Q128C 25mph fast hybrid commuter build/ride report

[emjay]

Executive summary: here's a pic of the more-or-less finished bike:

25mph on the flat @ ~600W, 20kg bike weight.


Warning: long post comming up This is mostly a brain dump of everything that I did for my recent build in the hope that it will be useful to somebody else considering the same, and so I can refer back to it when I next do a similar build. I'm going to write this in as much detail as I can while it's still fresh in my mind, but if there are any questions please ask.

Let me emphasize that I am a complete beginner at this; this is the first ebike I've ever built or even seen so take everything I say with a grain of salt and if I say anything stupid, please correct me in a reply!

Before I start, thanks are due to everyone who helped me with questions, especially d8veh, Nealh, anotherkiwi, KirstinS and awol. I'm going to write out the steps as if I did them all correct first time to make it easier to read, but I had to ask for helpl with basically every step.

For reference, my original "which kit?" thread is here:

http://www.pedelecs.co.uk/forum/threads/which-kit-12-mile-range-20mph-hub-motor-city-bike.28773/



__The donor bike__

The donor bike was a 2017 Specialized Sirrus disc - specs here:

https://www.cyclesuk.com/en/gb/Specialized-Sirrus-Disc-2017/m-58757.aspx

As others have pointed out, there's absolutely no need for a new bike, but I was having trouble finding a second hand one locally that had my desired combo of 700c wheels, disc brakes and a small frame, so when I pulled the trigger on an end-of-season deal and bought the Specialized.

__The kit__

The motor was a Q128C in a 700c wheel. I got the 36v 201rpm version with the intention of running it at 48V:

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

I got this controller:

https://bmsbattery.com/ebike-kit/552-s12s-500w-torque-simulation-sine-wave-controller-ebike-kit.html?search_query=S12S&results=14

and this 48V 14.5 Ah battery:

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

The battery was probably overkill for my original requirements, but the cost for the bigger battery was not too much and I though it might be handy to have a longer range sometimes.

I also got the LCD display:

https://bmsbattery.com/home/826-s-lcd6-lcd-meter-for-s-series-controllers.html?search_query=lcd6&results=1

various different torque arms, a generic throttle and some power assist sensors. I bought a few different types of torque arms and PAS sensors cos I didn't know which would fit my frame the best.

Continued...

 

[emjay]

__Fitting the motor__

This was by far the trickiest bit of the build process. I got the motor already built into a wheel, and the build quality was OK, nothing special. The spokes were very loose compared to what you'd get from a proper bike shop. Being quite light, I'm not too hard on spokes (i.e. have never broken one in many years of cycling) so I figured it would be fine. I will probably tighten up the spokes in the future when I get the right tool.

I took the cassette off the donor bike rear wheel and fitted it to the motor wheel. My first mistake was that I had the kind of cassette lockring removal tool that has the pin in the middle, which was fine for getting it off the donor wheel (which had a hollow quick release axle) but obviously didn't fit on the motor wheel with its solid axle. A bit of "modification" of the tool with a hacksaw fixed it, but if you're buying one for this purpose get the one that looks like this:

https://www.amazon.co.uk/Silverline-240618-Cassette-Lockring-Removal/dp/B00J3AA4NQ/ref=sr_1_3?ie=UTF8&qid=1506455589&sr=8-3&keywords=cassette+lockring+removal+tool

I then took the disc rotor off the donor wheel and put it on the motor wheel. When I fitted the wheel into the dropouts, the casing of the motor hub was hitting the brake caliper. So I had to take the old 160mm rotor off, fit a new 180mm rotor, and fit a 180mm adapter to the frame to move the caliper further away from the hub. If you're planning a build like this, I suggest you plan to fit a 180mm rotor if the bike doesn't already have one. There are various other ways round the problem like filing down the caliper or fitting a low profile caliper, but changing the rotor size was easy and fixed the problem completely.

Once I had the wheel sitting in the dropouts I noticed that they were a bit shallow and the axle was not sitting fully in them, so I filed the dropouts a bit with a round file.

I noticed that the torque nuts supplied with the motor were nowhere near engaging with the dropouts - the dropouts were just too shallow. Filing them deep enough to allow the torque nuts to engage would have involved removing a load of material and leaving the dropout area of the frame very thin, so I just decided not to use the torque nuts and build a torque arm instead.

I tried a few different torque arms until I found one that fit in a good position. I then measured the distance from the fixing hole in the torque arm to the closest brake caliper mouting hole, then drilled a 6mm hole in the right place in the second bit of the torque arm. Hopefully this photo of the non-drive side makes it clearer:

I ended up having to use a longer M6 bolt to secure the second bit of the torque arm to the caliper mount. The bolt goes through the torque arm, then through a few washers to make it the correct distance from the frame, then through the caliper mounting hole on the frame and into the threads on the caliper adapter. As you can see in the photo, my torque arm isn't the neatest - there is a stray hole from a previous fitting attempt, and I should probably remove the unneeded bit at the end.

In the picture you can also see the stays for a mudguard, which I fitted at the same time I put the wheel on. The mounting hole for the mudguard stay is directly behind the torque arm, but I just sandwhiched the stay between the frame and the torque arm and the friction was enough to hold it in place nicely.

Here's a photo of the non-drive side from above:

Starting at the hub, it goes:

- washer
- dropout
- spacer
- torque arm
- axle nut
- black plastic cover

For completeness sake, here's the drive side:

nothing very interesting going on here. From the hub it goes:

- washer
- dropout
- axle nut

I fitted the motor so that the cable emerges from the axle pointing down, which I think should make water less likely to run into the end of the motor.

Tip: during the process of fitting the wheel I probably put it in and out of the dropouts dozens of times, so I removed the rear derailleur during fitting so that it was easier to just drop it in.

 

[emjay]

__Fitting everything else__

With the motor on, the rest of the build went pretty smoothly. I fitted a frame bag to hold the battery and controller. I was originally going to use the very nice frame-mounted battery bracket that came with the battery, but I am sometimes going to have to leave the bike locked up and didn't want a big, obvious battery sitting on the frame. In the end I'm very happy with the frame bag, it keeps everything nicely contained and makes me more confident about waterproofness as well. Since I wasn't using the frame mount I took the mounting bit off the battery leaving me with just a neat two-prong terminal to connect to.

Here's a shot of the handlebars from roughly riding position (ignore dog sneaking into the shot - I didn't notice him when I was taking this :

On the left I have the throttle and LCD buttons in between the grip and the brake. This was surprisingly easy to fit and surprisingly comfortable to actually use. The LCD fits in the center of the bars.

__Wiring__

The cables for the throttle and LCD go to the stem and into the frame bag through a hole in the top. The cable from the motor comes from the back wheel, along the chain stay, up the down tube and into the bag through the same hole. Once inside the frame bag, everything connects to the controller, including the power cables from the battery.

Here's the right hand side of the bike, you can see the cables going into the frame bag:

Here's a closer shot of the right hand side, with the motor cable coming from the downtube and entering in the same hole:

Here's a slightly awkward shot of the inside of my frame bag - as you can see there isn't much room to spare with a big battery plus controller in there:

There should be a bit more room once I've tidied up some of the wiring.


__First ride__

Surprisingly, everything worked fine first time

First off, this bike is heavy. With everything installed, it weighs just over 20Kg. However, all the weight is nicely centered and secured, so pushing it around and pedaling unassisted it just feels like a very heavy normal bike.

The indicated no-load speed, with the back wheel off the ground, was 27mph. To tell the LCD that my wheel size was 700c I had to put it into setup mode, which was not documented anywhere in the manual, so for anyone else who buys it you have to hold down both up and down within 5 seconds of powering on. This also lets you change from Km to miles.

On the flat, with the throttle fully open, I was getting an indicated speed of around 25mph with no pedalling. I checked the speed on the LCD against a GPS reading and it seems pretty accurate, so I'm happy to trust the LCD speed in the future. The bike was an absolute blast to ride: smooth, silent, predictable power delivery, good handling and I got used to using the throttle in a few minutes. The motor had no problem maintaining 25mph on long stretches so I'm very confident that I'll be able to average 20mph on my commute. Power draw was around 500-600 watts on the flat @ 25mph. I saw it peak at around 1000W on a hill with wide open throttle.

I didn't see any movement from the axle or torque arms, so I'm happy that they're doing their job. I did around 10 miles with the throttle wide open and was still at 3 out of 4 bars of battery, so I'm feeling good about managing a 20 mile round trip without charging if I have to.

On the return leg of the ride I found a long straight road and did a solid 5 minutes at 25pmh, then stopped to check the tempterature - the motor and controller were barely warm to the touch, so no worries there. Next time I go out I'll bring an IR thermometer and find a hill to give it a proper torture test.

__Next steps and questions__

Firstly, and most importantly, is there anything in any of my photos or descriptions that looks/sounds like a bad idea? My test ride went fine, but if I have any problems waiting down the line I'd like to hear about them now

Now that I'm happy everything is working OK, I really need to tidy up the controller wiring inside the bag. I'm planning on soldering everything that I can directly to the controller, as I should never have to remove it except for maintenance.

I'm going to fit a pannier rack for carrying more stuff. I will try commuting a few times with the throttle, then fit the PAS so I can see which one I like better.

Do I need to have some sort of kill switch? In other words, if the throttle fails, will it fail closed or open?

I have these two bits from the kit left over - can anyone tell me what they are:

Any questions, comments, or advice appreciated!

 

[awol]

Nice.
I'm not sure you need the washer on the inside of the non-drive side dropout, then just loosen and reposition the brake caliper.
Your battery should easily do 20miles.
The parts in the last photo are a motor plug protector cover for during delivery/motor storage and a jst plug to trip out the cruise control and looks like some spare bullet pins+green covers.
Fit the PAS too, they are great to use.
I like your throttle, where did you get it?

 

[Nealh]

Clear plastic bit is the motor wire cover to protect the exposed pins in transit etc. The blue wire connector is for cruise control and joins the black and blue wired SM2 connector together.
PAS uses less power so will increase range, throttle makes you lazy. Throttle if any issue will be in the open position, one brake cut off or a kill switch/button would be good (rain/moisture shorting is the usual culprit ).
The motor wire looping up in to the frame bag would be neater entering at the bottom from the frames seat tube, burn a neat hole with a hot solder iron. Also just keep an eye on the drive side with no torque washer.

 

[Nealh]

GFT frame bag was it imported or sourced here ?
Also liking the throttle not seen that model before.

 

[Deleted member 4366]

Don't be tempted to fit the cruise control unless you have brake switches. Fit the PAS as soon as you can. You'll like it much more than the throttle, and it gives access to lower power without affecting the speed.

 

[R0881E]

Interesting, thanks

I am still deciding on my donor bike right now and haven't purchased anything as it will affect my wheel size.

Have you ridden further trips to ascertain your range with that setup yet?

 

[emjay]

Thanks all!

I put a washer on the inside of both sides as I read somewhere that it was better to have a larger surface area to clamp the axle between the dropouts. If they're not needed then I might remove them and re-align the brake caliper as you suggest, it would certainly make getting the hub into the dropouts a bit easier.

The throttle was this one that I found on ebay:

http://www.ebay.co.uk/itm/Wuxing-Thumb-Throttle-Both-Ways-Right-or-Left-Hand-Electric-Bike-Ebike-Scooter/282629555893?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

there were a bunch of others but I thought this looked like it would be easy to fit (which turned out to be the case).

Good idea about putting a hole in the bag: I have a fair bit of modification to do to the bag anyway (mostly sewing in something to hold the controller securely when I take the battery out to charge).

The bag itself I just found on ebay:

http://www.ebay.co.uk/itm/2017-GFT-MEDIUM-Half-Bicycle-Frame-Bag-Battery-Electric-Bicycle-E-bike-Lithium-/162684412224

We'll see how it holds up over time, the quality of the materials/stitching is nothing special but it's definitely the right shape for the job

Think I'll skip cruise control, I can't picture any roads round here on which it would be useful. PAS at some point soon and I'll see how it rides with that. I know that the throttle makes me lazy, but the whole point of building the bike is for me to be lazy or rather so that I can cycle a 25 mile round trip during the day and still have energy for running/kettlebells in the evening

I haven't done any more trips yet to figure out range; when I have time I'll go ride a circular route that doesn't take me too far from home and see how far I get before the battery runs out.

Is the lack of a torque arm on the drive side going to cause me any problems? I could probably rig up a second torque arm using the bits that I've got, though I'd have to make a p-clip to attach it to the frame as there are no convenient mounting points on that side.

 

[Deleted member 4366]

If you ride at 24mph without pedalling, you'll find yourselfin trouble.

 

[Steve A]

Thanks all!

I put a washer on the inside of both sides as I read somewhere that it was better to have a larger surface area to clamp the axle between the dropouts. If they're not needed then I might remove them and re-align the brake caliper as you suggest, it would certainly make getting the hub into the dropouts a bit easier.

The throttle was this one that I found on ebay:

http://www.ebay.co.uk/itm/Wuxing-Thumb-Throttle-Both-Ways-Right-or-Left-Hand-Electric-Bike-Ebike-Scooter/282629555893?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

there were a bunch of others but I thought this looked like it would be easy to fit (which turned out to be the case).

Good idea about putting a hole in the bag: I have a fair bit of modification to do to the bag anyway (mostly sewing in something to hold the controller securely when I take the battery out to charge).

The bag itself I just found on ebay:

http://www.ebay.co.uk/itm/2017-GFT-MEDIUM-Half-Bicycle-Frame-Bag-Battery-Electric-Bicycle-E-bike-Lithium-/162684412224

We'll see how it holds up over time, the quality of the materials/stitching is nothing special but it's definitely the right shape for the job

Think I'll skip cruise control, I can't picture any roads round here on which it would be useful. PAS at some point soon and I'll see how it rides with that. I know that the throttle makes me lazy, but the whole point of building the bike is for me to be lazy or rather so that I can cycle a 25 mile round trip during the day and still have energy for running/kettlebells in the evening

I haven't done any more trips yet to figure out range; when I have time I'll go ride a circular route that doesn't take me too far from home and see how far I get before the battery runs out.

Is the lack of a torque arm on the drive side going to cause me any problems? I could probably rig up a second torque arm using the bits that I've got, though I'd have to make a p-clip to attach it to the frame as there are no convenient mounting points on that side.

Regarding bag, I'd have gone for one from Alpkit they can make them bespoke and are now totally waterproof, invaluable in winter.

 

[emjay]

If you ride at 24mph without pedalling, you'll find yourselfin trouble.

Don't worry, I can do a good impression of working hard for the benefit of anyone watching

 

[emjay]

Regarding bag, I'd have gone for one from Alpkit they can make them bespoke and are now totally waterproof, invaluable in winter.

Thanks for the suggestion, I will definitely take a look - I'm pretty sure this won't be the last frame bag I buy. Looks like this:

https://www.alpkit.com/products/stingray

would be ideal for storing battery+controller with room left over!

 

[Nealh]

Danielr is a forum member, I forgot he had ebay listing.

 

[Forge Custom]

Thanks for the suggestion, I will definitely take a look - I'm pretty sure this won't be the last frame bag I buy. Looks like this:

https://www.alpkit.com/products/stingray

would be ideal for storing battery+controller with room left over!

Just ordered mine from here.
http://www.bike-bag.co.uk/

 

[emjay]

Found a bit more time to work on the bike today, and had another shake-down ride. I've soldered the motor leads (power and sensors) directly to the controller, and re-routed the cable in through the bottom of the bag as per Nealh's suggestion. This removed quite a lot of unnecessary cable length from the bag and made it a bit neater inside.

I did the same with the LCD wires, then fitted the PAS. Got the cranks off easily enough, but the bottom bracket end just refused to unscrew (and I was taking big chunks out of the incredibly soft metal and mushing up the splines) so in the end I just epoxied the sensor on to the BB shell, which worked fine.

Riding with the PAS is very nice and intuitive - I just need to get out of the habit of slowly pedalling forward to downshift when coming to a stop. I had time for a slightly longer test ride: 19 miles in 51 minutes @ 22mph average. This time I got the battery down to 2 out of 4 bars before I had to call it a day. I was deliberately being as hard on the battery as I could; full power assist all the time and minimal work from me. With this longer ride I could notice the power drop a bit more, I was doing 27mph on the flat hot off the charger and 24mph on the same stretch at the end of the ride.

 

[anotherkiwi]

Are you sure your BB end is metal? Some are plastic and a real ..... to remove. I had to fix mine with epoxy paste after which it did 3200 km without moving

 

[emjay]

It's metal all right, but very soft and the splines are so shallow that the tool just started chewing them up as I turned. It had probably been way over-torqued by whoever installed it (as happens annoyingly often with bikes... that's a rant for another day.... RIP my knuckles as I try to get yet another over-tightened pedal off

 

[Nealh]

Sounds good and you got the bike you was looking for.
The diy route is often the way to go to get the performance you require to match your needs.

 

[Deleted member 4366]

The battery voltage when empty is 75% of what it is when full. current is fixed by the controller, so the change in voltage has a direct effect on power.

Note that 2 bars out of 4 isn't half full. It's more like 1/3 full.