Has anyone created a Mid-drive electric bike?

Has anyone created a mid-drive electric bike?  I'm using parts from:  http://www.sickbikeparts.com/catalog/product_info.php?cPath=21&products_id=29&osCsid=uc9u80gtpmv25k2hgqcqjspgi1 but I'm looking for advice on the subject in general.  I'm adding a 600w geared electric motor to either a cruiser or a 700cc hybrid.

rickharris4 years ago
I see no reason to have any problems where you put the motor - try to keep the centre of gravity low though.

The battery pack will weigh more than the motor.

Electric motors tend to be like sound systems you have to take care what they claim - Many do not quote the continuous rating for the motor to make it look better - A 600 watt peak power motor will only be perhaps 200 - 250 watts continuous and even then will need cooling.

You might expect 20MPH out of it - Wind drag is a big factor when you approach 20 MPH - Perhaps look at velomobiles as an alternative

jongscx (author)  rickharris4 years ago
It's a 600W continuous 1k peak brushed DC motor geared run at 550 rpm unloaded at 36V.

Mid-drive refers to where the motor power is transferred. I will effectively add a freewheel to the crank and drive it with the motor, allowing me to further control the motor's gearing. If I let it, I think my 21 speed could reach 40mph.

I'm using 6x 6v/14aH SLAs because of cost. When I've perfected the system, I'm switching to modified power drill batteries, either NiCd or LiPo.

I'm not doing this to save gas or be environmentally friendly but as a statement, so the "cool/bamf" criteria rules out a recumbent velo.
Your 21 speed chain and derailleur will never carry that much power.
LeeG Re-design4 years ago
So use small standard sized wheel motorcycle parts. You will probably have to make some changes and decisions to fit those and keep it all safe. There will be a hit in weight. Maybe look for an old Honda Cub scooter or similar motorbike to take parts from. They were 90-125cc variants and so should handle the power. You may have to change the spokes so it might be worth going armed with some measurements before buying anything.