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#11
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program to compute gears, with table
On Friday, September 8, 2017 at 10:45:07 AM UTC-7, Emanuel Berg wrote:
Graham wrote: So if your definition of gear is roll out in mm then it looks close. Do not forget to include the tyre. Right, perhaps I should change "gear" into "roll out" if that's the agreed-upon term. Perhaps I should even make it print the formulae first thing. And I'll include the tyre. Excellent There's always a slight error this way. The radius of a tire and hence it's circumference changes slightly with pressure and/or weight of the rider. |
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#12
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program to compute gears, with table
On Friday, September 8, 2017 at 10:52:22 AM UTC-7, Emanuel Berg wrote:
Skip Montanaro wrote: * Why the 1.0 divisor when computing gear? As explained, otherwise it'll be integer division. But I think that qualifies as a hack (not an ugly hack tho) so there is no shame in spotting it an "error" * You can skip the radius and use wheel (diameter) directly in computing the circumference. Right! * It never occurred to me to do this in Lisp. I always just use an online calculator, like: http://www.gear-calculator.com/?GR=D...&SL=2.6&UN=KMH Let's agree there is no need to do it in Lisp. Only a desire That's an eight speed setup. For the most part you can REALLY set an 8 speed up nicely to have only two clumsy steps - the two highest gears. And you in general only use these while riding downhills so it is not worth making these ratios closer. So exactly why are they changing to 10, 11 and now 12 speeds. These have weaker chains, much faster wearing drive components and less sure shifting. |
#13
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program to compute gears, with table
Frank Krygowski wrote:
I first did such a thing in the 1970s, using Fortran. Cool! Fortran (Formula Translation, 1957) sounds like the perfect idea. Perhaps the formating (output report) should be left to COBOL tho (Common business-oriented language, 1959). Today I think the hipsters at the universities would use Haskell (1990). But I formatted it as a compact table in rows and columns. You could have one row for each chainring, one column for each rear cog. A matrix, 2x8. The idea with having it 8x3 was that the third column would be the "roll out" and that would be sorted vertically. But perhaps I'll add a feature to flip it later. Another useful trick is to plot the gear development on a logarithmic scale, so the change from one gear to the next is scaled as the percentage change. Plotting using a separate row or a separate symbol for each chainring makes clear which gear is "next" in your gear progression. Yes, I thought about doing that. Perhaps with ASCII art or using gnuplot which I did some cool plots with. Here is one: http://user.it.uu.se/~embe8573/figur...e-inverted.png -- underground experts united http://user.it.uu.se/~embe8573 |
#14
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program to compute gears, with table
David Scheidt wrote:
The style is awful. In straight common lisp [...] Ha! I've heard about the bicycle style police but I always thought that refered to shaved legs and keeping the helmet straps to the inside of the sunglasses scalps! Or wait... should it be the other way around? Well, styles make fights, and "pushing" is never part of my game plan. But it does look neater with `dolist' and `push' and it might be more efficient as well as I don't know the intricacies of append and collect. Not that it will ever matter in this case, of course. -- underground experts united http://user.it.uu.se/~embe8573 |
#15
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program to compute gears, with table
Joerg wrote:
Why make things complicated? It isn't - it's fun I do such stuff with spreadsheets. When done, feeding a CLI tool with data from the shell is faster and more pleasant (cooler) than using a spreadsheet. It can then also be combined with other such tools, tho I admit that probably won't happen in this case (?). A spreadsheet is of course a fine way to do it as well. That's what they were invented for. Programming languages were also invented for this kind of... computing -- underground experts united http://user.it.uu.se/~embe8573 |
#16
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program to compute gears, with table
David Scheidt wrote:
I rewrote his code in common lisp in less time than it takes excel to start. It really doesn't get any faster than these lovely small shell tools you gotta give me more and more cuz you're the one that I adore (Zodiac 1996) -- underground experts united http://user.it.uu.se/~embe8573 |
#18
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program to compute gears, with table
John B. wrote:
"well, we do still have a few 9 speed chains left". Anyone feel free to elaborate on this. How and why should the chain be different with different cassette/chainring configurations? And is there a "notation" do describe this? Usually makes it easier to understand... -- underground experts united http://user.it.uu.se/~embe8573 |
#19
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program to compute gears, with table
On Sat, 09 Sep 2017 06:46:59 +0200, Emanuel Berg
wrote: John B. wrote: "well, we do still have a few 9 speed chains left". Anyone feel free to elaborate on this. How and why should the chain be different with different cassette/chainring configurations? And is there a "notation" do describe this? Usually makes it easier to understand... The rear sprocket spacing is closer as the number of cassette cogs goes up, so narrower chains. The over all length of the cassette is limited by the distance between the rear drop outs as the wider the cassette the more the hub flange on that side must be offset and thus the angle of the spokes decreases. -- Cheers, John B. |
#20
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program to compute gears, with table
John B. wrote:
The rear sprocket spacing is closer as the number of cassette cogs goes up, so narrower chains. The over all length of the cassette is limited by the distance between the rear drop outs as the wider the cassette the more the hub flange on that side must be offset and thus the angle of the spokes decreases. Okay? Is that the reason you simply cannot make the back fork wider? At some point the spoke angle will make for a wheel that isn't strong enough? -- underground experts united http://user.it.uu.se/~embe8573 |
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