Well if you like
… I could give you the source, but most of it concerns the GUI and reading default ratios from a file (this makes it easy to make a ‘flavor’ of my calculator for different bikes gearboxes without entering the code, just change the input file
) … anyway, the only bit you are concerned with would be the actual calculations function. So this is the fundamental maths/calculations behind it all!!! in Pseudo code format, with comments (depicted by/started with a ‘ ):-
‘If wheel was turning at engine speed, with wheel circumference in cm; work out distance that would be traveled in miles per hour
SpeedCalculationWithoutReduction = ((WheelCircumfarance/100000) * (RPM * 60)) * 0.621371) 'Circumferance in KM, Revvs per hour, KM to Miles
‘ now work out reductions:-
Reductions = primaryreduction * gearratio * (rearsprocket / frontsprocket) ‘gearratio is the gearbox reduction e.g. from the specs, 6th is 23/27 (0.851), primaryreduction is also from specs
‘ Now reduce the wheel speed using the calculated overall reductions:-
SpeedInGearAtRPM = SpeedCalculationWithoutReduction / Reductions
‘ Here are the gear ratios for SV650:-
‘Pimary - 2.088 (71/34)
‘1st - 2.461 (32/13)
‘2nd - 1.777 (32/18 )
‘3rd - 1.380 (29/21)
‘4th - 1.125 (27/24)
‘5th - 0.961 (25/26)
‘6th - 0.851 (23/27)
‘Standard sprockets for an SVS 44rear 15front
So a worked example:-
Input:-
200cm circumference, 10500rpm, 6th gear, 15t Front, 44t Rear.
SpeedCalculationWithoutReduction = ((200/100000) * (10500 * 60)) * 0.621371) = 782.9275
Reductions = (71/34) * (23/27) * (44 / 15) = 5.21801
SpeedInGearAtRPM = 782.9275/5.21801 = 150.0433
i.e. at 10500 in top with a 2m circumference rear tyre, you would theoretically be doing 150.0433mph!!!
Clear??
Note: presuming the variables are populated, the 3 lines of code in
BOLD is all you need to do the calculations ... I made this into a little function and then set up a loop to feed in different values for the variables, reading them from the text boxes ... its all good clean fun and time better spent* than looking at mucky pictures of Angelina Jolie!!
*well more productivly spent!!