Several Yuba Mundo Builds

[Kiwi]

I will add all these to my for sale thread when they are manufactured and proven.

Here is the concept for the YuNu adapters. (note only for 171 series and developers kit. Not sure about 360 yet)

There will be 3 types of Nuvinci adapter for the Yuba.
1, YuNu keys. These simply fill in the missing space in the drop outs. They would be fine for pedal only setups or 300w or less setups. Also provide for chain tensioning. Needed to position the axle with the following torque plates.

2. Static Torque plates, like the plates for standard motors, only cut to suit the Nuvinci. You will need a chain tensioning device with these. Suitable for hi power setups. Good for mid drive setups if you can shift the motor mount to tension the chain.

3. Tensioning torque plates. These allow for the tensioning of the chain in high power mid drive applications. I will release these for standard rear hub motors, for use as single speed.

Keys shown below.


Static plates



Tensioning torque plates


And adjuster


Now, the reason the adjuster has indexing is so the weight of the bike always pushes the reaction plate against the frame tube.
If it was just a slot, then the reaction plate could slide down, effectively useless. So when you set it to tension your chain, you choose the index below so the plate pushes on the frame before the chain tension stops it from moving.

Complete




Not sure of cost yet. The keys will be cheap, the static arms will be about $40 a pair including the keys, the adjustable ones probably about $50 a pair. So not too bad.

[snowranger]

Great work Kiwi. You addressed all my needs concerning the nuvinci.

I'm wondering how the disc brake compatibility works with an adjustable axle position.

[Kiwi]

...yep, thats a tricky one. Not very well. That would require yuba making slotted disk mounts at the same angle as the wheel drop out. If you had a large rotor, an adapter could be made.

[Alan B]

Very nice work.

I'm considering a V4 Mundo with two rear hubmotors. One in the rear wheel, and one mounted just forward of the rear wheel driving the rear wheel via 1:1 cogs and chain. The cogs would be mounted on the motor disc mounts. The motors might be a pair of HS3540's. Do you think there is room for the chainline? Would it be difficult to mount the forward motor?

[Kiwi]

I am going to look at fitting the HS/NC/Xlyte in the space, but it looks tight. A simpler way would be to have the second motor in the front wheel.

[urbancommuterstore.com]

Very nice work.

I'm considering a V4 Mundo with two rear hubmotors. One in the rear wheel, and one mounted just forward of the rear wheel driving the rear wheel via 1:1 cogs and chain. The cogs would be mounted on the motor disc mounts. The motors might be a pair of HS3540's. Do you think there is room for the chainline? Would it be difficult to mount the forward motor?

I was going to go that route before I finally settled into what I currently built for the V3.3/V4. Achieving a good chainline is impossible not unless you use a jackshaft and another fixed gear cog to line up to the rear motor's disc rotor mount. You will also be limited to using 26 x 2.0 or narrower rear tire. Chain rubbing on the side walls will be an issue too with wider 2.3 / 2.4 Maxxis Hookworm tires or Schwalbe Big Apples.

[Alan B]

Interesting point. Wonder why there is not enough room for chain on the left side. Seems like no problem on the right side.

Maybe the disc brake mount is not far enough out. That probably depends on the motor in question.

Thanks, will look at that.

By the way, your motor setup looks nice. Which hubmotor is that, or what are its specs?

[urbancommuterstore.com]

It's a MAC 8T Geared Hub Motor. The Hub's mounting holes are too near the rear drop out. If you situate a chain coming from the motor mount, it will rub on the chain stay. With the setup you mentioned, aligning both left sides of the hub motors will be hard plus the chain rub on the chain stay. As kiwi have mentioned, the second hub motor will be ideally up in the front fork.

[Alan B]

Putting the hubmotor in the front fork is one way to do it, but it is far from ideal. I would prefer to have a suspension front fork, and this is not a good combination for a hubmotor. The traction of the front wheel is not great, and loss of traction there leads to an instant loss of control. With a heavy bike the rear wheel has nearly all the traction. The front wheel has only a fraction of it.

Doubling the power to the rear wheel is in many respects much more desirable. And if it can be worked out, much easier than dealing with all the front wheel issues.

Thanks for looking at this.

The biggest problem is finding a mounting and chainline for the central motor. Seems that folks have been able to do this with central motors on many other bikes, but perhaps the Yuba frame is in some way unsuitable. It looks like the V4 frame has a lot more space for this than previous frames, but perhaps this is not the case.

[teklektik]

I have a Mundo V4 with front and rear BMC V2S hub gear motors and the arrangement works out very well. I have a left thumb toggle to cut the front motor in or out (both run from the same throttle) and actually only kick it in for hills. I do wish for some suspension, but 95% of the time it's a great ride. On the flats and low grades, the rear motor pushes things along nicely, but kicking in the second motor is like night and day. In a real pinch, a second left thumb toggle suppresses the CA current limiting and the two motors run flat out to chew up hills. This thumb toggle approach (w/o requiring release of the grips) makes it effortless to select the amount of motor/current to apply much in the manner of diddling an index shifter.

On pavement the front wheel spins briefly from a dead stop if I launch with both motors and no limiting to bolt across a high traffic intersection (not recommended to extend gear life BTW), but otherwise for street use the front hub motor is well behaved since the bike is usually already rolling along at a good clip when it's cut in for a boost.

So, I guess the point is that in my case, I do not off-road the heavy cargo bike and common stand-alone front motor issues do not arise in this dual motor application because of the controls and particular use case. If you give this a try, I'll wager you will like it ....

[Kiwi]

I have been playing around the last few days with my new ezee mundo. I slapped a rear 8x8 in it along with leaving the front ezee. Both on seperate systems, 8x8 48v20A, ezee 36v22amps. Can run around on the 8x8, then when the hills come hit the ezee. With both motors it hauls up hills, even with low power setups on each motor. Its not a bad set up as I still get regen braking, but am not turning a DD motor on the front. Motor speeds with this set up seem to work well together.

[teklektik]

Kiwi - I think our riding experiences with dual motor rigs are very similar. However, I chose to use the same BMC V2S gear motors front and rear so the load would always be equally shared regardless of load, speed, and throttle setting. This may not be necessary, but it has worked out well and the result is a system that reaches a few percent higher speed on the flat above what a single motor will do, but gets there PDQ. The nifty part is the available torque for hill climbing: Running rear-only, a hill may cause the bike to grind down under 10mph, but kicking in the second (front) motor will suddenly accelerate up the hill. Having the manual thumb toggles mentioned above lets you switch to two motors in advance so you don't actually ever experience this kind of slowdown and recovery... when you eyeball an impending demanding climb, you just back off the throttle briefly, kick in the second motor, and sweep up the throttle to maintain the current speed smoothly but with twice the torque on tap. With freewheeling gear motors, it all happens in a blink without a glitch.

I run the motors current limited to 800W each - 33% above the rated 600W but they are never more than warm to the touch. This dual motor approach seems a good way to easily and safely pull 1600W while keeping the ability to be thrifty on the flat. By suppressing the CA limiting for a few minutes, you can easily pull 2.4KW to crest tough hills. I have a solid 30+ mile range on a 48v 20Ah Headway pack (to 80% discharge) over mixed hilly/flat New England terrain with occasional short 15+% grades. Time will tell, but the rig does not heat or protest in any way and operates smoothly and effortlessly.

There is really not a lot of available descriptive material on dual motor builds but it seems safe to say that many of the conventional anecdotal experiences with single front motor builds may not be directly applicable - a dual motor build is (or can be) a different animal in the same manner that AWD cars offer advantages over certain (similar) troublesome control and traction characteristics of FWD.

For those readers that are leery of reported gear motor failures (stripped gears or melted windings), I can only note that most appear to have arisen from gross overpowering and high power dead starts. A Cycle Analyst is a 'must' and can easily limit power to keep these torquey motors in the specified operating envelope, making them an attractive choice for hauling a heavy cargo bike up substantial hills. I use a single standalone CA that limits total power to 800W when running a single motor and 1600W when switched to two (on the fly) with a common battery, shunt, and CA (this gimmick would not be as effective if the front and rear motors/controllers/wheels were not identical...).

[Kiwi]

Our main Yuba, me and son taking a 200l barrel full of bird netting to neighboring farm. Had to counter balance about 10 deg.

[Rifle]

Ha! If only you had to take two of those.

Finally got my friends bike together like 2 months late (just in time for winter... :/) cuz he destroyed the BMS. Gonna run 72v 22amp on a 9C 2710 rear. Might up the amps to 25 if it doesn't climb well enough. That'd put us at slighty more watts than your dual set-ups but I'm bettin' probably still not as good hill climbing since there's no geared motor in the equation. His lady lives up probably a 10% grade. Hopefully it's enough to get them up it.

[Kiwi]

I turned up at the BMX track with my kids on the back of the cargo, one of the senior racers asked for a go. This is what happened. Spent the next hour taking kids for rides around the track.

[ryan]

Hahaha! Awesome! I want to see it get some air.

[thewall241]

Nice Kiwi, good to see the yuba tearing up the track. Hey there is a cromo-lite frame on TM at the moment, not quite a d-8 but could still be a pretty solid start for a FS build.

[Kiwi]

Yeah I saw that. I really want the d8 as the shock is out of the way. I plan on cutting the frame and mid mounting a dd hub motor driving a nuvinci at the rear. I might be better off to start from scratch.

[ryan]

Hi fellow Yuba builders. Just wanted to let you know that I'm gaining ground on my v4 build with running board battery enclosures. The last of the parts are coming in over the next few weeks. I figured I'd share a couple shots along the way.

running-board 1.jpg (131.14 KiB) Viewed 555 times

running-board 2.jpg (152.77 KiB) Viewed 555 times

running-board 3.jpg (155.18 KiB) Viewed 555 times

Any other builds lately?

[ohzee]

I am going to do one in about a month or start and wow I think I know what I want to emulate.

love your holders how does that extra weight feel front wheel seem any different ?

Great work man.

[ryan]

Lol. No weight just yet. All talk so far.

My batteries get here later this week. I'll be running 18S4P (roughly 66.6v32Ah or 2131W-hr) in the running boards. It's going to be a tight fit, but I'll make it work.

My new motor (x5404) is still in China, so who knows when it gets here. I'll run the 5304 until it comes.

Here's the build thread.

[teklektik]

ryan- To minimize flex you may want to consider bolting up a front-to-back piece of angle or square tubing roughly parallel to the chainstay, under the bottom sideloader and inside the Mundo sideloader frame. An alternative might be a long rectangular solid inner panel fastened between the top and bottom decks on the inside face with cutout on the bottom for axle nut/derailleur. When you hit a bump, sideloader batteries pretty much try to launch into orbit and then re-enter to the core of the Earth. There's a lot of mass in play there that really wants to have its way; if it's attached to the sideloader, the unsupported area of the sideloader near the axle nut tends to flex up and down while bolted points around the edge are held in place.

With a separate metal/rigid battery box hung out on the sideloader things aren't too bad, but in your case the Mundo LDPE decks may result in cell assembly twists and flexes on every bump (Bzzzt! Bzzzt!).

I have sideloaders made of HDF which are loads more rigid than the Mundo ones, and they still get twanged pretty good by attached battery boxes. Anyhow - just a heads-up for something to keep your eye on - or maybe a little time-filler add-on while you're waiting for parts to arrive .

[itselectric]

Hi fellow Yuba builders. Just wanted to let you know that I'm gaining ground on my v4 build with running board battery enclosures.

Ryan:
That is an excellent idea for battery storage! May I copy your idea on my next Yuba build?

How are you planning to keep the enclosure water proof?

Ken

[Kiwi]

Hi All.

I have ordered 32 Yubas!
Anyone in NZ want one?

Also in development, universal battery case internal 300x150x110 (ping upto 36v20 or 48v15) or lipo.
Designed for Yuba but will fit most rigid frames.

Front and rear torque plates available, also nuvinci rear adapters available, both static and adjustable for chain tensioning.

Perhaps, later, a midmount bracket. Have worked it out on paper, still cant fit a 9C or xlyte, maybe if we turned of the spoke flange.

In build a 72v conversion using ezee batteries, lyen controller, NC 2808 front.

Kiwi.

[ryan]

Ryan:
That is an excellent idea for battery storage! May I copy your idea on my next Yuba build?

How are you planning to keep the enclosure water proof?

Ken

1) You can only copy if you promise to improve it. (and then share it here for others to improve on)

2) I'm unsure right now. I'm thinking of wrapping the packs in some yoga mats for padding. And then heat shrink most everything else. I don't typically ride in down pours so if it's generally resistant I'm probably alright. Any other ideas?