RobByers

RobByers

Member
I bought a new torque wrench. I misred the scale the first time I used it. End result, I overtorqued an AN3-5A on my upper rudder hinge bracket. :eek: Yep, it broke. I can't reach the back side to twist the shaft out of the nutplate. What the heck do I do now?
 
alpinelakespilot2000 said:
Go to the hardware store and buy a screw extractor kit. Cost about $7-10 in the tool section at Lowes or Home Depot. Good luck.
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Thanks. What are the chances I gooned up the nutplate? I am hoping, by design, the neck of the AN bolt breaks before the threads yield. I'll never get that nutplate out without taking the skin off. :(
 
plate nut

I would install a new plate nut. they are not as strong as the stop nuts normally used. better be safe on the rudder.
 
Nut plate extraction.

It will probably be impossible to extract the bolt. If possible drill out the nut plate and replace it. Something similar happened to me when my torque wrench failed. So much for Harbor Freight torque wrenches. It worked for a while then failed.
 
If I overtorqued a bolt enough to break it, I would change the nutplate.....Expecially since it is on the rudder!

Get over the shock and drill the rivets out holding the skin, only take out what you have to to get access.

Drilling out rivets is a normal part of building an airplane. Go slow and don't make a bunch of oversize holes.

Fix it and move on........
 
Rope trick

Hi Rob,

It sounds like you are ready for the "Rope Trick". You are in luck as the area your nutplate is located, is not hard to get to, you have good size lighting holes less than a foot away so this will be easy.

First drill out the nut plate with the sheared bolt still in it, if possible do it so that when it is free you can shake it out of the top end of the vertical stabilizer.

Now for some fun, take a length of safety wire ( 0.020 works fine) about twice as long as the distance from the end of the fin to the bolt hole you just emptied (about 2.5 feet long). Put a washer twisted on the end of the wire (end of wire through center of washer, fold wire back next to its self and twist about three turns) that will end up outside the spar so that it will not get pulled through the bolt hole. With a little work you start the other end of the wire in through the bolt hole from the bracket side of the spar and work it out of the first lighting hole(nearest hole to the spar).

Now you should have the safety wire going in the bolt hole and out the top of the vertical stabilizer. Make a small aluminum square about 3/8 inch to the side from any scrap you have and drill a # 52 hole in the center, it may be easier if you drill first and then cut the small square. Slide a nut plate on the wire so that the flat side is set to end up against the spar (wire through the center hole in the nut plate the same as the bolt would enter) and let it slide down the wire, now add the small square you made above to the wire and let it slide on some. Bend the wire back on its self and twist a knot in it so that the little square can not slip off.

Now you can pull on the washer end of the wire until you get the nutplate flat against the inside surface of the spar. Use a small diameter awl to line up the rivet holes of the nut plate with the rivet holes in the spar and insert a 3/32 silver cleco into one of the rivet holes. The nut plate is now where you need it.

Use two CCR-264SS-3-2 pulled rivets to secure the nut plate to the spar and you can cut the wire and shake the inside end out of the top of the vertical stabilizer.

It is simpler than it sounds and can be used any place you can fine both ends of the wire.

Good luck.

Best regards,
Vern
 
Vern, that is a very clever idea that I hope I don't ever have to use! But I will try to remember it.
 
I don't mean to belittle your situation, but that isn't a disaster. A disaster is breaking a chunk off of your canopy or dropping a pneumatic squeezer in the middle of your completed wing (I have seen the results of both).

If you're worried about the nutplate, drill out those pop rivets...swap the nutplate out. You'll be done in an hour.

For future reference and for all future builders...the proper torque for AN3 and AN4 bolts is much smaller than you may expect. The difference between the proper torque and the torque required to break the bolt is huge.
 
..ok...THAT would be a disaster. I hope I don't do those also! Thanks to all. The extractor got the bolt out and the nutplate seems ok. I am going to move on and possibly tackle swapping the nut plate later. :eek:
 
Was your torque wrench an inch-pound or foot-pound wrench? These bolts are torqued to inch-pounds. At the foot-pound level you could easily snap the bolt and any replacement bolts. Check the torque tables in your Standard Aircraft Handbook, supplied with your kit. You will find most of the bolts in the 12 are torqued to inch-pounds.


Art Pennanen
 
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ARPENN said:
Was your torque wrench an inch-pound or foot-pound wrench? These bolts are torqued to inch-pounds. At the foot-pound level you could easily snap the bolt and any replacement bolts. Check the torque tables in your Standard Aircraft Handbook, supplied with your kit. You will find most of the bolts in the 12 are torqued to inch-pounds.


Art Pennanen
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It was inch-lb. I meant to back off fromt he 25 in-lb reference mark on the veriner adjustment but twisted it the wrong direction and ended up at 30 in-lb instead of 20 in-lb. I got to the point where I thought it "felt" ike it was getting kinda tight, the wrench went click followed very quickly by "snap." I do have to wonder if the bolt was defective though because the thing was only set to 30 in-lb for and AN-3 which is listed as 20-25 in-lb. Very humbling and a mistake I will not make again. I am thinking the "rope trick" might be the avenue of my salvation.
 
RobByers said:
It was inch-lb. I meant to back off fromt he 25 in-lb reference mark on the veriner adjustment but twisted it the wrong direction and ended up at 30 in-lb instead of 20 in-lb. I got to the point where I thought it "felt" ike it was getting kinda tight, the wrench went click followed very quickly by "snap." I do have to wonder if the bolt was defective though because the thing was only set to 30 in-lb for and AN-3 which is listed as 20-25 in-lb.
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That bolt should have been good for a lot more than 30 in-lb. I'd suspect a problem with the torque wrench, or with the way you are using it. The "click" at low torque settings can be quite subtle on some torque wrenches. I had one helper, who claimed to have used "click" torque wrenches before, miss the click and twist off an AN-3 bolt. Lesson learned for me - do critical tasks myself.

When was the last time the torque wrench was calibrated, and what was the error in the range of 30 in-lb? You could do a rough accuracy check yourself, using known weights at a measured distance from the wrench.
 
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