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[sdg_77]

Thanks Anto - we both spend most of our time on the middle chainrings,  and only use the big-dog for wooshing down hills.

No idea what to think about the motor power.  I am an electrical engineer so I'm assuming a bigger motor will have better current handling capacity in the controller and so be more reliable, at a cost of some weight and of course cash.
Against that, a smaller motor ought not to drain the battery so quickly, or get up hills quite so well.

regards
sdg.

[jags]

sdg if i had the money (i don't) i'd have that bafang motor on my Audax tomorrow
my 2 bikes have been gathering dust this past year due to back pain i find it impossible to get up hills and theres plenty of them where i live.

i'm not to worried about speed but saying that i'd want that motor to hit 25mph on the flat .
average speed over say 40 to 50 miles 13mph.
and i wouldn't want to change my drop bars,another concern would be all that wiring,i'm a geek for keeping my bikes in pristine condition so wouldn't want wires hanging about spoiling the look of my bike 
saying that tho,i'd give one of the grand kids away for that bafang conversion.

anto.

[Andre Jute]

Steve, have you considered fitting a Rohloff hub gearbox to your wife's bike? It has 14 usable gears, spaced about 13% apart, 526% range, and can be geared as low as she can keep her balance; we have some stump-puller transmissions on the forum here. Personally, for a tourer (and for a utility bike and a commuter for that matter) I consider a Rohloff a better first option, with fewer limiting factors, than going straight to an electrified bike.

If a Rohloff is out of the reckoning, I'll answer your questions:

First of all, forget anything but the 250W* motor. With a bigger motor comes a bigger battery consumption (or less range), more weight that has to be dragged along. Secondly, borrow or rent an electric bike to ascertain if your wife will be happy pedalling along the extra weight when the motor is not in use. If you fit a 750W motor, your wife will have to drag a battery three times as large, and sooner or later the police will take an interest. And forget about 25mph too; sure, I've ridden up there on occasion, but I have an humongous battery, and I'm never further than 20-25kph from home unless I know that I'll sleep next to a plug that night. The other number Anto threw out, averaging 13, is good, but it is 13-15kph not mph, which is what my pedal pals and I average over the course of a year (we live in countryside that is all hills, all the time -- the few pieces of flat roads carry lethal amounts of traffic at lethal speed, and the hard shoulder, or any shoulder, keeps disappearing). You have to approach electrifying a bike realistically, even humbly; it just isn't a roadracer's option, which is what Anto appears to think!

The Bafang BB motor generally comes with a 46T chainring but that isn't set in stone; maybe your supplier will swap it out for you. In any case, a different tooth-count chainring is under a tenner from China, and, since it is steel, you'll never wear it out. I have a 44T chainring on my bike, which appears to me to be the smallest the Bafang BB motor will take that will also suit a Chainglider, an amenity I insist on on all my bikes. The chainring is dished to claw back tread width, so if you want another type of chainring, it could be an expensive custom job; some ali chainrings are available but while the Italian ones are beautiful, they're also about a fifth of the price of the complete kit. I'm well satisfied with the steel chainring (it's 20 years since I last bothered with a fast-wearing ali chainring). Before I fitted the centre motor my transmission was 38x16T (I in the middle of a couple of rounds of heart surgery), and I thought that I would use the motor more because of the 44T chainring, but that hasn't happened and the longer legs have turned into a good thing for my health too.

If your wife cannot or does not want to pull a 46 or 44T chainring, there's an alternative that lets her keep her entire transmission, including the front derailleur: front hub drive. If that means she loses her hub dynamo, you can get B&M front and rear lamps that operate off the motor battery (36V nominal). See http://coolmainpress.com/BICYCLINGbuildingpedelec5.html
The front motor I had was the Bafang QSWXK and you can see here how I fitted it:
http://coolmainpress.com/BICYCLINGbuildingpedelec1.html
It comes as a full kit including an excellent battery, well-scaled to the motor, from the vendor I recommend. A complete installation of the front motor, including new lamps, came out a third cheaper than the centre motor installation, in both cases including the battery. The front motor needs a bit more care than the centre motor: I burned mine out in 3500km, but my bike carries more weight -- my painting gear is on it all the time -- than most fast tourers would contemplate, and I have a heavy throttle thumb. It was rebuildable but I bought it only as an experiment, so I didn't bother, just went straight for a centre motor better scaled to my requirements and habits, which has now exceeded the mileage of the front motor without any sign of stress. For a motor to last a very long time, you may wish to swap out the nylon gears for the available and pretty cheap steel gears.

I've no idea how the kit brake levers compare with the Thorn-supplied brake lever; I just left those brake levers in the box because I bought special hydraulic brake interrupters.

* And forget what an electrical engineer knows about the relationship of Watt to horsepower etc. The CE regulations allow the manufacturer to say how strong the motor is, and nobody checks on it. As an associated fact: These Bafang motors are so popular because of their heritage, their origins in the famous offroad BPM motor, which started at about a real 350W but was optimized for torque and so "appeared" to be a 250W motor. Torque is by far more useful than Watt as a measure of the utility of a motor for a tourer's bike. Watt is useful only for the speed freaks.

[Andre Jute]

Jags says:

another concern would be all that wiring,i'm a geek for keeping my bikes in pristine condition so wouldn't want wires hanging about spoiling the look of my bike

I just folded up the extra wiring and tie-wrapped it to the handlebars. I make a point of swooping through the forecourt of the garage where all the cafe racers sit outside in their latex with their lattes and their shiny unused bikes so that they can see all that surplus wiring. Sometimes I slow down to enjoy the grimaces settling over their faces longer.

Seriously, Anto, if that is your criterium, sorry, I mean criterion, you'd better give up the idea of building an electric bike, because the only bikes that have hidden wiring are the ones designed from the ground up as electric bikes, and you wouldn't want to be seen dead on one of those with their obviously ali, obviously thickened tubes, besides which their motors and controls will be crippled, which isn't what you want by a mile. You just can't build a electric bike on a steel road frame without several visible wires running back and forth. On my Trek Smover, the full auto Di2 bike, I got so fed up with cables I couldn't shorten (too many wires inside, too fine for my soldering skills), that one day I took a piece of spiral computer-cable tidy from my study to the bike, and just folded the surplus cable away in it; it worked because the spiral cable was the same colour as the bike. Scroll down to the cockpit view for a good look at the cable tidy:
http://coolmainpress.com/BICYCLINGsmover.html
With the centre motor you have several more cables than with the Smover or the front motor. True, they're modular (loose cables with waterproof plugs) and if you give up the unit they connect, for instance the fascia, you also lose the cable, but some things are essential for the operation of the bike, like the button cluster.

[jags]

cheers Andre your a feckin genius 

[sdg_77]

If a Rohloff is out of the reckoning, I'll answer your questions:

Many thanks Andre - a Rolhoff is out of the reckoning - Gill is looking for assistance rather than extra gears.

I'll go through your notes over the next day or so - but thank you for the reply - I have been away for a few days and hadn't seen it.
Some of the YouTube videos I have found point to chain rings and devices to keep the chain in place so I'll look at the chainglider too.

[url]https://www.youtube.com/watch?v=rcYVyuDC6e8&t=6s[url]

This video (Australian) shows a Lekkie chain ring with a different tooth profile so I might take a look at one of those if I get the opportunity.
The extra brake sensors look to be the way to keep the original brake levers too 

Gill is around 60kg so I'm expecting that might give her a little extra range from the battery.  I'll just have to check what will fit into her 48cm frame.

regards
sdg.

[jags]

i ride a 48cm Thorn audax i reckon the bafang motor will fit no problem ,the chainring that comes with that kit isn't for this kid looks like something cheap you would see on a  kids bike Sorry Andre ....

[Andre Jute]

The question in fitting a BB motor to a small bike is usually ground clearance. The Bafang BB motors can be swivelled around the BB shell until snug to the downtube to give a bit more ground clearance.

the chainring that comes with that kit isn't for this kid looks like something cheap you would see on a  kids bike Sorry Andre ....

Into, I find it good enough, and it replaced a highly polished Surly stainless ring that I was very fond of. The Bafang chainring has the right chainline for the Rohloff, works a treat, and it lasts and lasts; I also had excellent experience with an Indian steel chainring on another bike when I told the supplier just to put on the cheapest crankset he had until I decided what would suit the aesthetics of the bike; I liked it so much I rode on it c8 years until I found Stronglight crankset I liked. If you hate the Bafang OEM chainring, sand it down lightly and paint it with aerosol enamel, bake it in your wife's oven, and you have a custom job.

[sdg_77]

Well - that was interesting ....

Finally ordered the Bafang Kit from Eclipse once they had them in stock,  fitted it to the bike with a 44 toth chainwheel and had problems with the chain a new Shimano HG riding up onto the top of the teeth and then falling off.

Put the original 48 tooth on, without the chain guard and all is ok - chain guard on and still ok!

So far the bike has just been to the end of our street and back - should be able to try a longer ride soon(ish)

Thanks to everyone for their help - particularly Andre.

Might try a 36 tooth bling ring if all is ok as I think that will be closer to the original middle chainring where Gill did most of her pedalling.

sdg.

[Andre Jute]

Put the original 48 tooth on, without the chain guard and all is ok - chain guard on and still ok!

I'm not enamoured of the chainguard that come with the Bafang BBS. It might be OK if your wife cycles only in lycra, no exceptions, but the minute she starts cycling in street clothes, it becomes a danger. I invariably cycle in street clothes and chucked off the chain guard on the first day of what was going to be a week's trial -- after it twice ate the bottom of my khakis and nearly caused a gravel rash incident or worse in the space of only minutes, within pushing distance of home; it was just as well I had started uphill and was going slowly. I fitted the Chainglider on standby for the next week's test, and never looked back.

Thanks to everyone for their help - particularly Andre.

Happy to help. One hand washes the other.

Might try a 36 tooth bling ring if all is ok as I think that will be closer to the original middle chainring where Gill did most of her pedalling.

I haven't looked into the bling rings recently as I'm perfectly happy with Bafang's OEM fit and forget steel ring. After over 10K of what I expected to be hardwearing experiments, like running chains for their entire life on the factory lube, no cleaning or extra lube ever, inside a Chainglider, the steel ring appears unmarked. My kick is a maintenance-free, no bother bike you just get on and ride when the notion takes you, or the rain stops for an hour, so the steel ring and I are a match made in heaven.

However, be sure the 36 tooth ring is well made in both the machining (not cut too thin "around the corners" to get the dish depth) and the engineering senses (not so much offset that it wrecks the bottom bracket bearings which are part of the Bafang motor and likely to be a pain to rebuild, etc) before you splash out many shekels for it. I seem to recall that a 38T ring from an Italian firm which looked almost as heavily made and long-lasting, in the photos anyway, as the flat, thick Thorn OEM ring well-known here, about a hundred euro landed in these islands, was at one stage the minimum tooth count offered for precisely these reasons.

Something else you might consider is that the control circuitry that came with the BBS, besides the throttle, has nine different speeds or levels of pedelec assistance, acting like a gearbox in itself (you can group these so that the thing appear appears to have only 5 or 3 electronic gears) which, if mounted under her thumb, can be used to keep her cadence in the range she's used to, and to give the rear gear cluster some protection against the torque of the motor. I came to cycling too late to learn a butterfly cadence, so I mash through, using my heart rate monitor like other cyclists use a cadence meter, together with the 5 electrical gears I have set plus the top half of the Rohloff gears to control my exertion to within one heartbeat. And of course for downhill thrills in the Rohloff's three overdrive gears.

[sdg_77]

Yes - we're definitely both pedal spinners so getting down to more like the middle ring would help with that.

Went out for a short ride yesterday and Gill says  with the 48T ring on the pedals are turning slower than she would like.
I'll have another go with fitting the 44 tooth ring.

I don't have a problem with the Bafang ring - a little agricultural perhaps but not poorly made.
The plastic chain guard however ....

Just had a chat with Brighton eBikes.  Lekkie have a 40 tooth dished ring which will fit with the BBS01/02 when the reduction gear casing is replaced with a smaller version - I'll wait and see how much that costs before making a decision.

The 36 tooth is not dished and would result in a harsh chain line on the bigger sprockets.

regards
sdg.

[sdg_77]

Apologies re the lengthy delay in updating this saga ... but the end result is a success 

The original/standard 48 tooth Bafang chainwheel was too large for Gill to make much use of the rear sprocket cluster - she was mostly cycling on the largest two sprockets.  We did try a Bafang 44 tooth but this would not fit with the 9 speed Shimano chain - which worked fine with the 48.  Personally - I think the 44 tooth wheel was either cut from thicker steel or had too much paint applied.  So I got in touch with Brighton eBikes and we have ended up with a Lekkie Bling Ring 42 tooth as this will fit onto the motor unit without modifications. There is a 40 tooth version but that come with a replacement outer cover for the motor unit gear casing - as you might imagine - costs a lot more.

With the new ring fitted we went off on holiday to Scotland (motorhome touring) and had a few days out on the bikes.  For us, this is a success as Gill is now not feeling like she has to struggle to keep up and I'm not either worrying she is not enjoying the route or stopping to let her catch up.  We did a route along the Solway coast to Caerlaverock Castle and the Wetlands reserve on a greyish breezy day.  On the way out she had the assistance set on 2 or 3 and we were able to talk comfortably as we went along.  As time went by and the breeze picked up, she wound the assistance up and finished the day on 6 or 7.  Into a headwind for the last 10 or so km we arrived back both in about the same state of tiredness.

I did make up an aluminium adaptor for the battery box to allow it to fit onto the Thorn bottle lugs, but aside from that the fitting went pretty much straightforward.

Worth watching videos of the fitting process if you want to have a go - its not difficult but the supplied instructions are not good.  I found this Rev Bekka video easy to follow. 
https://www.youtube.com/watch?v=rcYVyuDC6e8

Very impressed with the assistance from Brighton eBikes too - If I convert one of my own bikes I'll probably buy the kit from them.

photos to follow - possibly when I have tidied up the wiring and battery box adaptor :-)

Thanks to all for your advice etc.
sdg

Edit:  Caerlaverock Castle not Culzean and spell checked :-)

[Andre Jute]

Congratulations! Look forward to your photos.