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Breaking bolts on empennage...

O

OldAndBold

Well Known Member
OK, what am I doing wrong here?

I am trying to bolt the center elevator bracket to the rear spar ( HS-411BPP / VA-146 to HS-609PP) using the specified bolts AN3-5A / AN960-10 washers / AN365-1032 nuts ). I am trying to torque them to 25 inch pounds using a brand new CDI 1501 MRMH torque wrench. I am holding the bolt head with a box end wrench and torquing the nut with the torque wrench.

Three of the bolts sheared off just as the wrench clicked. The one that remains is loose in the hole - it was torqued to the value but the bolt turns freely in the hole. I am pretty sure I used the correct bolts (I measured and looked it up). The bolts came out of bag 615 "Misc empennage hardware". The nuts had the plastic looking inserts inside. The bolts are gold/brass colored with "AFC" and "X" on the heads and fit in a 3/8" socket.

All three bolts sheared off with about two threads showing. I was not using much force.

Advice/Ideas???

Thanks in advance

John Babrick
 
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John,

Are you possibly reading foot pounds instead of inch pounds maybe? I've done that.

The amount of force needed when properly torqued is suprisingly small - I remember thinking 'this can't be more than finger tight' at the time.

Best,
Doug
 
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The wrench says...

The wrench has a large scale labeled in IN LBS ranging from 20 to 150 or 2.8 to 16.4 Nm. I am pretty sure I have that right.
 
I sheared off those four bolts too. It does not take much more torque to shear off those bolts. I replaced the bolts and nuts and double checked my torque wrench setting and it worked. Give another try and see what happens. The bolts are cheap and you can order more.

Ted
RV-9A, 126 hrs
 
Used wrench wrong maybe...

The torque wrench has a switch that apparently changes the direction of the ratchet. I didn't think the thing had a ratchet. I apparently had this switch in the center between settings and had no ratchet action. That might be the problem.
 
Wow! Something is very wrong here. Just as a quick reality check, 24 in-lbs is equivalent to a 1 lb pull at the end of a two foot long wrench, or 2 lbs on a one-footer. It is also about what you get with a good one-handed turn of a nut driver. I would be inclined to say that something is wrong with your tool/technique, but that doesn't explain the one that's torqued but still turning in the hole. Is there a chance the unthreaded portion is too long and the nut is cranking down into it? I should also mention that the click at 25 in-lbs is almost imperceptible, so maybe you're missing it. In any case, if you really are only going to 25 in-lbs and they are breaking, then you've got some counterfiet hardware.

P.S. I just read the other posts and have got to add that there is no freakin' way that 25 in-lbs would even come close to breaking these or any other bolt of this size unless it was junk! Check your wrenches folks cuz something here just can't be right.
 
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In the interest of science I just took a an3-14 bolt, piled a bunch of washers on it, followed by a nut. I stuck one end in my vise and started torquing the nut, starting at 20 and increasing in 5 in-lb increments. Everything held up fine and then at 95 in-lbs the threads stripped. There's no way in heck that 25 in-lbs could snap a healthy bolt.
 
It sounds like the length is wrong and you are not pulling torque until the nut is bottomed on the threads...would explain the twisating off and the loose bolt.

Place the bolt throught the assembly and look for any shoulder protruding through, with the mating parts clamped together. Washers on AN bolts are added to adjust grip length, there should be no shoulder showing above the nuts seating surface...if the shoulder of the bolt protrudes beyond the surface of the mating materials, add one AN washer. If the shoulder still protrudes beyond the washer, add a second washer under the head of the bolt, and on the other side. If that does not work, add one more washer, or get the next shorter bolt.

The spec allows up to three AN washers per fastener.

An easy reference is a book called "race car fasteners" or something similar it is written by Carroll Smith, and is the last in a series "Tune to Win" "Drive to Win", "Think to Win"...the fastener book has been nicknamed "screw to win".

The key is to have sufficient clamping load, but the AN bolt is designed for shear load in this application, and that load should be born only by the shoulder of the bolt.
 
Craftsman Torque Wrench

I use a Craftsman torque wrench. I, too, was surprised at how little effort was needed to get the nearly imperceptible "click".
 
useless trivia

not intending to hijack the thread here, but Alex DeDominicis got his call sign 'gorilla man' by over-torqueing several bolt heads off the bolts when starting out on his first RV (-6) kit.

<grin>

d

OK, back to the original thread....
 
John 25 inch lbs is hardly anything at all. As a matter of fact if you have a torque wrench that works and read properly, you will wonder if the bolt is tight enough at that setting. If you are snapping them off you can bet something is not working properly with that torque wrench.

-Jeff
 
OK, I now know how to use a torque wrench...

OK, thanks for the help. I was doing a number of things wrong:

First, I didn't have the ratchet switch set correctly.

Second, I was pulling so hard that I was probably off the scale. Not knowing what the "click" was supposed to feel like, I pulled until the ratchet let loose - probably at about 120 inch pounds.

Third the click is really a "tilt" of the handle, so if you don't hold the handle correctly you will not feel the tilt.

Fourth, the torque required is much less than you would think.

I used four bolts and nuts from the fuse kit. I wonder when it will be that I realize that I am four bolts short later on...

Thanks for the help all.

JCB

(One weekend - two rivets replaced and four bolts installed. I will be flying in no time!)
 
I've said it before and I'll say it again, get a dial type torque wrench. I've used both and the dial type is much easier. Much simpler to look at a dial than to feel for a barely noticeable "click".
 
Or....Have Both!

jlfernan said:
I've said it before and I'll say it again, get a dial type torque wrench. I've used both and the dial type is much easier. Much simpler to look at a dial than to feel for a barely noticeable "click".
Click to expand...
Deciding on a click type OR a dial type (only one or the other) is probably a topic for the "never-ending-debate" section... ;)

Personally, I have both, but use the click type most of the time. I don't often find a convenient position to read the dial type, and once you learn what "the click" feels like, you'll never mistake it. With the right training, each has its place.

Paul
 
Ironflight said:
Deciding on a click type OR a dial type (only one or the other) is probably a topic for the "never-ending-debate" section... ;)

Personally, I have both, but use the click type most of the time. I don't often find a convenient position to read the dial type, and once you learn what "the click" feels like, you'll never mistake it. With the right training, each has its place.

Paul
Click to expand...

I have both too. I'll go one further though. Clamp a few bolts in a vise and torque them to spec. Helps to calibrate the wrist, which I find useful as sort of a mental "sanity check". Break a few too, for the same reason. Of course I've never ever broken a bolt while torquing it myself, oh no...
 
Hijack???

I hope this isn't a hijacking but since we're on the subject, how can you determine what the torque of a nylon lock nut is to add to the 25 in. lbs needed for final torque? I've read were others have suggested measuring the resistance of the nylon nut (or platenut) then add that to the torque requirements of the bolt/nut being torqued. My wrench has no markings below the "25" on the shaft so I'd have no way to know what the resistance is for the nylon nut (or platenut) being installed.
 
I have found that using a small 1/4 ratchet drive and socket for 3/16 bolts works best. Tighten to firm and you should be fine. :)
Tom
2 time repeat offender
RV3s 2000+ hours
 
Robert M said:
I hope this isn't a hijacking but since we're on the subject, how can you determine what the torque of a nylon lock nut is to add to the 25 in. lbs needed for final torque? I've read were others have suggested measuring the resistance of the nylon nut (or platenut) then add that to the torque requirements of the bolt/nut being torqued. My wrench has no markings below the "25" on the shaft so I'd have no way to know what the resistance is for the nylon nut (or platenut) being installed.
Click to expand...

After careful thought, some measurements, and a lot of research, I decided that the drag from the nut is typically somewhere around the difference between the high and low range for the nut, so I personally just torque the nylocs to the top of the range and call it good. I torque everything else to the middle of the range. YMMV...it's just what I do. I know it's not exact but neither is my torque wrench.
 
Robert M said:
How can you determine what the torque of a nylon lock nut is to add to the 25 in. lbs needed for final torque?
Click to expand...

I have a small KD 1/4-inch beam type torque wrench with a scale of 0 to 60 inch pounds. It's great for AN-3 bolts. With this type of torque wrench, you can see how much "drag" is caused by the nylon nut. I find it reads about 5 to 7 inch pounds when I first begin to tighten the bolt into the nut. I usually torque to about 30 to 32 inch pounds total.

http://www.toolsource.com/ost//prod...1321&mscssid=X6UKC070E7A99PGLB4820SR8UGSC5MNE
 
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Ironflight said:
Deciding on a click type OR a dial type (only one or the other) is probably a topic for the "never-ending-debate" section... ;)

Personally, I have both, but use the click type most of the time. I don't often find a convenient position to read the dial type, and once you learn what "the click" feels like, you'll never mistake it. With the right training, each has its place.

Paul
Click to expand...
I bought a digital torque wrench from Avery which is made by CDI [Snapon Co]
It has a aural tone as well as bright led lights so you dont need to look at the dial. The nice thing is that if you go over the torque value requested, it screams like a banshee. At first I thought Id wasted money on this "fancy" wrench, but now I find it invaluable and use it on the bike, boat etc. I bought the 1/4 inch drive as the scale is just perfect for aircraft hardware. EJ
 
Beam type...

DeltaRomeo said:
not intending to hijack the thread here, but Alex DeDominicis got his call sign 'gorilla man' by over-torqueing several bolt heads off the bolts when starting out on his first RV (-6) kit.

<grin>

d

OK, back to the original thread....
Click to expand...

One good reason to use this type of wrench...

2608.gif


Might not be as accurate (but at the low torques we are talking about, the "clickers" are not at their best), but way easier to read...

I bought both the TW-1 and TW-2 and I am quite impressed with them for the cost.
They should be easy to calibrate yourself...
Buy locally at your favorite bicycle store or get on-line.

UPDATE

I went and checked the Snap-On 1/4 inch adjustable click torque wrench accuracy specification, and they don't even quote an accuracy for under 40 in-lbs. They only rate it as a 40 to 200 inch lb device. As far as I can tell, this $200 wrench is the only adjustable "clicker" one they make that is 1/4 inch drive.


gil in Tucson
 
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rv9builder said:
I have a small KD 1/4-inch beam type torque wrench with a scale of 0 to 60 inch pounds. It's great for AN-3 bolts. With this type of torque wrench, you can see how much "drag" is caused by the nylon nut. I find it reads about 5 to 7 inch pounds when I first begin to tighten the bolt into the nut. I usually torque to about 30 to 32 inch pounds total.

http://www.toolsource.com/ost//prod...1321&mscssid=X6UKC070E7A99PGLB4820SR8UGSC5MNE
Click to expand...

Oh man, that is perfect Mark! :D I'll have one of these in short order and it won't break the bank. :cool:
 
Where we use them...

Pirkka said:
The best tools I've found for this purpose are CDI torque wrenches from Avery Tools. The worst thing is the price... :eek:

http://www.averytools.com/cart/showcategory.aspx?categoryid=55&resetfilter=true
Click to expand...

Same problem as the clickers I mentioned above... the manufacturer (and the standard ANSI specifications) do not even rate then for use under 20% of full scale - 48 in-lbs in our case...

COMPUTORQ3 will operate in any of four torque units, foot pounds (Ft. Lbs.), Inch Pounds (In. Lbs.), Newton Meter (NM) or Kilogram Centimeter (Kg. CM.). Accuracy: ? 2% CW of readings from 20% to 100% of full scale ? 3% CCW of readings from 20% to 100% of full scale. N.I.S.T. traceable certificate of calibration included.

I still like the beam type... :)

gil in Tucson
 
AN3 vs. AN4

I have wondered for a long time why Vans uses AN 3's and not AN 4's. I'm sure I know the answer, but I always thought the 3's were small when you think about "ALL" the bolts that hold the wings on. I think it's important to keep the tail attached too :) and I think about that flying through turbulance.
 
JACKR said:
I have wondered for a long time why Vans uses AN 3's and not AN 4's. I'm sure I know the answer, but I always thought the 3's were small when you think about "ALL" the bolts that hold the wings on. I think it's important to keep the tail attached too :) and I think about that flying through turbulance.
Click to expand...
Weight, Cost, and lack of necessity!
 
Calibration

Here is an easy way to calibrate your torque wrench.


Put the square head that goes into the socket into a vice. Then measure the distance from the center of the square head to a place on the end of the wrench. For an example lets say the distance is 8 inches. Then take a weight and hang it from the wrench on a string or chain. multiply the weight times the distance and that is the current torque on the wrench. Compare the current torque to the torque displayed on the wrench. If the weight is 3 pounds then 3 lbs X 8 inches is 24 inch pounds (2 ft lbs). If you have a click type wrench the procedure is the simular. Measure the distance and pick your weight. Then set the wrench to the torque. Apply the load and the torque wrench should click when the weight is applied. High quality torque wrenches should have a adjustment to calibrate the torque wrench.
 
JonathanCook said:
... Then take a weight and hang it from the wrench on a string or chain...
Click to expand...

Just make sure the wrench is horizontal... otherwise you will have to use trigonometry...
 
Wrench weight

JonathanCook said:
Here is an easy way to calibrate your torque wrench.


Put the square head that goes into the socket into a vice. Then measure the distance from the center of the square head to a place on the end of the wrench. For an example lets say the distance is 8 inches. Then take a weight and hang it from the wrench on a string or chain. multiply the weight times the distance and that is the current torque on the wrench. Compare the current torque to the torque displayed on the wrench. If the weight is 3 pounds then 3 lbs X 8 inches is 24 inch pounds (2 ft lbs). If you have a click type wrench the procedure is the simular. Measure the distance and pick your weight. Then set the wrench to the torque. Apply the load and the torque wrench should click when the weight is applied. High quality torque wrenches should have a adjustment to calibrate the torque wrench.
Click to expand...

Jonathan ... if I understand your method correctly, you are ignoring the actual weight of the wrench. This will cause a significant error at the values we are talking about... or will offset the actual calibration zero point...

gil in Tucson... a bit confused...
 
An easier and possibly more accurate way might be:

form a 20 inch lever (bar) with a 1/4 inch hole exactly in the center

mount the torque wrench in the vice vertically

place the 20 inch bar on the torque wrench horizontally (should read 0 inch pounds as the equal lengths of bar on either side perfectly balance each other)

hange a weight on one end of the bar

1 pound should equal 10 inch pounds, 2 pounds=20 inch/pounds etc

calibrate say at 10, 20, 30, and 40 inch pounds (1,2,3,4 pounds)

This should make the non-clicker and far cheaper type of wrench PERFECTLY accurate????????????????????


Grant
 
Makes sense....

grantcarruthers said:
An easier and possibly more accurate way might be:

form a 20 inch lever (bar) with a 1/4 inch hole exactly in the center

mount the torque wrench in the vice vertically

place the 20 inch bar on the torque wrench horizontally (should read 0 inch pounds as the equal lengths of bar on either side perfectly balance each other)

hang a weight on one end of the bar

1 pound should equal 10 inch pounds, 2 pounds=20 inch/pounds etc

calibrate say at 10, 20, 30, and 40 inch pounds (1,2,3,4 pounds)

This should make the non-clicker and far cheaper type of wrench PERFECTLY accurate????????????????????


Grant
Click to expand...

Grant... that makes sense.... :)

You should be able to get the accuracy to as good as you can read the pointer/dial, which has marks every 2 in-lbs... should be good enough... :)

gil in Tucson
 
Bolt Torque

Almost all of the bolts, with a few exceptions, are loaded in shear. The torque specs for nuts in shear vs compression are wildy different. I would suggest that the tolerances of the bolts and nuts we are using in these kits, with exception of the spar, and maybe even there, would not require any of them to be torqued. I have never heard of any RV accident related to under or overtightening bolts.
You can not effectively get a torque wrench on 80% of the bolts anyway, even with a crows foot, extension, or other device.
Now, I am not saying not to do everything in your power to do it right, but it is really hard to screw up AN hardware with an appropriate sized wrench.
 
Torque tools

I bought a click type torque screwdriver made by Utica, now owned by Apex.

I used to rebuild mags with it on the company's Part 135 421c every 500 hours, per the service bulletin on them. They fly in the mid 20k altitudes and could be finicky it the distributor blocks.

Anyway, you had to use this tool, to accurately torque the fasteners in the Mags, both for the points and the distributor blocks. The tool I have goes up to 36in lbs and down to 2in lbs. I had it calibrated yearly, it always came out on target.

I am telling you if you are breaking bolts at 24in lbs, something is seriously wrong!

Either the wrench, the operator or the fastener and its associated assembly.
I would suspect things in that order, but not count out the possibility of any of these, maybe more than one. :eek:

If you have been torquing other fasteners with a tool you find defective, replace them and the nuts that went with them.
 
torque em all if you can

there isnt any reason you cant torque 99% of the bolts on these. maybe some of the wing bolts on the a model are a pain in the arse. but with a welder and some sacrificial craftsman tools you can torque most if not all the fasteners. those little an-3s are just to elastic for me. they go on quite a ways after 32 in. lbs (incl. drag torque) before breaking at around 70-90in. lbs
you may get away with overtorqued bolts for a while but with the extra tension on the bolt it will fail sooner than a properly torqued bolt. and IMHO they are to small already.YMMV
 
All of the bolts are oversized for the application in my opinion. These planes where designed to be built by amatures. I see a lot of people getting in trouble using torque wrenches inproperly thinking they have to torque everything. Almost all of the bolts in an RV are designed for Shear Loads, yet we use Tension nuts. That gives us a torque range between 12 - 25 inlbs (no drag). Oh, that is torque range as tested in a lab, in lab temperatures and conditions.
It is really hard to screw up if you have any mechanical inclination at all. So, if you are snapping off bolts, you are at a point you need some help from an experienced builder.
I spoke with Vans in regard to overtorquing. The opinion I received was that while not hard to do, it would be doubtfull that even an overtorqued bolt that did not strip or break would fail in the air. It has never happened to their knowledge and you know there are a lot of airplanes out there with under and overtorqued AN3's.
My advice to this builder breaking bolts. Get an experience person to assist you. Hand torque your bolts with an appropriate wrench, check with your calibrated torque wrench, get the feel, and start putting your airplane together. You wont fall out of the sky.
 
I used a torque nut driver for almost all the fasteners and never had any trouble reaching them. Instead of clicking, this tool lets go at the right torque.
 
But the ad reads.....

rv9builder said:
I have a small KD 1/4-inch beam type torque wrench with a scale of 0 to 60 inch pounds. It's great for AN-3 bolts. With this type of torque wrench, you can see how much "drag" is caused by the nylon nut. I find it reads about 5 to 7 inch pounds when I first begin to tighten the bolt into the nut. I usually torque to about 30 to 32 inch pounds total.

http://www.toolsource.com/ost//prod...1321&mscssid=X6UKC070E7A99PGLB4820SR8UGSC5MNE
Click to expand...
The ad says that the pointer moves left and right. It does not move, the torque arm moves. But look on the bright side, AT LESS THAN 1oz, (see ad) they can ship it for 39 cents. Here is a tool you could have in the A/C all the time................?

How about this.... clamp a micro switch to the scale, a watch battery and a l.e.d. set the torque in the vice (see above) and go to work! That really makes this a great deal.

Warren

p.s. I guess I should make this clear, when the arm moves to the correct setting, the pointer will press the micro switch and the light will go on.
Your done...
 
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gasman said:
The ad says that the pointer moves left and right. It does not move, the torque arm moves. But look on the bright side, AT LESS THAN 1oz, (see ad) they can ship it for 39 cents. Here is a tool you could have in the A/C all the time................?
Click to expand...

Well, not quite- I have this torque wrench and it weighs in at 8 oz. without its cardboard box.
 
captainron said:
Well, not quite- I have this torque wrench and it weighs in at 8 oz. without its cardboard box.
Click to expand...
Just pointing out two errors in the ad......... thanks
BTW is it any good?

Warren
 
gasman said:
Just pointing out two errors in the ad......... thanks
BTW is it any good?

Warren
Click to expand...

It's great, perfect for what we're doing and it will read the Nylok "drag" which you can factor into your final torque. The price is right, proving that in this case spending more doesn't get you more.
 
Torque wrenches

szicree said:
I used a torque nut driver for almost all the fasteners and never had any trouble reaching them. Instead of clicking, this tool lets go at the right torque.
Click to expand...

That is actually what my Utica Torque screwdriver does too. It clicks and lets go, until you hit another click spot at the same torque. :cool:

When you lock on a short Snap-on wobble socket, the whole setup becomes pretty easy to use.

keep it as straight as you can or you will get deviation in desired results, 10-15 degrees, no big deal when you selected the mid range spec.
 
wow!

GAHco said:
That is actually what my Utica Torque screwdriver does too. It clicks and lets go, until you hit another click spot at the same torque. :cool:

When you lock on a short Snap-on wobble socket, the whole setup becomes pretty easy to use.

keep it as straight as you can or you will get deviation in desired results, 10-15 degrees, no big deal when you selected the mid range spec.
Click to expand...
Must be a good tool.....Are your tools tax deductable?

Selected Item
Cat. No. Item Description Regular Price Online Price Qty. Buy It!

KT100 Utica 20-Piece Adjustable Torque Screwdriver Kit, 20 to 100 in-oz $425.00 $404.00

Related Items
Cat. No. Item Description Regular Price Online Price Qty. Buy It!
KT130 Utica 43-Piece Adjustable Torque Screwdriver Kit, 20 in-oz to 30 in-lb $785.00 $746.00

KT30 Utica 24-Piece Adjustable Torque Screwdriver Kit, 6 to 30 in-lb $450.00 $428.00

KTT1 Utica 29-Piece Adjustable Torque Screwdriver Kit, 5 to 20 in-oz $559.00 $531.00

TS100 Utica TS-100 Adjustable Torque Limiting Screwdriver, 20 to 100 in-oz $223.00 $212.00

TS30 Utica TS-30 Adjustable Torque Limiting Screwdriver, 6 to 30 in-lb $223.00 $212.00

TS35 Utica TS-35 Adjustable Torque Limiting Screwdriver, 6 to 36 in-lb $223.00 $212.00

TT1 Utica Adjustable Torque Limiting Screwdriver, 5 to 20 in-oz $360.00 $342.00
 
Ill check it out.

gasman said:
Must be a good tool.....Are your tools tax deductible?
Click to expand...

Actually I bought mine about 20 years ago when I fixed planes for a living.

It is an awesome little tool.

It was 90 buck back then, I will check the model number and report back.

It is not something I have stocked but with enough interest we might get a good deal on a group buy.

I will let you know as soon as I can. :cool:
 
Snapping bolts is easy

Growing up on the farm, dad had a torque wrench that actually spun after you got the proper torque. I got used to that system. So we get to the RV build and I set in the torque display and crank away until six bolts were ruined and laying on the shop floor. I assumed the wrench would "spin" when it reached critical torque. It spun alright. Almost out of my hand. My buddy about threw a screwdriver at me when he saw what I had done. I was on torque wrench probation. The "click" is almost imperceivable on these small torque wrenches. How was I to know? He started to use that sound every time I picked up any wrench or screwdriver....you know, the "piiiing" when the metal stress equals 100%. "Ping"...don't ruin that bolt also!!!" "Ping".

Pat Garboden
Ozark, MO
 
GAHco said:
Actually I bought mine about 20 years ago when I fixed planes for a living.

It is an awesome little tool.

It was 90 buck back then, I will check the model number and report back.

It is not something I have stocked but with enough interest we might get a good deal on a group buy.

I will let you know as soon as I can. :cool:
Click to expand...

Well I got the picture, but forgot to write down the model# I think it was
TS-35

For a view of the whole thing...

Torque_Driver&Attachments.jpg
 
thanks for setting me straight

Originally Posted by JACKR
I have wondered for a long time why Vans uses AN 3's and not AN 4's. I'm sure I know the answer, but I always thought the 3's were small when you think about "ALL" the bolts that hold the wings on. I think it's important to keep the tail attached too and I think about that flying through turbulance.


Weight, Cost, and lack of necessity!
__________________
Mel Asberry..DAR
EAA Tech Counselor/Flight Advisor
Specializing in Amateur-Built and Light-Sport
Dallas area
RV-6 Flying since 1993

Your right Mel, lots of weight difference between 3's and 4's and I am absolutly sure there is a lack of necessity! But I never gave the COST any thought at all. I checked the price of AN3A's vs AN4A's at WICK's the those 4's are "ONE CENT EACH" higher than 3's. Thanks for pointing that out to me :rolleyes: Your on top of every detail :)
 
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