|
|
Thread Tools | Display Modes |
#11
|
|||
|
|||
Horst link bending forces
On Fri, 2 Feb 2018 08:21:36 -0800, sms
wrote: On 2/1/2018 8:37 PM, jbeattie wrote: On Thursday, February 1, 2018 at 3:38:32 PM UTC-8, Joerg wrote: On 2018-02-01 11:26, jbeattie wrote: On Thursday, February 1, 2018 at 10:24:16 AM UTC-8, Joerg wrote: Yesterday on the MTB I had to look downwards between my legs to see what made a rattling noise on the bike, saw some brush tangled in the rear and hit both brakes quite hard. That's when I noticed how much the upper diagonal strut in a Horst link bends when applying a lot of brake force. The center of it bows down several tenths of an inch and also outward a little. It's a pretty beefy strut: http://www.analogconsultants.com/ng/bike/Muddy4.JPG Similar on other bikes: https://ep1.pinkbike.org/p5pb9586988/p5pb9586988.jpg One can see such bowing also on aircraft wings which as built and tested to high stress standards. They make the spars out of stuff such as 7178 which I assume bike mfgs don't: https://www.popularmechanics.com/fli...-stress-tests/ Has anyone else with a Horst link bike taken a look while applying the rear brake hard? Can this fatigue the strut to the point where it eventally breaks? Should I shore that up with maybe an L- or U-profile strapped around it? I am asking because I use my MTB for transportation a lot and ride about 2000mi a year on it, hard, not just the occasional weekend loop. It'll see hundreds of such strut load cycles per ride. Yes, everything breaks after enough fatigue cycles, particularly aluminum -- which has no fatigue threshold. Even small amplitude fatigue cycles will affect aluminum. It will break. Not necessarily. Next time you fly sit right behind a wing and watch closely what happens at rotation time (when the pilot pulls up and the aircraft becomes airborne). The wing will bend so much that its tip is now several feet higher than it was in its resting state. In turbulent weather it'll then continue to flex up and down like he https://www.youtube.com/watch?v=tr5qkjlE77Y https://www.youtube.com/watch?v=NYsFk4I14N8 Yet these aircraft have a service life of 30 years. And then typically get sold to the freight dogs or lesser devloped countries for another 30 years or so. It's aluminum. My question is whether the typical upper Host link strut on a MTB can take similar dynamic stresses and for how long. If Boeing made them I'd have no doubt but Boeing does not build MTBs. All parts made by a decent company are tested to failure or to the end of a test protocol. Call the company and see how many fatigue cycles it took to fail your linkage. Then count your cycles and go from there. When you get to the magic number, don't ride anywhere near mountain lions. I would put in an optical sensor to count the cycles and then do a replacement after every 10,000 cycles. If you look closely practically every part on a bike bends under a load. Notably, the front forks, the handle bars, the brake arms, the main frame ..... Few of which cause failure and physical injury that the O.P. mentions in a separate post. -- Cheers, John B. |
Ads |
#12
|
|||
|
|||
Horst link bending forces
On 2018-02-02 16:35, John B. wrote:
On Fri, 02 Feb 2018 08:01:18 -0800, Joerg wrote: On 2018-02-01 17:07, John B. wrote: On Thu, 01 Feb 2018 15:38:39 -0800, Joerg wrote: On 2018-02-01 11:26, jbeattie wrote: On Thursday, February 1, 2018 at 10:24:16 AM UTC-8, Joerg wrote: Yesterday on the MTB I had to look downwards between my legs to see what made a rattling noise on the bike, saw some brush tangled in the rear and hit both brakes quite hard. That's when I noticed how much the upper diagonal strut in a Horst link bends when applying a lot of brake force. The center of it bows down several tenths of an inch and also outward a little. It's a pretty beefy strut: http://www.analogconsultants.com/ng/bike/Muddy4.JPG Similar on other bikes: https://ep1.pinkbike.org/p5pb9586988/p5pb9586988.jpg One can see such bowing also on aircraft wings which as built and tested to high stress standards. They make the spars out of stuff such as 7178 which I assume bike mfgs don't: https://www.popularmechanics.com/fli...-stress-tests/ Has anyone else with a Horst link bike taken a look while applying the rear brake hard? Can this fatigue the strut to the point where it eventally breaks? Should I shore that up with maybe an L- or U-profile strapped around it? I am asking because I use my MTB for transportation a lot and ride about 2000mi a year on it, hard, not just the occasional weekend loop. It'll see hundreds of such strut load cycles per ride. Yes, everything breaks after enough fatigue cycles, particularly aluminum -- which has no fatigue threshold. Even small amplitude fatigue cycles will affect aluminum. It will break. Not necessarily. Next time you fly sit right behind a wing and watch closely what happens at rotation time (when the pilot pulls up and the aircraft becomes airborne). The wing will bend so much that its tip is now several feet higher than it was in its resting state. In turbulent weather it'll then continue to flex up and down like he https://www.youtube.com/watch?v=tr5qkjlE77Y https://www.youtube.com/watch?v=NYsFk4I14N8 Yet these aircraft have a service life of 30 years. And then typically get sold to the freight dogs or lesser devloped countries for another 30 years or so. It's aluminum. My question is whether the typical upper Host link strut on a MTB can take similar dynamic stresses and for how long. If Boeing made them I'd have no doubt but Boeing does not build MTBs. [...] True that all large aircraft wings flex - the outriggers on a B-52 will be some 6 feet above the ground with empty tanks :-) If you are worried about your bike's rear strut why not just reinforce it. You have explained how clever it is to use a hose clamp to prevent a nut from loosening why not use the same technique to hold a reinforcing brace on your MTB? https://tinyurl.com/yaklvuy6 Figure 14 shows a bridge using plates attached with clamps as reinforcement. I know how to do that but wanted to know how much bending is normal. IOW whether reinforcement is necessary. Hence my post here. Clamping a reinforcement to the bar back there ain't as easy as a steerer hose clamp. That area can't have anything protruding and potentially slicing open a leg in case of a crash. If you are seriously worried about injuries resulting from a crash it would seem logical to simply get rid of the bike before the anticipated failure. As someone who has done aircraft maintenance you surprise me. Ever heard the term crashworthiness? Mountain bikers do crash once in a while. Par for the course. It has been more than a year for me I think but some day my number will come up again. All it takes is a violent tire blow-out. As for clamps see https://tinyurl.com/y97t6n2b The 19th shows a clamp that can be installed without protruding parts and several other examples are shown further down the page. The kind with the "U-turn screws" is what I'd probably use if needed and then cap nuts on the ends. Towards the wheel it'll be tight, not much room. -- Regards, Joerg http://www.analogconsultants.com/ |
#13
|
|||
|
|||
Horst link bending forces
On Fri, 02 Feb 2018 16:50:56 -0800, Joerg
wrote: On 2018-02-02 16:35, John B. wrote: On Fri, 02 Feb 2018 08:01:18 -0800, Joerg wrote: On 2018-02-01 17:07, John B. wrote: On Thu, 01 Feb 2018 15:38:39 -0800, Joerg wrote: On 2018-02-01 11:26, jbeattie wrote: On Thursday, February 1, 2018 at 10:24:16 AM UTC-8, Joerg wrote: Yesterday on the MTB I had to look downwards between my legs to see what made a rattling noise on the bike, saw some brush tangled in the rear and hit both brakes quite hard. That's when I noticed how much the upper diagonal strut in a Horst link bends when applying a lot of brake force. The center of it bows down several tenths of an inch and also outward a little. It's a pretty beefy strut: http://www.analogconsultants.com/ng/bike/Muddy4.JPG Similar on other bikes: https://ep1.pinkbike.org/p5pb9586988/p5pb9586988.jpg One can see such bowing also on aircraft wings which as built and tested to high stress standards. They make the spars out of stuff such as 7178 which I assume bike mfgs don't: https://www.popularmechanics.com/fli...-stress-tests/ Has anyone else with a Horst link bike taken a look while applying the rear brake hard? Can this fatigue the strut to the point where it eventally breaks? Should I shore that up with maybe an L- or U-profile strapped around it? I am asking because I use my MTB for transportation a lot and ride about 2000mi a year on it, hard, not just the occasional weekend loop. It'll see hundreds of such strut load cycles per ride. Yes, everything breaks after enough fatigue cycles, particularly aluminum -- which has no fatigue threshold. Even small amplitude fatigue cycles will affect aluminum. It will break. Not necessarily. Next time you fly sit right behind a wing and watch closely what happens at rotation time (when the pilot pulls up and the aircraft becomes airborne). The wing will bend so much that its tip is now several feet higher than it was in its resting state. In turbulent weather it'll then continue to flex up and down like he https://www.youtube.com/watch?v=tr5qkjlE77Y https://www.youtube.com/watch?v=NYsFk4I14N8 Yet these aircraft have a service life of 30 years. And then typically get sold to the freight dogs or lesser devloped countries for another 30 years or so. It's aluminum. My question is whether the typical upper Host link strut on a MTB can take similar dynamic stresses and for how long. If Boeing made them I'd have no doubt but Boeing does not build MTBs. [...] True that all large aircraft wings flex - the outriggers on a B-52 will be some 6 feet above the ground with empty tanks :-) If you are worried about your bike's rear strut why not just reinforce it. You have explained how clever it is to use a hose clamp to prevent a nut from loosening why not use the same technique to hold a reinforcing brace on your MTB? https://tinyurl.com/yaklvuy6 Figure 14 shows a bridge using plates attached with clamps as reinforcement. I know how to do that but wanted to know how much bending is normal. IOW whether reinforcement is necessary. Hence my post here. Clamping a reinforcement to the bar back there ain't as easy as a steerer hose clamp. That area can't have anything protruding and potentially slicing open a leg in case of a crash. If you are seriously worried about injuries resulting from a crash it would seem logical to simply get rid of the bike before the anticipated failure. As someone who has done aircraft maintenance you surprise me. Ever heard the term crashworthiness? Nope, never heard the term used in conjunction with the word "aircraft". I've heard the term "preventative" and even seen aircraft with what are called "Egress" systems but never an aircraft designed to be "crashworthy". I did some research and the term seems to be primarily associated with airbags in the Sikorsky UH-60 Black Hawk and the Boeing AH-64 Apache helicopters but no mention in other aircraft ranging from large aircraft like the B-52 to small ones like the F-15. In fact one reference reported that air bags were not built into commercial aircraft at all. Given the reliability of air bags, as evidenced by the recall of more then a million air bag equipped automobiles, perhaps a different term should be applied. Mountain bikers do crash once in a while. Par for the course. It has been more than a year for me I think but some day my number will come up again. All it takes is a violent tire blow-out. As for clamps see https://tinyurl.com/y97t6n2b The 19th shows a clamp that can be installed without protruding parts and several other examples are shown further down the page. The kind with the "U-turn screws" is what I'd probably use if needed and then cap nuts on the ends. Towards the wheel it'll be tight, not much room. Well, then don't spend any time or effort in strengthening the struts. After all it is not as though a huge portion of the 18 million bicycles sold in the U.S. between 2013 and 2015 have broken. -- Cheers, John B. |
#14
|
|||
|
|||
Horst link bending forces
On 2018-02-02 18:33, John B. wrote:
On Fri, 02 Feb 2018 16:50:56 -0800, Joerg wrote: On 2018-02-02 16:35, John B. wrote: On Fri, 02 Feb 2018 08:01:18 -0800, Joerg wrote: On 2018-02-01 17:07, John B. wrote: On Thu, 01 Feb 2018 15:38:39 -0800, Joerg wrote: On 2018-02-01 11:26, jbeattie wrote: On Thursday, February 1, 2018 at 10:24:16 AM UTC-8, Joerg wrote: Yesterday on the MTB I had to look downwards between my legs to see what made a rattling noise on the bike, saw some brush tangled in the rear and hit both brakes quite hard. That's when I noticed how much the upper diagonal strut in a Horst link bends when applying a lot of brake force. The center of it bows down several tenths of an inch and also outward a little. It's a pretty beefy strut: http://www.analogconsultants.com/ng/bike/Muddy4.JPG Similar on other bikes: https://ep1.pinkbike.org/p5pb9586988/p5pb9586988.jpg One can see such bowing also on aircraft wings which as built and tested to high stress standards. They make the spars out of stuff such as 7178 which I assume bike mfgs don't: https://www.popularmechanics.com/fli...-stress-tests/ Has anyone else with a Horst link bike taken a look while applying the rear brake hard? Can this fatigue the strut to the point where it eventally breaks? Should I shore that up with maybe an L- or U-profile strapped around it? I am asking because I use my MTB for transportation a lot and ride about 2000mi a year on it, hard, not just the occasional weekend loop. It'll see hundreds of such strut load cycles per ride. Yes, everything breaks after enough fatigue cycles, particularly aluminum -- which has no fatigue threshold. Even small amplitude fatigue cycles will affect aluminum. It will break. Not necessarily. Next time you fly sit right behind a wing and watch closely what happens at rotation time (when the pilot pulls up and the aircraft becomes airborne). The wing will bend so much that its tip is now several feet higher than it was in its resting state. In turbulent weather it'll then continue to flex up and down like he https://www.youtube.com/watch?v=tr5qkjlE77Y https://www.youtube.com/watch?v=NYsFk4I14N8 Yet these aircraft have a service life of 30 years. And then typically get sold to the freight dogs or lesser devloped countries for another 30 years or so. It's aluminum. My question is whether the typical upper Host link strut on a MTB can take similar dynamic stresses and for how long. If Boeing made them I'd have no doubt but Boeing does not build MTBs. [...] True that all large aircraft wings flex - the outriggers on a B-52 will be some 6 feet above the ground with empty tanks :-) If you are worried about your bike's rear strut why not just reinforce it. You have explained how clever it is to use a hose clamp to prevent a nut from loosening why not use the same technique to hold a reinforcing brace on your MTB? https://tinyurl.com/yaklvuy6 Figure 14 shows a bridge using plates attached with clamps as reinforcement. I know how to do that but wanted to know how much bending is normal. IOW whether reinforcement is necessary. Hence my post here. Clamping a reinforcement to the bar back there ain't as easy as a steerer hose clamp. That area can't have anything protruding and potentially slicing open a leg in case of a crash. If you are seriously worried about injuries resulting from a crash it would seem logical to simply get rid of the bike before the anticipated failure. As someone who has done aircraft maintenance you surprise me. Ever heard the term crashworthiness? Nope, never heard the term used in conjunction with the word "aircraft". I've heard the term "preventative" and even seen aircraft with what are called "Egress" systems but never an aircraft designed to be "crashworthy". Seriously? jaw drops https://flightsafety.org/hs/hs_jan-feb90.pdf I did some research and the term seems to be primarily associated with airbags in the Sikorsky UH-60 Black Hawk and the Boeing AH-64 Apache helicopters but no mention in other aircraft ranging from large aircraft like the B-52 to small ones like the F-15. In fact one reference reported that air bags were not built into commercial aircraft at all. Given the reliability of air bags, as evidenced by the recall of more then a million air bag equipped automobiles, perhaps a different term should be applied. This term is very widely used in aircraft design and also the design of components. Almost everything inside an aircraft must be designed with crashworthiness in mind or it will (hopefully) be flagged down in the design review. Among the things I do for a living is also the design of aerospace parts. For example, critical devices that are supposed to remain intact after a not quite "wrinkle-free" landing have to withstand some of G-force and nothing is allowed to come loose in the process. Mountain bikers do crash once in a while. Par for the course. It has been more than a year for me I think but some day my number will come up again. All it takes is a violent tire blow-out. As for clamps see https://tinyurl.com/y97t6n2b The 19th shows a clamp that can be installed without protruding parts and several other examples are shown further down the page. The kind with the "U-turn screws" is what I'd probably use if needed and then cap nuts on the ends. Towards the wheel it'll be tight, not much room. Well, then don't spend any time or effort in strengthening the struts. After all it is not as though a huge portion of the 18 million bicycles sold in the U.S. between 2013 and 2015 have broken. MTB? You've got to be kidding. That's why MTB riders carry cable ties and sometimes duct tape. http://www.socaltrailriders.org/inde...n-frame.21124/ -- Regards, Joerg http://www.analogconsultants.com/ |
#15
|
|||
|
|||
Horst link bending forces
On Sat, 03 Feb 2018 07:39:28 -0800, Joerg
wrote: On 2018-02-02 18:33, John B. wrote: On Fri, 02 Feb 2018 16:50:56 -0800, Joerg wrote: On 2018-02-02 16:35, John B. wrote: On Fri, 02 Feb 2018 08:01:18 -0800, Joerg wrote: On 2018-02-01 17:07, John B. wrote: On Thu, 01 Feb 2018 15:38:39 -0800, Joerg wrote: On 2018-02-01 11:26, jbeattie wrote: On Thursday, February 1, 2018 at 10:24:16 AM UTC-8, Joerg wrote: Yesterday on the MTB I had to look downwards between my legs to see what made a rattling noise on the bike, saw some brush tangled in the rear and hit both brakes quite hard. That's when I noticed how much the upper diagonal strut in a Horst link bends when applying a lot of brake force. The center of it bows down several tenths of an inch and also outward a little. It's a pretty beefy strut: http://www.analogconsultants.com/ng/bike/Muddy4.JPG Similar on other bikes: https://ep1.pinkbike.org/p5pb9586988/p5pb9586988.jpg One can see such bowing also on aircraft wings which as built and tested to high stress standards. They make the spars out of stuff such as 7178 which I assume bike mfgs don't: https://www.popularmechanics.com/fli...-stress-tests/ Has anyone else with a Horst link bike taken a look while applying the rear brake hard? Can this fatigue the strut to the point where it eventally breaks? Should I shore that up with maybe an L- or U-profile strapped around it? I am asking because I use my MTB for transportation a lot and ride about 2000mi a year on it, hard, not just the occasional weekend loop. It'll see hundreds of such strut load cycles per ride. Yes, everything breaks after enough fatigue cycles, particularly aluminum -- which has no fatigue threshold. Even small amplitude fatigue cycles will affect aluminum. It will break. Not necessarily. Next time you fly sit right behind a wing and watch closely what happens at rotation time (when the pilot pulls up and the aircraft becomes airborne). The wing will bend so much that its tip is now several feet higher than it was in its resting state. In turbulent weather it'll then continue to flex up and down like he https://www.youtube.com/watch?v=tr5qkjlE77Y https://www.youtube.com/watch?v=NYsFk4I14N8 Yet these aircraft have a service life of 30 years. And then typically get sold to the freight dogs or lesser devloped countries for another 30 years or so. It's aluminum. My question is whether the typical upper Host link strut on a MTB can take similar dynamic stresses and for how long. If Boeing made them I'd have no doubt but Boeing does not build MTBs. [...] True that all large aircraft wings flex - the outriggers on a B-52 will be some 6 feet above the ground with empty tanks :-) If you are worried about your bike's rear strut why not just reinforce it. You have explained how clever it is to use a hose clamp to prevent a nut from loosening why not use the same technique to hold a reinforcing brace on your MTB? https://tinyurl.com/yaklvuy6 Figure 14 shows a bridge using plates attached with clamps as reinforcement. I know how to do that but wanted to know how much bending is normal. IOW whether reinforcement is necessary. Hence my post here. Clamping a reinforcement to the bar back there ain't as easy as a steerer hose clamp. That area can't have anything protruding and potentially slicing open a leg in case of a crash. If you are seriously worried about injuries resulting from a crash it would seem logical to simply get rid of the bike before the anticipated failure. As someone who has done aircraft maintenance you surprise me. Ever heard the term crashworthiness? Nope, never heard the term used in conjunction with the word "aircraft". I've heard the term "preventative" and even seen aircraft with what are called "Egress" systems but never an aircraft designed to be "crashworthy". Seriously? jaw drops https://flightsafety.org/hs/hs_jan-feb90.pdf :-) You are reading a document that was published by Bell as part of a sales pitch made 30 years ago. The seat test and the required dummy standards were resulted from knowledge gained during the Works on effects of deceleration carried out by Colonel John Paul Stapp some 70 years ago. I did some research and the term seems to be primarily associated with airbags in the Sikorsky UH-60 Black Hawk and the Boeing AH-64 Apache helicopters but no mention in other aircraft ranging from large aircraft like the B-52 to small ones like the F-15. In fact one reference reported that air bags were not built into commercial aircraft at all. Given the reliability of air bags, as evidenced by the recall of more then a million air bag equipped automobiles, perhaps a different term should be applied. This term is very widely used in aircraft design and also the design of components. Almost everything inside an aircraft must be designed with crashworthiness in mind or it will (hopefully) be flagged down in the design review. Among the things I do for a living is also the design of aerospace parts. For example, critical devices that are supposed to remain intact after a not quite "wrinkle-free" landing have to withstand some of G-force and nothing is allowed to come loose in the process. Mountain bikers do crash once in a while. Par for the course. It has been more than a year for me I think but some day my number will come up again. All it takes is a violent tire blow-out. As for clamps see https://tinyurl.com/y97t6n2b The 19th shows a clamp that can be installed without protruding parts and several other examples are shown further down the page. The kind with the "U-turn screws" is what I'd probably use if needed and then cap nuts on the ends. Towards the wheel it'll be tight, not much room. Well, then don't spend any time or effort in strengthening the struts. After all it is not as though a huge portion of the 18 million bicycles sold in the U.S. between 2013 and 2015 have broken. MTB? You've got to be kidding. That's why MTB riders carry cable ties and sometimes duct tape. http://www.socaltrailriders.org/inde...n-frame.21124/ And how many of the 18 million or so bikes sold from 2013 - 2015 broke. Or even easier, how many bicycles in California broke in the same period? -- Cheers, John B. |
#16
|
|||
|
|||
Horst link bending forces
On 2018-02-03 14:53, John B. wrote:
On Sat, 03 Feb 2018 07:39:28 -0800, Joerg wrote: On 2018-02-02 18:33, John B. wrote: On Fri, 02 Feb 2018 16:50:56 -0800, Joerg wrote: On 2018-02-02 16:35, John B. wrote: On Fri, 02 Feb 2018 08:01:18 -0800, Joerg wrote: On 2018-02-01 17:07, John B. wrote: On Thu, 01 Feb 2018 15:38:39 -0800, Joerg wrote: On 2018-02-01 11:26, jbeattie wrote: On Thursday, February 1, 2018 at 10:24:16 AM UTC-8, Joerg wrote: Yesterday on the MTB I had to look downwards between my legs to see what made a rattling noise on the bike, saw some brush tangled in the rear and hit both brakes quite hard. That's when I noticed how much the upper diagonal strut in a Horst link bends when applying a lot of brake force. The center of it bows down several tenths of an inch and also outward a little. It's a pretty beefy strut: http://www.analogconsultants.com/ng/bike/Muddy4.JPG Similar on other bikes: https://ep1.pinkbike.org/p5pb9586988/p5pb9586988.jpg One can see such bowing also on aircraft wings which as built and tested to high stress standards. They make the spars out of stuff such as 7178 which I assume bike mfgs don't: https://www.popularmechanics.com/fli...-stress-tests/ Has anyone else with a Horst link bike taken a look while applying the rear brake hard? Can this fatigue the strut to the point where it eventally breaks? Should I shore that up with maybe an L- or U-profile strapped around it? I am asking because I use my MTB for transportation a lot and ride about 2000mi a year on it, hard, not just the occasional weekend loop. It'll see hundreds of such strut load cycles per ride. Yes, everything breaks after enough fatigue cycles, particularly aluminum -- which has no fatigue threshold. Even small amplitude fatigue cycles will affect aluminum. It will break. Not necessarily. Next time you fly sit right behind a wing and watch closely what happens at rotation time (when the pilot pulls up and the aircraft becomes airborne). The wing will bend so much that its tip is now several feet higher than it was in its resting state. In turbulent weather it'll then continue to flex up and down like he https://www.youtube.com/watch?v=tr5qkjlE77Y https://www.youtube.com/watch?v=NYsFk4I14N8 Yet these aircraft have a service life of 30 years. And then typically get sold to the freight dogs or lesser devloped countries for another 30 years or so. It's aluminum. My question is whether the typical upper Host link strut on a MTB can take similar dynamic stresses and for how long. If Boeing made them I'd have no doubt but Boeing does not build MTBs. [...] True that all large aircraft wings flex - the outriggers on a B-52 will be some 6 feet above the ground with empty tanks :-) If you are worried about your bike's rear strut why not just reinforce it. You have explained how clever it is to use a hose clamp to prevent a nut from loosening why not use the same technique to hold a reinforcing brace on your MTB? https://tinyurl.com/yaklvuy6 Figure 14 shows a bridge using plates attached with clamps as reinforcement. I know how to do that but wanted to know how much bending is normal. IOW whether reinforcement is necessary. Hence my post here. Clamping a reinforcement to the bar back there ain't as easy as a steerer hose clamp. That area can't have anything protruding and potentially slicing open a leg in case of a crash. If you are seriously worried about injuries resulting from a crash it would seem logical to simply get rid of the bike before the anticipated failure. As someone who has done aircraft maintenance you surprise me. Ever heard the term crashworthiness? Nope, never heard the term used in conjunction with the word "aircraft". I've heard the term "preventative" and even seen aircraft with what are called "Egress" systems but never an aircraft designed to be "crashworthy". Seriously? jaw drops https://flightsafety.org/hs/hs_jan-feb90.pdf :-) You are reading a document that was published by Bell as part of a sales pitch made 30 years ago. The seat test and the required dummy standards were resulted from knowledge gained during the Works on effects of deceleration carried out by Colonel John Paul Stapp some 70 years ago. The principle is still the same. As is the law. [...] As for clamps see https://tinyurl.com/y97t6n2b The 19th shows a clamp that can be installed without protruding parts and several other examples are shown further down the page. The kind with the "U-turn screws" is what I'd probably use if needed and then cap nuts on the ends. Towards the wheel it'll be tight, not much room. Well, then don't spend any time or effort in strengthening the struts. After all it is not as though a huge portion of the 18 million bicycles sold in the U.S. between 2013 and 2015 have broken. MTB? You've got to be kidding. That's why MTB riders carry cable ties and sometimes duct tape. http://www.socaltrailriders.org/inde...n-frame.21124/ And how many of the 18 million or so bikes sold from 2013 - 2015 broke. Or even easier, how many bicycles in California broke in the same period? Only a small fraction, mainly because most bikes become garage queens. Garage queens become dusty but they don't get hurt. There is one guy here in the NG who broke several Cannondale frames. One of the more serious accidents in our family happened when my dad's bicycle frame broke. -- Regards, Joerg http://www.analogconsultants.com/ |
#17
|
|||
|
|||
Horst link bending forces
On Sunday, February 4, 2018 at 7:17:29 AM UTC-8, Joerg wrote:
On 2018-02-03 14:53, John B. wrote: On Sat, 03 Feb 2018 07:39:28 -0800, Joerg wrote: On 2018-02-02 18:33, John B. wrote: On Fri, 02 Feb 2018 16:50:56 -0800, Joerg wrote: On 2018-02-02 16:35, John B. wrote: On Fri, 02 Feb 2018 08:01:18 -0800, Joerg wrote: On 2018-02-01 17:07, John B. wrote: On Thu, 01 Feb 2018 15:38:39 -0800, Joerg wrote: On 2018-02-01 11:26, jbeattie wrote: On Thursday, February 1, 2018 at 10:24:16 AM UTC-8, Joerg wrote: Yesterday on the MTB I had to look downwards between my legs to see what made a rattling noise on the bike, saw some brush tangled in the rear and hit both brakes quite hard. That's when I noticed how much the upper diagonal strut in a Horst link bends when applying a lot of brake force. The center of it bows down several tenths of an inch and also outward a little. It's a pretty beefy strut: http://www.analogconsultants.com/ng/bike/Muddy4.JPG Similar on other bikes: https://ep1.pinkbike.org/p5pb9586988/p5pb9586988.jpg One can see such bowing also on aircraft wings which as built and tested to high stress standards. They make the spars out of stuff such as 7178 which I assume bike mfgs don't: https://www.popularmechanics.com/fli...-stress-tests/ Has anyone else with a Horst link bike taken a look while applying the rear brake hard? Can this fatigue the strut to the point where it eventally breaks? Should I shore that up with maybe an L- or U-profile strapped around it? I am asking because I use my MTB for transportation a lot and ride about 2000mi a year on it, hard, not just the occasional weekend loop. It'll see hundreds of such strut load cycles per ride. Yes, everything breaks after enough fatigue cycles, particularly aluminum -- which has no fatigue threshold. Even small amplitude fatigue cycles will affect aluminum. It will break. Not necessarily. Next time you fly sit right behind a wing and watch closely what happens at rotation time (when the pilot pulls up and the aircraft becomes airborne). The wing will bend so much that its tip is now several feet higher than it was in its resting state. In turbulent weather it'll then continue to flex up and down like he https://www.youtube.com/watch?v=tr5qkjlE77Y https://www.youtube.com/watch?v=NYsFk4I14N8 Yet these aircraft have a service life of 30 years. And then typically get sold to the freight dogs or lesser devloped countries for another 30 years or so. It's aluminum. My question is whether the typical upper Host link strut on a MTB can take similar dynamic stresses and for how long. If Boeing made them I'd have no doubt but Boeing does not build MTBs. [...] True that all large aircraft wings flex - the outriggers on a B-52 will be some 6 feet above the ground with empty tanks :-) If you are worried about your bike's rear strut why not just reinforce it. You have explained how clever it is to use a hose clamp to prevent a nut from loosening why not use the same technique to hold a reinforcing brace on your MTB? https://tinyurl.com/yaklvuy6 Figure 14 shows a bridge using plates attached with clamps as reinforcement. I know how to do that but wanted to know how much bending is normal. IOW whether reinforcement is necessary. Hence my post here. Clamping a reinforcement to the bar back there ain't as easy as a steerer hose clamp. That area can't have anything protruding and potentially slicing open a leg in case of a crash. If you are seriously worried about injuries resulting from a crash it would seem logical to simply get rid of the bike before the anticipated failure. As someone who has done aircraft maintenance you surprise me. Ever heard the term crashworthiness? Nope, never heard the term used in conjunction with the word "aircraft". I've heard the term "preventative" and even seen aircraft with what are called "Egress" systems but never an aircraft designed to be "crashworthy". Seriously? jaw drops https://flightsafety.org/hs/hs_jan-feb90.pdf :-) You are reading a document that was published by Bell as part of a sales pitch made 30 years ago. The seat test and the required dummy standards were resulted from knowledge gained during the Works on effects of deceleration carried out by Colonel John Paul Stapp some 70 years ago. The principle is still the same. As is the law. [...] As for clamps see https://tinyurl.com/y97t6n2b The 19th shows a clamp that can be installed without protruding parts and several other examples are shown further down the page. The kind with the "U-turn screws" is what I'd probably use if needed and then cap nuts on the ends. Towards the wheel it'll be tight, not much room. Well, then don't spend any time or effort in strengthening the struts.. After all it is not as though a huge portion of the 18 million bicycles sold in the U.S. between 2013 and 2015 have broken. MTB? You've got to be kidding. That's why MTB riders carry cable ties and sometimes duct tape. http://www.socaltrailriders.org/inde...n-frame.21124/ And how many of the 18 million or so bikes sold from 2013 - 2015 broke. Or even easier, how many bicycles in California broke in the same period? Only a small fraction, mainly because most bikes become garage queens. Garage queens become dusty but they don't get hurt. There is one guy here in the NG who broke several Cannondale frames. One of the more serious accidents in our family happened when my dad's bicycle frame broke. Everything breaks after enough fatigue cycles. I've failed a bunch of frames, but have never been injured because of one, and for you, a failed rear linkage will not put you over the bars. I've seen injuries with fork failures (TK being a prime example) and with early Al MTB front-end failures. I saw some front-ends detach, although after big impacts that would have ejected the rider in any event. I'm not in the know with MTBs, but it seems that suspension failures would just result in a crippled bike rather than a crippled rider. If you are concerned, you need to buy a steel hard-tail fat bike -- or a full rigid steel fat bike. -- Jay Beattie. |
#18
|
|||
|
|||
Horst link bending forces
On 2018-02-04 09:41, jbeattie wrote:
On Sunday, February 4, 2018 at 7:17:29 AM UTC-8, Joerg wrote: On 2018-02-03 14:53, John B. wrote: On Sat, 03 Feb 2018 07:39:28 -0800, Joerg wrote: On 2018-02-02 18:33, John B. wrote: On Fri, 02 Feb 2018 16:50:56 -0800, Joerg wrote: On 2018-02-02 16:35, John B. wrote: On Fri, 02 Feb 2018 08:01:18 -0800, Joerg wrote: [...] As for clamps see https://tinyurl.com/y97t6n2b The 19th shows a clamp that can be installed without protruding parts and several other examples are shown further down the page. The kind with the "U-turn screws" is what I'd probably use if needed and then cap nuts on the ends. Towards the wheel it'll be tight, not much room. Well, then don't spend any time or effort in strengthening the struts. After all it is not as though a huge portion of the 18 million bicycles sold in the U.S. between 2013 and 2015 have broken. MTB? You've got to be kidding. That's why MTB riders carry cable ties and sometimes duct tape. http://www.socaltrailriders.org/inde...n-frame.21124/ And how many of the 18 million or so bikes sold from 2013 - 2015 broke. Or even easier, how many bicycles in California broke in the same period? Only a small fraction, mainly because most bikes become garage queens. Garage queens become dusty but they don't get hurt. There is one guy here in the NG who broke several Cannondale frames. One of the more serious accidents in our family happened when my dad's bicycle frame broke. Everything breaks after enough fatigue cycles. I've failed a bunch of frames, but have never been injured because of one, and for you, a failed rear linkage will not put you over the bars. It's the top strut that could break. Won't put me over the bar but could cause an all day (or night) walk. BTDT, after a rear tire blew and lost a chunk of material. I've seen injuries with fork failures (TK being a prime example) and with early Al MTB front-end failures. I saw some front-ends detach, although after big impacts that would have ejected the rider in any event. I'm not in the know with MTBs, but it seems that suspension failures would just result in a crippled bike rather than a crippled rider. It depends. If my rear shock detached the bike would bottom out. The posterior mount of that loosened twice, last time on Wednesday, but now I learned the symptoms and carry a 2nd 5mm Allen wrench in a pocket so I can check tightness once in a while without having to unpack the tool kit. If you are concerned, you need to buy a steel hard-tail fat bike -- or a full rigid steel fat bike. I need full-suspension because of a lower back issue. I am hoping some day there will be a Ti-frame for a 29er, or at least 27-1/2" suitable for 3" tires. However, I am thankful that my current bikes are not carbon fiber (the road bike is Reynolds steel, as it should). Fat bikes aren't suitable for the trails I use because their tires would fail very soon. -- Regards, Joerg http://www.analogconsultants.com/ |
#19
|
|||
|
|||
Horst link bending forces
On 2/4/2018 12:59 PM, Joerg wrote:
On 2018-02-04 09:41, jbeattie wrote: If you are concerned, you need to buy a steel hard-tail fat bike -- or a full rigid steel fat bike. I need full-suspension because of a lower back issue. I am hoping some day there will be a Ti-frame for a 29er, or at least 27-1/2" suitable for 3" tires. However, I am thankful that my current bikes are not carbon fiber (the road bike is Reynolds steel, as it should). FWIW, the fork that broke on our tandem was Reynolds 531. I don't blame Reynolds. I blame the custom frame builder, Jim Bradford, who without telling me substituted track-gauge fork blades in place of tandem gauge. The wall thickness was only 1/3 what it should have been. -- - Frank Krygowski |
#20
|
|||
|
|||
Horst link bending forces
Frank Krygowski wrote:
FWIW, the fork that broke on our tandem was Reynolds 531. BTW I've heard that number (531) doesn't specify some property of the steel but is a designation/name so one can refer to the product. -- underground experts united http://user.it.uu.se/~embe8573 |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Rats show the forces behind capitalism | His Highness the TibetanMonkey, Creator of the Movement of Tantra-Hammock[_2_] | Recumbent Biking | 2 | July 14th 10 06:26 PM |
Forces on Cranks | Andre Jute[_2_] | Techniques | 132 | May 10th 10 03:37 AM |
Gyroscopic forces revisited | [email protected] | Techniques | 183 | November 1st 07 02:00 PM |
Forces on spokes | bicycle_disciple | Techniques | 420 | September 27th 06 10:53 PM |
Turner, so errm you know that horst link we said was invaluable | spademan o---[) * | Mountain Biking | 12 | October 16th 05 08:02 PM |