My project for the Christmas holls.

[John Rumm]

Have wheels, will travel:

[Tim+]

Chapeau. I have thought about doing a conversion but we met a couple riding a pair of very nice Ribble e-bikes and fell for the attraction of those!

Curious pulley mechanism for the front mech. Where a pull in that direction is required it?s more normal to run the front changer cable under the bottom bracket and then back up.

Tim

[John Rumm]

Yup they look rather neat and self contained. I presume the battery is in the down tube?

We got SWMBO and Pendleton Somerby since she did not really have one worth converting, and they do a dinky enough version she can get on!

Yup it's a slightly odd arrangement - most of the cable run is inner only, with a couple of short sections of outer to get from the shifter to the start of the cross bar - all runs are unsleeved along that, and then a very short section to get form there to the top of the rear forks. Seemed easier to go with that since there is no place to anchor the outer at the bottom and the pulley was already there.

[RJH]

Excellent!

I've been looking to do something similar on an old/spare bike I have. But I was looking at the drive train type - simply becasue I tried one and it was impressive, and it sort of seems to be preferable. I was looking at something like this:

Bafang BBS02B 48V 750W Mid Drive Motor

Any particular reason for your choice of hub motor?

[Theo]

Bafangs have a good reputation - the go-to choice for many e-bike builders. However in Europe e-bikes are limited to 250W so that motor wouldn't be suitable (I think that's continuous power; the starting current is much more) unless it was an off-roader.

I'm not familiar with Shengyi but it may be they're a cheaper/less well known brand. Woosh are a good source of value-for-money kits. Hub motors are easier to install on many bike geometries.

The problem with sourcing your own parts is the batteries - if you import the packs from China they're above the 100Wh limit of some kinds of air freight, which makes shipping quite expensive. It can make sense to DIY your own pack, if you have a good source of 18650 cells and know what you're doing (BMS, nickel strip, spot welder). People like Woosh import by sea freight which takes some of the edge off shipping costs.

Theo

[John Rumm]

Yup nice, but that would legally give you a motorbike in the UK if used on the road. It would be very good for off road use though. Especially as the power is delivered through the chain set, so you can take advantage of the existing gearing for extra hill climbing performance.

(IIUC they even do a 1kW version of that)

Of the various similar motors, woosh suggested that one with the 48V pack would be would be a good choice to get enough torque for heavier riders...

On a very brief comparison so far, it certainly has a bit more grunt up hills when compared to the (non geared) 250W Bafang hub motor on SWMBO's.

[Paul]

Look at the numbers, for how often they're changing out the chain.

A hub motor, not involving the chain, means the chain lasts as well as it does now.

When I was a kid, there was no such thing as chain wear. You ruined the bicycle some other way, before the teeth on the gears were far gone enough to care or the chain stretch mattered. But the dimensions of stuff change when you're doing 7, 8, or 9 speed hubs. And the way the shifting process works, the precision machining, all adds up to making things wear faster.

You can find discussion threads, comparing the virtues of hub drive versus the other kind.

Paul

[RJH]

I'd intend to use it mainly off road. I am aware of the limits, but sort of figured that if I wasn't tearing about the police would have better things to do? Plenty of private electric scooters around for example.

Yes, the battery seems to be the main cost - and uncertainty - variable. I'd like to make my own, but I don't seem to be good enough at the welding side of things.

[Thomas Prufer]

How did the "ordered this, ordered that work" out for you?

A friend had a worn-out drive earlier this year: chain, 10 speed cassette, and the two larger of three chain rings were iffy, bottom bracket too much play. So much wear that the chain would slip under load in most gears. So: buy new, pop in parts, adjust, done. Easy and no chance of surprises if you get the 1:1 identical parts.

I couldn't get the parts online, not even "reasonably close" parts. "Delivery in

5 weeks", over about seven weeks. Gave up on ordering myself, rather than getting each part from a separate supplier, getting killed on the postage, and the finding a HG80 and CN60 don't match well, or something.

Ended up going to a local store, who dug through their remaining inventory. Ended up paying about three times what "standard" parts would have cost, because all they had left was (presumably better) parts from the more expensive "racing" lines. "10-speed system" didn't help as it's a bit uncommon, but the store said all parts were universally in short supply, both at their supplier and in the internet stores.

People buying more new, fixing old, riding more to avoid public transportation, and little new parts coming out of the Far East all came together.

Thomas Prufer

[RJH]

Yes, as reply elsewhere, I'm thinking of taking the chance on something that won't be used for on-road in the main.

Seems a good choice on that basis - just wondering why hub. 250W crank versions available:

From my very limited research it seems as a general characteristic they're better. But plenty of other variables.

The Bosch drive train type I had a go on was pretty much flawless - very subtle kicking in/out, and it simply added to whatever I put in in a fairly linear way. It needs constant pedalling of some sort to work, and fell to a crawl on a very steep hill - but still kept going.

The Halfords own rear hub version (on a Halfords free 6 hour trial bike) had a very unnatural control system. It would kick in/out after a period of 30 crank rotations or some such. And the motor engagement was less smooth. But did the job, and seemed no less powerful than the Bosch when it was on.

A big issue for me was the battery. It was only about 2/3 charged according to the crude meter when I picked it up, but was pretty much flat after about 10 miles. The similarly sized Bosch had plenty left (>3/4 from full) over the same journey. Hardly a conclusive test but enough for me to be cautious about battery provanance.

[RJH]

Yes, good point. I'd expect the marketing boys to get on that, with chain (etc.) upgrades. Hopefully the engineering departments won't be too far behind ;-)

My main concern is the whole bottom bracket assembly. The bikes I've seen in places like Halfords have a lot of additional support, and it does seem like a lot of weight to bolt on to what is a highly stressed part of the bike. Whether that's a real world problem or not for me and my donor bike . . . not sure.

Yes, from my limited reading people seem to prefer the crank mounted motors, and insofar as cost is a measure of anything, all of the expensive bikes use them. But a lot of signal/noise in the online discussions.

[Tim+]

The downside is that your average bike chain & gear system might well struggle to cope with the power. Too much welly in too high a gear would probably knacker your chain and rear sprockets in short order. My daughters e-bike has a habit of throwing it?s chain when she forgets to change down for hills.

A hub motor whilst being more limited in torque isn?t going to stress the transmission.

Tim

[The Natural Philosopher]

In fact its torque could be increased by making it bigger. Another option is rim mounted magnets and three or more rim mounted coils.

Very high torque

[John Rumm]

Yup, I expect the chance of getting caught are vanishingly small unless actually involved in an accident.

Might be different in the big cities, since pinching eBikes, de-restricting them, and using them for street robberies, seems to be the in thing for the gangs that were using stolen mopeds. Apparently the ebike being quieter in approach, and less conspicuous when ridden by "youths".

(If one were a little devious of mind, I suspect a crafty Arduinio "filtering" the feedback from the rotation sensor could allow more performance with the max speed and wheel size parameters left untouched in the config menu of the UI)

For that one very specific task (spot welding tabs on batts) there is a relatively cheap machine you can get from the likes of ali express)

[John Rumm]

Depends on your definition of better. For off road use they compromise the ground clearance in some cases (not much since they typically don't hand down more than the chain wheel). They put lots of extra load on the chain - and so you get high gear train wear rates and broken chains if you are not careful. They are also slightly more "complicated" and so viewed by some as less reliable.

That seems like a pretty poor rotation detection. It might be it only had a spoke sensor and needed several wheel rotations to detect movement. The (better) magnetic discs have a dozen segments, and so will detect movement in a partial turn of the crank rather than the wheel)

Yup making sure they are real Samsung or similar branded cells will help. From my very limited experience with mine (9 miles - most of them in a hurry and pushing it to get out of the drizzle!), much on the max assist level and using the thumb throttle a fair bit, the battery is still showing "full".

I will probably update the wiki page as I get more real world performance data...

[John Rumm]

ok mostly - I could generally get the bits I needed on Amazon for next day, and in a few cases same day delivery.

Needless to say, that was not the plan at the outset, but it turns out the bike was somewhat more shagged than anticipated :-)

Yup, generally the chain and sprocket teeth looked ok (although I think there is one broken tooth on the rear on one cog). It tended to be the less obvious and visible stuff on mine that was showing its age.

(I was also resisting the urge to change things for the sake of it - like thinking I could stick an 8 gear cassette on the back, but then that would mean changing the 7 speed shifters which I had already bought by then)

Not my experience fortunately - but keep in mind I was not going for anything particularly exotic or high end - just entry level Shimano kit mostly.

Yup, it's going to bite. In my case I would normally prefer to support a decent local bike shop (of which a few still remain around here), but given the current situation combined with this being a "slotted in" project that was worked around other things, I was less keen this time.

[Theo]

30 crank rotations seems absurdly high, but something like that is a cheapskate way of doing things. The motor can't handle the starting torque so they expect the rider to provide that bit, and then kick in once the bike has a small bit of speed going. It's usually a fraction of a crank rotation though.

The better bikes have torque sensors, so the assist is with aligned your pedal pressure, rather than just noticing the pedals are going round.

The 'crude meter' is probably just a voltmeter, and they're pretty useless for measuring lithium cells (I hope it used lithium, not lead acid!). It's common for the meter to show 'full' or '2/3' a long way down the discharge curve, and then suddenly crash to almost nothing - or pessimistically show empty a long way before it's actually empty. The meter will also show empty any time you accelerate, due to the voltage drop, but return to normal when you remove the load.

A proper BMS will be coulomb counting, which is probably what the Bosch is doing. That gives you a figure based on the Wh remaining, and isn't bothered by voltage drops.

Theo

[Theo]

I think a lot of the reason expensive bikes use them is because it's what's provided by the Bosch/Panasonic/etc systems. Bosch have captured a lot of the European market, and so if you go for a £3K e-bike it'll probably have a frame built around the Bosch drive system. If you go for a £600 e-bike it'll probably have a Chinese drive system, which go for hub motors because they're simpler and cheaper.

Theo

[Animal]

and the added benefit of picking up free hardware as you ride :)