BBS02 Yuba Mundo w/thru axle Build

[gtiowa]

For my first e-bike build I chose a Yuba Mundo cargo bike. I purchased a frameset and 750 watt BBS02 mid-drive from Dan at Ichi Bikes. The first step was to grind off the cantilever posts front and back since I was going to be running disc brakes. Yuba uses 14mm dropouts with bmx hubs. After seeing Sam's (mechanic at Ichi) Mundo modified to use a thru axle I decided to go that route. I made some adapters and had Sam weld them in place for me. A mid drive paired with a thru axle is a good combo since you don't have to worry about the axle getting pulled out of alignment.

Next was the battery pack build. Since I had never built one before, I decided to go with Headway cells since they could be bolted together.

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I built a 2P16S pack with the cells in two sections so that I could put 16 cells on each side of the bike, then I made some wooden frames to put the cells in and enclosed them with a sheet of plexiglass on each side. I put the bms in a project box mounted behind the seat tube.
I decided to integrate the headlight, tail light, and horn with handlebar controls and power it all off of the main pack using a DC to DC converter. So the project box also contains fuse panels, relays, and a dimmer for the headlight so that I can have high / low beam. On the cover side of the box is a switch for the amp and a keyed switch tied into the brake cut off circuit. On the seat tube side of the box is an anderson powerpole connector for charging the battery.

I mounted the atv led headlight to a secondary handlebar stem.

After a couple of rides I decided that all I was missing was some tunes. So, I put a pair of 4" speakers in a pvc enclosure up front and mounted a little bluetooth amp for it on top of the project box next to the DC to DC converter.



Since I decided to keep this project a street legal build and have a 20 mph max assisted speed I replaced the 48 tooth chainring with a 38 tooth using an adapter from California E-Bike.

I'm using a sram x4 shifter so that I can run a 6/7/8-speed chain instead of a narrower 9 or 10 speed chain and I put a 7-speed cassette on with a spacer against the wheel.

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On top of the rear deck is an axle holder for towing another bike. I can actually sag another bike rider and their bike with this setup. The bike is a blast to ride and my daughter has plenty of room on the back even with the bags on it.

 

[ohzee]

That's one nice looking yuba. Nice job mounting those batteries never even thought about doing it like that.

Love that thru axle. Something about the yuba I hate. Curious where you got that head light looks like it pumps out some lumens.

 

[gtiowa]

The light is a MICTUNING Brand 4.5" 20W 2500 lumen spot from Amazon. It is very bright but the beam pattern doesn't work too well for a bike light. It's a spot light so to actually take advantage of the lumens you have to aim it for distance but then it doesn't illuminate directly in front of the bike. So I ended up shining it down and have a really bright circle of light in front of me. I'm going to replace it with a flood light and see if that works better.

 

[tomgopher]

cool build! Could you explain or link to what is involved in doing the thruaxle conversion?

 

[gtiowa]

For the thruaxle conversion I modified a t-nut so that it would fit in the back of the dropout. I used a grinder and a file to round off half of one side. I did this with two nuts and then had the threads on one of them drilled out with a 12mm drillbit. I purchased the t-nut from Enco. (Model #319-8950 M12 X 1.75 14MM TAPPED GIBRALTAR METRIC T-NUTS) The t-nut with threads was welded to the drive side dropout and the other t-nut was welded on the non-drive side. The axle that I'm using is a RockShox Maxle Lite 135 x 12mm.

 

[gtiowa]

Current headlight 2400 lumen flood. Lights up the immediate area much better than the spot light that was on it before.

Delivering a bike to a friend.

Delivering a truck wheel withe the use of a trailer.

 

[Bikengineer]

It looks cool, I'm also building a Yuba from frame. my plan was to use a IGH nexus-3 but the weaker axle in 14mm dropouts has made me re-think it. On top of that getting axle adapters here has been tricky. I emailed Ichi about the hub choice and local Yuba dealer and they both questioned it's durability. Have a go but it might fail was their verdict.
The idea of a 12mm through axle like you've done opens up the choice of parts to current MTB standards as the 14mm options with disc and freehub are both limited and expensive. The stock Yuba wheel for example uses freewheel which limits the gearing choice.
Another option I was toying with was using a Hope pro 2 Evo hub and converting to 14mm but am not sure it's possible as it's not listed as an option.

 

[jtrops]

It is really unfortunate that the Yuba uses 14mm axles. The design of a freewheel hub necessitates the stronger axle, where the design of a modern freehub supports the axle to prevent much of the bending/breaking that used to be commonplace on freewheel hubs.

The Nexus 3 is a recreational hub. It is not designed to handle much load. So if you don't plan on hauling much it might be ok, but i would look at a more robust hub. I have an old Fichtel and Sachs 3spd hub that i think would be more than adequate, but you'd have to go vintage for something like that.

Adapting a thru axle hub to take a 14mm axle is a really good idea. The adapters should be very easy to make from existing 10mm QR adapters. 14mm nutted axles are readily available (although the length may be a little tricky, try Yuba for one?).

 

[gtiowa]

Added some graphics to the side of the battery boxes.

 

[tomgopher]

thanks for the axle explanation, which wheels(hub and rim combo?) are you using? Did you do anything special to front wheel

 

[gtiowa]

The front and rear hubs are Azonic Outlaw Recoil. Since I wanted 36 spoke wheels with a thru axle, my options were limited. The rims are SUNringle MTX 33. I figured a DH wheel build would be a good choice for a cargo bike. Nothing special about the front wheel other than being 36 spoke.

 

[stoney]

This is a good build. I love how he made a through axle adaptation