Jackshaft Hopeless gearing?

Charles Laypool

Active Member
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Joined
Feb 5, 2016
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Location
Mass. Usa
Im just trying to figure out what gearing is best for me with a jackshaft kit

If my motors Max rpm is 5500 and its internal gear reduction is 4.1 so my output sprockets rpm is 1341.4634146
So 10t to 17t is 1.7:1
(789.09612623 rpm)
17t to 10t is 1.7
(469.17419194 rpm)
10t to 44t is 4.4444444444
(105.49413453 rpm(at the pedals)
44t to 36t is 1.2222222222 (86.313382798 rpm(to rear tire)
Now if i calculate

Axle teeth / Pedal teeth = gear ratio.

Sprocket RPM / Gear Ratio = Wheel RPM (wRPM)

Tire circumfrence in feet * wRPM = feet per minute.

Feet per minute * 60 = feet per hour.

Feet per hour / 5280 = miles per hour.

1st----9mph
2nd-10mph
3rd-12mph
4th-16mph
5th-18mph
6th-21mph
7th-24mph
8th-27mph

Now i really hope im doing something wrong i ordered my shift kit im jus waiting to get it but i want to get best gearing and these results are crap someone enlighten me
 
If my motors Max rpm is 5500 and its internal gear reduction is 4.1 so my output sprockets rpm is 1341.4634146
So 10t to 17t is 1.7:1
(789.09612623 rpm)
17t to 10t is 1.7
(469.17419194 rpm)

What is going on here? You are going from 10T to 17T at 1:1.7 for 1341 to 789 RPM. And, then you are going from 17T back to 10T for 789 to 469 RPM. Wouldn't it be back to 1341 RPM? Also, there is a 10% power reduction when using a jackshaft apparently. Cheers
 
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