Retrobike Electric Bike Conversion

[Jamiedyer]

A good place to start for modern up to date reliable motors is on the cargo bike sites. I ride a Big Dummy and there is a million and one threads regarding using electric assist or turbo as they put it. Used on a lot of cargo machines in the States with most longtail and cargo manufacturers selling at least one model built around a electric specific frame such as the Yuba Spicy Curry. Very popular and very easy to fit by the sounds of it, a lot of people retro fit them to their Big Dummies, Usually they are the mid frame motors running of the Bottom Bracket with a battery on the downtube.
I see them quite a bit and often think of one when we are out and about in the middle of nowhere with a child weighing 20 kilo on the back with a load of gear in the bags and his little bike getting towed along, but otherwise I don't really ever think of getting one .
Just thought it might give you guys who are interested another place to look as it seems to be the big thing in some cargo bike circles.

This company seems to be at the higher end but is getting a bit of a following.
https://www.eradkits.com/shop/e-rad-100 ... r-assembly

The usual suspects are always worth a look, Bosch, Panasonic and Shimano have either just released an updated one or a new one from memory.

Jamie

 

[tufty]

On the stealth install, it's a Gruber / Vivax Assist:
https://www.electricbike.com/gruber-assist/

Actually I'm quite impressed at 200W!!!

It is NOT cheap though!!!

Yeah, that's basically what I'm after doing. Sourcing bits from aliexpress, obviously.

I've given it quite some thought.

Motor-wise, a brushless DC motor to fit down a seat tube is going to run ~ 80€ for something capable of pushing around 4-500W (but those are chinese watts, so probably more like 300 max). rated speed is generally around 6000rpm, with a 3:1 bevel gear reduction (about 10€) at the BB that's 2000rpm, so we need a reduction of about 30:1 to get that down to a reasonable cadence (or maybe 100:1 to get maximum power at lower cadence, when you're struggling, and tail off at the upper end). For that you want a planetary reducer on the end of the motor, another 50€ or so to get one with proper metal gears, although I may be able to bodge something with a couple of cordless driver gearboxes and the lathe.

The actual BB drive part means butchering a square taper cartridge bottom bracket, increasing axle diameter with some weld and then turning it back down (in order to be able to slip the freewheel and gears over the cup), gutting a freewheel and modding to fit that, and working a bevel gear over the top of that. Easy enough with the tools I have at hand. Downside is that it probably precludes using a BB with integrated torque sensor, not quite sure how they work and certainly not keen on attacking one with a grinder. They're expensive, too.

Then there's the electronics and batteries, pretty much of the shelf items.