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One critical bolt missing!

S

Steve Barnes

Well Known Member
Went to move my RV6 in the hangar and one wheel had a point of very bad resistance while rolling. It would catch and let go while rolling it around. It felt like a disc was badly bent. Further inspection revealed that one of the three #4 bolts that hold the rim halves together was totally missing and the halves pulled away a little. (I know what you are thinking. NO I didn't forget to put it in). Somehow it must have broken and both parts of the bolt/nut were missing (probably at the bottom of someones swimming pool).

Here's my thoughts; I probably have under torqued the bolts thinking that the tire pressure would do that. If there was a little working room for the bolt/nut to move because of under torqueing it may have caused the nut to break at the threads.

Anybody else have this happen or any ideas.

Steve Barnes Owner of Fairings Etc.
 
Do you know the answer?

If a bolt is holding a 1000 lb weight, an eye is on bolt end, a different eye is on the nut end. a washer is in between. You torque the bolt with an initial tension of 1000 lbs. Now you lift the weight.

What is the tension load on the bolt?
 
For any weight, 0 to 1000 pounds, the tension on the bolt is unchanged. Heavier weights will start to stretch the bolt, increasing tension. It acts just like a strong spring, with the washer allowing extention but not contraction.
 
Yes!

That is what I was thinking Bill. With the tire pressure the rims may have slightly pulled apart with bolt stretch with out enough torque being applied. So the question is; torque the bolt before or after the tire is inflated?

Steve
 
Note also, at least if you have the same Cleveland wheels that I do, that the torque specs for the AN4 bolts are quite a bit higher than normal.
 
Steve Barnes said:
That is what I was thinking Bill. With the tire pressure the rims may have slightly pulled apart with bolt stretch with out enough torque being applied. So the question is; torque the bolt before or after the tire is inflated?
Steve
Click to expand...

Before!!!!
 
Yes, it is 1000lbs, the load simply transfers from the washer to the external load. Bob had a good physical description. And like Mel says "Before!"

Just replace the bolts and torque to the wheel manufacturer's specification.
 
Not exactly, although that's the common expectation.

For the shank portion of the bolt -what's happening is that the axial stiffness of the entire joint (bolt plus washer) carries the load. The bolt will carry a share of the load based upon it's fraction of the total axial stiffness, in addition to the preload, which the shank alone carries (the washer being in compression from the preload). Of course this is before separation.

I've seen that fraction typically be in the range of 10% to 20% but of course it'll vary considerably depending on the joint's geometry.

After separation the bolt carries the entire load.

Dave
 
David Paule said:
Not exactly, although that's the common expectation.

For the shank portion of the bolt -what's happening is that the axial stiffness of the entire joint (bolt plus washer) carries the load. The bolt will carry a share of the load based upon it's fraction of the total axial stiffness, in addition to the preload, which the shank alone carries (the washer being in compression from the preload). Of course this is before separation.

I've seen that fraction typically be in the range of 10% to 20% but of course it'll vary considerably depending on the joint's geometry.

After separation the bolt carries the entire load.

Dave
Click to expand...

I agree Dave, I did not want to provide a complete analysis of abutment, but the OP was concerned he had over stressed the bolt from the load (tire pressure) and thus was considering lowering the preload (torque). Clearly, this is one of the few applications of a grade 5 bolt that is designed for a tension load and not a shear loading. The example was an attempt to illustrate that lowering the torque was not appropriate.
 
David Paule said:
Not exactly, although that's the common expectation.

For the shank portion of the bolt -what's happening is that the axial stiffness of the entire joint (bolt plus washer) carries the load. The bolt will carry a share of the load based upon it's fraction of the total axial stiffness, in addition to the preload, which the shank alone carries (the washer being in compression from the preload). Of course this is before separation.

I've seen that fraction typically be in the range of 10% to 20% but of course it'll vary considerably depending on the joint's geometry.

After separation the bolt carries the entire load.

Dave
Click to expand...

Yes, I agree. My statement was correct only if the washer is incompressible - which, compared to the steel bolt, is not likely a good approximation.
 
Steve Barnes said:
...case of under torqueing it may have caused the nut to break at the threads.

Anybody else have this happen or any ideas.
Click to expand...

Early in the flying of my -8 I discovered that one nut had sheared off. There was no wheel split/separation evident and the bolt was still in place. My concern was that I had over-torqued the nut. A Dash 4 bolt (or is it a Dash 3) is not that big and it would seem to me over torque would be a bigger issue than under-torque.

I replaced all three bolts, nuts and washers and carefully torqued to the spec written on the Cleveland instructions inside the wheel. I haven't had a problem since. That was about 8 years ago.

Chris
 
And on a -3 AN bolt, to a guy that's used to cranking on automotive and compressor parts, that specified torque is surprisingly low. It's easy to overtorque them if you are relying on a calibrated wrist that's used to heavier steel hardware.
 
timely tie bolt torque topic

Newbie alert. Basic question. First main tire change this weekend. Two of six nuts would not hold 90 inch pounds. As number two gave way it occurred to me that perhaps none of these nuts should have been reused. Should you replace them all....or is it acceptable to see if they hold torque value?

Tom Little
RV 9A
bought not built....
lovin' it just the same
 
arviator said:
Newbie alert. Basic question. First main tire change this weekend. Two of six nuts would not hold 90 inch pounds. As number two gave way it occurred to me that perhaps none of these nuts should have been reused. Should you replace them all....or is it acceptable to see if they hold torque value?
Tom Little
RV 9A
bought not built....
lovin' it just the same
Click to expand...

If you are talking AN4, the recommended torque value is 50-70 in lbs.
It is acceptable to reuse nyloc nuts if you cannot turn them by hand.
 
arviator said:
Newbie alert. Basic question. First main tire change this weekend. Two of six nuts would not hold 90 inch pounds. As number two gave way it occurred to me that perhaps none of these nuts should have been reused. Should you replace them all....or is it acceptable to see if they hold torque value?

Tom Little
RV 9A
bought not built....
lovin' it just the same
Click to expand...

STOP.
Something's not right, this should not happen, leave alone twice. Are you sure you are using the correct torque? Is 90 in-lbs stamped on your wheel half? Torque wrench calibrated? Are these the correct nuts (not just the ones you removed, someone else may have installed incorrect ones).
 
Thanks gentlemen,

Yes, the torque value on the rim is 90 inch pounds....and yes that is a higher than normal value for an AN4 bolt....but the rated max for these bolts is 100 inch pounds. The nuts are correct, just reused.

I am using a new torque wrench, set values checked and rechecked, but it was not calibrated right out of the box. I will do that.....but to me it makes sense to use new nuts as well.
 
arviator said:
Thanks gentlemen,

Yes, the torque value on the rim is 90 inch pounds....and yes that is a higher than normal value for an AN4 bolt....but the rated max for these bolts is 100 inch pounds. The nuts are correct, just reused.

I am using a new torque wrench, set values checked and rechecked, but it was not calibrated right out of the box. I will do that.....but to me it makes sense to use new nuts as well.
Click to expand...

Maybe more mundane: Did the bolt or nut threads have oil or grease on them? Pretty sure the spec is for "dry threads". If they are lubricated they will attain a higher than desired stretch.
 
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