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Gearing and Motor Selection with 26" tires ground up from scratch

Thank you so much for operating your website and for facilitating the wealth of information you have here. I’ve lost quite a bit of time here and plan to lose quite a bit more!

 

So here is what I’m trying to figure out.   I am taking a standard bike with 26” wheels and converting into a scooter (see picture attached of something that I'm modeling after but with more room for the power components and with brakes so the deck will be longer and probably thicker so as to store components inside/underneath).  I want to add a motor, batteries, controller, etc. 

 

I’m not worried about how to assemble it or fabricate it; I’ve got that covered.  I can fabricate the frame, weld, fabricate mounting hardware, etc., and I already have my donor bike.  My real concerns are as follows:

 

What size motor should I use? Naturally more power is better but how much is too much or not enough? I expect the finished product to weigh 100+ pounds and I am another 190 pounds. 

 

What about batteries? I want a balance between power and time of use. I want to be able to go 20 miles (on flat ground/road) but I want the ability to accelerate reasonably and hold a decent top speed. Lipo over lead acid presumably?

 

Most befuddling to me is the gear ratio.  If the motor has 11 teeth what should the rear wheel sprocket be?  Bigger rear wheel sprocket is more torque; smaller is higher speed?  What is the happy medium where I twist the throttle and it doesn’t stand still but also has a respectable top speed of at least 25-30+ mph (35+ is better)? What is a reasonable expectation? From what I’ve read I would need a geared motor because of the 26” tire size but when I put a 500 rpm motor and various sprocket sizes into the calculator, I get like 5-15 mph which isn’t what I’m after.  If I drop to a 1:1 gear ratio I get speed but I’m sure no acceleration?  If I used your 48V Brushless motor with 4800 RPM and gear it to a 90-tooth sprocket, I get a ton of speed (like 45mph) and I am guessing plenty of torque/acceleration, too? But I’m guessing I’ll overheat the motor and burn it out? Naturally I want it fast and quick and long lasting, etc. basically the holy grail but I know that's not likely to happen.  Confused. 

 

I want to figure most of this out before I get too far down the fabrication path so I know what I’ll be using and know where on/in the frame it will need to go and how much room I need to make for the motor, batteries, and controller. Any wisdom you can share is greatly appreciated.

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