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#51
October 27th 17, 02:28 AM
posted to rec.bicycles.tech
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Why do some forks and frames have brake rotor size limits?
On 10/26/2017 8:19 PM, Tim McNamara wrote:
On Thu, 26 Oct 2017 13:22:07 -0400, Frank Krygowski wrote: And ISTM that this is yet another example of "safety inflation." For decades and decades, cyclists rode in all weather using caliper brakes. They removed their hands from the brake levers to shift gears. They rode at night using halogen or even vacuum headlight bulbs powered by dynamos, and in daylight with no lights at all. They had shoes without custom attachments to the pedals. They wore cloth caps, or no caps at all. They rode wearing clothing with natural, non-blinding colors. Now every one of those practices is portrayed by some as scandalously risky. Sheesh! Careful, Frank! Someone will confuse you with a conservative. Although these days even the "new conservatives" are no longer conservative. They're just mad that their lives suck, looking for some payback and usually blaming the wrong people. Principled actual conservatives are sadly becoming rara aves. The current political environment may be more complex than you imagine: https://www.harpercollins.com/978006...blican-like-me Frankly, conservatives no longer understand Republicans. At least I do not. -- Andrew Muzi www.yellowjersey.org/ Open every day since 1 April, 1971 
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#52
October 27th 17, 04:01 AM
posted to rec.bicycles.tech
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Why do some forks and frames have brake rotor size limits?
On Thu, 26 Oct 2017 13:40:21 -0400, Radey Shouman
wrote: Surely the first step is just internal air passages in the brake disks, as used in motor vehicles for years and years. Any other coolant is a big step up in difficulty. Unfortunately that would be a major modification. Air is a lousy way to move heat. https://www.engineeringtoolbox.com/thermal-conductivity-d_429.html Air 0.024 W/mK Aluminum 205 W/mK Cast iron 58 W/mK Water 0.58 W/mK (ignores enthalpy from vaporization) If the brake disk were red hot, it would take quite a bit of air blown at the disk to cool it down. Water would drop the temperature far quicker. I'm not certain, but my guess(tm) is that the holes in the automobile brake disk were to reduce weight, not for air cooling. Rather than transplant an automotive brake disk onto a bicycle, it might be easier be a bit creative. I could build a sandwich of two disks, with copper or aluminum pipes in between. Getting water into the pipe(s) will be a problem, but I have some ideas. As the brake disk spins, hot water is ejected. One disk is larger diameter than the other. The break shoes hit only the large diameter disk. The small disk is just there to increase the surface area and support the pipe(s). The axle length and dropout spacing will need to be tweaked to accommodate the increased diameter. Or, if you want something cheaper, make the brake disk hollow and out of two solid disks. Essentially a can. Drill some tiny holes around the circumference. Fill the can with water before every downhill run. The spray of hot water will keep the disk cool. Or, if you want something crude, and inverted water bottle dripping water onto the brake disk. Aim the drip just ahead of the calipers so that the disk will need to rotate a bit less than 360 degrees before getting to the calipers. The water should have evaporated before it can "lubricate" the brakes. Unfortunately, if you drip water on a cold brake disk, it's likely to get the brake pads wet, which will probably result in a regrettable incident. Maybe this isn't such a great idea. Ok, maybe a direct contact method. Clamp a wire brush onto the seat stay and press the brush against the brake disk. Pump water through the brush and onto the brake disk as needed. Hopefully, the red hot brake disk will not melt the wire brush bristles. That should get the water to where it's needed without worrying about it evaporating before it makes contact. Hmmmm... this tea tastes funny. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
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#53
October 27th 17, 05:04 AM
posted to rec.bicycles.tech
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Why do some forks and frames have brake rotor size limits?
On Thu, 26 Oct 2017 20:01:13 -0700, Jeff Liebermann
wrote: On Thu, 26 Oct 2017 13:40:21 -0400, Radey Shouman wrote: Surely the first step is just internal air passages in the brake disks, as used in motor vehicles for years and years. Any other coolant is a big step up in difficulty. Unfortunately that would be a major modification. Air is a lousy way to move heat. https://www.engineeringtoolbox.com/thermal-conductivity-d_429.html Air 0.024 W/mK Aluminum 205 W/mK Cast iron 58 W/mK Water 0.58 W/mK (ignores enthalpy from vaporization) If the brake disk were red hot, it would take quite a bit of air blown at the disk to cool it down. Water would drop the temperature far quicker. I'm not certain, but my guess(tm) is that the holes in the automobile brake disk were to reduce weight, not for air cooling. Rather than transplant an automotive brake disk onto a bicycle, it might be easier be a bit creative. I could build a sandwich of two disks, with copper or aluminum pipes in between. Getting water into the pipe(s) will be a problem, but I have some ideas. As the brake disk spins, hot water is ejected. One disk is larger diameter than the other. The break shoes hit only the large diameter disk. The small disk is just there to increase the surface area and support the pipe(s). The axle length and dropout spacing will need to be tweaked to accommodate the increased diameter. Or, if you want something cheaper, make the brake disk hollow and out of two solid disks. Essentially a can. Drill some tiny holes around the circumference. Fill the can with water before every downhill run. The spray of hot water will keep the disk cool. Or, if you want something crude, and inverted water bottle dripping water onto the brake disk. Aim the drip just ahead of the calipers so that the disk will need to rotate a bit less than 360 degrees before getting to the calipers. The water should have evaporated before it can "lubricate" the brakes. Unfortunately, if you drip water on a cold brake disk, it's likely to get the brake pads wet, which will probably result in a regrettable incident. Maybe this isn't such a great idea. Ok, maybe a direct contact method. Clamp a wire brush onto the seat stay and press the brush against the brake disk. Pump water through the brush and onto the brake disk as needed. Hopefully, the red hot brake disk will not melt the wire brush bristles. That should get the water to where it's needed without worrying about it evaporating before it makes contact. Hmmmm... this tea tastes funny. Years ago I saw heavy logging trucks, operating in the mountains near the Yuba river in California, with what appeared to be water cooled drum brakes. The water seemed to be piped from a tank directly to the brake drums with - I'm guessing here - about 1/2" nominal water pipe sized pips and hoses. It was quite obvious when they turned the water on and off. -- Cheers, John B.
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#54
October 27th 17, 05:36 AM
posted to rec.bicycles.tech
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Why do some forks and frames have brake rotor size limits?
On 10/26/2017 9:28 PM, AMuzi wrote:
On 10/26/2017 8:19 PM, Tim McNamara wrote: Careful, Frank!Â* Someone will confuse you with a conservative. Although these days even the "new conservatives" are no longer conservative.Â* They're just mad that their lives suck, looking for some payback and usually blaming the wrong people.Â* Principled actual conservatives are sadly becoming rara aves. The current political environment may be more complex than you imagine: https://www.harpercollins.com/978006...blican-like-me Frankly, conservatives no longer understand Republicans. At least I do not. Does anyone understand the current Republicans? -- - Frank Krygowski
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#55
October 27th 17, 06:45 AM
posted to rec.bicycles.tech
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Why do some forks and frames have brake rotor size limits?
On Fri, 27 Oct 2017 11:04:29 +0700, John B.
wrote: Years ago I saw heavy logging trucks, operating in the mountains near the Yuba river in California, with what appeared to be water cooled drum brakes. The water seemed to be piped from a tank directly to the brake drums with - I'm guessing here - about 1/2" nominal water pipe sized pips and hoses. It was quite obvious when they turned the water on and off. I did some Googling and found that the water cooling system was mostly found in Hayes HDX logging trucks: http://www.hankstruckpictures.com/hank_rabe_pacific_story.htm "This truck also was equipped with two Williams exhaust brakes, Lear electric retarder on the driveshaft and a water tank for spraying water on the brake drums to keep them cool. This was a state of the art modern and huge truck in 1963." There are some YouTube videos of the Hayes HDX but none show the water cooled braking system in action. There are some comments indicating that it sometimes belched steam. Also, the water cooling seems to be for emergency use, not for regular stopping. http://www.eng-tips.com/viewthread.cfm?qid=339285 "The water idea was for a one-time emergency use, not continuous. How much do you think would be needed to save overheated brakes and slow the rig to a safe speed or stop it?" Same with the bicycle idea. When the brakes get hot enough to melt the pads, it's time for some water cooling. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
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#56
October 27th 17, 09:11 AM
posted to rec.bicycles.tech
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Why do some forks and frames have brake rotor size limits?
On Wed, 25 Oct 2017 07:53:11 -0700, Joerg
wrote: On 2017-10-24 17:21, John B. wrote: On Tue, 24 Oct 2017 11:47:12 -0700, Joerg wrote: On 2017-10-24 07:27, wrote: On Tuesday, October 24, 2017 at 2:19:48 AM UTC-7, John B. wrote: On Mon, 23 Oct 2017 10:09:20 -0700, Jeff Liebermann wrote: On Mon, 23 Oct 2017 12:48:29 +0700, John B. wrote: On Sun, 22 Oct 2017 20:51:15 -0700, Jeff Liebermann wrote: On Mon, 23 Oct 2017 07:02:08 +0700, John B. wrote: But re disc brake cooling F1 car brakes appear to work with the discs red hot. In the 1,000 degree (F) range. And they use Carbon Fiber discs too :-) And everyone knows that CF is better. "Thermal Conductivity of Carbon Fiber, and other Carbon Based Materials" http://www.christinedemerchant.com/carbon_characteristics_heat_conductivity.html "So...Is Carbon Fiber a good heat conductor? As usual the answer is "it depends." The short answer is NO not when regular carbon fiber is made up in regular epoxy and expected to conduct heat across the thickness. IF a highly carbonized pan fiber with graphite or diamond added, is measured for heat transmission in the length of the fiber it is very good and can rival and exceed copper." On the other hand, they seem to work pretty well :-) See https://www.youtube.com/watch?v=h5JcHAEmIYM for a visual indication of heat dissipation. :-) Impressive. I'll assume it's a carbon-carbon rotor, since all F1 cars seem to using them. Undoubtedly so. But if the advantage of "carbon" bikes can be extolled that a carbon-carbon frame must have twice the bragging rights :-) http://www.racecar-engineering.com/technology-explained/f1-2014-explained-brake-systems/ (4 pages) "A typical road car uses a cast iron brake disc with an organic brake pad. In an F1 car, though, the same material is used for both disc and pad, and this material is known as carbon-carbon - a significantly different material to the carbon-fibre composites used in the rest of the car" In other words, the F1 brakes are NOT made from CF. Some detail on Formula 1 brakes: https://www.youtube.com/watch?v=ev6XTdlKElw Fun destroying brakes: https://www.youtube.com/watch?v=KslGsXMgmqg The brake starting at 4:45 sure looks like CF but I'm not sure. Maybe twin disk brakes would be easier? http://nuovafaor.it//public/prodotto/75/nccrop/DOPPIO_FRENO_CROSS_ENDURO.jpg https://i.ytimg.com/vi/Pvwj-WWlKkg/maxresdefault.jpg https://gzmyu4ma9b-flywheel.netdna-ssl.com/wp-content/uploads/2011/09/Gatorbrake-dual-hydraulic-front-disc-brakes-carbon-rotors01.jpg https://lh4.googleusercontent.com/-cDfAFWrGR6Q/VHKPsm-f6YI/AAAAAAAAX10/2FCyj87xs0g/s640/14%2520-%25201.jpg https://www.minibikecraze.co.uk/wp-content/uploads/bs0978.jpg https://endless-sphere.com/forums/viewtopic.php?f=28&t=56268 Given the coefficient of friction between a 1.25" wide rubber tire (32mm) and a wet road probably dragging the feet will work. :-) Joerg's experience is with full suspension MTB's. These things are incredibly heavy and long wheelbased. He has his judgement of disks and it is no doubt quite accurate for his experience and riding. I have disks on a much lighter and shorter wheelbased bike. I know the failings up close and personal. I simply cannot imagine WHY a person would want a more complicated system than that offered by the Campy Skeleton brakes. The reason can be summed up in one word: Rain :-) But last Sunday I started out my "weekend" ride in the rain. It had been raining nearly all night and the roads had a lot of water on them - note we have been having floods here in Bangkok lately - but it appeared that the rain was ending so off I went. Unfortunately my weather forecasting facility wasn't working very well and I rode 20 Km of a 30 Km ride in light rain and flooded roads in many places. I was splashing through water in some places and cars were splashing through (and splashing me) in others. Of course, Sunday is much lighter traffic then on work days but still, Bangkok is rated as one of the cities with the most chaotic traffic in the world, and I did have to stop suddenly several time, on flooded roads with wet wheels and brakes. My brakes worked just as they do in the dry. Back brake stops me somewhat slowly and front brake stops rather suddenly, both brakes together provides best stopping. No long wait after grabbing a brake lever although I did think of you with your stopping problems and I have the feeling that the brake lever pressure might be a tiny bit more to stop in the rain but if it was it was so little that it couldn't be quantified. But of course I am using quality brake pads. Why it costs me US$12.12 a wheel just for pads alone.... but they do last a year or more. It seems Californian rain and Thai rain aren't the same. When it rains heavily and I have to do a surprise emergency stop after not having used the brakes for a while there is 1-2sec of nada, absolutely nothing. It makes no difference whatsoever whether I use $17 high-falutin Koolstop rain-rated pads or $4 Clarks pads. The experience of other riders around here and in this NG is similar. Which, to be honest, I find a little mystifying as I've had pretty constant success with conventional brakes. Frankly, I can't believe this is solely because I'm somehow so uniquely skilled or that y'all are all in the awkward squad I do see a number of people here and many who are not here who seem to have ridden for years using conventional brakes without complaint and some of the blogs I read don't even talk about brakes. Dave Moulton, for example. An old fellow, used to race bikes, came to the U.S. in about 1979 and built frames commercially for years, now retired, has one entry in his blog about brakes - "centering side pull brakes". Another blog from the long distance side of the bicycleing world, The Blayleys, who are into Audex's and who apparently each ride in the neighborhood of 10,000 miles annually, mentions Vee brakes in reference to a Tandem while a photo of them on a tandem on their web page shows disc brakes. On the other hand, when she discusses a "good brevet bike she simply says that the "brakes must clear the fenders and probably long reach caliper brakes will suffice". In short, it seems that brakes just don't seem to be a hot subject in much of the cycling fraternity. I might comment that I've ridden coaster brakes, drum brakes, rod pull brakes, cantilever brakes, side pull single pivot caliper brakes, double pivot caliper, Vee brakes and for one short ride a cable disc brake. and at the time I rode them I found all the brakes to give acceptable service. Well with one exception, rim brakes and chrome plated steel rims were sometimes a bit iffy :-) -- Cheers, John B.
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#57
October 27th 17, 09:15 AM
posted to rec.bicycles.tech
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Why do some forks and frames have brake rotor size limits?
On Thu, 26 Oct 2017 20:19:42 -0500, Tim McNamara
wrote: On Thu, 26 Oct 2017 13:22:07 -0400, Frank Krygowski wrote: And ISTM that this is yet another example of "safety inflation." For decades and decades, cyclists rode in all weather using caliper brakes. They removed their hands from the brake levers to shift gears. They rode at night using halogen or even vacuum headlight bulbs powered by dynamos, and in daylight with no lights at all. They had shoes without custom attachments to the pedals. They wore cloth caps, or no caps at all. They rode wearing clothing with natural, non-blinding colors. Now every one of those practices is portrayed by some as scandalously risky. Sheesh! Careful, Frank! Someone will confuse you with a conservative. Although these days even the "new conservatives" are no longer conservative. They're just mad that their lives suck, looking for some payback and usually blaming the wrong people. Principled actual conservatives are sadly becoming rara aves. I think I'd have to ask "what is a conservative"? They don't seem to the same as the ones I knew when I was a kid :-) -- Cheers, John B.
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#58
October 27th 17, 09:24 AM
posted to rec.bicycles.tech
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Why do some forks and frames have brake rotor size limits?
On Thu, 26 Oct 2017 13:37:00 -0400, Radey Shouman
wrote: Joerg writes: On 2017-10-24 17:21, John B. wrote: On Tue, 24 Oct 2017 11:47:12 -0700, Joerg wrote: [ ... ] The reason can be summed up in one word: Rain :-) But last Sunday I started out my "weekend" ride in the rain. It had been raining nearly all night and the roads had a lot of water on them - note we have been having floods here in Bangkok lately - but it appeared that the rain was ending so off I went. Unfortunately my weather forecasting facility wasn't working very well and I rode 20 Km of a 30 Km ride in light rain and flooded roads in many places. I was splashing through water in some places and cars were splashing through (and splashing me) in others. Of course, Sunday is much lighter traffic then on work days but still, Bangkok is rated as one of the cities with the most chaotic traffic in the world, and I did have to stop suddenly several time, on flooded roads with wet wheels and brakes. My brakes worked just as they do in the dry. Back brake stops me somewhat slowly and front brake stops rather suddenly, both brakes together provides best stopping. No long wait after grabbing a brake lever although I did think of you with your stopping problems and I have the feeling that the brake lever pressure might be a tiny bit more to stop in the rain but if it was it was so little that it couldn't be quantified. But of course I am using quality brake pads. Why it costs me US$12.12 a wheel just for pads alone.... but they do last a year or more. It seems Californian rain and Thai rain aren't the same. When it rains heavily and I have to do a surprise emergency stop after not having used the brakes for a while there is 1-2sec of nada, absolutely nothing. It makes no difference whatsoever whether I use $17 high-falutin Koolstop rain-rated pads or $4 Clarks pads. The experience of other riders around here and in this NG is similar. I don't understand the difference myself. When it's really raining, meaning there's a continuous film of water on the road and a rooster tail shooting forward off the front tire, I ride like a little old lady, because of the delay in braking. Especially when it's dark, and leaves and other blown down crap cover the road. I suspect that may be the secret. I've never been "doored", perhaps because if I have to ride past a line of parked cars where a door might be opened I either slow down or ride further enough away that a door wouldn't hit me. -- Cheers, John B.
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#60
October 27th 17, 09:34 AM
posted to rec.bicycles.tech
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Why do some forks and frames have brake rotor size limits?
On Wed, 25 Oct 2017 08:59:46 -0700 (PDT), wrote:
On Tuesday, October 24, 2017 at 5:22:03 PM UTC-7, John B. wrote: On Tue, 24 Oct 2017 11:47:12 -0700, Joerg wrote: On 2017-10-24 07:27, wrote: On Tuesday, October 24, 2017 at 2:19:48 AM UTC-7, John B. wrote: On Mon, 23 Oct 2017 10:09:20 -0700, Jeff Liebermann wrote: On Mon, 23 Oct 2017 12:48:29 +0700, John B. wrote: On Sun, 22 Oct 2017 20:51:15 -0700, Jeff Liebermann wrote: On Mon, 23 Oct 2017 07:02:08 +0700, John B. wrote: But re disc brake cooling F1 car brakes appear to work with the discs red hot. In the 1,000 degree (F) range. And they use Carbon Fiber discs too :-) And everyone knows that CF is better. "Thermal Conductivity of Carbon Fiber, and other Carbon Based Materials" http://www.christinedemerchant.com/carbon_characteristics_heat_conductivity.html "So...Is Carbon Fiber a good heat conductor? As usual the answer is "it depends." The short answer is NO not when regular carbon fiber is made up in regular epoxy and expected to conduct heat across the thickness. IF a highly carbonized pan fiber with graphite or diamond added, is measured for heat transmission in the length of the fiber it is very good and can rival and exceed copper." On the other hand, they seem to work pretty well :-) See https://www.youtube.com/watch?v=h5JcHAEmIYM for a visual indication of heat dissipation. :-) Impressive. I'll assume it's a carbon-carbon rotor, since all F1 cars seem to using them. Undoubtedly so. But if the advantage of "carbon" bikes can be extolled that a carbon-carbon frame must have twice the bragging rights :-) http://www.racecar-engineering.com/technology-explained/f1-2014-explained-brake-systems/ (4 pages) "A typical road car uses a cast iron brake disc with an organic brake pad. In an F1 car, though, the same material is used for both disc and pad, and this material is known as carbon-carbon - a significantly different material to the carbon-fibre composites used in the rest of the car" In other words, the F1 brakes are NOT made from CF. Some detail on Formula 1 brakes: https://www.youtube.com/watch?v=ev6XTdlKElw Fun destroying brakes: https://www.youtube.com/watch?v=KslGsXMgmqg The brake starting at 4:45 sure looks like CF but I'm not sure. Maybe twin disk brakes would be easier? http://nuovafaor.it//public/prodotto/75/nccrop/DOPPIO_FRENO_CROSS_ENDURO.jpg https://i.ytimg.com/vi/Pvwj-WWlKkg/maxresdefault.jpg https://gzmyu4ma9b-flywheel.netdna-ssl.com/wp-content/uploads/2011/09/Gatorbrake-dual-hydraulic-front-disc-brakes-carbon-rotors01.jpg https://lh4.googleusercontent.com/-cDfAFWrGR6Q/VHKPsm-f6YI/AAAAAAAAX10/2FCyj87xs0g/s640/14%2520-%25201.jpg https://www.minibikecraze.co.uk/wp-content/uploads/bs0978.jpg https://endless-sphere.com/forums/viewtopic.php?f=28&t=56268 Given the coefficient of friction between a 1.25" wide rubber tire (32mm) and a wet road probably dragging the feet will work. :-) Joerg's experience is with full suspension MTB's. These things are incredibly heavy and long wheelbased. He has his judgement of disks and it is no doubt quite accurate for his experience and riding. I have disks on a much lighter and shorter wheelbased bike. I know the failings up close and personal. I simply cannot imagine WHY a person would want a more complicated system than that offered by the Campy Skeleton brakes. The reason can be summed up in one word: Rain :-) But last Sunday I started out my "weekend" ride in the rain. It had been raining nearly all night and the roads had a lot of water on them - note we have been having floods here in Bangkok lately - but it appeared that the rain was ending so off I went. Unfortunately my weather forecasting facility wasn't working very well and I rode 20 Km of a 30 Km ride in light rain and flooded roads in many places. I was splashing through water in some places and cars were splashing through (and splashing me) in others. Of course, Sunday is much lighter traffic then on work days but still, Bangkok is rated as one of the cities with the most chaotic traffic in the world, and I did have to stop suddenly several time, on flooded roads with wet wheels and brakes. My brakes worked just as they do in the dry. Back brake stops me somewhat slowly and front brake stops rather suddenly, both brakes together provides best stopping. No long wait after grabbing a brake lever although I did think of you with your stopping problems and I have the feeling that the brake lever pressure might be a tiny bit more to stop in the rain but if it was it was so little that it couldn't be quantified. But of course I am using quality brake pads. Why it costs me US$12.12 a wheel just for pads alone.... but they do last a year or more. This is something I just can't understand. Indeed there is a millisecond or two delay for the brake shoe to excise the water directly in front of the initial application of the brake but after the brake shoe touches the rim it pushes any water in the way off without floating the shoe above it. I see no reason whatsoever for disk brakes and their complications even on most MTB's since a good V-Brake is longer lasting, just as effective, cheaper and doesn't require special wheels and frame and fork changes. Well, "cause I want 'em" is, I guess, a valid reason. But not necessarily proof of superiority :-) -- Cheers, John B.
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