Gear ratio - Grubee 2 gearbox

hlombard

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One Grubee website lists the ratio of the Grubee 2 Skyhawk gearbox as 4.2:1. Someone heer calculated it at 1.83:1 ???

I counted the teeth on my gearbox and calculate the ratio as 3.7:1

Please confirm my calculation:

Gear 1: 35 / 54 = ratio of 1.54

Gear 2: 20 / 48 = ratio of 2.40

Overall ratio = 1.54 x 2.40 = 3.70 ?

Then you have the reduction from the 11 tooth sprocket to 56 tooth sprocket on the wheel: 11 / 56 = 5.09

Thats an overall ratio for the setup of 18.85:1

Can you math-heads please check?

Thanks
 
Thought this spreadsheet might help. Please check my math, I'm not an engineer.
 

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