DIY Mid Drive E-Bike Part 2: Making a Freewheeling Crank

Hello everyone, in this video I will be showing you the process of modifying a bicycle crank so that it can spin under motor power while keeping the pedals stationary, but still allow normal pedaling. Many metal cut off wheels were harmed in the making of this video. As always, feel free to comment any suggestions, insights, or questions. Thanks for watching!

[@follfatih]

Great vid chap keep it up!

[@TheAfricanGarage]

You should definitely cover up your threads while welding, else you're gonna have a hard time later. That being said, great video man.
I look forward to seeing your progress. #subscribed

[@engineeringdiy6311]

Thanks for the comment! Absolutely, that was a oversight. Will do next time👍

[@thecontinuingadventureso-qs5zm]

Hello Young Man. Just a hint for You, a battery 4" angle grinder is an invaluable tool. Best Wishes : - )

[@engineeringdiy6311]

@@thecontinuingadventureso-qs5zm haha yes it’s on the budget👍

[@BekzodBotirov-qd9dv]

Сделал я так-же. Но, он быстро рассыпался.

[@Full_Throttle_no_Brakes]

This freewheel crank you are doing. The ideal is you use the biggest chainring possible with smallest motor sprocket possible and the smallest chainring possible from the crank to the cassete then use the bicycle gears for the acceleration or top speed.
To calculate gear ratio = (driven sprocket ÷ drive sprocket) x (driven sprocket ÷ drive sprocket) to have your gear ratio and compare with the ratio recommended for your motor.
This design benefits greatly from high rpm. So higher battery voltage you can use, the better.

[@engineeringdiy6311]

Absolutely! By sequencing the power from small/big--small/big sprockets, the torque to the wheels is maximized, and the gearing allows me to stay in the motor's "powerband". I did the calculations you mentioned in part 1 of this series. And yes, higher voltage is definitely my friend here because that also reduces the amperage requirement, which translates into less heat and strain on the battery.

[@Full_Throttle_no_Brakes]

Which motor are you going to use?@@engineeringdiy6311

[@markifi]

you can't depend on those terrible ratchets they're made to be a consumable item unfortunately

[@TheAfricanGarage]

Well, I think it'll work fine since the power from the motor wont need the ratchet freewheel to be engaged, but rather disengaged. Cheap freewheels are usually only problematic in the case of engagement.

[@engineeringdiy6311]

@@TheAfricanGarage Yes, this bike will majority of the time be used under full motor power, however I will definitely be on the look out for any mechanical problems with the freewheel during testing.