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Author Topic: Motorcycle speed in gears  (Read 37176 times)
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sofadriver
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« on: December 20, 2014, 04:30:28 AM »

Been a long time since Algebra 1.

Can anyone change this around to find speed?


            speed x 336 x pri x gear x     big   
RPM =                                            small
            -------------------------------------------
                            diameter

Thanks in advance
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Mike in Tacoma

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stay`tee
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« Reply #1 on: December 20, 2014, 06:56:18 AM »

mph = (rpm x tyre radius) / (primary x drive x final x 168),,   cool
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sofadriver
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« Reply #2 on: December 20, 2014, 08:01:43 AM »

mph = (rpm x tyre radius) / (primary x drive x final x 168),,   cool

Thanks, stay'tee.

Couldn't get that to work with the 168 (although 491mph would be coolish!).
Seems to work with 336, though.

I come up with 138mph and that works for me!
I've got more sprockets and more rpm than the figures I used.
But I'm still hoping for a little tailwind!  grin
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Mike in Tacoma

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55chevr
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« Reply #3 on: December 20, 2014, 10:16:05 AM »

http://www.cosportbikeclub.org/misc/SpeedCalc.html


This is plug and play - no algebra
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« Reply #4 on: December 20, 2014, 11:05:02 AM »

Let:
S: speed (MPH)
D1: primary drive ratio (clutch wheel motor sprocket, etc.)
D2: secondary drive ratio (rear sprocket transmission sprocket, etc.)
G: individual transmission ratio (2.50, etc.), direct drive high gear = 1.00
T: tire diameter (inches)
R: engine speed (revolutions per minute)

S = (T R .002975) (D1 D2 G)
R = (S D1 D2 G) (T .002975)
D1 = (R T .002975) (S D2 G)
D2 = (R T .002975) (S D1 G)

« Last Edit: December 20, 2014, 11:09:03 AM by panic » Logged
sofadriver
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« Reply #5 on: December 20, 2014, 12:50:16 PM »

interesting.......

sta'tee's method - 138mph

55chvr's online calculator - 178mph

panic's method - 144mph

 huh
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Mike in Tacoma

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Stan Back
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« Reply #6 on: December 20, 2014, 12:53:17 PM »

I'd use the 178 -- it's faster.  Just say it's the Exit Speed if it doesn't match your time slip.
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sofadriver
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« Reply #7 on: December 20, 2014, 12:58:13 PM »

I'd use the 178 -- it's faster.  Just say it's the Exit Speed if it doesn't match your time slip.

my choice, too!  grin
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Mike in Tacoma

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Vinsky
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« Reply #8 on: December 20, 2014, 01:24:05 PM »

Here's one that covers just about ever variation you can come up with.
http://www.rbracing-rsr.com/gearspeed.html
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John
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« Reply #9 on: December 20, 2014, 02:13:22 PM »

Have you tried the gearing calculator that Sumner put together? It allows you change sprockets to compare in addition to transmission gears. It's down 2 threads here.
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« Reply #10 on: December 20, 2014, 07:40:24 PM »

55chevr's page is correct - if you input your tire size and drive ratios correctly. The 178 mph result is a GIGO error.


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stay`tee
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« Reply #11 on: December 20, 2014, 09:31:48 PM »

whats a "GIGO" error,  huh,,

in relation to the formula i posted, (primary x drive x final), "drive" is the ratio of the drivin gear, eg 5th @ 1.130,, "final" is the ratio of front to rear sprocket, eg 18/42 = 2.33,,  cheers,,
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Stainless1
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« Reply #12 on: December 20, 2014, 09:48:52 PM »

Garbage in garbage out...  cheers

Post the particulars and I'll put it thru our calculator
« Last Edit: December 20, 2014, 09:51:34 PM by Stainless1 » Logged

Stainless
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MSA Bockscar Lakester #1000 my fastest mile 245 and change, 84 ci turbobusa motor... but Corey's 233 MPH H/BFL record is still 3MPH faster than mine.
sofadriver
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« Reply #13 on: December 20, 2014, 10:52:42 PM »

Garbage in garbage out...  cheers

Post the particulars and I'll put it thru our calculator

Thanks, Stainless.

Final drive.....3.4
1st....2.54
2nd....1.89
3rd....1.5
4th....1.25
5th....1.09
6th....0.96
front sprocket - 17. rear is 35.
tire is 23.5" (120/60-17)
13,500 rpm

I'm going to try 55chevr's calculator again, too.
« Last Edit: December 20, 2014, 10:54:41 PM by sofadriver » Logged

Mike in Tacoma

"aww, what the hell - let's just do it".............

100cc APS/G #833
sofadriver
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« Reply #14 on: December 20, 2014, 11:07:05 PM »

duhhhhh

i was entering tire diameter where the cosportbike calculator was asking for rim diameter

i'll go stand in the corner now
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Mike in Tacoma

"aww, what the hell - let's just do it".............

100cc APS/G #833
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