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#91
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program to compute gears, with table
Radey Shouman wrote:
the much deeper instruction pipelines "deeper instruction pipelines", is that like the many transformations of graphical data before it appears on the screen, or a shell parsing of a text string with UNIX tools, i.e. done_value=$(a | b | ... | n) ? If so, are the extra steps because of new capabilities the CPU has that wasn't there before? -- underground experts united http://user.it.uu.se/~embe8573 |
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#92
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program to compute gears, with table
On Tuesday, September 12, 2017 at 8:43:49 AM UTC-7, Emanuel Berg wrote:
John B. wrote: Because, as Andrew told you, it will fit. On the other hand, as Andrew told you, if a 6 speed it won't shift well. I think it would make more sense if Shimano put just one digit, or one set of digits, on their boxes, which refered both "fits" and "shifts well". It is the intuition as well. For example if I had a 6 casette from Shimano, then put on a 6/7/8 chain, and it didn't shift well, the thought wouldn't hit me the chain/casette combination could be the problem, but I suppose one will have to get used to disinformation even from the most iconic manufacturers. Well, that's a hard subject isn't it? As a friction shifting chain on a freewheels it shifts almost perfectly as friction shifters do. The problem is with Brifters. |
#93
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program to compute gears, with table
On Tuesday, September 12, 2017 at 11:58:38 AM UTC-7, Frank Krygowski wrote:
On Tuesday, September 12, 2017 at 3:53:29 AM UTC-4, John B. wrote: On Tue, 12 Sep 2017 06:00:09 +0200, Emanuel Berg wrote: Sir Ridesalot wrote: Many times he asks a question then disagrees with what those experts like Andrew who know the RIGHT answer tell him. So let's hear it, why do Shimano put such obvious disinformation on their product boxes? Because, as Andrew told you, it will fit. On the other hand, as Andrew told you, if a 6 speed it won't shift well. I might add that I have used a 10 speed chain with a 9 speed cassette and a 9 speed chain with a 10 speed cassette, and they worked to my satisfaction although Shimano certainly do not state it will work on the box. Didn't Shimano advertise derailleurs as being "9 Speed" when they were precisely the same geometry as their previous derailleurs? I'm not sure of that Frank. I think that the angles were improved over time.. I know that I have a Campy long arm rear derailleur that doesn't shift as well as a short arm newer model. The way the arms rotate and drop are much better on the short arm. That seems to be my experience with the Shimano stuff as well. |
#94
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program to compute gears, with table
On Tuesday, September 12, 2017 at 1:19:25 PM UTC-7, Radey Shouman wrote:
John B. writes: On Mon, 11 Sep 2017 08:23:48 -0700 (PDT), wrote: [ ... ] Yesterday I rode on a 35 mile ride. On the way out into a headwind I averaged a little less than 14 mph. I had a cup of coffee while in the city square the worst band I ever heard was making awful noises. When I was in a band if we had played that badly on our first try in a rehearsal we would have quit. On the way back the wind had reversed and I had a hard time maintaining 12 mph for most of the way. By the time I got home I was exhausted. Do you think that I could improve my performance with an 11 or 12 speed? I know my limits and it isn't playing as if I was Chris Froome. Something I've always wondered about is how in the world can I ride an out and back course and have a head wind both ways :-( With some reasonable assumptions I think you can show that this is actually true, in a sense. Suppose for example the wind is blowing at right angles to your (perfectly straight) direction, and that it happens to be blowing at exactly your ground speed, v. The apparent wind will be at 45 degrees your heading, at a velocity of sqrt(v^2 + v^2) = sqrt(2)*v. For turbulent flow, the drag force is approximately proportional to the square of the wind speed, so the drag force will be twice the drag force you would see in still air, F. (At this point we have assumed a cylindrical bike & rider, meaning that the coefficient of drag is the same from the front as the side, since drag from the side is normally greater, this is conservative). Fortunately the drag force acts at 45 degrees to your course, so the drag component that holds you back is cos(45 deg)*F = (2/sqrt(2))*F = sqrt(2)*F ~= 1.414 F This is as true on the way out as it is on the way back, hence you really do have an effective head wind both ways. Radey - I'm an engineer and understand mathematics. I also understand that on most of the courses I ride I get a complete 180 degree swing in the direction of the winds due to prevailing wind pattern change as the temperature between the coast and the valley changes from the morning to afternoon. I was simply expressing frustration that I happen to live in a place where it always appears to oppose me whereas others living in the valley can have a tail wind in both directions. It was really nice on a Century down near Gilroy when the end 20 miles was down a hard tailwind and I could maintain 28 mph. |
#95
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program to compute gears, with table
Here is what Wikipedia says: [1]
With derailleur equipped bicycles, the external width of the chain also matters, because chains must not be too wide for the cogset or they will rub on the next larger sprocket, or too narrow that they might fall between two sprockets. Chains can also be identified by the number of rear sprockets they can support, anywhere from 3 to 11, and the list below enables measuring a chain of unknown origin to determine its suitability. * 6 speed – 7.8 mm (5/16") * 7 speed – 7.3 mm (9/32") * 8 speed – 7.1 mm (9/32") * 9 speed – 6.6 to 6.8 mm (1/4 to 9/32") * 10 speed – 6.2 mm (1/4") (Shimano, Campagnolo) * 10 speed (Narrow) – 5.88 mm (7/32") (Campagnolo, KMC) * 10 speed (Narrow, Direction) – 5.88 mm (7/32") (Shimano CN-5700, CN-6700, CN-7900) * 11 speed – 5.5 mm (7/32") (Campagnolo, KMC, Shimano CN-9000) Interesting that the 7 and 8 are the same in inches, but not in mm. $ units -t '7.3 mm' '1|32 in' 9.1968504 $ units -t '7.1 mm' '1|32 in' 8.9448819 [1] https://en.wikipedia.org/w/index.php...&printable=yes -- underground experts united http://user.it.uu.se/~embe8573 |
#96
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program to compute gears, with table
On Tue, 12 Sep 2017 17:43:43 +0200, Emanuel Berg
wrote: John B. wrote: Because, as Andrew told you, it will fit. On the other hand, as Andrew told you, if a 6 speed it won't shift well. I think it would make more sense if Shimano put just one digit, or one set of digits, on their boxes, which refered both "fits" and "shifts well". Well, apparently it makes sense to Shimano... It is the intuition as well. For example if I had a 6 casette from Shimano, then put on a 6/7/8 chain, and it didn't shift well, the thought wouldn't hit me the chain/casette combination could be the problem, but I suppose one will have to get used to disinformation even from the most iconic manufacturers. There is no disinformation at all. The chain will fit 6,7,8 speed cassettes. And that is just what they told you. -- Cheers, John B. |
#97
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program to compute gears, with table
On Tue, 12 Sep 2017 11:58:34 -0700 (PDT), Frank Krygowski
wrote: On Tuesday, September 12, 2017 at 3:53:29 AM UTC-4, John B. wrote: On Tue, 12 Sep 2017 06:00:09 +0200, Emanuel Berg wrote: Sir Ridesalot wrote: Many times he asks a question then disagrees with what those experts like Andrew who know the RIGHT answer tell him. So let's hear it, why do Shimano put such obvious disinformation on their product boxes? Because, as Andrew told you, it will fit. On the other hand, as Andrew told you, if a 6 speed it won't shift well. I might add that I have used a 10 speed chain with a 9 speed cassette and a 9 speed chain with a 10 speed cassette, and they worked to my satisfaction although Shimano certainly do not state it will work on the box. Didn't Shimano advertise derailleurs as being "9 Speed" when they were precisely the same geometry as their previous derailleurs? - Frank Krygowski I'm not sure about that. I suspect that the "pull distance" may be a bit difference if the derailer is designed to work in an indexed shifter system. But as far as reaching the other side of the cassette" I've used a 7 speed derailer to shift a 9 speed cassette. Am old Shimano "600" I believe it was. I replaced it with a more modern derailer as I thought the "new one" looked nicer. -- Cheers, John B. |
#98
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program to compute gears, with table
On Tue, 12 Sep 2017 16:19:21 -0400, Radey Shouman
wrote: John B. writes: On Mon, 11 Sep 2017 08:23:48 -0700 (PDT), wrote: [ ... ] Yesterday I rode on a 35 mile ride. On the way out into a headwind I averaged a little less than 14 mph. I had a cup of coffee while in the city square the worst band I ever heard was making awful noises. When I was in a band if we had played that badly on our first try in a rehearsal we would have quit. On the way back the wind had reversed and I had a hard time maintaining 12 mph for most of the way. By the time I got home I was exhausted. Do you think that I could improve my performance with an 11 or 12 speed? I know my limits and it isn't playing as if I was Chris Froome. Something I've always wondered about is how in the world can I ride an out and back course and have a head wind both ways :-( With some reasonable assumptions I think you can show that this is actually true, in a sense. Suppose for example the wind is blowing at right angles to your (perfectly straight) direction, and that it happens to be blowing at exactly your ground speed, v. The apparent wind will be at 45 degrees your heading, at a velocity of sqrt(v^2 + v^2) = sqrt(2)*v. For turbulent flow, the drag force is approximately proportional to the square of the wind speed, so the drag force will be twice the drag force you would see in still air, F. (At this point we have assumed a cylindrical bike & rider, meaning that the coefficient of drag is the same from the front as the side, since drag from the side is normally greater, this is conservative). Fortunately the drag force acts at 45 degrees to your course, so the drag component that holds you back is cos(45 deg)*F = (2/sqrt(2))*F = sqrt(2)*F ~= 1.414 F This is as true on the way out as it is on the way back, hence you really do have an effective head wind both ways. I was thinking of days when I ride what I call my short route. It is a square loop in the city on which the two longer legs are essentially due north and due south. I set out and on the south leg the wind was directly in my face. then the "cross wind" leg, about 1 km and protected by tall buildings and then the north bound leg. Again wind directly in my face. There are traffic lights on both the north and south legs and the wind doesn't stop blowing when I stopped at a red light :-) -- Cheers, John B. |
#99
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program to compute gears, with table
On Tue, 12 Sep 2017 16:30:42 -0400, Radey Shouman
wrote: John B. writes: On Tue, 12 Sep 2017 06:06:56 +0200, Emanuel Berg wrote: John B. wrote: That isn't true at all. I have definitely improved the speed of a C program by using an assembler language sub routines and even had two C compilers that would compile the same program into two different sizes that performed the same "test" program at two different speeds. Obviously two different programs will be of different sizes and run at different speeds. But that wasn't what I said at all. As I said the same code compiled on two different compiler resulted in both a different size compiled application and, as well, a speed difference when running. With compilers to do optimization, and with much increased hardware to make optimization unnecessary to begin with, there is close to zero gain re-writing C into assembler, and its Except when it does make a difference. an undertaking that isn't proportional to that gain. So it is rather done when there is a need to manipulate hardware directly or in ways which the high-level language isn't suited for. I'm not sure that is correct in all cases although of course modern computers run at speeds that make the slower software appear to be satisfactory. But I did a search on the question "is modern software written in assembler" and the first hit replied: "Probably more than most people think, especially in the microcontroller field. I write in assembler when it's appropriate, which for the kind of work I do is most of the time I write in assembler every day, not on any rational basis, but because that's how my boss did it back in the day. The big difference between new processors and old, from my point of view, is the much deeper instruction pipelines. In order to get the most from these machines one should write in the least straightforward way possible, doing a little of this, then a little of that, so that there is as long a time as possible between setting some register's value and using it. Compilers are good at this, human beings not so much, especially when the code has to be debugged and modified at some time in the unknowable future. On the other hand, in assembler one may use the low level processor behavior to make sure things are done in an efficient way -- for example carry and overflow conditions are straightforwardly but non-portably checked. In C, if you want to make sure the compiler does what you think it should you have to check the generated assembly, and possibly contort your code to make your intention "clear". Ultimately I disassembled the two test programs from the two different C compilers and found that the difference between the two was that the Microsoft compiler saved the state, all the registers, etc., then called the "sub routine" then recovered the state, all the registers, etc., and went on to the next step. A sort of bullet proofing I guess you'd call it. The other compiler apparently figured that the programmer knew what he was doing and if you wrote "write("Good Morning\n");" it just went ahead and did it. -- Cheers, John B. |
#100
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program to compute gears, with table
John B. wrote:
There is no disinformation at all. The chain will fit 6,7,8 speed cassettes. And that is just what they told you. I can't speak for anyone else, but I'm interested in equipment that works and works well, and if it doesn't, I don't care if it fits or not. -- underground experts united http://user.it.uu.se/~embe8573 |
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