Folding mid drive conversion options?

Well, that 16+ pound motor would go in a Brompton the same way that a Cummins diesel would go in a Miata. Which is to say, you can do that, but it would negate the best things about both parts.

i think the problem is that the steel brompton which weighs 30% more than Ti but costs 5x less and is more proven for durability, weighs a good 25 lb already, so 1000w might help. But 500w geared maybe would help on hills
 
Hi, all i'm currently modelling a CYC Stealth Gen 3 mid drive to see if it fits on a Brompton. Witch could give impressing results if it works, i'm using a 2 speed no fender Brompton with eventually custom carbon wheel to make it pretty light !
Currently its running a DD from Grin Tech and as power goes, its awesome, plenty of torque and a top speed in pedal assist of 48km/h, but its heavy, so i'm hopping the CYC can fit without to much impacting the fold. I estimate the final E-Brompton weight to about 33 pounds + with a mid drive the bike as a better balance when folded VS hub driven Brompton that currently weight about 41 pounds without the battery (as a carry the battery in a separate bag) and sometime fall to the motor side because of uneven weight when folded. I've contacted Grin Tech to see if any Pendix Style mmid drive with their Grin All Axle would come out but they dont have any plan for someting like that :(
 
I have two electric Bromptons. One is the factory Electric Brompton and the other is the geared front hub motor kit from Grin. The factory bike looks more polished, but the kit has a throttle as well as a torque sensor and a bit more power (the factory bike has to comply with UK laws). The LIGO batteries from Grin can supposedly be brought onto a plane, but I haven't tested that yet. I can throw both bikes in the back of my Subaru wagon with lots of room to spare and take them on vacation.

There is no way I would want to go much faster than 25 mph on a Brompton with its twitchy steering. The motors I have are fine for short hills and getting around town. For me, a mid-drive wouldn't really help with how I use the bikes. I suppose if you had some really long steep hills it might help, but you don't really have that many gears on a Brompton and three of the gears on a six speed are part of an internally geared hub in the rear that is not really designed for a powerful motor. If you need a wide range of gears, you are better off with a different folding bike like a Bike Friday.
 
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