Don Patrick

Don Patrick

Well Known Member
I was bolting on the 411 centre bearing to the rear spar and confirmed the proper torque was 20-25 in/lbs for the bolt. I purchased a brand new torque bar and the first 3 bolts went on no problem but the 4th snapped? I set the torque for 23 in/lbs...is it normal for the odd bolt to snap?

Thanks
 
At 23 in/lbs, the nuts won't even feel like their tight enough. Is that the way it was with the first three? Any chance of using ft/lbs?

L.Adamson --- RV6A
 
Bolts Breaking?

No, they don't randomly break...in fact, I've never broken an AN bolt when using the proper torque. Some suggestions:

1. Not sure what brand of torque wrench you're using. Good ones come with a calibration certificate. Double check the wrench. No certificate/expired calibration? If it's a good wrench, get it re-calibrated.

2. If the wrench checks out, examine the rest of the bolts to see if they have any visual flaws.

3. Call Van's and let them know what you've found (assuming your wrench is okay).

Good luck,
Mike
 
Don Patrick said:
No, they were tight enough and the book does say 20-25 inch/pounds...
Click to expand...

I didn't say it well enough. By the book, which is 20-25 in/lbs; when you torque the nut, it just really won't feel as tight, as if you were torquing without a torque wrench. But that's what you want.

If something's snapping, then perhaps the wrench was set at ft./lbs.

L.Adamson
 
Highly unlikely that it snapped at 23 in/lbs. 23 in/lbs is about what you can muster holding a 1/4 ratchet on the center head and twisting without any strength.
 
Some thing is really wrong here, 20-25 inch/pound is really not that much force and AN3 can withstand more force then that. So, either the torque wrench is really off or it was a really faulty bolt.

Where did its snapped from, the threaded side or the grip?
 
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The obvious question is whether you snapped it off at 20 something inch-pounds or 20 something foot-pounds. Many torque wrenches won't indicate 20 something inch pounds - it is off scale on the low side.
 
The torque to simply rotate an AN3 in a plastic stop nut (AN365?) is around 10 in-lbs, or almost half of the proper total torque. Not reasonable it broke at 25.
 
To clarify just how low this torque is, I did mine with a torque screwdriver. It's a pretty good twist with only one hand, but nowhere near enough to snap a bolt. I suspect you've mistakenly used a foot pound wrench, thus cranking on 12 times the proper torque. If that is the case, you'll need to replace the other bolts since they are now stretched.
 
less than expected

The first time I used my new inch-pound torque wrench, it lightly clicked as soon as I moved it on the nut. I kept turning and realized something was wrong. I set up a fixture and tested my wrench and found it to be extremely accurate full scale. Problem was my being used to foot-pounds. With the AN3 bolts, if you only snug them down a little before reaching for the torque wrench they are probably too tight.
Alex brought up a good point concerning locknuts. If they take 10 inch-pounds to turn by themselves and you want 25 inch-pounds, set your wrench to 35 inch-pounds.
 
Broke Mine Also - Lesson Learned

I snapped off a couple of AN3 bolts on the same fixture until I realized that my Craftsman "click-type" torque wrench really doesn't click at low torque, the head just kind of leans over and touches the barrel. At 20-25 inch pounds I can deflect the head of the wrench with my thumb pressed against the side of the ratchet mechanism.
 
John Tierney said:
I snapped off a couple of AN3 bolts on the same fixture until I realized that my Craftsman "click-type" torque wrench really doesn't click at low torque, the head just kind of leans over and touches the barrel. At 20-25 inch pounds I can deflect the head of the wrench with my thumb pressed against the side of the ratchet mechanism.
Click to expand...

I have several sizes of Craftsman click wrenches. The smaller unit clicks with "certainty". 25 inch pounds would be about 1/3rd of it's range.

L.Adamson
 
Thanks for all of the responses, much appreciated. There are several things I will be looking at:
Removing the other 3 bolts and having the torque wrench checked for proper calibration. The torque wrench is brand new, of good quality, and was recently calibrated. I?d be surprise if it was that, but hoping it is that.
The bolts will be replaced. The settings were at exactly 23 in/lbs. Plans call for 20-25 in/lbs.
The one bolt may very well of had a fault in it. Not a whole lot of force was even applied to it. I?m going to send Van?s a picture of it as it was a clean snap.
Of interest, I had a direct reply by way of email from a forum member, which wasn?t posted here. I don't know if it was to offer some insight or other. I'm not quite convinced that purchasing a torque wrench to correctly set torque settings as recommended by the manufacturer is a "waste of money", even for an AN3 bolt...going by "feel" doesn't do it for me, especially when aircraft have lost tail sections in flight. Plus there are other bolts that require proper torque settings later in the build, which for me justifies the expense.
As far as the bolt being counterfeit, I don?t believe that Van?s would send such items in their kits?My father is a NDT technician and from time to time, the most well built parts at times do contain flaws, cracks, hairline fractures, etc, and until some stress or force is applied, it looks good. I hope I just had a defective one. In any event, Van?s will be made aware of it and I will post back on the conclusion from the torque wrench.

Much thanks folks!
 
I had problems in the very few stages of my RV building experience.

When I received my QB wings, I had to unscrew and retorque 4 bolts on the aileron bracket. Those bolts which go on hidden platenuts riveted on the blind side of the longeron.

I noticed that bolts were factory-torqed at approx. 75 inch./lbs.
So, I had the terrible idea to retorque them at that level and one of them got stripped. I had to disassemble all the 100 or so screws and bolts on the fuel tank to get to that platenuts, remove them and the stripped bolt, reinstall new ones.

What I would like to underline is that it took 75/80 inch./lbs. to strip that bolt.
At 23 inch./lbs. I guess it is not possible that the bolt was faulty. At 23 inch./lbs. one can tighten the nut almost with fingers. I guess your torque wrench had something wrong.
 
In thirty plus years of building/wrench turning, I have seen a total of one AN bolt snap with less than recommended torque. It was a tensioning bolt on a throttle control and had very minimal torque. The head had a crack that was obviously there when it was installed. The aircraft owner looked the situation over and spilled his groceries. He spent days going over the whole ship, as well he should. Was it counterfeit? No idea, but it was 20 years ago. It can happen...

Bob Kelly
 
John Tierney said:
I snapped off a couple of AN3 bolts on the same fixture until I realized that my Craftsman "click-type" torque wrench really doesn't click at low torque, the head just kind of leans over and touches the barrel. At 20-25 inch pounds I can deflect the head of the wrench with my thumb pressed against the side of the ratchet mechanism.
Click to expand...
Funny that you mention this... I had a friend return 2 Craftsman wrenches because he kept breaking AN3 bolts. He brought the third wrench over to my house and when I showed him the how the wrench lightly clicks and "leans" when the torque setting is acheived all he said was, "Ooooohhhhhhhh, I was waiting for the wrench to go click-click-click, so I kept tightening."

Yes, I applied the requisite Dope Slap to the back of his head. :D
 
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Reminds me of the lumberjack

who, having spent his first day ever with a chain saw, actually cut LESS lumber than he had with a hand saw!

His foreman said "Hmmm, there must be something wrong with the saw".

So he flips the on switch, gives the the starter chord a good pull and the saw fires right up!

The startled lumberjack exclaims, "What's that NOISE?" :D:D
 
"It's better to be thought a fool than to open your mouth and remove all doubt!"

One of my favorite quotes. I sat through many a meeting with this quote in mind.:)
 
RV7Factory said:
Funny that you mention this... I had a friend return 2 Craftsman wrenches because he kept breaking AN3 bolts. He brought the third wrench over to my house and when I showed him the how the wrench lightly clicks and "leans" when the torque setting is acheived all he said was, "Ooooohhhhhhhh, I was waiting for the wrench to go click-click-click, so I kept tightening."

Yes, I applied the requisite Dope Slap to the back of his head.
Click to expand...

Do I know you? Nah, couldn't have been me because I didn't return my wrench. But I made the same assumption that it would work by spinning once a certain torque was reached. I didn't break any AN3s but I ended up replacing a bunch because they were over-torqued 200-300%.

Come to think of it, I'd like a torque wrench that operated that way. It's too easy to keep on torquing after the click, especially when there are distractions. A micro-stop torque wrench, hmmmm ...
 
We'll, looks like it is a "user" error on my part with the torque wrench. I removed the other 3 bolts and one slight turn of the nut and they all broke. It's pretty clear that they were all completely over torqued! Good to learn here early on.

Met with a friend of mine today that has a special torque wrench, specifically for light torques used in sluminum blocks and such. I'll have a look and "feel" of that first before putting it back on the project.

Thanks for all the tips and comments folks...
 
As a point of reference, you can take one of those spring scales that are used to weigh fish and give a two pound pull at the end of a one foot wrench. Or hang a pint of beer off the end of a two foot wrench. Obviously not much torque.
 
I've been happy with these from CDI:

clickdim.jpg


I seem to recall this place had the best prices...

http://www.emaxaction.com/cdiclickwrenchatemax.aspx

I have several, but the 501 is most useful - 10-50 in-lb range.

And yes, I was really surprised the first time I put a torque wrench at 20 in-lbs on an AN-3 at how little it took (compared to what I *thought* was the right amount beforehand). Lord knows how many bolts I overtorqued in my lifetime, working on cars, bicycles, etc. LOL!
 
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