 30 in-lb.

The second guy said - -"just a warning, you have to take off the rudder to get the lower fairing on - I could not get out that taper pin."

How to remove - You can assume that it was highly torqued and contact stress is on the order of yield strength of 4130 (63,100 psi). The very reason they stay put. My plan would be to center punch and drill a #40 hole or #30 hole in the center of the taper pin, and drill 1/8" short of exiting the opposite end. Maybe more, we really don't want to break off the end. Then expand the hole until it nearly reaches the thread diameter. Lastly use or make a pin punch to fit in the hole and use it (with a heavy mass backer on top) to drive out the stress relieved pin. Twisting, heating, penetrating oil is useless for helping as both materials will expand the same.

I should say - make the pin from someone very strong - like "piano wire" it is on the order of 200ksi, so it can handle the pounding and not expand into the hole. Just leave a short piece extended so it is less likely to bend.

Oops - yours is in from the bottom, so needs to be driven from the top. This is more tricky - -OK - stress relief with a #30 bit will still help, but hammering from inside the fuse is an issue. I might compare tapers and use something like an HF stepless taper drill to open up the large end with the intention of using the original taper reamer to work the hole larger until the wall is thin enough to easily be tapped through from the top. EEK! this is a tough one.

The Theory: Drilling the hole, relieves some of the contact stress, and using the pin punch tends to stretch the pin on impact thus reducing the diameter as it does so. Using this theory worked very successfully for me in removal of a couple of thousand VW valve guides.
 
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Kroil is the best I have ever found for getting stuck things apart.

I would give it a good soaking with Kroil, then using a drift try to drive it out. Do not use a pointed punch, it will expand the end and make things worse.

A possible way is to use an air hammer if you can get one in there. The repeated impacts seem to make a major difference vs. using a hammer. Tapered fit stuff usually needs a good sharp impact-----think ball joint or Morse taper chuck.

If you are going to replace the tail spring, try using heat?
 
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Applying a little heat (heat gun or propane torch) to the stinger near the taper pin should make removal a lot easier

Warren S
Minneapolis
 
Well, got it out. I pulled the rudder and one elevator off so I could get into the tailcone a bit easier and without banging up something with a hammer. I soaked it in some kroil for a while. Then had a buddy with some needlenose vice grips grab the fat end and put some twist and pull on the fat end while I used a drift pin on the narrow end and eventually it loosened up and came out. Difficult to do because of the angle, about 15 degrees off centerline. Whew! I was not looking forward to trying to center drill that pin to try to relieve some of the stress.

Another option we thought of was to drill and tap the pin and thread a bolt in there and use a slide hammer to pull it out (rather than pushing with a drift pin) - in case anyone is reading this down the road with a similar problem that might be worth a try.

Thanks for all the suggestions, happy that I didn't need to attempt any more than I did.....

When it gets replaced, I'm going to use a longer pin so that there is more of the fat end sticking out to grab if it ever becomes necessary again (hopefully not). And the stinger will get a fresh coat of paint now.

Cheers,
Greg
 
Well, got it out. I pulled the rudder and one elevator off so I could get into the tailcone a bit easier and without banging up something with a hammer. I soaked it in some kroil for a while. Then had a buddy with some needlenose vice grips grab the fat end and put some twist and pull on the fat end while I used a drift pin on the narrow end and eventually it loosened up and came out. Difficult to do because of the angle, about 15 degrees off centerline. Whew! I was not looking forward to trying to center drill that pin to try to relieve some of the stress.

Another option we thought of was to drill and tap the pin and thread a bolt in there and use a slide hammer to pull it out (rather than pushing with a drift pin) - in case anyone is reading this down the road with a similar problem that might be worth a try.

Thanks for all the suggestions, happy that I didn't need to attempt any more than I did.....

When it gets replaced, I'm going to use a longer pin so that there is more of the fat end sticking out to grab if it ever becomes necessary again (hopefully not). And the stinger will get a fresh coat of paint now.

Cheers,
Greg

Excellent!!, glad it came out that way. The drill etc would absolutely be the last resort. I ordered 2 extra taper pins for the time mine must be removed.
 
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