Omnium cargo e-bike conversion what to choose?

Jali

1 µW
Joined
Feb 15, 2018
Messages
2
Hi,

New member from Copenhagen.

I have a Omnium cargo bike that i would like to electrify.

A have a really hard time deciding which path to choose in regards to setup.

I ride 9 km to and from work every day. Copenhagen is mostly flat and the bike paths are packed.
The bike would usually not cary a heavy load.

What I wish to accomplish is a realiable low maintanence setup with a range of 40-60 km able to do up to 35-40 km/h (I do not mind pedaling all the time) and help me carry the occassional load.
I would also like it to be as simple as possible. Still use my hydrailic brakes and only have some kind of battery indicator on the bars, no fancy screen please :)
(I'm 80 kgs and the bike around 17 kgs)

I have been tempted by the bafang mid drives but they seem to be to high maintanence, irritating at gear shifts and wear the drivetrain to quickly to my taste. Also the angle of the downtube is not optimal.

The bike has a 20" front wheel so i'm thinking that some kind of hub motor could be a good choise - but what to choose?

I have been reading for two days straight and i'm only more confused.
Geared or DD? Cheap Chineese ok or should I look elsewhere?

This is the Omnium cargo: https://goo.gl/images/v1Gv2p

All suggestions would be much appreciated
 
Jali said:
What I wish to accomplish is a realiable low maintanence setup
DD motors are generally the lowest maintenance, as long as you have them built into a good reliable wheel.

If you're generally going at the higher speeds your system is setup for (motor wind vs voltage vs wheel size) then it'll be relatively efficient and stay cool.

If you're riding in stop/start traffic and not cruising at a constant speed it won't be as efficient, and will warm up more, but if you're not using high power it shouldn't be an issue.

A geared hubmotor is next lowest maintenance, and will probably be a little more efficient in the start/stop traffic situation.

A middrive will have chain and chainring wear to deal with, but if you're shifting gears like you would to pedal, then it is going to be efficient at whatever speed you are at any time.


with a range of 40-60 km
You'll want to determine approximate power usage (wh/mile) to figure out how big a battery you'll need. Typical power usage for a 48v system is probably around or less than half an amphour per mile (Ah/mile), or <20Wh/mile, if you ahve start/stop traffic and are carrying cargo, dependign on terrain and wind.

Speed uses power, but so does stop/start traffic (more with a load than without, and the heavier it is, and hte more often you have to start from a stop, the worse the power usage is.)

A middrive thru the pedal chain, shifted properly will use less power on that kidn of riding than either DD or geared hub, but they'll all use about the same if speeds are constant most of the time.


I would also like it to be as simple as possible.
DD hub is simplest, as long as wheel is well built.

Still use my hydrailic brakes
rim? disc?

any mdidrive would leave them just as they are either way, and so should any hubmotor wheel, as long as you make sure the rim is the right kind for rim brakes, and as long as the hubmotor has disc mounts and clears your calipers.

and only have some kind of battery indicator on the bars,
Lots of throttles that have a simple voltage-type indicator, iether analog (bar graph or just "full / ok / empty" 3 LEDs) or digital (voltmeter display), so taht's easy.

But an indicator that actually shows you how much power you've used is better, because there's not all that much difference in voltage as the pack goes down. Takes a while to get used to what empty vs almost empty vs more full is like if all you have is voltage. :)

With a wattmeter (analog or digital) that actually shows you how many watthour you've used, you can always compare that with how many wh you know your pack has in it.



The bike has a 20" front wheel so i'm thinking that some kind of hub motor could be a good choise - but what to choose?
Disadvantages:
--The small wheels with big hubs are not as strong as big wheels with big hubs, all else the same.
--front hubs will have less traction (except when you're loaded down up there) than rear.
--lower speed for smaller wheel, for the same voltage and motor winding

Advantages:
--higher torque for smaller wheel, meaning better "gear ratio" from motor to ground, so startups take less power for less time.

Geared or DD? Cheap Chineese ok or should I look elsewhere?

Cheap stuff does fine as long as you don't need warranty service (you probably wont' get any), but some of it is better than others, like the KT Kunteng types (poke aorund the forum for those to see what I mean). However, those "better" ones use a display to program / setup the system, and to choose your assist levels, etc. You could put the display in the batteyr case/bag so it isn't in your way, and just put buttons to it (for power-on and off, and changing any assist levels/etc you might want to do).

Better stuff mostly has a warranty to stand by it if it breaks, but costs more; sometimes it has more features or is just plain a better product overall.


Batteries are the one thing I would go for a good *local* place with a warranty, because you can't ship a defective battery, so even if it has a warranty you can't get it back to the seller if they're not local to you so you can take it in. Or learn to service your own, which can be on the complicated side, if you run into problems with it, if it's not well-made.
 
Curious what Ebike motors are permitted there, are these the current regulations on ebikes in Denmark over a certain output level?

be at least 16 years of age;
have a moped license;
have liability insurance for high speed e-bike;
ride on the mandatory cycling path; and
have a moped license plate (blue plate)
 
Hi Amberwolf,

Thank you for your reply. That's greatly appreciated :)

Raisedeyebrows,
Max 25 km/h only with pedal-assist, no mores than 250W, no throttle allowed.
No plates, no special insurance, no license.
Cycling paths should be used where available (e-bike or not) otherwise on the road.

I'm really not that worried about that, I won't be building a speed monster and will be riding responsibly.
I have been biking in Copenhagen for the last 8-10 years on a fixed gear bike with a front brake only (also illegal) with no problems.

Morning traffic typically looks like this: https://vimeo.com/141516172
 
This one calls for a mid drive, in my opinion. 350w bafang would be good. If any wattage labels appear, just remove them.

The other solution would be a rear direct drive motor, in the slowest wind model you can find. However, to realistically carry large weights, a DD would need more power, like 1000w. In slow enough wind, it would not be obviously high powered. But these motors can be hard to get in that slow of a wind.

The bafang is easy to get, and will carry tons of weight if you just ride in low enough gear. Most of the more recent models of electric cargo bikes are sporting mid drives now.
 
Back
Top