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Selecting An Appropriate Bolt



 
 
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  #81  
Old April 21st 17, 05:42 PM posted to rec.bicycles.tech
Doug Landau
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Posts: 925
Default Selecting An Appropriate Bolt

On Thursday, April 20, 2017 at 8:22:05 PM UTC-7, John B Slocomb wrote:
On Thu, 20 Apr 2017 14:25:46 -0700 (PDT), Doug Landau

On Thursday, April 20, 2017 at 2:17:23 AM UTC-7, John B Slocomb wrote:
On Wed, 19 Apr 2017 22:37:15 -0700, Art Shapiro
wrote:

On 4/17/2017 1:52 PM, Doug Landau wrote:

Get a new stem. This one is a flawed design. There is built-in problem with the shape of the part, and that is a lack of remaining metal around the bolt hole. The stem has been made bigger around the front bolt hole to overcome this, but it still has the 2-bolt-1-failure problem. The traditional shape does not make this concession to ease-of-handlebar-change, and carefully places the single bolt in the rear where there is plenty of metal surrounding the threads.
The traditional design is both less likely to experience a bolt failure, and - in the wild guess dept., be more likely to hold on to the bars and remain usable in the event that one does.


I'm he OP. It so happens that the rear bolt was the one that snapped,
which seems to contradict your assertion about the design's weak point.

Ads
  #82  
Old April 22nd 17, 01:40 AM posted to rec.bicycles.tech
John B Slocomb
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Posts: 331
Default Selecting An Appropriate Bolt

On Fri, 21 Apr 2017 07:11:43 -0700 (PDT), wrote:

On Friday, April 21, 2017 at 3:16:14 AM UTC-7, John B Slocomb wrote:
5On Thu, 20 Apr 2017 23:41:53 -0400,
wrote:

On Fri, 21 Apr 2017 10:21:56 +0700, John B Slocomb
wrote:

On Thu, 20 Apr 2017 12:55:36 -0400,
wrote:

On Thu, 20 Apr 2017 16:17:14 +0700, John B Slocomb
wrote:

On Wed, 19 Apr 2017 23:56:34 -0400,
wrote:

On Thu, 20 Apr 2017 09:52:15 +0700, John B Slocomb
wrote:

On Wed, 19 Apr 2017 18:23:53 -0400,
wrote:

On Wed, 19 Apr 2017 18:43:02 +0700, John B Slocomb
wrote:


Metric thread pitch is described totally different than inch size
bolts. Inch size is threads per inch. Metric thread is thread pitch -
so in inch size bolts, a higher number is a finer thread - in metric a
higher number is a coarser thread. A 6X10 metric bolt is 6mm with a
thread pitch of 1mm crest to crest (or root to root - however you want
to measure it)

Who cares, along as the people involved know what you are talking
about? Ant metering system is just that, a system which works for
those that use it.

The old method of measuring gear ratios on a bicycle was to use "gear
inches" which described the diameter of a wheel that would move the
distance in one revolution. Rather archaic today but made perfect
sense to those that used it.


As far as the "grade" of the bolt - a "grade 8" is NOT always better
than a "grade 5" or even, possibly, in some cases, a "grade 2"

A grade 2 or grade 5 bolt may bend and stretch - and still hold, where
a grade 8 would simply snap. It depends on what kind of load is being
carried by the bolt - and how it is torqued. On the same vein, a bolt
that is undertorqued CAN fail faster than one that is overtorqued. A
properly tensioned bolt is "pre-stretched" just enough that any cyclic
load does not stretch the bolt any farther, so the bolt does not
fatigue in use.

An exciting theory and technically correct. although I would comment
that I've yet to see an under torque bolt break.

It's far from "theory" - I've seen numerous head bolts and manifold
bolts fail that were attributed to being under-torqued on vehicles
that were not properly PDId, and quite a few bolts that failed in
shear because they were not properly tightened, and/or the holes were
not properly de-burred, allowing the bolt to loose tension.
No use arguing with Slocumb though - you'll never get anything
through his thick skull.

You must have a tremendous amount of experience with nuts and bolts.
As I mentioned I've been fooling with them things for about 70 years
now and frankly I've never seen "numerous" head bolts fail. Yes, I've
seen head bolts fail, but I would use the term "rarely" not
"Numerous". I would have to say that if you have seen numerous head
bolts fail then you are associating with some very incompetent
mechanics.

And how does one determine that they were under torqued after they
have failed?
Notb incompetent mechanics - but poor factory assembly.

Don't take my word for the FACT the problem exists.

See:
http://www.croberts.com/bolt.htm
In particular Picture #10.

As for broken head bolts - see:
https://www.bimmerforums.com/forum/s...ken-Head-Bolts

Also see: http://www.boltscience.com/pages/Failure%20Modes.swf
and:
https://www.hiretorque.co.uk/failure...bolted-joints/
-Particularly item #3
3. Fatigue Failures

Fatigue failures typically occur within a couple of threads, where the
bolt engages into the internal thread. Failure is then reached due to
the high stress gradient within the region.

Fatigue failures can be particularly hazardous because they often
occur with no visible warning signs and the failure is often sudden.
Fatigue failures are often unknowingly avoided in gasketed joints
simply because the required crush for the gasket often dictates a
torque or bolt tension that minimizes the risk of a fatigue failure.
However, changing to a new gasket type later on which requires less
crush may be the initial cause of bolt fatigue failure.

It is not unusual to assume that a bolt has failed due to overload
when it has in fact failed from fatigue, which can also be a
consequence of self-loosening.

Also:
http://www.bluetoad.com/article/Bolt...0/article.html
and:
http://www.onallcylinders.com/2014/0...ener-failures/

Also:
https://www.excelcalcs.com/engineeri...-joints-fail?/
The first cause listed:
Insufficient Clamp force? - Usually by applying a measured torque load
to the nut bolted joints are tightened to achieve a specific clamp
load. Even under the most extreme applied loads, the clamping force
must prevent joint movement between clamped parts. Movement includes
both opening of the joint to form gaps and slipping. Loads applied to
the joint may be axial forces (in the direction of the bolt axis)
and/or shear forces (perpendicular to the bolt axis). If slippage
occurs then the joint may fail by the bolt loosening. If a gap in the
joint opens then a bolt failure by fatigue is more likely to occur.
Typically bolt fatigue failures occur because of insufficient preload
rather than poor fatigue strength of the bolt. Improving the method of
tightening can reduce the scatter in bolt preload and help guarantee
the minimum required clamping force

Pay particular attention to the sectionfollowing the "bolted
joint.xls" link which explains things in pretty plain language.


You may have worked on machines, including aircraft without fully
understanding what you were doing or why.

You are probably right although the A.F. thought I was competent. Or I
guess that they did as they kept promoting me and they had me managing
divisions for them. Shoot, they even had me writing the skill level
tests for my career field one time.Then when I retired from that job I
hired on as a mechanic again and ended up some years later being
promoted to "Operations Manager" for a fair to middling sized company
in Indonesia.

Peter principal at work? It was all "Government work"

You are trying to spell "sour grapes" perchance?


Not a chance!!!! I've worked for enough idiots without having to work
for for politicians and bureaucrats.


But one isn't working for a politician when in the service. At least
not when assigned to units that actually have a mission. For example,
I was assigned to one of the two reconnaissance squadrons in the A.F.
equipped with a super long focal length camera. One in Asia and one in
Europe. When you fly missions designated by headquarters USAF they
aren't politicians directing you. I was assigned to the "Gun Ship
Squadron" (puff the magic dragon) where we bragged that if we got
there before they actually got inside the wire we never lost a post.
Not too many politicians there either. Then, lets see, I was assigned
to one of the wings that was flying the SAC airborne nuclear flights,
very serious folks those nuclear chaps, and, oh yes, we provided
support for the U-2 flights over Cuba that told y'all that the
missiles weren't there.

Not many politicians in the operational military (as opposed to the
training units).


Teaching in the public school system was enough politics for me.

Sure, you get a fat pension which I'll have to do without - and I
could have if I'd stayed teaching.


Nope, it is rather a thin pension compared to my active duty pay. You
see, what with longevity pay, overseas pay, flight pay, quarters and
rations, etc., active service personnel may draw nearly double their
base salary. When retirement arrives you receive (for 20 years) only
1/2 of your base salary.


You're talking about Operation Chrome Dome and I went on several of those flights. 24 hours over the north pole isn't a great deal of fun. There isn't hardly any heat or insulation in a B52.


There is heating and pressurization in a B-52. The Crews certainly
don't wear the old fleece lined flying clothes that the B-17 and B-24
crews wore :-) And B-52's fly a lot higher (where it is a lot colder).

But I was talking about the possibility of being late with the
launching of one of the relieving aircraft. Not something that any
Wing Commander cared have happen :-)
  #84  
Old April 22nd 17, 01:40 AM posted to rec.bicycles.tech
John B Slocomb
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Posts: 331
Default Selecting An Appropriate Bolt

On Fri, 21 Apr 2017 09:42:35 -0700 (PDT), Doug Landau
wrote:

On Thursday, April 20, 2017 at 8:22:05 PM UTC-7, John B Slocomb wrote:
On Thu, 20 Apr 2017 14:25:46 -0700 (PDT), Doug Landau

On Thursday, April 20, 2017 at 2:17:23 AM UTC-7, John B Slocomb wrote:
On Wed, 19 Apr 2017 22:37:15 -0700, Art Shapiro
wrote:

On 4/17/2017 1:52 PM, Doug Landau wrote:

Get a new stem. This one is a flawed design. There is built-in problem with the shape of the part, and that is a lack of remaining metal around the bolt hole. The stem has been made bigger around the front bolt hole to overcome this, but it still has the 2-bolt-1-failure problem. The traditional shape does not make this concession to ease-of-handlebar-change, and carefully places the single bolt in the rear where there is plenty of metal surrounding the threads.
The traditional design is both less likely to experience a bolt failure, and - in the wild guess dept., be more likely to hold on to the bars and remain usable in the event that one does.


I'm he OP. It so happens that the rear bolt was the one that snapped,
which seems to contradict your assertion about the design's weak point.

Art

And, if I remember correctly, after only 15 years too :-)

This is false logic. There are at least 15 parts on your bike; by your policy we should expect catastrophic part failure once per year.


I'm not quite sure what you are trying to say. A bolt that broke after
15 years of use is somehow associated with something that breaks
annually?


Exactly. If your stem fails once in 15yrs, on the average, and so does your seatpost, and so do your bars, forks, and crank, then something will fail every three years.


Why do you equate the failure of one part to the failure of any other
part? Does the fact that the tree in your front yard fell down mean
that your house will fall down? Or that because Joe Boudrou was hit by
a car while crossing the street mean that you can't cross roads as you
are certainly next?

You don't have faulty logic. You have no logic at all.


It is a ridiculously high failure rate.

  #85  
Old April 22nd 17, 02:12 AM posted to rec.bicycles.tech
Doug Landau
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Posts: 925
Default Selecting An Appropriate Bolt

On Friday, April 21, 2017 at 5:40:37 PM UTC-7, John B Slocomb wrote:
On Fri, 21 Apr 2017 09:42:35 -0700 (PDT), Doug Landau

On Thursday, April 20, 2017 at 8:22:05 PM UTC-7, John B Slocomb wrote:
On Thu, 20 Apr 2017 14:25:46 -0700 (PDT), Doug Landau

On Thursday, April 20, 2017 at 2:17:23 AM UTC-7, John B Slocomb wrote:
On Wed, 19 Apr 2017 22:37:15 -0700, Art Shapiro
wrote:

On 4/17/2017 1:52 PM, Doug Landau wrote:

Get a new stem. This one is a flawed design. There is built-in problem with the shape of the part, and that is a lack of remaining metal around the bolt hole. The stem has been made bigger around the front bolt hole to overcome this, but it still has the 2-bolt-1-failure problem. The traditional shape does not make this concession to ease-of-handlebar-change, and carefully places the single bolt in the rear where there is plenty of metal surrounding the threads.
The traditional design is both less likely to experience a bolt failure, and - in the wild guess dept., be more likely to hold on to the bars and remain usable in the event that one does.


I'm he OP. It so happens that the rear bolt was the one that snapped,
which seems to contradict your assertion about the design's weak point.

Art

And, if I remember correctly, after only 15 years too :-)

This is false logic. There are at least 15 parts on your bike; by your policy we should expect catastrophic part failure once per year.

I'm not quite sure what you are trying to say. A bolt that broke after
15 years of use is somehow associated with something that breaks
annually?


Exactly. If your stem fails once in 15yrs, on the average, and so does your seatpost, and so do your bars, forks, and crank, then something will fail every three years.


Why do you equate the failure of one part to the failure of any other
part? Does the fact that the tree in your front yard fell down mean
that your house will fall down? Or that because Joe Boudrou was hit by
a car while crossing the street mean that you can't cross roads as you
are certainly next?

You don't have faulty logic. You have no logic at all.


My logic is perfect. I made no such absolute statements, my statement is prefaced with your 15 year period. You seem impressed with that as an MTBF for an 6mm bolt. I am reminding you that that bolt is not the only such part on the bike, (it has a twin in the seatpost, for example), and so to calculate your average E.T. between scary failures, you must divide that by the # of such parts on the bike.

Viewed in this light, 15 years is an unacceptably high failure rate.

Yes, I am assuming that you would be similarly impressed by a set that failed only once in 15 years, and by such a post, and such fork, and such a bars. Hence the opening "If". Again: IF your stem breaks once in 15 years, AND so does your seat, your post, your forks and bars, THEN, you will have a scary failure once every three years, on the average.

Remember, our friend Jobst died recently from injuries resulting from a frame failure. He had been riding the frame since 1962 or something like that.. Now, I'm not saying anything one way or the other about that event. I am not trying to argue that it should have lasted longer, nor, on the other hand, that he shouldn't have ridden it as long as he did. But I think that it provides an interesting reference point.

-dkl


  #86  
Old April 22nd 17, 02:33 AM posted to rec.bicycles.tech
AMuzi
external usenet poster
 
Posts: 8,467
Default Selecting An Appropriate Bolt

On 4/21/2017 8:12 PM, Doug Landau wrote:
On Friday, April 21, 2017 at 5:40:37 PM UTC-7, John B Slocomb wrote:
On Fri, 21 Apr 2017 09:42:35 -0700 (PDT), Doug Landau

On Thursday, April 20, 2017 at 8:22:05 PM UTC-7, John B Slocomb wrote:
On Thu, 20 Apr 2017 14:25:46 -0700 (PDT), Doug Landau

On Thursday, April 20, 2017 at 2:17:23 AM UTC-7, John B Slocomb wrote:
On Wed, 19 Apr 2017 22:37:15 -0700, Art Shapiro
wrote:

On 4/17/2017 1:52 PM, Doug Landau wrote:

Get a new stem. This one is a flawed design. There is built-in problem with the shape of the part, and that is a lack of remaining metal around the bolt hole. The stem has been made bigger around the front bolt hole to overcome this, but it still has the 2-bolt-1-failure problem. The traditional shape does not make this concession to ease-of-handlebar-change, and carefully places the single bolt in the rear where there is plenty of metal surrounding the threads.
The traditional design is both less likely to experience a bolt failure, and - in the wild guess dept., be more likely to hold on to the bars and remain usable in the event that one does.


I'm he OP. It so happens that the rear bolt was the one that snapped,
which seems to contradict your assertion about the design's weak point.

Art

And, if I remember correctly, after only 15 years too :-)

This is false logic. There are at least 15 parts on your bike; by your policy we should expect catastrophic part failure once per year.

I'm not quite sure what you are trying to say. A bolt that broke after
15 years of use is somehow associated with something that breaks
annually?

Exactly. If your stem fails once in 15yrs, on the average, and so does your seatpost, and so do your bars, forks, and crank, then something will fail every three years.


Why do you equate the failure of one part to the failure of any other
part? Does the fact that the tree in your front yard fell down mean
that your house will fall down? Or that because Joe Boudrou was hit by
a car while crossing the street mean that you can't cross roads as you
are certainly next?

You don't have faulty logic. You have no logic at all.


My logic is perfect. I made no such absolute statements, my statement is prefaced with your 15 year period. You seem impressed with that as an MTBF for an 6mm bolt. I am reminding you that that bolt is not the only such part on the bike, (it has a twin in the seatpost, for example), and so to calculate your average E.T. between scary failures, you must divide that by the # of such parts on the bike.

Viewed in this light, 15 years is an unacceptably high failure rate.

Yes, I am assuming that you would be similarly impressed by a set that failed only once in 15 years, and by such a post, and such fork, and such a bars. Hence the opening "If". Again: IF your stem breaks once in 15 years, AND so does your seat, your post, your forks and bars, THEN, you will have a scary failure once every three years, on the average.

Remember, our friend Jobst died recently from injuries resulting from a frame failure. He had been riding the frame since 1962 or something like that. Now, I'm not saying anything one way or the other about that event. I am not trying to argue that it should have lasted longer, nor, on the other hand, that he shouldn't have ridden it as long as he did. But I think that it provides an interesting reference point.

-dkl



Not a frame failure. He hit a pavement barrier while
descending at speed, broke his femur and suffered a
post-surgical stroke.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971


  #87  
Old April 22nd 17, 03:35 AM posted to rec.bicycles.tech
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Posts: 445
Default Selecting An Appropriate Bolt

On Fri, 21 Apr 2017 17:16:02 +0700, John B Slocomb
wrote:



You missed the point. Because fine threads are at a shallower angle
then coarse threads the clamping (linear) force is greater for the
same torque.

Didn't miss the point - it was just too obvious to comment on.
  #88  
Old April 22nd 17, 03:37 AM posted to rec.bicycles.tech
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Posts: 445
Default Selecting An Appropriate Bolt

On Fri, 21 Apr 2017 06:49:50 -0700 (PDT), wrote:

On Thursday, April 20, 2017 at 2:25:50 PM UTC-7, Doug Landau wrote:

This is false logic. There are at least 15 parts on your bike; by your policy we should expect catastrophic part failure once per year.


Because weight is now being stressed over anything else we, unfortunately, can expect at least one catastrophic failures per year.

Though I'm back to steel bikes I had a set of the top of the line Campy aluminum wheels. I did a local ride with a nice 12% climb and strong decent. That is a 40 mph drop. After I got back to town and was about a quarter mile from home a spoke broke on perfectly flat and what passes for smooth road around here. The rim distorted so much I had to carry the bike the remaining quarter mile. If this had happened on that decent... The wheel only had about 3-4,000 miles on it since new.

And likely the spokes were not tight enough. Low tension spokes WILL
break.
  #89  
Old April 22nd 17, 03:46 AM posted to rec.bicycles.tech
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Posts: 445
Default Selecting An Appropriate Bolt

On Fri, 21 Apr 2017 07:08:45 -0700 (PDT), wrote:

On Thursday, April 20, 2017 at 11:30:03 PM UTC-7, James wrote:
On 21/04/17 13:35,
wrote:
On Fri, 21 Apr 2017 10:21:56 +0700, John B Slocomb
wrote:


And it depends what you are threading the bolt into. Using fine
threads in coarse grained cast iron is generally NOT a good idea.

As far as the actual "thread area" there is very little difference. If
you double the TPI the threads are only half as deep, but there are
twice as many threads so the total load bearing area is not much
different.


Thread area isn't the issue that John brought up.


That's what I was getting at with the discussion on course and fine threads. If you use course threads the bolt is not as strong as a fine thread because the area of the metal inside of the threads is smaller.

It used to be said that you could tighten fine threads to a higher torque because there was more "leverage" from the fine thread but that isn't the case at all.

So if you are designing a bolt into an iron casting you use course threads but have to use one size larger than you would if it were a finer grain metal and a fine threaded bolt.


Basic engineering. also -. Use a grade 8 coarse bolt of the same size
as a grade 5 fine and you are close if there is no contraindication to
use a hard bolt

Engineering isn't a case of choices as the Germans insist. Designing something to the lightest by making an design to the irreducible minimum while expecting the highest performance is simply asking for troubles. The English are another example. When I had a local mechanic troubleshoot my electrical system to find out why my battery was dying it turned out to be the battery had bitten the dust. It would only hold a charge for a couple of hours. While we were talking he pointed to a Jaguar coupe. That car had a four speed manual transmission that had failed. Anyone knows that manual transmissions do not fail. The replacement cost? $12,000 on a ten year old car. Jaguar would not stand behind their car. If some cheesy plastic part had failed that would be one thing - but manual transmissions DO NOT FAIL. Particularly when it's a little old lady that drives it like she's at Le Mans. She double shifts down better than I can.


Manual transmissions DO fail. I've rebuilt many of them over my career
- bad syncros, worn or broken shift forks, bad bearings, broken teeth,
broken drift pins in the shift rails, brunelled gears, and roasting
from running out of oil are the main culprits.

Spread across all brands - Datsun (Nissan) Toyota, Chevy, Ford,
Chrysler, BMC, VW, AMC and Mazda as well as tractors - also trucks as
well as cars - even International Loadstar school busses.

  #90  
Old April 22nd 17, 03:47 AM posted to rec.bicycles.tech
external usenet poster
 
Posts: 445
Default Selecting An Appropriate Bolt

On Fri, 21 Apr 2017 07:11:43 -0700 (PDT), wrote:



Nope, it is rather a thin pension compared to my active duty pay. You
see, what with longevity pay, overseas pay, flight pay, quarters and
rations, etc., active service personnel may draw nearly double their
base salary. When retirement arrives you receive (for 20 years) only
1/2 of your base salary.


You're talking about Operation Chrome Dome and I went on several of those flights. 24 hours over the north pole isn't a great deal of fun. There isn't hardly any heat or insulation in a B52.

Even over the equator at 20,000 feet it's DAMNED COLD!!!
 




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