Retrobike Electric Bike Conversion

[Trebz]

Hi All

A post for open discussion about Retro Electric bike conversions.

I'm planning one based on an old steel frame. Maybe a Kona Explosif. I'm bored and need a project.

Here's a few links to whet your whistle:

https://www.thesmallgreenroom.com/electric-bike-kits

http://www.electricbikeconversions.co.u ... sion-kits/

https://pedalease.co.uk/index.php?rt=pr ... path=67_73

 

[mattuuk81]

Sorry,

Not a big fan of the hub motor type.
I'd be going BB mounted motor, personally.

Something like a Bafang. They have the controller integrated and you can actually use the torque they produce on your gears.

They go from a street legal (UK) 250W to a mind-blowing 1000W out of the box option (which many have "tweaked").

Overall, I like them more conceptually as better weight placement and better use ability. Also - 48 or 52V dolphin battery on bottle mount makes for a neat install...

Cheers

Mathew

 

[M-Power]

Re:

Interesting thread. Logging in. Need summink sensible for the wife but not 1000W :shock: or il get smooooooked.

 

[tufty]

My message seems to have disappeared, maybe I didn't hit send.

I'm interested in this, although I don't want, or need, 250W or 500W, let alone 1000W of power. I'm looking into a totally stealth "down the seat tube" motor with modified bottom bracket, 100-200W max. Motors for a 27.2 seat tube are hard to come by, need to find a frame with more space, I think. Not sure how to go about the assist "programming", my gut feel implies use of a strain gauge, the harder you're pushing on the pedals the more it assists. For that I reckon I can get away with a motor controller chip and a few passives.

If you can restrict yourself to road tyres, something like the gboost or other friction drive system might be a decent approach. Lightweight with no permanent modification.

 

[mattuuk81]

I'm pretty sure a system like that made some waves in cyclocross not that long ago.

Having said that, I'm sure there is a German system that works on decal assist as it interfaces on the crank anyway.

I'll look it up.

I'd question the value though - 100W, not sure it would be worthwhile. Brushless 250W hub motors are now basically the size of a dyno hub.
Battery can be out in a saddle pack.

Like the clean lines idea though!

 

[FluffyChicken]

Re:

Trebz, stop faffing and ride a bloody bike.

(Sez me hahaha, need to do that myself).

 

[tufty]

I'd question the value though - 100W, not sure it would be worthwhile.

I think it depends what you're after. A good amateur rider can put out 200-250w continuous for an hour or so, if I'm honest I probably don't hit that, 20 minutes is probably my max duration pushing hard. Blame the years of smoking, (and probably just "the years") amongst other things. Drop the level a bit, though, and I can grind on for hours; an assist of only 50w or so should allow that.

Just bought a (second-hand, end of rental season) cube electric 29er for my wife. 250W Bosch mid drive. The thing's a goddamned rocket ship, at least up to 30km/h (and allegedly can be derestricted totally, providing assist to >75km/h levels, the thought terrifies me). On my last day off, I tried riding the thing up to work. My commute is 16 kilometers, 900m positive climb; even in "economical" mode I didn't break a sweat or drop below 25km/h. Unfortunately (for me) and fortunately (for mrs tufty), it's a medium, and not terribly comfortable if you need an L / XL.

I'm not afraid of pedalling, even pedalling hard - on the other hand, I'm not Lance Armstrong ; an extra 100-200W would make the ride to work easy as opposed to a grind. The positive tradeoff of lower power being less weight, and the negative side being "still having to do half the work". I can live with that, I think.

 

[FluffyChicken]

Re:

He's a retro "e-bikes" conversion

 

[FluffyChicken]

Re:

Maybe grab some ideas for DIY from the assisted balance bike (so not an e-motorbike) https://www.powver.org/draisine-200-0/

 

[mattuuk81]

Haha. Somebody actually refreshed the "retro" conversion recently. I'm not going to look it up though.

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!!!

I've ridden a few variant of ebike, and my favourite it still the mid-motor type.
The bosh ones are good, but need special frames etc.
Yes - even 250w feels like a rocket ship - biggest I've tried is a 750w bafang equipped hardtail. That was a bit scary to be honest, i had to set the assist down to get used to it.

The other consideration is battery voltage and capacity. I've seen some people ride with a bunch of cells in a backpack - not sure I like the idea of that myself, but each to their own!

Keep us updated if you go ahead with any of this - would be cool to see.

Edit: on the pedal assist/ load assist: most systems seem to use some simple hall sensors. Normally one on the wheel for speed (you know, max 25kmh - quick way on hub motors to go faster... ), one on the cranks and normally one on the brakes to cut the motor...