Several Yuba Mundo Builds

[grindz145]

I'm really regretting not building up a Yuba Mundo, instead of my xtracycle conversion. I managed to snap the rear of the Xtracycle clear off. It's a bit of a design flaw inherent in having a fully configurable setup. Looking at the design of the Yaba Mundo, I think I will weld the whole frame up to be a similar geometry to the Mundo by extending the the chromo up to the main bicycle frame.

 

[teklektik]

kiwi- Question: The V4 frames are approx 6" between cranks (2.75"L and 3.25"R of centerline). In two of your battery-box-in-frame images the BB cartridge seems to be protruding a bit on the left (I'm unfamiliar with the V2 frame - it's flush in V4). Were your battery boxes narrow enough to clear the stock crank setup or did you replace the stock Mundo cartridge with a slightly longer one to get more left crank clearance?

 

[boostjuice]

kiwi- Question: The V4 frames are approx 6" between cranks (2.75"L and 3.25"R of centerline). In two of your battery-box-in-frame images the BB cassette seems to be protruding a bit on the left (I'm unfamiliar with the V2 frame - it's flush in V4). Were your battery boxes narrow enough to clear the stock crank setup or did you replace the stock Mundo cassette with a slightly longer one to get more left crank clearance?

I think the word your looking for is 'spindle' rather than 'cassette'. The latter refers to a rear gear cluster.

 

[teklektik]

[I think the word your looking for is 'spindle' rather than 'cassette'. The latter refers to a rear gear cluster.

Thanks! Quite right - I actually meant to type 'cartridge' but brain missed a beat (stock is VP-BC73 113mm) Fixed.

 

[Kiwi]

HI, the battery case is 120mm wide and there is 14mm clearance between the crank arms and the battery case. This is with the standard crank axle and crank arms.
Sorry about the metric.

I am hoping to get the V4 frames (at least 1) some time soon. My thought would be to design a new box that goes behind the seat post, now that is clear. Try to get 36v20ah in there, or 48v15ah. This would get the weight lower in the frame, though it is pretty good in the triangle.

 

[teklektik]

HI, the battery case is 120mm wide and there is 14mm clearance between the crank arms and the battery case. This is with the standard crank axle and crank arms.

... My thought would be to design a new box that goes behind the seat post, now that is clear. Try to get 36v20ah in there, or 48v15ah. This would get the weight lower in the frame, though it is pretty good in the triangle.

Thanks again for the helpful build info. 120 + 2*14 = 148mm ~= 5.8in which is about the same as the V4 dimension.

The 'stokemonkey space' looks invitingly large but the cranks and chain intrude in unpleasant ways making it a bit of a 3D form-factor puzzle. I am using Headway cells but took a quick look at Ping cells after your post since your images seem to suggest a more compact pouch cell construction (or LiPo?). Although it was straightforward to configure 48v10AH of 38120S Headway in there, the standard Ping battery (300x105x150mm) for your desired V/AH ratings does not fit.

UPDATE: However, it appears that a battery of Ping cells could be squeezed in using an asymmetrical battery enclosure and a two block custom battery package: for 48v15AH - 225x105x150mm (36v15AH) over the chain and 75x105x150mm (12v15AH) beside the chain. The basic Ping 'battery build unit' = 12v5AH = 1.0x4.1x5.9in = 25x105x150mm (not strictly true, but a useful simplification if parallel 12v5AH cell groups are constrained to reside in the same block of cells). Each brand of cell presents its own packaging issues, but it's nice to see that some of the more common battery solutions can use this space.

I'd be interested in your thoughts when you can get one of the new frames in hand...

 

[Richard N]

Hello Kiwi

I hate to bump a thread with the same question but I was wondering how your build with the batteries located in the area below the Mundo's running boards is going? Details of how you are doing it and the batteries you are using would be great, pictures would be awesome too.

Regards
Richard

 

[Kiwi]

Hi,

I have had custom long packs made by ping, so 36v10ah either side.
However, I have put this project on hold as I wait for the V4 cargo to arrive.
Once I get that I will build it up with the "hidden" batteries.

....waiting.

 

[Richard N]

Hi,

I have had custom long packs made by ping, so 36v10ah either side.
However, I have put this project on hold as I wait for the V4 cargo to arrive.
Once I get that I will build it up with the "hidden" batteries.

....waiting.

Outstanding, will you be doing 36v20ah or 72v10ah? I can't wait to see the results.

 

[Kiwi]

Well, I have run it on 72v before, naturally its great, but we dont need all that speed. I have a NC and new Crystalyte hubs, so might run 36 at 40-50amps.
Or 72 and set the controller up to half speed with a push button "boost" to full speed for fun.

I am working to have rear torque arms for the V4 mundo in the next few weeks for those who want to put NC or Xlyte on the rear.
Fronts a bit later.

 

[ryan]

Updated schematic for Kiwi's torque arms (without the 11.1mm mistake):



Any recommendation on thickness?

 

[Kiwi]

Please note above is for version 2 mundo.
To use this design on version 4 mundo, change vertical dimension (16mm) to 21mm. Also change angle (70deg) to 65 deg.

For sale, zinc plated 6mm (1/4") rear mundo torque plates.
I have both V2, new V4 model (improved over above design) now suits, xlyte, NC and Ezee rear motors.

Also, some respect, please use the design to make one for your self, but please don't make them and sell them, if you want to sell them, contact me I am more than happy to come to an agreement for resale.

Kiwi.

 

[auraslip]

Hey kiwi,
These are some of the nicest conversions I've seen. Any chance I could do an ebike of the week feature on them? Thanks!

 

[MikeFairbanks]

I just stumbled on this thread.

Those are killer! Great job, Kiwi.

Man, NZ must be a cool place to have such creative things going on.

It's got to be Gandolf. That dude could inspire anyone.

 

[Kiwi]

..well I did have Andy Sirkis (Gollum) riding one of the cargo's the other day when I was doing a demo to the Weta guys.

auraslip..would be honored.

 

[auraslip]

Thanks kiwi, it turned out great. Enjoy!

https://sites.google.com/site/shelbyelectro/Bike-of-the-week/EV-labs-Yuba-Mundo

 

[teklektik]

Slotted axle adapters now available directly from Yuba:
http://yubaride.com/yubashop/product.php?id_product=67

 

[Richard N]

Slotted axle adapters now available directly from Yuba:
http://yubaride.com/yubashop/product.php?id_product=67

Interesting, I wonder how well they work. It seems like Kiwi's design offers a longer lever and potentially a firmer hold on the axle.

 

[Philistine]

I have just powered up a Yuba Mundo V4, with 48V(13S)@40amps, on a X5304. Kiwi kindly sent me some of his torque plates from his initial run (for the V3), and they worked great, but didn't quite fit (hence his new design being longer and wider). As soon as he has them made up (the new wider longer ones) I will be buying a pair from him. I could be wrong, but I wouldn't be that confident that those Torque Washers from Yuba would be strong enough to hold the axle (on 48V with a 5304). I could be wrong, but in my view that is designed for their "Ezee" model, which is probably a low amp 36V motor (certainly legal for US purposes anyway I am sure). I could be wrong, but I wouldn't be confident that merely a washer holding the axle inside the dropout would be enough. You would be relying on the washer not cutting into the frame (being not much bigger than the axle itself). I would much rather a torque plate that held itself with more surface area like Kiwi's does.

Just my two cents.

I will post up photos of my Yuba build in the next few days. I have two kids seats on it, it is so practical.

 

[teklektik]

Slotted axle adapters now available directly from Yuba:
http://yubaride.com/yubashop/product.php?id_product=67

Interesting, I wonder how well they work. It seems like Kiwi's design offers a longer lever and potentially a firmer hold on the axle.

I could be wrong, but I wouldn't be confident that merely a washer holding the axle inside the dropout would be enough. You would be relying on the washer not cutting into the frame (being not much bigger than the axle itself). I would much rather a torque plate that held itself with more surface area like Kiwi's does.

The Mundo washers are stainless and a nice fit; they seem an easy means to get on the road if you are not running with monster power and heavy loads. However, I share your thoughts that a longer effective torque arm would inspire more confidence, particularly grinding a cargo bike up hills.

In any case, they solve the axle size adaptation issue, opening the door to more conventional torque arm strategies. With the axle positioned using the Mundo washers, high torque issues can be addressed using off-the-shelf torque arms - there is plenty of room to drill the trailing side of the rear Mundo dropout plate to bolt one of many retail torque arms with only minor tinkering. Kiwi's solution is very slick but the washers can afford a readily available component of a fully retail solution. I can see this as the strategy of choice for bike shops.

 

[Philistine]

I wasn't thinking that the washers could warp or bend, but rather that the washer could dig into the frame (being that the washer is such a small surface area, so could cut into the frame and misshape the dropouts. For example, running 13S/40amps, with Kiwis first run torque arms (that he made for the V3, so they were not long enough for my V4), the points are digging into the frame. Never underestimate the force of torque from these axles is my view, and the point I am making is with those washers the surface area is so small, I personally think they would dig into the frame. The point I am trying to make is, the washers don't do much more than what happens when a 10mm axle slides tightly into a standard dropout, you still add torque "arms" because the axle will simply slice into the frame dopout, how would this be any different? The whole point about torque arms is that they increase leverage and surface area to stop rotation, the washers simply make the axle a tight fit in the dropout, they add very little leverage or surface area. My view is those washers would be good for 200W or 800W (or whatever the US legal limit is), but over 1000W and I would want to see a "real" torque arm. Just my view as someone who has underestimated torque arm matters and consequently blown dropouts and controllers over 5 times in other bikes.

 

[teklektik]

Philistine wrote: My view is those washers would be good for 200W or 800W (or whatever the US legal limit is), but over 1000W and I would want to see a "real" torque arm. Just my view as someone who has underestimated torque arm matters and consequently blown dropouts and controllers over 5 times in other bikes.

The short form:
I believe we share the same concern over the washers being a total solution, but I see value even if they turn out to only be a partial solution. There are two issues with rear drive Mundo builds: adapting the shaft size to the 14mm Mundo dropout slot and addressing the usual torque issues with the flatted hubmotor shaft in the dropouts. The Kiwi plates as well as the Mundo washers attempt to address both problems with a single solution. I believe that the washers do effectively address the size problem although they make me uncomfortable as an unproven solution to the (high) torque problem. We seem to differ in that I am certain that they provide a substantially improved situation for the torque issue in comparison to the standard 10mm dropout/bare shaft situation. Until there is some market experience with them, the nervous folks (me, for instance) can add a standard 'real' torque arm as insurance to get a readily available two part solution. This is simply an alternative to obtaining Kiwi's custom plates from NZ.

The long form:

Philistine wrote: I wasn't thinking that the washers could warp or bend, but rather that the washer could dig into the frame (being that the washer is such a small surface area, so could cut into the frame and misshape the dropouts.

Since I have a pair of washers in hand, I was giving a a 'mini-review' to indicate that the washers are of a strong material and have a good fit to the dropout - they are new and most readers have never seen one. This was only to take any questions about implementation off the table (the quality of the materials or accuracy of the machining), either of which could degrade functionality separate from evaluation of the design strategy.

Philistine wrote: The point I am trying to make is, the washers don't do much more than what happens when a 10mm axle slides tightly into a standard dropout, you still add torque "arms" because the axle will simply slice into the frame dropout, how would this be any different? The whole point about torque arms is that they increase leverage and surface area to stop rotation, the washers simply make the axle a tight fit in the dropout, they add very little leverage or surface area.

I think you are overlooking the geometry of the washers. The length of the torque arm is primarily concerned with minimizing the force at the contact or fastening point of the effective torque arm in order to minimize dropout/frame deformation that will lead to failure. In the case of the standard hubmotor/dropout scenario w/o torque arm, the small geometry requires very little dropout deformation to allow the shaft to rotate (14mm shaft, 10mm shaft face, 10mm dropout: (14-10)/2 = 2mm radially). In the case of the Mundo washer, a relatively large amount of deformation would need to occur to allow rotation (28mm washer diameter, 25mm face, 14mm dropout: (28-14)/2 = 7mm radially) ). These require deforming very different amounts of metal and present very different situations. This is not to say that the washers will hold 2000W, but they appear very much stronger than the standard bare shaft scenario.

And in the end, this element of the design is not particularly important if an auxiliary 'real' torque arm is added, leaving the washers to primarily solve the shaft size issue....

 

[auraslip]

If yuba made these with clamping dropouts, they would be the go to bikes for serious electric work bikes.

 

[teklektik]

If yuba made these with clamping dropouts, they would be the go to bikes for serious electric work bikes.

An interesting thought, although I suspect that the immediate Yuba strategy (re: Mundo washers) is less an attempt to get ahead of the rear-wheel-conversion pack and more about just becoming a viable competitor. With the recent StokeMonkey-friendly frame change and the new washers, Yuba seems to have leveled the playing field for DIY/3rdParty rear wheel electrification where before they were at a market disadvantage because of difficulties associated with unusable frame space and the plus-sized rear axle...

 

[Philistine]

I agree with all your points Teklektik. Personally I am considering getting the washers, and also using the Kiwi plates as well.

Currently I use the V1 Kiwi plates (which as I said are too short, so they start to rotate), and I also run (on both sides) Ebikes.ca torque arms, held on with steel hose clamps. Keeping in mind that I do use ebrakes, so the force wrenches both ways. But the force/torque has been such that it has forced my axle down the dropout, and caused the hoseclamps on both sides to break. As I said, the torque plates are not long enough, nor wide enough currently, but the force is such that the twisting of the plate forces the axle down the dropout (and splitting both hoseclamps). I think the washers would be a good addition, as currently there is no immediate force holding the axle (being that the dropouts are 14mm). I think when run together (ie the washers, and the torque plates), it will be a great combo.

Cheers, Phil.