Which kit? 12 mile range, 20mph, hub motor, city bike

Hi folks,

Another "which kit" question. The mission is a ~24 mile round trip which I'd like to be able to do at ~20 mph with minimal assistance (i.e. arriving not out of breath and not having to take a shower). No significant hills - the largest grade is probably about 5%. Leaning towards a hub motor. I have no donor bike yet, am planning on sorting the kit first then finding a bike to match - probably some sort of commuting/city bike. Budget flexible; not concerned about road-legality.

Any suggestions?

Just about any of the medium sized hub-motors with a 48v controller and 48v battery of at least 12Ah should do the job. my favourite motor is the Q128C because it's so smooth and quiet. the main thing you need to look out for is the winding speed of the motor. For 20 mph cruising, you need at maximum speed of about 24 mph, so somewhere around 240 to 260 rpm for a 48v one or around 200 rpm for a 36v one run at 48v.

For the donor bike, any bike with a triangle frame and disc brake mounts should be OK. It's possible to fit the pedal sensor to any bottom bracket, but one with space between the crank and the BB tube will be the easiest, otherwise think about upgrading the crankset to a Shimano m590 crankset with 48T large chainring or similar. Cost about £60. You'll need at least 44T for 20 mph pedalling.

Thanks for such a quick and concise reply! A few follow up questions...

It looks like this is the only place to get the motor:

https://bmsbattery.com/ebike-kit/769-q128c-135mm-500w-rear-driving-ebike-hub-motor-wheel-ebike-kit.html

This is the one I want, in 201rpm, 36V in whatever wheel size I pick, right?

Is there any community consensus on the best type of controller to get? The same site has a whole bunch; would this one:

https://bmsbattery.com/ebike-kit/788-s12sh-800w-35a-torque-simulation-sine-wave-controller-ebike-kit.html

picked more or less at random, be suitable?

In terms of batteries, here's one pulled from that site which looks suitable:

https://bmsbattery.com/ebike-battery/537-48v18ah-lifepo4-shrink-tube-ebike-battery-pack-battery.html

but I'm guessing from the rather sparse design that it's intended for folks who want to make their own mounting solutions.... I've seen some pictures of conversions with very neat downtube mounted batteries - would I have to get this from somewhere else?

A setup I had and rode at one stage that would easily do this is

Bpm front hub from BMS battery (36v)

A basic no hall 48v controller

A 16ah 48v battery (actually I had a 36v 16ah and a 11.1v lipo booster battery set up of 15.6ah hooked up in series)

OK, after a bit more advice I am arriving at this proposal for the setup:

Q128C motor @201rpm, 36V:

https://bmsbattery.com/ebike-kit/769-q128c-135mm-500w-rear-driving-ebike-hub-motor-wheel-ebike-kit.html#/213-rpm-201/42-voltage-36v

36V/48V 500W 9Mosfets 20A Brushless DC Torque Simulation Square Wave Controller with speed sensor and PAS:

http://pswpower.com/peng/iview.asp?KeyID=dtpic-2016-3F-3VM4.50CMJ

Whale 48V 14.5Ah Lithium Ion Frame Battery 29E Samsung Cells

http://eclipsebikes.com/product_info.php?products_id=111

Plus torque arms, LCD, charger ETC. How is this kit looking? I know that the battery will be heavy, but I'm not too worried about handling - I'm expecting to often be riding with panniers full of shopping anyway. Are there any incompatibilities I'm not seeing?

Also, where do people usually keep the controller? I'm planning on having a pannier rack permanently on the bike, so maybe in a top bag e.g.

https://4bvcf231p0yn3098v01g91om-wpengine.netdna-ssl.com/wp-content/uploads/1784-vaude-silkroad-m-trunk-bag-stock.jpg

any thoughts appreciated.

I'm pretty sure the Q128C is a sensored motor so probably this controller would be a better option for that motor.

http://pswpower.com/peng/iview.asp?KeyID=dtpic-2016-3F-33C0.50CGS

or the S12S and LCD3 from BMSBattery since you are already paying postage from there.

I have my controller and battery in a bag like you've linked to as well.

Awol is correct you need the Sine Wave controller then it will run so quiet you will want one to use for the air rushing by.

You can also get one of the S series controller from BMSB as all are made by Kunteng, even the integrated 09/ battery controller is a KT.

Thanks all! Controller swapped out. Is there any consensus about which is the best/easiest PAS to fit out of these:

https://bmsbattery.com/59-pas

?

It depends on which type of bottom bracket you have and how much space there is. in terms of performance, I haven't noticed any significant difference from any of the types of PAS. It's the controller's software and hardware that has the biggest effect. They're fairly cheap from BMSB, so get a couple of different ones. The dual hall sensor ones are normally handed, so they only work on one side.

Show a picture of your BB from underneath, then we can comment further.

I don't actually have the donor bike yet, so I'll take your advice and order a few different ones then see what fits when I source a bike.

Now I am wondering about putting a battery in a bag on the pannier rack rather than mounting on downtube. Given that I'm planning on having a rack permanently on the bike, and having a top bag for holding the controller, maybe it would be a good idea to have the battery in there as well. Pros: more stealthy; might be handy to have something with a strap to carry the battery in. Any cons? I guess the weight would be higher up.

Keep it in the triangle if you can. A rear battery can work, but not with a pannier rack. The rack needs to be much further back when you fit panniers to stop your heels from hitting the bags. That's not a good position for the battery. If you're going to install it behind the seat, it needs to be as far forward and as low as possible, like this one that has about 80% of the weight in front of the axle:

Look at this one, where most of the battery weight is behind the axle. That's not good.

http://ebike-sales.co.uk/wp-content/uploads/2015/09/Custom-Ladies-Thumb.jpg

OK folks, after much helpful advice that's the kit ordered. Now sniffing around for a donor bike. I'm probably looking for a hybrid/commuter type bike, something that can take mudguards and a rack, with disc brakes. I might be able to get hold of a Sirrus disc, which would seem to fit the bill:

https://www.tredz.co.uk/.Specialized-Sirrus-Disc-700c-2017-Hybrid-Sports-Bike_96715.htm

This would give me racks front and rear, plus it has the 48T chainring and and 8 speed cassette. Can anyone spot anything that would stop it being a good fit for the kit I've picked?

If you have ordered the Q128c, check the bike has a splined

cassette and not a threaded freewheel.

OK folks, after much helpful advice that's the kit ordered. Now sniffing around for a donor bike. I'm probably looking for a hybrid/commuter type bike, something that can take mudguards and a rack, with disc brakes. I might be able to get hold of a Sirrus disc, which would seem to fit the bill:

 

https://www.tredz.co.uk/.Specialized-Sirrus-Disc-700c-2017-Hybrid-Sports-Bike_96715.htm

 

This would give me racks front and rear, plus it has the 48T chainring and and 8 speed cassette. Can anyone spot anything that would stop it being a good fit for the kit I've picked?

There's no point in buying a new bike. It doesn't give you any advantage. You can get a twice as good used one for the same money or the same one for half the price. I get all my bikes used from Ebay. They're always as good as new. My mate got a perfect Carrera Kraken with hydraulic brakes for £110 from Facebook ads.

http://www.ebay.co.uk/itm/Boardman-Hybrid-Team-Bicycle-Medium-Frame-/142481607723?hash=item212c90cc2b:g:R0cAAOSwa3ZZmal6

http://www.ebay.co.uk/itm/Excellent-Condition-MX-Boardman-Comp-Hybrid-Bike-21-Frame-/272808164849?hash=item3f84a23df1:g:JHYAAOSwi-NZlJAL

http://www.ebay.co.uk/itm/Specialised-Sirrus-Comp-Medium-hybrid-/332353639758?hash=item4d61d2154e:g:WIkAAOSw0DlZnIUc

There's no point in buying a new bike. It doesn't give you any advantage. You can get a twice as good used one for the same money or the same one for half the price. I get all my bikes used from Ebay. They're always as good as new. My mate got a perfect Carrera Kraken with hydraulic brakes for £110 from Facebook ads.

I agree with one exception, the bike you want doesn't have a second hand market, all my bikes since I was 12 have been hand me downs, attic or skip finds.

I looked for a trike and they are as rare as hens teeth so the price is high and the ones I found that suited my use and budget were so far away that transport costs put the price so near to the price of a new one it wasn't worth buying second hand.

There's no point in buying a new bike. It doesn't give you any advantage. You can get a twice as good used one for the same money or the same one for half the price. I get all my bikes used from Ebay. They're always as good as new. My mate got a perfect Carrera Kraken with hydraulic brakes for £110 from Facebook ads.

Problem I find is they are generally pickup only and miles away.

OK folks, thanks again for all the advice... donor bike and kit will hopefully be arriving some time this week, so I should be a able to write up a build report sometime soon.

Is there a thread anywhere which details how to install one of these hub kits? My impression from the BMSbattery website is that the kit is unlikely to come with legible instructions :-) It all seems quite self-explanatory, but I'm sure it's the kind of thing where doing things in a particular order makes it easier, etc.

Start with the motor. You'll probably need to file your drop-outs to get it in. Put the disc on it, then try it in the frame. Most likely, you'll need a single washer extra normal 12mm washer on the disc side to get the disc to line up with the caliper. The drive side is easier. You only have to make sure that top gear doesn't rub on the frame. You might need another washer. If you do it will need to be a narrow (not thin) one.

Then look at the rim to see if it's in the middle of the frame. if it's not, you have to get out the spoke key and dish it.

When you're happy with the wheel, go and buy three tennis balls and Google how to juggle. keep practising until you can do the normall juggling, including the bit where you chuck every third one much higher in the air. Once you've mastered that, you're ready to tackle the installation of the throttle because it takes a fair amount of juggling to find a position that you're happy with. Sometimes it's easy, and sometimes you have to change something.

The battery is easy unless you have a shark (08) type, which most likely will require extra rivnuts to be installed in the frame. Even with the dolphin (09) ones, I like to add an extra rivnut anyway.

Installation of the PAS depends on which type and size of BB you have. Yours is a square taper, so it might be easy if there's enough space. If there's no space, there's lots of options.

Luckily, you don't really need brake switches. The wiring is usually straight-forward. If you have loads of spare wire because they're too long, you can cut and solder them or hide the surplus in a toolbag. that works very well if you put the controller in the bag too.

They're pretty simple. Stick it on the axle on the disc side, chuck the original tie-bar and make your own to tie it to the disc caliper fixing or any other solid point. You can modify the original tie-bar, but you need a 5% cobalt drill to drill it and an angle grinder to cut it.

OK, managed to get a couple of hours to work on the project today but have run into a few snags, looking for some (more!) advice.

I got the cassette and disc onto the new rear wheel without any trouble. Then I found that the hub motor housing was hitting the caliper, so had to add a bunch of washers to space it out. Because of that, I then had to add a bunch of washers between the hub and the dropout. And because of that, I had to add a bunch of washers between the disc and the disc mount to move it back in line with the caliper.

So currently everything is aligned fine and the wheel is sitting happily in the dropouts. I'm not too happy about my rear disc hanging out off a stack of washers, but am ordering some proper disc mount spacers to fix that.

The main problem I have now is that the torque washers supplied with the motor are currently doing absolutely nothing - here's a high resolution pic of the disc side:

The dropouts are relatively shallow, and there's probably enough material that I could start filing them to allow the torque washer to engage. But I'd be a bit worried about removing so much material from a pretty important area of the frame.

I also have torque arms and have cobbled together a bar to attach it to the caliper mount on the disc side:

Now I have the measurements I think I can probably build a more convincing version out of thicker metal, which may avoid the need for the torque nuts altogether.

Any advice?

You should file your drop-outs deeper and reshape them to the shape of the axle.Put the anti-rotation washer in a strong vice and bash the tab right over until it's approx at right angles.

Your torque arm doesn't look right. Ideally, you want the tie-bar at a right-angle to the arm itself. There's four ways you can put the torque arm on the axle. Try the other three to see which gives the best angle.

The disc spacing doesn't look right either. You've spaced the axle away from the frame, then spaced the disc away from the motor back towards the frame. Surely, one is cancelling the other out. Normally, you have the disc hard up against the motor, then a single washer on the axle to line it up with the caliper.

Thanks for the quick reply. I'll take a look at filing the dropouts and modifying the torque washers. Any suggestions on the best tools for filing? I have hand files but would definitely be prepared to try a quicker way :-)

You're absolutely right about the two sets of washers cancelling each other out - the problem is that I need the washers on the axle to prevent the hub housing rubbing against the brake caliper.