#181
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Bike adjustments
David Scheidt writes:
Mark J. wrote: :On 12/13/2019 8:34 AM, Frank Krygowski wrote: : On 12/13/2019 11:01 AM, Radey Shouman wrote: : John B. writes: : : : I remember a story that at Wright-Patterson AFB (one of the : development bases) they had a 10 foot long slide rule in a temperature : controlled room for doing really accurate calculations I don't know : whether that is true, however it does sound possible. : : That sounds like a tall tale to me. : : ISTR hearing of oversized slide rules being used for additional : accuracy. But I never heard they were in a temperature controlled room, : and I doubt they would need that. The relevant parts would expand or : contract at the same rate. : : Even back in the thirties heavy : computations were done digitally by rooms full of "computers", many of : them mathematically inclined women, using ten key adding machines and : passing slips of paper to one another.Â* Richard Feynman describes this : kind of work during the Manhattan project. : : The excellent movie _Hidden Figures_ covered that in great detail. : : There were other shortcut computation methods before calculators and : computers became so cheap.Â* Graphs for actual lookup were popular.Â* You : could buy graph paper at a technical book store with half a dozen : variations on the scales: log-log, semi-log, probability ... : : :-) And I still have - somewhere! - my stock of at least a dozen types : of graph paper. (Not that a retiree has much use for them...)Â*Â* But I : did appreciate an unusual Christmas gift: Graph paper sticky notes. : : Building nomograms was a useful art, and using them a basic skill.Â* In : the chem lab, functions were integrated by cutting them out in filter : paper and weighing them on the analytical balance.Â* Every field had its : set of graphical methods for calculation, from the really graphical, : like lofting plans for ships or planes, to the more mathematical, like : designing distillation columns. : : I wonder how many people here have used a planimeter? : https://en.wikipedia.org/wiki/Planimeter : An analog one with a vernier scale? :I've used a planimeter, but I think it was just for demonstration in a :teaching situation. It was a nice "Made in West Germany" model - which :attests to both its quality and its age. As an undergrad I had to do an :exercise deriving the theoretical basis for a planimeter's operation, :but I never saw one until years later, when it was essentially obsolete. I've used one in the last decade. Except it wasn't the sort of mechanical device you're thinking of it. it was a rather large pen thing, that you pushed a button, and then traced your object of interest. After you were done you pushed the button (or maybe another one). it then told you the perimeter and area of the shape you'd traced, both the atual values, but also according to the scale you'd told it. It belonged to an interior designer, she used it to make material estimates from drawings done at the client's site. In the office the cad software did all that for her/ I think ti stored the data so you could import the traced shapes into the cad system later. Years ago I wrote a program to convert polygon data collected by hand on a digitizer tablet to area and arclength. Surprisingly simple with the help of Dr. Green. Never used a real mechanical planimiter. |
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#182
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Bike adjustments
On Fri, 13 Dec 2019 13:46:40 -0600, AMuzi wrote:
On 12/13/2019 1:14 PM, Mark J. wrote: On 12/13/2019 8:34 AM, Frank Krygowski wrote: On 12/13/2019 11:01 AM, Radey Shouman wrote: John B. writes: I remember a story that at Wright-Patterson AFB (one of the development bases) they had a 10 foot long slide rule in a temperature controlled room for doing really accurate calculations I don't know whether that is true, however it does sound possible. That sounds like a tall tale to me. ISTR hearing of oversized slide rules being used for additional accuracy. But I never heard they were in a temperature controlled room, and I doubt they would need that. The relevant parts would expand or contract at the same rate. Even back in the thirties heavy computations were done digitally by rooms full of "computers", many of them mathematically inclined women, using ten key adding machines and passing slips of paper to one another. Richard Feynman describes this kind of work during the Manhattan project. The excellent movie _Hidden Figures_ covered that in great detail. There were other shortcut computation methods before calculators and computers became so cheap. Graphs for actual lookup were popular. You could buy graph paper at a technical book store with half a dozen variations on the scales: log-log, semi-log, probability ... :-) And I still have - somewhere! - my stock of at least a dozen types of graph paper. (Not that a retiree has much use for them...)  But I did appreciate an unusual Christmas gift: Graph paper sticky notes. Building nomograms was a useful art, and using them a basic skill. In the chem lab, functions were integrated by cutting them out in filter paper and weighing them on the analytical balance. Every field had its set of graphical methods for calculation, from the really graphical, like lofting plans for ships or planes, to the more mathematical, like designing distillation columns. I wonder how many people here have used a planimeter? https://en.wikipedia.org/wiki/Planimeter An analog one with a vernier scale? I've used a planimeter, but I think it was just for demonstration in a teaching situation. It was a nice "Made in West Germany" model - which attests to both its quality and its age. As an undergrad I had to do an exercise deriving the theoretical basis for a planimeter's operation, but I never saw one until years later, when it was essentially obsolete. During my teaching career, I was "in charge" of the department's historical artifacts - this means I was the only person who didn't want to throw them out - so I hoarded the slide rules, including a 6' one (for teaching, as David pointed out), the planimeter, and a host of other "pedagogical tools." Mark J. "pedagogical tools." The Good Sisters needed only an 18 inch wooden ruler to make their point. Very effective too. There were two schools in my home town. the Parochial School and the Public School. So the story went Junior had to hold hrs hands out for the Sister and the next day his father complained to the Father that his kid had been beaten. The Good Father was said to have replied, "take your kid out of school". I've always thought that was a refreshing idea. "If you don't like it here just leave". -- cheers, John B. |
#183
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Bike adjustments
On Friday, December 13, 2019 at 4:06:25 PM UTC, David Scheidt wrote:
10 foot slide rules existed, but they were for teaching. You could get very decent extended accuracy on a slide rule. For quick calculations in the boardroom I had a six-inch Pickett rule in my briefcase; it came in a saddle leather pocket case with a spring clip, but my clothes were cut without pockets, so in the briefcase. First one here looks like mine: https://duckduckgo.com/?q=Pickett+po...284_h6wp.j pg I still have it somewhere, but my family are asleep already and I don't want a search to wake them. But for serious work behind closed doors I had a helical rule with cylindrical parts sliding over each other. It fitted into a wooden box about two feet long, and had special statistical functions. It was built for actuaries, or at least I saw it first in the head actuary's office at an insurance company a cousin was chairman of, complete with life-expectancy tables; I immediately ordered one from the German firm who had supplied theirs and who still had two in stock. I wish I still had it. But I don't see it in the images on the net, though it was similar to this one, and made first in the same era, the 1870-somethings to about WW2. I can't remember what mine cost (I probably never asked) but the accountant had a fit when the invoice arrived. Scroll down to "Thacher's Calculating Instrument" on this page: http://www.gizmology.net/sliderules_mine.htm It was replaced by the first personal computer, Olivetti's Programma 101 and then by the 203: https://royal.pingdom.com/the-first-pc-from-1965/ Here's a restored Programma 203 in action, without its beauty-covers: https://www.youtube.com/watch?v=pTErXxa2-Og Until recently I wore a basic E6B rotary flight computer on my wrist to do what the well-known Jeppesen used to do for me. Jeppesen types he https://duckduckgo.com/?q=Jeppeson+E...es&i a=images and my wrist flight computer he http://coolmainpress.com/andrejutewatches.html#Navihawk For those of you who know the Blue Angels version, which I also had, the yellow indices rather than red is because mine is a prototype that didn't go into production. Andre Jute Toolfondler |
#184
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Bike adjustments
On Friday, December 13, 2019 at 7:28:06 AM UTC-8, Sir Ridesalot wrote:
On Friday, 13 December 2019 10:22:31 UTC-5, jbeattie wrote: On Friday, December 13, 2019 at 4:16:43 AM UTC-8, Duane wrote: wrote: On Friday, December 13, 2019 at 6:20:03 AM UTC+1, jbeattie wrote: On Thursday, December 12, 2019 at 8:07:35 PM UTC-8, James wrote: On 12/12/19 3:02 pm, Ralph Barone wrote: James wrote: With disc brakes you would only need to flip the axle quick release and take the wheel out, and not need to fiddle with the brakes at all. Yeah, but if I unintentionally squeeze my brake levers on my canti equipped bike with no wheel installed, it’s a pretty easy recovery. It's a non-issue with mechanical disc brakes too. You might be thinking of hydraulics? I'm not so keen on them, like I'm not so keen on electronic gear shifting. Its a 20 second fix, assuming one squeeze is enough to prevent re-installation of the wheel. I prefer hydraulic to cable discs for braking feel and the fact that the pads are self-adjusting, but cables are fine, too - except on my CAADX commuter because of the long cable run in housing caused a lot of drag, and the return springs on the BB5 were weak. I definitely prefer hydro discs on that bike. -- Jay Beattie. I bought a cross bike after disks brakes became available for them (never wanted a crossbike with canti lever brakes; they are really crap for that kind of riding). First cable disks. Never liked them on my cross bike. I had more issues with them than I have with my current hydraulic disks. Never had any issues with these hydraulic brakes in almost six years now. My 'biggest problem' is breaking in the pads which is the same for cable discs. I don't understand why people prefer cable discs on off road bikes for off road riding with a lot of mud. Glad I'm not hydrau phobic. Like you said you have to squeeze really hard to get into trouble reinstalling you wheel and then it is an 20 seconds fix with your tire lever. It is not something that happens just by accident on a regular basis. Lou Isn’t there a spacer or clip or something to keep the pads in place when taking off the wheel? I haven’t tried disc brakes but friends that put their bikes on my roof rack seem to have something like that. Doesn’t seem like a big issue. It isn't a big issue. The usual problem with disc bikes and roof racks are through axles. Your friend apparently had an adapter or a non-through axle bike. -- Jay Beattie. The warning I read about a few years ago was that if you took the wheel off a disc brake bike after using the brakes a lot and you accidentaly squeezed the brake lever that the pads(iirc) could then fuse together. Cheers I suppose that would be possible since the pads are metallic and very hard braking CAN heat them to the level that they can fuse. But unless you're racing on a very very fast course with hard turns I can't see how you could use them that hard. |
#185
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Bike adjustments
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#186
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Bike adjustments
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#187
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Bike adjustments
On 15/12/19 2:06 pm, Tom Kunich wrote:
On Saturday, December 14, 2019 at 6:46:36 PM UTC-8, James wrote: A phobia of hydraulics? No, I don't have one of those, but I appreciate the simplicity and reliability of cables. I don't need self adjustment or extra light feel. My grip strength is pretty good. I gave up my desk job and retired at about age 40, and now spend time hobby farming. Anyone who works on the land is likely to have fairly good grip strength. You don't consider hydraulics which are used on every single auto in the world as simplistic and reliable? Just making you think about what you said. Simplistic and reliable compared with cable operated bicycle brakes? No. Why don't they rely on hydraulics for the handbrake? -- JS |
#188
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Bike adjustments
Bicycle hydraulic brakes are not nearly as reliable or durable as any such brakes used on a motor vehicle (even a cheap motorcycle or scooter).
Also, bicycles don't have the sort of long, tortuous brake line routing that makes cable brakes a bad choice for many motor vehicles. Hydraulic bicycle brakes are just a vanity feature that introduces new modes of failure and service requirements, without bringing any measurable benefits to offset the drawbacks. |
#189
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Bike adjustments
On Sunday, December 15, 2019 at 7:20:01 AM UTC+1, James wrote:
On 15/12/19 2:06 pm, Tom Kunich wrote: On Saturday, December 14, 2019 at 6:46:36 PM UTC-8, James wrote: A phobia of hydraulics? No, I don't have one of those, but I appreciate the simplicity and reliability of cables. I don't need self adjustment or extra light feel. My grip strength is pretty good. I gave up my desk job and retired at about age 40, and now spend time hobby farming. Anyone who works on the land is likely to have fairly good grip strength. You don't consider hydraulics which are used on every single auto in the world as simplistic and reliable? Just making you think about what you said. Simplistic and reliable compared with cable operated bicycle brakes? No. Why don't they rely on hydraulics for the handbrake? -- JS Hmm, I don't know if a cable operated handbrake is a good example. You never had a frozen cable? I had and that was really a PIA. In all manuals of the cars I had with a cable operated handbrakes it was advised not to use it in wet freezing weather, just put the car in second gear. After my incident I just did that. Never used a handbrake except for getting started on a hill. I don't know how it works in my current car with an automatic transmission but I'm sure there is no cable in there. Anyhow all of my hydraulic disc brakes proved to be extremely reliable, never had any issues with them on three of my bikes. YMMV. For off road riding in the winter it was quite good today. My cross bike looked like this after todays ride: https://photos.app.goo.gl/ZjpqaJLvVsGfqT366 Lou |
#190
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Bike adjustments
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