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#81
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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. |
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#83
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Selecting An Appropriate Bolt
On Fri, 21 Apr 2017 11:25:02 -0400, Frank Krygowski
wrote: On 4/20/2017 11:43 PM, wrote: On Fri, 21 Apr 2017 10:21:56 +0700, John B Slocomb wrote: A friend, who was an EWO on B-52's, once commented that it wasn't exactly confidence building to go to war armed with equipment built by the lowest bidder :-) "a loose gaggle of compromises flying in close formation" - which is why I'm building my own - - - Building your own plane? Sure, there is a whole bunch of them out there building airplanes in their garage. Google "home built airplane". |
#84
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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
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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
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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
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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
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Selecting An Appropriate Bolt
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#89
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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
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Selecting An Appropriate Bolt
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