Brief summary of idea: convert bottom bracket to live axle (lose the pedals, yes that will make it a motorcycle, but so will having multiple speeds anyway). I am using an agk transmission currently, so I would run a chain from the jackshaft output to a shaft going through the bottom bracket. I would run the live axle to a 3 speed internally geared hub.
Putting aside for the moment the question of how I will secure the live axle, here is how I will run my gearing. The gearing on the jackshaft is 11t clutch to 28t input sprocket. That will remain the same. I will run a 35 chain from a 10t output sprocket to a 22t sprocket on the engine side of the live axle. I will run a 9t on the "pedal" side of the live axle, and a 22t external sprocket on the hub. This will give me an overall ratio of 13.69:1
My main question. Am I understanding the ratios of the internally geared hub correctly? It says 1st gear is 0.75 of overall ratio. That would mean I multiply 13.69 by 0.75, and I come up with 10.26:1. Second gear is direct drive, so that would keep me at 13.69:1. 3rd gear is 133 per cent of overall, or 13.69 x 1.33, which gives me 18.2:1. Are these calculations correct, or am I missing something? If everything is correct, then I have figured out what gearing I want to run. This will give me a top speed of 36mph in 1st gear, 27mph in second gear, and 20mph in 3rd gear. This is with 24" wheels. Basically all I need to know right now is if I'm understanding the overdrive and underdrive gear ratios correctly. I will post more questions as I think of them.
Putting aside for the moment the question of how I will secure the live axle, here is how I will run my gearing. The gearing on the jackshaft is 11t clutch to 28t input sprocket. That will remain the same. I will run a 35 chain from a 10t output sprocket to a 22t sprocket on the engine side of the live axle. I will run a 9t on the "pedal" side of the live axle, and a 22t external sprocket on the hub. This will give me an overall ratio of 13.69:1
My main question. Am I understanding the ratios of the internally geared hub correctly? It says 1st gear is 0.75 of overall ratio. That would mean I multiply 13.69 by 0.75, and I come up with 10.26:1. Second gear is direct drive, so that would keep me at 13.69:1. 3rd gear is 133 per cent of overall, or 13.69 x 1.33, which gives me 18.2:1. Are these calculations correct, or am I missing something? If everything is correct, then I have figured out what gearing I want to run. This will give me a top speed of 36mph in 1st gear, 27mph in second gear, and 20mph in 3rd gear. This is with 24" wheels. Basically all I need to know right now is if I'm understanding the overdrive and underdrive gear ratios correctly. I will post more questions as I think of them.
