Virtual Build Project - Yuba Mundo Urban Transporter System

[Richard N]

The question you probably want to ask first is how much thrust does your planned bike require at your planned speed. Use a bicycle power simulation to determine that first (you may want to do it for level, and your worst case hill, at appropriate speeds for each). Then, for each motor, adjust the throttle to produce that amount of thrust at that speed. Then you can actually compare the results at that speed and see the efficiency, as well as how much throttle is required.

On these wide open throttle graphs you posted, looking at the thrust at 20mph is telling you the maximum thrust it can produce at that speed, and the efficiency and power at that maximum thrust. So you can't tell what the efficiency at the actual thrust you will be using is.

I sort of tried to do that back on page one, I do have some hills around here but none are really long or overly steep. I've estimated the best I can without topo maps or GPS readings that my steepest hill will be 10% for no more than a few typical city blocks, 200 yards at the longest, best guess.

Keeping in mind that I'm building a cargo bike I loaded it right up with weight and I came up with a power requirement of 1638 watts for that 10% grade and a speed of 15kmh or just under 10mph, that same load on the flat would need 390 watts. The cargo unloaded totals were, hill 806 watts and flat 325 if I recall correctly, I honestly can't remember what I put the bikes+cargo weight at but it would have been around 450lbs.

I'll go back over to the motor simulator and have another crack at it.

 

[Alan B]

None of these motors get near 1638 watts. So if that is right you need to consider other options.

 

[Richard N]

None of these motors get near 1638 watts. So if that is right you need to consider other options.

I did notice that, I've wondered if 72v might not be a better option but what I'm reading is that for a first build it's definitely better to stick with 36 or 48 volts.

 

[Alan B]

Well you need to decide if you want to meet your requirements or not. I suspect 10kph is going to cook hubmotors, so if you really want to do that you need to look at other propulsion choices. If you want to make a simple first build to get some experience then perhaps the Mundo is not the best platform. Or you need to scale your load/gradient requirements back.

 

[Richard N]

Well you need to decide if you want to meet your requirements or not. I suspect 10kph is going to cook hubmotors, so if you really want to do that you need to look at other propulsion choices. If you want to make a simple first build to get some experience then perhaps the Mundo is not the best platform. Or you need to scale your load/gradient requirements back.

I was putting in weight figures that fit with the maximum capacity of what the bike can carry, realistically 100lbs of cargo is closer to the mark. I want the Mundo so I'll look for compromises as needed. Thanks for the help btw, it's appreciated.

 

[teklektik]

Also my thinking is with the side platforms I can make some nice wood platforms that have a compartment on the underside that's a few inches deep which can hold battery packs or chargers, maybe tools or parts... I don't know yet but I'll think of some way to make a couple of pseudo trunks.

The stock Mundo sideloader frame component is actually configured more as a midline support for the GoGetter bags than as an around-the-edge support frame for side loader decks. The bags rest comfortably on the rails w/o any deck in place and as a result the rails do not protrude really far. This rail placement pretty much precludes storage designs to exploit the space between the chain stay and sideloader rail since the gap is only 4.5" - 5" (non-rectangular). This area is not entirely unusable, but if you want to pursue the 'sideloader concealed battery' approach, you might have better luck building a deck-box entirely above the rail as a kind of thick deck.

Also - re: battery boxes hanging below the sideloader rails: the under-sideloader area is about the most vulnerable point on the bike. Clipping a curb and crushing an under-loader battery box could give you that I'm-being-pursued-by-a-tiny-Chernobyl feeling.

From your requirements, it sounds like you are going to have little success concealing the size battery you will need, so just stick it in the frame where the weight distribution will be better.

I am sad to hear that the Yuba Mundo has a few issues with factory threads and welds being messy.

I'm not sure that clearing the threads on a bare frame that came straight from paint should be viewed as a 'thread issue'. I have a 2011 V4 and all the threaded inserts are square and the threading is of good quality with good thread depth. The many unused threaded rack and sideloader inserts come pre-loaded with stainless cap screws. The welds are also all of good quality: no grapes, gaps, or undercutting but not all smooth as glass either. I would characterize some of them as 'workmanlike' rather than 'artful' (Timex vs Rolex - but we all know what a Timex does...).

 

[Richard N]

Also my thinking is with the side platforms I can make some nice wood platforms that have a compartment on the underside that's a few inches deep which can hold battery packs or chargers, maybe tools or parts... I don't know yet but I'll think of some way to make a couple of pseudo trunks.

The stock Mundo sideloader frame component is actually configured more as a midline support for the GoGetter bags than as an around-the-edge support frame for side loader decks. The bags rest comfortably on the rails w/o any deck in place and as a result the rails do not protrude really far. This rail placement pretty much precludes storage designs to exploit the space between the chain stay and sideloader rail since the gap is only 4.5" - 5" (non-rectangular). This area is not entirely unusable, but if you want to pursue the 'sideloader concealed battery' approach, you might have better luck building a deck-box entirely above the rail as a kind of thick deck.

Also - re: battery boxes hanging below the sideloader rails: the under-sideloader area is about the most vulnerable point on the bike. Clipping a curb and crushing an under-loader battery box could give you that I'm-being-pursued-by-a-tiny-Chernobyl feeling.

From your requirements, it sounds like you are going to have little success concealing the size battery you will need, so just stick it in the frame where the weight distribution will be better.

Thank you for your reply.

About the under slung battery idea, I keep looking at the size of that space and comparing that to the size of ready made packs and also to the size of various individual cells trying to work out what will fit. I pretty much come to the conclusion that nothing off the shelf would work, least wise not in the manner I was considering. Once I'm able to figure out what motor and battery combination will get me close to what I would like to realize from an electric Mundo, I'll be better able to determine if custom built split packs would fit inside such a narrow and long space.

Cheers
Richard

 

[Archer]

Well well,the rumored price of 550-600 for the Sun Atlas Cargo bike may have changed,I was on Veloverde site and noticed the Sun listed at 900.00.Of course the 900 maybe their price and not others but keep in mind Veloverde's other bike prices are at MSRP which I would assume is the same for the Sun.

Time will tell,if it's MSRP 900,a bit of a let down as price was one of the attractions to this bike.



http://tinyurl.com/3kf76u9

 

[Richard N]

I think I would have to say, not having ridden any of these bikes, that for my tastes and considering price, that the Mundo is the best bang for the buck IMO.

 

[urbancommuterstore.com]

Yuba came out with the V4 already. They made a few more changes to the frame. There is more room for a bigger Lifepo4 battery pack. Check it out. Btw, I am currently testing my mid-drive system for the Yuba Mundo. It can fit both V3.3 and V4 frame versions. It's currently in prototype stage so it's too ugly to post pics. I will be posting pics soon of the final product. Im just finalizing the design before it goes to my machinist. Im currently using an Aotema Rear Direct Drive Motor for it. It's a 750W motor that can be bumped up to 1500W. For batteries, I'm just using cheap 36V 12A SLA for testing. So far, Im getting good miles out of it, seems to be more efficient when you get to use all your gears.

 

[Richard N]

Yuba came out with the V4 already. They made a few more changes to the frame. There is more room for a bigger Lifepo4 battery pack. Check it out. Btw, I am currently testing my mid-drive system for the Yuba Mundo. It can fit both V3.3 and V4 frame versions. It's currently in prototype stage so it's too ugly to post pics. I will be posting pics soon of the final product. Im just finalizing the design before it goes to my machinist. Im currently using an Aotema Rear Direct Drive Motor for it. It's a 750W motor that can be bumped up to 1500W. For batteries, I'm just using cheap 36V 12A SLA for testing. So far, Im getting good miles out of it, seems to be more efficient when you get to use all your gears.

Looks like they have removed two supports from the top rack and added one to the front extending down to the seat tube.

I'd be very interested in reading about what you've come up with, please post up some pics when you closer to a completed final product. What sort of range are you currently getting using the SLA batteries? Is this is a system similar to the Stokemonkey in that the cranks always turn or is there a freewheel involved?

I think I prefer the look of the V3.3 Mundo myself.

 

[ryan]

Richard, I spoke to a friend about a 36 to 48 ring adapter. Here's his feedback:

- option A would be best: cheaper to machine, the step in option b wouldn't be precise enough to carry any weight anyway.
- plan would be to water jet the ring and holes. Then tap out threads on the inside 36, due to limited space for bolts on the x5. Coat the whole thing. Then screw in the ring with 36 screws and build the wheel normally to 48 custom length spokes.

Needless to say this would be costly. What are your thoughts?

Something else I've been thinking about is trying to keep a 48 spoke wheel in the rear when doing a rear hub install.

What would be the consequences of having a set of rings machined to fit onto the hub and bolt up to the holes for the spokes, the ring would then have on it's outer diameter holes for a 48 spoke rim.

Would there be a problem with moving the spokes outward in this manner, as in the option A picture below? Or should the rings be machined with a recess on the inside so that the same horizontal plane is maintained, option B?

Option A

Option B

Thanks
Richard

 

[ryan]

I'm also considering LiPo on the running boards. I'm thinking about buying two pair of the running boards and putting them roughly 1.7inch apart to accommodate a bunch of Turnigy nanoTech packs. I just need to hone in on the dimensions to figure out how much can fit down there. The battery should be pretty stealth then. They'll just look like thick running boards.

 

[Richard N]

I think option a. is certainly the easiest way to do it. I just had a look at the cad drawings for the x5 series and from what I'm reading the spoke flange is 11mm wide by 4.5mm thick. I think at that size there might be enough room for an acorn style nut and allen bolt. I wonder if threaded aluminum of that thickness wouldn't stretch and fatigue quickly and come loose... I think I'd feel much safer with it bolted with Loc-Tight on the threads.

I really like the idea of batteries in the running boards, I'd build boards out of wood and epoxy myself. It should work out great for you using LiPo, I'm most certainly going to be using LiFePo4 probably not enough room for me to put all of the battery inside of the space afford in the running boards. I was thinking about breaking the pack into three parts with one in each running board and the rest inside the frame along with the controller and charger(s).

I'm still having a devil of a time trying to figure out if I want 48v or 72v, I do know that I want at least 30ah and would gladly settle for 40ah.

 

[spinningmagnets]

Looking back, some of my comments may have sounded disparaging, and I want to restate that the Yuba Mundo is a great product. It is a good basic design, and their recent changes show that the company is sensitive to customer desires. The Stokemonkey is also a good product, but the open space in the place that the V4 Mundo will also allow for some competition from other E-drive systems.

I saw some names in this thread that I hadn't seen before, and did some Googling today, it apprears that the Yuba Mundo is outselling the rest at a more than 10:1 ratio. (Kona Ute, Trek Transport, Sun Atlas, Surly Big Dummy, Madsen). I have no info on the volume of Xtra-Cycle builds, and the Xtra-Cycle is also known to be a well-made product.

 

[Richard N]

Looking back, some of my comments may have sounded disparaging, and I want to restate that the Yuba Mundo is a great product. It is a good basic design, and their recent changes show that the company is sensitive to customer desires. The Stokemonkey is also a good product, but the open space in the place that the V4 Mundo will also allow for some competition from other E-drive systems.

I saw some names in this thread that I hadn't seen before, and did some Googling today, it apprears that the Yuba Mundo is outselling the rest at a more than 10:1 ratio. (Kona Ute, Trek Transport, Sun Atlas, Surly Big Dummy). I have no info on the volume of Xtra-Cycle builds, and the Xtra-CyCle is also known to be a well-made product.

I never read them as disparaging, if anything, it made me look closer at the choices I'm making. Everything I'm reading from owners is reinforcing my first impression of the Mundo as a solid well built cargo bike platform that makes an excellent base for an electric conversion. I can't wait until I get mine, everyday I do a little more reading and try to figure out what to order when the time comes. It's been great seeing what other people have been doing with this bike too, it's nice to see that I'm heading in the right direction for what I'd like to accomplish.

So far I've sorted out what I want for a motor and selected cell type and battery size, controller and charging are next on my research list.

 

[Lemlux]

I find much to like about the Yuba. My main concern relates to comments that the brazings and other fittings on bare frames are said to suffer from QC neglect. I'd want to specify my own components fir a build, but would hate to have to have someone spend hours on the frame getting it to accept components that should be no-sweat installations.

 

[urbancommuterstore.com]

Here is my latest build on an Orange Yuba Mundo V3.3