Gearing Ratios

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SlicerDicer

Guest
Ok here is my boggle.

Direct off engine is 12 tooth sprocket no gearing reduction.
Sprocket on bicycle for the shifter setup I want... 36 tooth thats for the equal to 1st gear.

That places the motor at 20mph in 1st gear with the clutch engaged. The clutch engages at 2300rpm.

At full engine speed thats 3600rpm placing the bike at 30mph.... This is unacceptable to me for this kinda speed haha... Consider there will be 7 speeds on this bike that I will be able to use with the motor it seems insane for that kinda speed in the 1st gear.

So my question I pose to you. How can I knock that down so I can use the gears in a realistic sense. I would really like to hit a top speed of only 40mph with the smallest sprocket on the cassete being around 18

As of right now that places it at 60mph!!! thats OMG fast.

so what would I need to do to shave 20mph off?

I am not a mechanic I am a computer nerd so if I explained this stupid I am sorry. My calculations may be off too!

I am going to be putting a low rpm quiet engine on the bike

G

gone_fishin

Guest
all i can envision is an intermediary reduction shaft...run the engine to a (guessing) 30 tooth sandwiched to a 10 tooth going back to the rear gears.

S

SlicerDicer

Guest
Augi how much torque would that create by reducing it like that? I think I could pull that off does anybody know how to calculate that?

3600rpm -> 12 tooth drive with the ratio 30 to 10 then 36 tooth in back? As well as maybe the speeds at 2300rpm?

I am going to be using nearly the identical engine to custom_tecumseh Just a newer model.

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gone_fishin

Guest
i would imagine the drivetrain would be nothing BUT torque that would eventually convert to speed as you climb up the gears. even in high gear, i'll bet it's a responsive suckah

(sorry can't help with the calculations)

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SlicerDicer

Guest
Augi thats my ultimate plan man!

I want TORQUE! for pulling power

Its going to be a 135cc tecumseh with 3.5hp I am not too worried about the fuzz around here busting me they all seem to think its the coolest thing they ever seen. Waving and smiling

The top end speed is not really my ultimate goal. I want to make sure I can at least do 25-30 however. Once I can be sure that it will hit that easy then I can mount a windshield I will tear off the pedals put on footpegs and leter rip

I found a steel mounting bracket for the tecumseh engine that is for go kart but I can have that welded onto the bike frame so it should add more structural support to the frame.

But I really want to be able to reduce it down so I can hit no more than 35-40mph thats my concern... Thou shalt not tempt thine speed!

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gone_fishin

Guest
you know what's going on here, don't ya? we're talking each other into some evil builds

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SlicerDicer

Guest
its your fault augi... you posted the Wisconsin now I am being obsessive

And the engine is only 100\$ so you cannot really argue with that price.

C

custom_tecumseh

Guest
SlicerDicer said:
its your fault augi... you posted the Wisconsin now I am being obsessive

And the engine is only 100\$ so you cannot really argue with that price.

Yeah, thats why I'm trying to go custom like you Slicer. I got my engine for \$75 with a centrifugal clutch included.

Good to see someone else going with a big block engine!

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SlicerDicer

Guest
not only that tecumseh but the engines I have a feeling are much higher quality than "super happy time"

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gone_fishin

Guest
got that right! i'm totally pumped even considering the possibility of building the beast

so what's the topic? oh yeah, gear ratios

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