SWXK Front Hub Motor Road Bike Build

First, thanks to motomech, LewTwo, John (rumped6), and everyone else at ES who helped me find the right parts to achieve my goals with this, my first build. This is a great community. This build started out with a 2012 MAC motor from John but unfortunately it wasn't playing nicely with the controller due to the advanced hall timing. I tried to relocate the halls and damaged a winding. So, long story short I picked up a Bafang SWXK from a neighbor (Bike Swift, https://www.bikeswift.com) to replace it.

Here's my bike, it's a 1993 Trek 1200 road bike with an aluminum frame and CrMo front fork. I wanted to use my existing bike for this build to keep costs down, and the steel front fork seemed like a better place to put a motor than a 126mm rear aluminum dropout.


I got a box of parts from BMS Battery today. Well packed, not missing anything, and I even got a hand written thank you note from Sherry who helped me place my order. Impressive.

The battery case is indeed the "jumbo shark" or "new hailong", as I suspected. It has a USB port and enough room for 65 cells, 13s5p. The sticker says 20Ah but it was advertised at 14.5Ah. The sine wave controller is built into the mount, it's in the small metal box. Looks like 6 FET and I think I see a shunt that could be modified for more power, though it seems like any extra heat in such close proximity to the cells would be a bad idea. Let me know if you guys see anything of interest, I don't really know much about controller internals/components.



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I got a handlebar extender from eBay and cut a piece of pipe to give me a good place to mount the throttle, LCD, control, and my bell.

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My water bottle rivnuts are too low to mount the battery on, so I got some hose clamps to slide it further up. I ended up shortening most of the cables for a cleaner installation. For the HWBS, I used the 2 connectors from the brake levers that came with my kit - one for the standard signal and ground, and one for the 5v supply, which I got from the throttle (I added an extra wire).





Overall, I'm happy with how it turned out. It goes fast enough for the bike paths around here, I can cruise at around 24mph when I want to, and it makes the 10% grade hills near my house seem easy. The PAS is really nice, I barely find a need for the throttle. Now I'm just counting the days until they open the bike lane on the bridge I take to work every day.



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Build Summary
Motor: Bafang SWXK from Bike Swift, https://www.bikeswift.com
Battery: 48v 14.5Ah 13S5P Panasonic NCR18650PF, https://bmsbattery.com/ebike-battery/819-48v116ah-case-08-bottle-panasonic-battery-pack-battery.html
Controller: Integrated into battery case, 18-20A sine wave, same as the one in this package https://bmsbattery.com/ebike-battery/774-48v116ah-case-08-bottle-panasonic-battery-pack-battery.html
Throttle: Thumb, same as the one in this package https://bmsbattery.com/ebike-battery/774-48v116ah-case-08-bottle-panasonic-battery-pack-battery.html
PAS: 8 pole, same as the one in this package https://bmsbattery.com/ebike-battery/774-48v116ah-case-08-bottle-panasonic-battery-pack-battery.html
Wiring: Motor wire and splitter harness, same as the ones in this package https://bmsbattery.com/ebike-battery/774-48v116ah-case-08-bottle-panasonic-battery-pack-battery.html
LCD: S-LCD3, same as the one in this package https://bmsbattery.com/ebike-battery/774-48v116ah-case-08-bottle-panasonic-battery-pack-battery.html
E-Brake: HWBS, https://bmsbattery.com/ebike-parts/459-hwbs-hidden-wire-brake-sensor-1pcs-parts.html
Torque Arm: Custom arm for SWXK from Bike Swift, https://www.bikeswift.com

Wow, this looks like it's going to be a nice clean build!

The battery case is indeed the "jumbo shark" or "new hailong", as I suspected.

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Thank you for the pictures. That indeed looks like a "next generation" design of the case and I suspect a tad taller that the original shark. I note it also has a metal plate for the mounting bolts (a nice improvement). It does appear that they had to work to get the controller in there. Perhaps there will be another integration in the controller design some time down the road. Looking forward to reading about your progress.

Don't put your wallet away just yet.

Motor: MAC 10T? 14T? Front Hub Motor from John (rumped6)

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I believe the frt. Mac only came in either 14T or 16T. Either way, it will be plenty fast, between 25 and 30 mph.

I see a shunt that could be modified for more power....

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With the 18 A sine wave controller, this will be a "soft start" system. Just as well, because w/the big motor and the skinny tire there will be a tendency for the tire to spin-out. I would hold off soldering the shunt til you see how strong that tendency is.

PAS: 8 pole

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If you don't want to remove the bottom bracket, you might want to consider the 2 piece disc from Grin;
http://www.ebikes.ca/shop/electric-bicycle-parts/torque-sensors/pas-12p-chr.html

Torque Arms: Front 12mm pair...

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Unfortunately, the Mac axles are 14 m/m and these T.A.s are so hard that they are impossible to grind by hand. The cost of hipping from the East will bring the cost up to the prices of them in the States($20), so you might as well order them from either Grin or Luna. Obviously, you would combine the T.A.(s) w/ anything else you might purchase.

LewTwo said:

That indeed looks like a "next generation" design of the case and I suspect a tad taller that the original shark. I note it also has a metal plate for the mounting bolts (a nice improvement). It does appear that they had to work to get the controller in there. Perhaps there will be another integration in the controller design some time down the road.

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Yea, the controller packaging is tight. I noticed that there is no real wire strain relief, but there are threaded holes in the metal casting for one, so I may try to add something. IMO, this pack is a hell of a deal. They are selling these 14.5Ah Panasonic Jumbo Shark packs for about the same price as the 11.6Ah version, which was a good deal already. If you don't mind the slight weight penalty of the 13 extra cells, it's a no-brainer. I don't have an original shark pack to compare, but I was surprised at how small the jumbo shark was. I'll try to get a weight measurement at some point. Luna has dimensions on this pack, https://lunacycle.com/48v-panasonic-17-5ah-jumbo-shark-ebike/

motomech said:

I believe the frt. Mac only came in either 14T or 16T

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Agreed, the only documentation that I could find shows 14 or 16T, as far back as the EM3ev site goes (2013). John originally bought the motor from Wake in this thread, https://endless-sphere.com/forums/viewtopic.php?f=31&t=65989, where it is claimed to be a 10T. I have discussed with neptronix who's owned an early 350w MAC motor and he was under the impression that it was a 9-9.5T. My best guess, with very limited knowledge of motor construction, is that the front motors take more turns to generate the same RPM as the rear motors because of their thinner stators. So maybe it's really a 14 or 16T motor, but it was once advertised as a 10T because it's about as fast as the rear 10T. I'm guessing that this motor is what's now called a 14T based on discussions with neptronix and pictures of the internals.

motomech said:

Unfortunately, the Mac axles are 14 m/m

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From what I've read and the drawing that LewTwo posted (https://endless-sphere.com/forums/download/file.php?id=208902), the axle on the front motor should be M12. I think the rear MAC uses M14.

motomech said:

Don't put your wallet away just yet

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I'm already daydreaming about a set of Schwalbe Marathons and some wired lights . Those can come later tho, I'm hoping that I have all the parts I need to get it running so that I can see how much I use it before I put any more money into it.

The Marathons are worth their weight in gold.
I'm currently using the less expensive Forte Gotham copies and their extra thick tubes and I can't see or feel any difference between them and the Schwables;
https://www.amazon.com/Forte-Gotham-Road-Mountain-Tires/dp/B017MDNGCQ

bchaney said:

motomech said:

Unfortunately, the Mac axles are 14 m/m

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From what I've read and the drawing that LewTwo posted (https://endless-sphere.com/forums/download/file.php?id=208902), the axle on the front motor should be M12. I think the rear MAC uses M14.

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The older Mac drawing's show 12mm axles. The New version shows 14mm axle. bchaney ordered the old version.

Yup, i have a mac front motor on a 700c wheeled bike too.. running a peak of 900w or so.. it's a torquey bugger and we've had the front wheel slip from time to time on sand. But the rider position is upright and therefore way more rider weight is on the rear than the front. If the handlebars are kept in the same position on this bike, front wheel slip will be less of an issue. But i'd still jam as wide of a tire on that front as possible.

My tire recommendation would be a schwalbe marathon plus... all the way. I've tried nearly every flat proof tire.. that one's a winner ( our roads are littered with goatheads )

hunting biker said:

I am wanting to build an electric bike out of a mongoose 24" x4" tire bike. Which motor should I use, front or rear wheel hub or friction, Where do I find the motor and components? Do I have to cut and thread spokes? WHAT ELSE SHOULD I BE WARY OF?
THANKS FOR THE HELP, HUNTING BIKER

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First: Read the following
https://endless-sphere.com/forums/viewtopic.php?f=3&t=66302
https://endless-sphere.com/forums/viewtopic.php?f=3&t=26488

Second: Update your Profile to include your location

Third: Start a new thread. Do NOT hijack another thread (I made the same mistake with my first post).

Updated the OP with current progress. A couple small snags but the one that has me more concerned is this:

The motor power "cuts out" at certain throttle position. The position varies... it seems like if I gradually increase the throttle it will cut out at a higher speed than if I floor it. If I push the throttle to a certain point, the motor will accelerate to that point and then the power will cut out - it will not maintain speed. I have to return the throttle to 0 and then push it again to get any power. Not sure if this is making sense, I could take a video if it doesn't. I have checked my P and C parameters and can't find anything that seems wrong.

I started a new thread for this issue, looks like it may have to do with the C2 parameter but idk what that actually controls - https://endless-sphere.com/forums/viewtopic.php?f=2&t=86439

One thing to keep in mind is that the MAC motors have a high pole count and high eRPM.. if a controller cannot handle the eRPM the MAC likes to operate at, it will stutter and do weird stuff like that.

I had issues with this in 2011.. until em3ev started selling a high eRPM compatible infineon clone.. at partial throttle, the controller would make the motor sutter along and you could hear the motor's freewheel going clack & clank.. Other controllers would do the same thing. Your controller from BMSBattery might have the same problem. That would be a shame because the integrated battery and controller unit is so cool.

neptronix said:

One thing to keep in mind is that the MAC motors have a high pole count and high eRPM.. if a controller cannot handle the eRPM the MAC likes to operate at, it will stutter and do weird stuff like that.

I had issues with this in 2011.. until em3ev started selling a high eRPM compatible infineon clone.. at partial throttle, the controller would make the motor sutter along and you could hear the motor's freewheel going clack & clank.. Other controllers would do the same thing. Your controller from BMSBattery might have the same problem. That would be a shame because the integrated battery and controller unit is so cool.

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I was thinking that may be the issue, but I've read that this controller has been used with the 260RPM Q100H which has 8 poles and 12.6:1 gear reduction, so 26208 eRPM. The MAC is maybe 280RPM, 16 poles, 5:1 gearing so 22400 eRPM. Seems like if it works with the Q100H it should work with the MAC.

I changed the C2 parameter on the LCD to 3 and the motor responds to all throttle positions now, and will spin up to 36mph unloaded. Does that sound like what your girlfriends bike did?

Best info I can find is that the C2 parameter has to do with the phase angle of the sine waves. Default value for C2 is 0 which I assume means 120 degree phase angle. There was one report of someone changing the value to 2 in order to get a 60 degree phase angle motor to run. Anyone know if the MAC uses a standard 120 degree phase angle or something else? I think this only matters with sine wave controllers and it sounds like most people run square waves with the MAC.

I just did a little more research and it sounds like older MACs had advanced hall timing... maybe this is causing the issue?

So I messed with the C2 parameter again and now all values give the motor the same no-load top speed and draw the same wattage. I set C2=0 and it seems to be working fine. Not sure if it was just a loose connection or what, I'm just happy its working. I have been distracted by other projects like a basement renovation recently, but I took a test drive and now I'm excited to get this bike finished. Updated the OP with progress.

Nice build. Looks a little like my aluminum drop bar bike!

I was wondering how you would do the throttle. Drop bars are a challange, and I see you found the flat bar throttles won't fit a drop bar.

Me, I used a pushbutton throttle. I can use a rheostat to modulate the power, but I'm just using it as a top speed boost, and it works well like that.

Enjoy!

The build is finally complete, see the OP for updates. I've ridden it the past few days and it's finally warming up a bit here so I'm looking forward to using it more. The only remaining issue is the one I posted here - https://endless-sphere.com/forums/viewtopic.php?f=2&t=87467. If anyone has and ideas, let me know. Thanks again for all the help, guys!

Well I ended up damaging my MAC motor so it was replaced with a SWXK, see last pic in OP.

Recently added some Schwalbe Marathons, fenders, and a new crankset. Will update pic soon.