Yuba Mundo FAT with BBS02 mid-drive

Hey all!

Haven't posted a build thread in a long time, but this project pulls from enough sources on Endless-Sphere that I feel it's my duty to post progress on this build just in case anything interesting comes up.

I have a Yuba Mundo V4.3 frame in matte black that I got for a VERY reasonable price. It has been sitting in the box for a number of months. This was originally going to be a TRANSMAG 3-4kW build, but I decided to leave those motors for a project that I'm not trying to pass off as a street legal bicycle.

Instead, I have a new-in-box BBS02 just delivered, my old PING 50V 15AH LiFePO4 battery from my previous commuter, and the frame. That's it. No bicycle components yet sourced, though I do have a rather extensive parts pile.

Plan is to run an Alfine8 (or Nuvinci360? Thoughts?) in a 50mm or larger 24" or 26" rim, 36 spoke rim with a 2.7-3.7 inch tire. Discs (mechanical or hydraulic) on both wheels, or certainly fronts.

Things I'm looking for advice/comment on:

Placement of the battery (and charger!). I've gotten used to having an on-board charger and being free to "fill-up" wherever I go) will be interesting. The main triangle (position B in the diagram) is where I had my PING in my last bike, and it's tight but I know I can get both the battery and charger in there. The rear triangle is very big on the Yuba, and my cardboard mock-up PING seems to fit in position A, though with the fat tire setup I'll have to double check. Interestingly, I considered position C for a while, which is very much out of the way BUT requires me to run a 20" wheel and a shortened crank, which seemed too much of a pain.

Tire selection: I live in Pittsburgh, and I'd like to have a good all-weather tire. I want a fat one for looks BUT MAINLY FOR POTHOLES. Our city has terrible road quality and I've broken SO many spokes on hubmotor bikes that I'm hoping a better wheel build and fat tires will make my ride acceptable. The other concern is flat tires, which I had a lot before I switched to Schwalbe Marathon Plus tires, which are almost flat-proof BUT are very stiff rolling and don't help the suspension/ride/pothole issue. Surly makes a bunch of cool tires for lots of $$$ (90-120!), but the Surly Black Floyd has a road-appropriate tread but is definitely the largest that will fit the frame at 3.8 inches. The Felt Bikes Thick Brick tire is a 3.0 tire (good middle ground for me) and is cheap at $25 bucks, but I have no idea about wear behavior or flat-proofness. Finally, there are a few 2.7 inch tire options out there that tend towards more offroad tread that I'd be willing to consider.

I'll post pics as this project comes along. It won't be revolutionary, but a mid-drive Yuba Mundo longtail fatbike with 1250 watts input should be the ol' reliable pikcup truck of ebikes, so I'm curious to see how it works out as a daily commuter.

-T

I'd love to find one of these reasonably priced to use as a commuter. Good luck with your build. I just finished a hybrid Trek FX build with the BBS02 and love it for commuting.

The chain might hit some of the fat tires you've mentioned, especially, in the lower gears.
Oh yeah.... you are using an internal geared hub.... never mind.

I look forward to watching your build. I have a yuba now that has been my primary bike for the last year.

I originally tried a urban commuter mid drive , but the mac motor was not up to what I needed to push thru it so now I have been running
a 5404 which so far has taken everything and then some , but damn is it heavy.

I have wondered about a chain drive like the bbs02 or LR/GNG.

I still want to put a front shock on mine also so Ill be curious to see what you do there.

Subscribed.

You've seen this yeah?

http://www.ichibike.com/blog/2014/6/8/Ichi_Blog/Fat_Electric_Cargo_Experiment_Pays_Off/ar/40/

I'm in the process of a similar build, with a V2 Mundo and less fatness.

Waiting on the 750W BBS02, found a 26" wheel built up with the original Nuvinci hub for the right price, will share when I've more to report.

Just today I put the 750w BBS02 on a 2014 Mundo 4.3 for commuting. Issues encountered:

- It needs a speedometer extension cable to setup the speedo sensor, as the attached cable is too short for the Mundo frame.
- The included trigger style throttle can be a pain with other trigger shifters on the bar. Give some thought to the right hand shift/throttle interactions. On mine, I'll be keeping trigger shifters for gearing and switching the Bafang over to a motorcycle style throttle. With an internal hub like a Nuvinci I'd probably do the opposite and the included throttle would be fine.
- I really wanted to fit a battery to the area between the seat tube and rear wheel; as it happens my frame pack battery is a just a hair to wide to fit there. I put it on the downtube, which is fine. With better planning I might have found a battery to fit back there. I'm trying to keep the cargo rack and accessories free of batteries.
- The short cable from the controller to the pedal assist level controller limits the options for the controller on the handlebar, as does the controller mount itself. On my bar (which is the current factory bar for a Mundo, with a big sweep), with the Bafang controller centered, there is no way to put the pedal assist level switch in the most convenient thumb position at the left hand. I'm still playing with it.

In spite of those issues, I got to ride it around a bunch. The lack of speedo sensor throws an error21 code, but the error did not prevent the system from working. I am impressed with this kit.

Update: I did in fact talk to Daniel, the guy who has the Yuba linked via the ichibike link. He actually voted AGAINST running a Nuvinci with this setup, as he went through 2 Nuvinci units with the Bafang and damaged them both. He's running a Rohloff, which obviously works great but isn't in my budget. The Shimano Nexus or Alfine 8 (same internals) costs about 1/10 the Rohloff and has been used in a few endless-sphere projects running MUCH high power levels without significant incident.

He got his wheelbuilds through choppersus.com . Their site shows some pretty impressive machinery and quality control being used to lace, true, load test, and retrue their wheelbuilds before shipping. The DHL65 rim from Weinmann is widely available in 26" 32 hole on line for about $50, but I can't find the manufacturer-available 24" or 36 hole sizes anywhere and that's what I need for a strong wheel and to match up with the 36h Nexus 8 hub. Apparently Choppers.us has these available.

He didn't report having any issue installing the Bafang BBSO2 kit. I guess the Yuba is so long that the speedo doesn't reach? I'll take some measurements.

So: current plan is to move forward with a wheelbuild using Weinmann DHL42 24" rims on a Shimano Nexus 8 roller brake hub with IM80 roller brake, then running 24"x3.0 tires (Felt Thick Brick balloon tires for spring and summer riding, Felt Berm Master for winter/snow riding). This wheelbuild (front disc and rear IGH) will cost about 440 shipped, which is not that bad in the end and should be robust.

Sorry for the disjointed post, trying to get the info down on paper before I forget.

Next up: Double Kickstand choices. Stock Yuba accessory is 75$, Rolling Jackass (highly recommended) is $350 !!!!!. Have to look into other options, including the Velo Orange double kickstand, which seems good for the price ($30 I believe)

Pulled the trigger on a DHL65, 57mm bead seat 26" wheel build from choppersus.com . 8 speed nexus roller brake rear, matching wheel built onto disc hub in the front. Should arrive in the next couple weeks.

For 26" tires, I've been looking at the Vee Rubber Speedster 26x3.5 (otherwise known as the Sunlite Crusher if you're looking for a wire bead tire), but I have heard some bad stuff about it in terms of flats and self-steer. I'll be running it at pretty high pressure so the self steer shouldn't be an issue, but I'm worried about flats.

I have a pair of Schwalbe Marathon Plus Touring tires that would fit, and probably look nice and fat (almost like a motorcycle tire profile), but it wouldn't give me any cushion on my ugly Pittsburgh PA roads.

Cream Fat Franks would look great but suffer a similar problem.

The BOA-G Tire (available in cream color also) look good and have a perhaps more confidence-inspiring tread pattern, but these are also tires made for cruisers and make me concerned about longevity.

I guess I'm just going to do a lot of playing around

I pulled the PING 48V15AH pack from my other ebike commuter (3000 miles and almost 500 cycles! but only to like 20% DOD) and need to find where in the Yuba to place it, as well as the cheapo Chinese charger to match. Because of weatherability, I'd like to seal up the battery and charger in a pretty air tight way like I did on my last commuter, but with an aircooled charger I'm not sure that works.

Recommendations on a 2-5A capable, 60V dumb charger that would be appropriate to charge my 16S Ping LiFePO4 battery (with its attached Signalab BMS)?

ttobiassen said:

Recommendations on a 2-5A capable, 60V dumb charger that would be appropriate to charge my 16S Ping LiFePO4 battery (with its attached Signalab BMS)?

Click to expand...

might wanna get this thorin - quite the opposite of dumb, but pretty neat:

http://endless-sphere.com/forums/viewtopic.php?f=14&t=60169&hilit=satiator

you have any pics of your bike yet? are you still around the corner from the shop?

my ebike is almost complete, also running a bbs02. i'llhaft swing by if you are.....

Len

ttobiassen said:

I have a pair of Schwalbe Marathon Plus Touring tires that would fit, and probably look nice and fat (almost like a motorcycle tire profile), but it wouldn't give me any cushion on my ugly Pittsburgh PA roads.

Click to expand...

What about Maxxis Hookworms in the 26x2.5". Great rubber and will still give you some good cushion. More of a three season tire though, I don't know how well they'll do in the snow.

ttobiassen said:

I pulled the PING 48V15AH pack from my other ebike commuter (3000 miles and almost 500 cycles! but only to like 20% DOD) and need to find where in the Yuba to place it, as well as the cheapo Chinese charger to match. Because of weatherability, I'd like to seal up the battery and charger in a pretty air tight way like I did on my last commuter, but with an aircooled charger I'm not sure that works.

Recommendations on a 2-5A capable, 60V dumb charger that would be appropriate to charge my 16S Ping LiFePO4 battery (with its attached Signalab BMS)?

Click to expand...

The BMSbattery alloy chargers are actually really good. http://www.bmsbattery.com/alloy-shell/25-alloy-shell-240w-lifepo4li-ionlead-acid-battery-ebike-charger.html

I've got that 240w one and it's been working great for the last 18 months. Fast and good quality. I'm planning a 1,000-ish mile trip this winter and I'll probably use a couple of their 600w chargers. I'll open them up and spray them with conformal coating to largely waterproof them.

If you want to go totally waterproof though you've got use a sealed charger, which means probably not much more than 2A charge rate. Kinda slow for that big ping, but it'd be much healthier for the battery in the long run.

[edit: I'll also be interested to follow your BBS02 experience. Where'd you pick it up? I think The BBS02 will be perfect for Pittsburgh. I really want to try one, but it'd be kind of wasted in Tel Aviv, which is flat as a pancake.]

mlt34 said:

What about Maxxis Hookworms in the 26x2.5". Great rubber and will still give you some good cushion. More of a three season tire though, I don't know how well they'll do in the snow.

Click to expand...

I don't have a Yuba Mundo, but I have Maxxis Hookworms and love them! I took my bike out in the snow and it would do wheelies before spinning out unless I leaned all the way over the bars. I would not go any faster than 15 mph in the snow with them but I had a fun time in the snow with the Maxxis Hookworms. The snow was pretty much fresh powder.

ttobiassen said:

For 26" tires, I've been looking at the Vee Rubber Speedster 26x3.5 (otherwise known as the Sunlite Crusher if you're looking for a wire bead tire), but I have heard some bad stuff about it in terms of flats and self-steer. I'll be running it at pretty high pressure so the self steer shouldn't be an issue, but I'm worried about flats.

Click to expand...

I have used the Vee Rubber Speedsters for months on the streets of Sacramento and love them. You are right about the self steer, as you do get that if you run low pressure. I have been running 26 lbs min, and it works great. These things roll so nice. The issue with flats on these is that the tread picks up so many small pebbles and of course small thorn tips too. I came up with a solution though. I cut a 29" thick-wall MTB tube down the inside so as to make a long strip and placed that over the inner tube, between the tire and tube. It is almost long enough but I rarely have a flat. I weighed the tube and the "strip" and it came out less weight than if I used slime and the tube. The only issue I have had is, the other day I ran over a sharp object that cut a 2" slice in my sidewall, but these are street tires. I really can't blame the tires for that. If you want to try them the best deal is Ebay for the Origin 8 Captiv-8er UL, which is exactly the same tire...just made for Origin by Vee Rubber. I got them for $52.99 delivered to my door. They are black sidewalls.

Electro-Fox

The Yuba is coming together!

I got the Sunlite Crusher (wire bead) tires mounted (with difficulty) on the DHL65 wheelbuild and they look sweet. They do NOT fit in the stock Yuba fork, which I am replacing with a Surly Pugsley (100 mm over-lockout version from 2012, since my hubs are 100 mm instead of the 135 common to newer fat bike builds).

There will be some shimming and such to get the chainline to line up, but the BBS02 mounted very easily. The Yuba doesn't have any brake or shifter cables running under the bottom bracket, so that was easy.

What will be probably the trickiest bit is mounting the Ping 48V15AH pack in the triangle. Despite the Yuba being a huge bike, it actually doesn't have a very big triangle, and the downtube has an aggressively oval cross section (seriously. Like 1.5x3 inch) which will be more difficult to make tube blocks for. I'm thinking some 3d printed adaptors will do the job.

I'll update when I have some more progress.

Looks deceivingly close to completion...

Did you get it finished? I've come across the same idea from a different angle. Currently my "goto" bike is an Xtracycle freeradical kit built on a sturdy Norco frame but it's impossible to get spare parts for in my part of the world so the Yuba frame kit stands out.
having built a couple FWD hubs and RWD hubs I was tempted to go 2WD but mid drive is next. I'm now ordering a Mundo frame, a 350 BBS01 and next is getting some fat wheels built.
Have always liked wide tyres 2.5" on my MTB's and 28-32mm on my road bikes but keen to go full fat or at least 3.5".
The longtail idea is almost mandatory as I have twinfants.
Tempted by BBBS02 but our limit is 200w or 250w pedelec and the 350w can always be made road legal if necessary.

Anyway enough about me tell me you got it done.

Now that this got bumped and I'm reminded, I'm curious too! The last picture was sweet looking, hopefully you've got it done and it's working great.

I've been driving the YUBA around for a couple months now. Certainly looks pretty sweet:





BUT! It is not without problems, some specific to the frame, Nexus IGH, and some with the BAFANG BBS02

Problem A: Yuba Dropouts in concert with unconventional Nexus shaft.

The Yuba is built to accept 14mm BMX-style super beefy axles, so it has a 14mm dropouts. The Nexus IGH is designed to fit into 10mm dropouts, so it has M10 threaded axles with 8mm flats. This presents a problem in terms of the fact that the IGH needs a very specific orientation for the shifter cable guide arm to be position correctly, as well as the fact that trying to adapt DOWN to a 10mm round with 8mm flats is pretty tough because that's not a lot to hold onto in order to prevent axle rotation with, in first gear, maybe up to 50 lb-ft of torque. The IGH adaptor thingies Yuba will sell you are aluminum and super sloppy in tolerance, so I didn't trust them. The dropout material is 5mm plate (~.197 inch), so a 3/16" (.1875) torque arm could be inserted INTO the dropout, sandwiched between the hub collar and the big nut you throw on when installing the hub. So, the first thing I did was laser cut .125" stainless steel (1/8" is the thickest my laser cutter can cut, so this was the lazy option) and threw them in there so I could start riding.



Trouble with this is that that's QTY2 1/8" thick stainless torque arms, which didn't end up working. 316 SS sheet is maybe Rockwell B 80-90 (ie, NOT on the C scale, which is sort of the minimum for something to be considered 'hard'). So, riding home after week 2, the axle rotated on me and broke a couple of the Nexus specific plastic indexer thingies, which I was luckily able to replace because a local bike shop had some spare ones sitting around. The 8mm 'flats' on the torque washer were basically threaded M10, so that sucks.

Having done the lazy thing the first time, I went crazy the second time. I non-contact laser scanned the dropouts on the YUBA, used surfacing software to reverse engineer the dropouts, matched a torque arm design in Solidworks to the dropout and frame, analyzed it in FEA, 3Dprinted a test piece, machined a practice piece out of acrylic, and then machined the final piece out of 1018 mild steel.



The new design *should* be able to take the torque. 1018 can't really be hardened easily, so I'm stuck with the hardness I have (high Rockwell B, low Rockwell C maybe), but the thickness of engagment on the brake side of the dropout is now .375 instead of .125, AND I laser cut another of the .125 'lazy washer' for the far side. There's a threaded hole for #8-32 thread with a grade 8, cadmium plated screw to preload the flatted shape in one direction, which should prevent it from wiggling around, though there's not a lot of room to wiggle anyway:



I have a friend sending some parts out for nickel plating, so I may send this part out in that batch to make it rust proof and to add a couple thousandths of material for wear purposes.


Problem B: Gearing of the BBS02

The stock sprocket that came with my 750W (actually 1000-1200W probably) drive is a 48t chainring. I have an 8 speed IGH with 307% gear range. My goal from the beginning of the project was to be able to take myself, my heavy bike, and a passenger (or other 200 pound cargo) up a 15% grade WITHOUT PEDALING OR OVERHEATING. It's a pretty tall order.

Currently, in top gear I'm electronically limited, but pretty much power limited: I get up to the 30mph limit the BAFANG stops you at, but only just. I feel like if I reduce the gearing by 25%, I won't necessarily lose 25% of my speed, and with aerodynamic effects having such a big role above 20mph, I'm guessing I'd still hit 27 or 28.

In lowest gear, with just me on the bike, it bogs down in 1st gear enough on a 20% grade that I feel compelled to pedal (paranoid about the motor overheating). So, to get me and another fatass up a 15% grade, I'm hoping a 25% reduction will do the trick, but it may not. I wish the BAFANG was on the simulator on ebikes.ca, and I'm guessing I'm not the only person who has wished that .

So, I'm making a custom spider to adapt from the weirdo bolt pattern of the BAFANG to a standard 110 BCD chainring. I don't want to use aluminum chainrings (seemingly the only singlespeed chainrings available online), so I went to a local shop and bought a second hand, approx 3mm thick STEEL chainring for $1 . It's 39t, which is a bit higher than I wanted (about 20% reduction only), but that should mean I still get almost 30mph, which is PLENTY of speed, if not a bit too much for this big bike. I'm used to a much smaller ebike with a pretty slack head tube angle, so the YUBA handles like a boat in comparison.

The lowest 110 BCD tooth count is probably 34t, which means the max reduction I can do without going down to 104 BCD is 30%, so hopefully that will be enough.

Problem C: Roller brakes

I opted for a roller brake hub build in the rear because that's what was available on choppersus.com for my fat rims. I had read that lots of cargo bike owners have them, recommend them, etc. I think the problem is that most cargo bike owners don't want to carry two 200 lb persons at 25-30mph. I would really have preferred some nice hydraulic discs in the rear. I may run a dual-pull lever and set it up so that the first cable engages the roller brake as soon as the lever is pulled, and the second cable engages a v-brake on the fat rim as you start to pull harder, thus granting better emergency braking. The rim isn't really designed to be braked on the rim section, but I figure I can set it up so that it won't wear normally and will only apply in an emergency situation. We shall see.

Problem D: Fat Tires

My tires are too fat. I need to put them on a diet. In the rear, I have about a mm of clearance, on a good day, from a certain portion of the frame. This is so close that gravel and debris picked up on the road on a rainy day rubs against the frame, causing eventual paint wear and rust in the long term, and an annoying noise while riding. The chain is also slapping against the sidewall from time to time, which can't be good. The tires are 26x3.5, though they run a little bigger than that I think. A 3.0 tire would have been plenty big, but I had some trouble getting ones that were actually decent rubber and not just some crappy tires for a beach cruiser. Suggestions on a 2.5-3.25 road-friendly fat tire are appreciated.

Overall, I'm not sure this project turned out as well as hoped, though it should prove to be a reliable commuter. Practicality, however, isn't always as fun as you want it to be. Anyway, ask any questions you have, and I'll try to remember to post updates!

I really enjoy and appreciate the update as I have been long considering the bbs02 for my yuba.

Running a 5404 in it now so I had similar issues with the rear dropouts. I installed kiwi adapters from the
link below and they were a great help. It was still a bit sloppy so on top of those I added some ebikes.ca
torq arms v2 and that pretty much kept it all nice and tight. Just a pita to remove.

http://endless-sphere.com/forums/viewtopic.php?f=31&t=31881



Your bike sure looks stealthy and light. I have a 24s 20ah a123 battery on the back rack in a box that is fine
until I stop and lean so always have to keep it in mind. Would love to have less weight just not sure if I
can give up the brutal exceleration I have now. People don't expect me to take off like I do.

Anyway thanks again for sharing I do get a lot out of your experiences.

5404 with 88.8V 20AH should be good for... 3000-4000 watts, depending on your controller. Sounds like a great time.

I'm pretty done with hubmotors for the time being because of a) practicality: I hate broken spokes and b) I like gearing. And I'm hesitant to go to a hubmotor that would be beefy enough to not break and powerful enough to not give a crap about gearing (CROmotors) because I like being a bit stealthy.

I do have a TRANSMAG around that would be good for 3-4kW at 48V or 4-5kw at 72, but I'd have to rethink the batteries. Even given how big the Yuba is, somehow fitting batteries into it is still tricky. I'd probably go with some big Headways (the 15ah units, 100Aish peak).

A NOTE ON THE TORQUE ARM: I did research the Yuba torque arm options. There are many. Yuba itself has an option that is pretty obviously weak but would work for a 250 or 500w application. I saw the ones on the forums, including the one you linked. I just want people reading to know that the one you mentioned will NOT work because of the Nexus IGH shaft output being a weird size compared to a normal bike axle OR a hubmotor axle. If he recut the design to a different spec it would work fine though.

-T

So how close do the speedsters come in terms of diameter? I was always thing of doing one of these with a fat 29er setup, such as Surly Knards 3.0, but wonder if the overall diameter would fit. If not they have the 26 inch Knards which are also 3 inches wide. So Knards in 3 inches wide, either 26 or 29 inch diameter whatever fits best. I used to use the Speedsters on my Fat Bike but flats were such a pain. I got the Knards 3.8 inch wide and love them, especially since I went tubeless, not flats at all...(knock on wood) The ride is really quite good and they have a round profile, no self steer and good on gravel roads too. I also wondered about using Surly Rabbit Hole rim on the Yuba too, as I think it would look cool. Of course I would not be loading mine down much, if I ever pull the trigger. I envy you being able to play around with it though.

I'm placing an order soon for a Bafang BBS02 on my Mundo 4.1.
Are people going with a 44t chainring? I've got occasional steep hills but mostly lower angle streets. Probably going to put a Velo Orange Chainguard on as well.
I'm also trying to put the battery behind the seat stay tube along the lines of what Yuba did with the eZee 10ah battery pack.


It has the advantage of not blocking the center triangle and still being lockable. The disadvantages are that it's a bit of a contrained space. The batteries Yuba included were only 10ah and I'm hoping for a 12 or 13ah at least. Additionally it moves the weight towards the rear which will already have cargo, passengers, etc
I was going to go with a left thumb throttle because I'm losing the triple chainring and front shifter anyway.

Following up on my inquiry from last year I thought I'd post a photo to show that indeed the rear battery rack (that's a 52v) does fit in the Mundo frame behind the seat stay -- but just barely. As you can see I used some flexible metal strips and hose clamps to attach the battery to the frame. I'm pretty happy with the result and glad to not have tied up the triangle and bottle cage area with a Dolphin pack. Cheers, Nico

Taking a long chained bicycle on jarring roads takes a toll on the drive train. Chain slap and buying 2-3x chain purchases at a time is a small PITA. In my case, I'm now at the point in my bike, I'm getting front chain drop (replace/upgrade the front cog), replacing the chain every 4-6 months, and hopefully not destroy & replace my rear rims <2 years time :lol: . I want the next revolution to be belted longtail Ebikes.