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Re: program to compute gears, with table
From: |
Graham |
Subject: |
Re: program to compute gears, with table |
Date: |
Fri, 8 Sep 2017 09:46:01 +0100 |
"Emanuel Berg" <moasen@zoho.com> wrote in message
86bmmlu54a.fsf@zoho.com">news:86bmmlu54a.fsf@zoho.com...
> Hey guys, does this look right to you?
>
> ;; (print-gears '(34 50) '(12 13 15 17 19 21 23 25) 622)
> ;;
> ;; =>
> ;;
> ;; 622 wheel
> ;;
> ;; chainring sprocket gear
> ;;
> ;; 34 25 2657.5360544880004
> ;; 34 23 2888.626146182609
> ;; 34 21 3163.7333982000005
> ;; 34 19 3496.7579664315795
> ;; 50 25 3908.1412566000004
> ;; 34 17 3908.1412566000004
> ;; 50 23 4247.97962673913
> ;; 34 15 4429.226757480001
> ;; 50 21 4652.549115000001
> ;; 34 13 5110.64625863077
> ;; 50 19 5142.291127105264
> ;; 34 12 5536.5334468500005
> ;; 50 17 5747.266553823531
> ;; 50 15 6513.568761
> ;; 50 13 7515.656262692309
> ;; 50 12 8141.960951250001
>
> (require 'cl-lib)
>
> (defun compute-gear (chainring sprocket wheel)
> (let*((pi 3.14159265)
> (radius (/ wheel 2.0))
> (circum (* 2 radius pi))
> (gear (* (/ chainring sprocket 1.0) circum)))
> (list chainring sprocket gear)))
>
> (defun gear (chainrings sprockets wheel)
> (let*((gears
> (cl-loop for c in chainrings
> append (cl-loop for s in sprockets
> collect (compute-gear c s wheel) )
> )))
> (cl-sort gears #'<= :key #'cl-caddr)))
>
> (defun print-gears (chainrings sprockets wheel)
> (let ((out-buffer (get-buffer-create "*Gears*")))
> (with-current-buffer out-buffer
> (erase-buffer)
> (insert (format "%s wheel\n\n" wheel))
> (insert "chainring sprocket gear\n\n")
> (let ((gears (gear chainrings sprockets wheel)))
> (cl-loop for g in gears
> do (let ((c ( car g))
> (s ( cadr g))
> (d (cl-caddr g)))
> (insert (format " %s %s %s\n" c s d))
> ))))
> (pop-to-buffer out-buffer) ))
>
> --
> underground experts united
> http://user.it.uu.se/~embe8573
Not sure about your code as I do not speak that language but a quick check
gives:
622*3.142*50/25=3908.648mm
So if your definition of gear is roll out in mm then it looks close. Do not
forget to include the tyre. See:
https://www.cateye.com/data/resources/Tire_size_chart_ENG.pdf
for approximate circumferences. Taking a 23mm tyre the above example would be:
2096*50/25=4192mm
Graham.
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