Good starter setup for Yuba Mundo in 2020?

[rajbot]

Hi folks:

I bought a Yuba Mundo many years ago and have toyed with adding a motor. However, the price of a "legit" build that most folks recommend (bafang mid-drive or, more recently, gmac rear hub) has been holding me back. I haven't used my Yuba much with my kids and I'm not 100% sure that making it an ebike will change that, so I don't want to pour a lot of money into a build that might not get used. I'd like to put together a starter setup for around $600 - 800 that will help me figure out if I want to go big.

Donor Bike: Yuba Mundo (v3? I think). Has been customized (by past owner) with front shock and hydro disc brakes.
Budget: $600 - 800
Location: Marin, CA. Most riding can be flat-ish, but I have to go up a (partially paved) fire road that has about 100 feet of 25%+ grade to reach my house. Ideally I'd like to ride that portion although I can get off and walk if that constraint brings the cost up too much.
Max Speed: Can make trade offs here. 15 - 20mph on flats is probably fine. An ideal situation is that my wife can ride the Yuba at a fast enough pace that it's fun to ride my road bike with her.
Max Range: 15 - 20 miles at 15 - 20mph? Willing to make tradeoffs here.
Wheel size: I believe they are 26"
Brake type: Disc
Rider/load weight: 260 lbs (around 180 lbs for the rider + let's say 80 lbs of kids). Load will mostly be on the back (kids, cargo)
Terrain: mostly flat, but have to deal with that short steep segment every ride (100 feet @ 25%+)
Usage: recreational, realistically probably 3 - 4 times a month. Hoping to ride with kids, rider may be my wife (less confident rider, if it matters)

Priorities:
1. Budget
2. Safe battery.
3. Getting up that hill segment (100 feet @ 25%+ grade). Am willing to abandon this requirement totally if it's impossible given budget.
4. Range
5. Top Speed.

Aware my budget is very tight, but perhaps a cheaper hub motor kit with a $400 - 500 battery from em3ev would work?

Wondering if I should be mostly looking at front hub builds because of the grade I'm trying to get up (when riding it I have to keep a lot of weight over the front wheel).

 

[E-HP]

Terrain: mostly flat, but have to deal with that short steep segment every ride (100 feet @ 25%+)

Do you have the ability to gain some speed before the steep segment (not starting from a standstill)? A hub motor is the cheapest route, and either a geared or direct drive would work for the rest of our requirements. I'm not sure how the geometry would be affected if you went down a wheel size or two on the rear, like the Spicy Curry, since that would get you more torque to the ground for a hub motor, but even if you can go to a 24" rim, you'd have some benefit there.

If your wife is willing to pedal up the short climb, that would be enough since the motor won't meltdown with that short of a climb, and with a rolling start shouldn't be an issue.
https://ebikes.ca/tools/simulator.html?batt=B4814_EZ&motor=MGRIN2708_SA&axis=mph&hp=150&cont=C35&cont_b=cust_28_60_0.03_V&motor_b=M2706&batt_b=B4823_AC&hp_b=0&wheel=24i&grade=25&kv_b=10.28

PS. what street are you talking about. I've ridden around on your side of the bay a few times.

 

[rajbot]

Do you have the ability to gain some speed before the steep segment (not starting from a standstill)?

Not really, it basically connects 90 degrees to a short bit of dirt/gravel, then off to the road (see link below). It's tricky to hit it with decent speed. Honestly, it's a tricky climb, I used to do it daily when I was commuting to work and I found it sketchy on an unloaded, ~ 20 lb bike (so much that I generally unclip a foot before making the climb, just in case). Basically impossible to climb if it's wet with road tire pressure.

A hub motor is the cheapest route, and either a geared or direct drive would work for the rest of our requirements.

TY for the pre-filled calculator! Any specific recommendations on hubs? Front or rear?

I'm not sure how the geometry would be affected if you went down a wheel size or two on the rear, like the Spicy Curry, since that would get you more torque to the ground for a hub motor, but even if you can go to a 24" rim, you'd have some benefit there.

Hmm, hadn't considered that, I'll look into it and see if others have done it. The tail is definitely a bit loosey-goosey with the kids on it and it would feel better with a lower center of gravity (apparently more common on the newer Yubas).

PS. what street are you talking about. I've ridden around on your side of the bay a few times.

It's the fire road connecting Midvale way in Tam Valley to Erica Rd. Unmarked on most maps, known as "Georgia Lane" on Strava. Here's a link that gets you to the midvale (bottom) side: https://goo.gl/maps/7RYZQfoHo3VQWkcX7 ... FWIW, a good "shortcut" if you don't want to ride the lower part of Shoreline on a bike, cutting up the fire road and then up Erica puts you a short distance from Panoramic -- it's basically traffic free.

 

[amberwolf]

I bought a Yuba Mundo many years ago and have toyed with adding a motor. However, the price of a "legit" build that most folks recommend (bafang mid-drive or, more recently, gmac rear hub) has been holding me back. I haven't used my Yuba much with my kids and I'm not 100% sure that making it an ebike will change that, so I don't want to pour a lot of money into a build that might not get used. I'd like to put together a starter setup for around $600 - 800 that will help me figure out if I want to go big.

One issue with a low budget is it usually means a small cheap battery...which doesnt' handle continuous high loads (like hills using a hubmotor) very well.

Motors can be "overloaded" for some period of time before they overheat to failure, less for geared hubs than for DD hubs, but you can still generally use a smaller motor to do a bigger job as long as it's not for very long at a time, and it has plenty of time to cool off between events.

A geared hub can often do more torque for the same weight of motor/battery/controller than a DD, but not for nearly as long, if it's being pushed to overheat.

Controllers though, and batteries, have to be able to sustain supplying that higher power, so even if you skimp on motor you probalby can't skimp on those and still do the job you want, especially if you have to stop before going uphill and can't carry momentum from a downhill (or even a straight). The simulator already linked should help show you how this can work.

Donor Bike: Yuba Mundo (v3? I think). Has been customized (by past owner) with front shock and hydro disc brakes.

This page shows how to tell which one you have
https://yubabicycles.freshdesk.com/support/solutions/articles/25000006729-what-version-is-my-yuba-mundo-
This page has some advice on adding a motor
https://yubabicycles.freshdesk.com/support/solutions/articles/25000006733-can-i-install-electric-pedal-assist-on-my-mundo-
Couldn't find anything definitive on what size wheels it uses, but there is a mention in an article on the site that they recommend Schwalbe 26" marathon tires, so that implies these use 26" wheels.

A 26" wheel won't climb (for the same hubmotor and controller and battery) as well as a smaller wheel. It will take more power to do the same job, and be harder on the battery. If you can get a sufficiently slower winding of the same hubmotor, then it would do effectively the same thing as a smaller wheel.

Actually using a smaller wheel creates some problems. Crank clearance to ground is less, and if you use the side racks, they may not clear the ground in turns. You might have to make all turns slow enough to stay completley upright rather than leaning into turns if you use a small enough wheel. (you'd have to check this first).

Additionally, the smaller the wheel, the worse it rides in other than smooth roads. I use 26" front and 20" rear on both my cargo bike and trike, and while the front isn't so bad even without suspension, the rear sucks on even slight washboardy pavement (common around here due to cars/trucks/busses distorting the hot pavement in the summer by braking and accelerating), and it's literally wheel-breaking (axles, rims) (and sometimes frame-breaking) on even mildly serious potholes. So my next trike will have "fat" 29"ers on all three wheels (the cargo deck will be suspended below the axles to greatly reduce COG to even better than it is with the 20" wheels).

Max Speed: Can make trade offs here. 15 - 20mph on flats is probably fine. An ideal situation is that my wife can ride the Yuba at a fast enough pace that it's fun to ride my road bike with her.

That kind of speed, on the flats with no winds, isn't hard to do even with really cheap stuff. The "$200" ebay kits (minus battery) could probably do that...on the flats, with no winds. Up hills...that's another story.

Max Range: 15 - 20 miles at 15 - 20mph? Willing to make tradeoffs here.

If it's on the flats, with no winds, it's probalby going to be something like 20wh/mile, maybe 25, to do 20mph on a bike like that. So if that 20 miles is under those conditions, then it would take about 20 miles * 25 wh/mile = 500wh to go that far. Assuming a 52v battery (14s) then that's only a 10Ah battery, which isn't all that big or expensive...but a smaller battery can't supply as much current as a bigger one, so it might not do as well on hills as one that has more Ah (more cells in parallel to share the load, etc). At a guess, probably $300-$400 for a cheap battery that will do 20miles at 20mph. Add a couple hundred up to double the cost, for better quality (and/or better customer service / warranty) stuff.

You may be able to use used EV-grade cells that bolt together (Leaf, panasonic, EIG etc) to build a better battery for cheaper...but it's something you'd want to read about a fair bit before jumping into. I don't recommend building your own 18650/etc battery to save money, because you won't, by the time you're done.

Rider/load weight: 260 lbs (around 180 lbs for the rider + let's say 80 lbs of kids). Load will mostly be on the back (kids, cargo)

What does the bike itself weigh? I'd guess it's 60-70lbs at least, so you have to add that in for hill power needs, as well as weight of the electrics (another 20-30lbs?).

Wondering if I should be mostly looking at front hub builds because of the grade I'm trying to get up (when riding it I have to keep a lot of weight over the front wheel).

The problem with a front hub on a hill is that when you don't have weight on the wheel, you don't have traction. Adding a few pounds of motor on the front *might* be enough to help with that, especially if you can put the battery in front of the rider, too. The more weight behind the rear axle, the worse the front traction will be. So if you carry any load (wiggly or not), put it between the axles, and it will help keep boht wheels on the ground. Put any load on the back behind the axle and it lifts the front. Put any load on the front in front of the axle and it lifts the rear (much less noticeable due to all the other weight already on the rear).

Front and rear each have advantages and disadvantages, which are listed in a bunch of FWD vs RWD type threads over the years, if you want to see those I can try to find some of them and link them here.

 

[rajbot]

Front and rear each have advantages and disadvantages, which are listed in a bunch of FWD vs RWD type threads over the years, if you want to see those I can try to find some of them and link them here.

Thank you! Helpful insights, especially on battery sizing (which I haven't really wrapped my brain around yet)! I will check out some of the FWD/RWD threads, but if there's ones you'd recommend, would love to check them out.

Leaning FWD at this point, now to see what's available. EDIT: hmm after reading a handful of threads sounds like it's tough to get FWD right, so back to considering RWD.

 

[rajbot]

Ok, at this point I'm considering an ebikeling 500w geared rear kit ($300-ish) and a EM3ev 48V (13S4P) Super Shark ($500-ish shipped) which takes me right around $800. Will do some research on this combo but curious to hear about any advice folks have on these options given my constraints.

 

[E-HP]

Ok, at this point I'm considering an ebikeling 500w geared rear kit ($300-ish) and a EM3ev 48V (13S4P) Super Shark ($500-ish shipped) which takes me right around $800. Will do some research on this combo but curious to hear about any advice folks have on these options given my constraints.

Sounds like good safe choices. Do you have link to the exact kit and battery to see the components?

 

[Hummina Shadeeba]

a good starter and ender setup in my mind is 100$ bucks of lithium iron cells (a lot less likely to catch on fire) from batteryhookup.com, the vesc6, and a leaf/ebay hub motor, and a two way throttle. i recommend these as it's what i got and being compact, able to do 6000 watts, at least an 800watthour battery, and get all the electronics for 700$ :...

you'd have to build the battery though, but not hard to do and im in san francisco and would do it for you for 100$.

 

[rajbot]

Ok, at this point I'm considering an ebikeling 500w geared rear kit ($300-ish) and a EM3ev 48V (13S4P) Super Shark ($500-ish shipped) which takes me right around $800. Will do some research on this combo but curious to hear about any advice folks have on these options given my constraints.

Sounds like good safe choices. Do you have link to the exact kit and battery to see the components?

Haven't gone deep on the kit yet, but am looking at the 36V 500w 26 inch kit (currently out of stock on their website, but avail elsewhere). Battery is at https://em3ev.com/shop/em3ev-48v-13s4p-super-shark-ebike-battery/ (read somewhere that the 36v kit controller can be set to run at 48v but can't locate at the moment).

 

[markz]

Not having enough power is always a downer man, always.

 

[Hummina Shadeeba]

Not having enough power is always a downer man, always.

If ur going to make the effort to build it do it so it has some power. 500 watts sucks. Any pure hub motor will be capable of a lot more and the battery likely as well so just get a controller that’s capable. You spend like 100$ more bucks on a more powerful controller and you’re there.

They’re rating their complete batteries under what they can do. And u could set the controller to the max battery current the cells could do but even set the motor current higher. https://em3ev.com/shop/em3ev-48v-13s4p-super-shark-ebike-battery/
Unless there’s a discharge limit in the batter but didn’t read that. They seem like nice cheap batteries

 

[Grautuefel]

I'd be somewhat cautious of a rear hub on the Yuba, for starters I do not know if the hub axles are designed to carry as much weight as the Yuba ones. Having a heavily laden Yuba myself (v4 with shopping, wife and two pups) climbing hills have a VERY strong tendency to lift the front wheel so the less weight on the rear the better.

Ill second the sentiment to not skimp of the batteries

 

[amberwolf]

Haven't gone deep on the kit yet, but am looking at the 36V 500w 26 inch kit (currently out of stock on their website, but avail elsewhere). Battery is at https://em3ev.com/shop/em3ev-48v-13s4p-super-shark-ebike-battery/ (read somewhere that the 36v kit controller can be set to run at 48v but can't locate at the moment).

Keep in mind that running a 36v kit at 48v has two caveats:

--the LVC for the 36v kit will be too high for a 48v battery, so you are then depending on the BMS to shut off the battery when it's empty, and that is harder on the battery than having the controller do it (because controller LVC is typically a bit higher than the battery LVC, as the latter is meant as a last-ditch protection against battery damage, and generally not intended to be used as the regular system protection). Some LVCs are adjustable, so if this kit's is, then set it to the 48v setting, and then you're ok. The battery meter may also not read correctly; it may always show the battery to be full, even when it is dead, right up to the point the battery shuts off to protect itself.

--the motor will run at a certain RPM at a certain voltage. If it's meant for "20mph in a 26" wheel at 36v", for instance, then it will run at 48v / 36v = 1.34x the speed at 48v. It'll also draw more current for the same throttle setting, which means more heat in motor and controller. (but it also means more torque ).

Thank you! Helpful insights, especially on battery sizing (which I haven't really wrapped my brain around yet)! I will check out some of the FWD/RWD threads, but if there's ones you'd recommend, would love to check them out.

Leaning FWD at this point, now to see what's available. EDIT: hmm after reading a handful of threads sounds like it's tough to get FWD right, so back to considering RWD.

My longbike, CrazyBike2, was orignally middrive RWD (powerchair motor/gearbox thru the pedal drivetrain). The first hubmotors I got were all FWD, so that's how I used them on it when I went hub (the MD kept destroying things due to frame twisting causing derailments, mostly due to poor frame design on my part at the time). FWD worked pretty well for most things, including the Death Races down in Tucson at a kart track a couple times. Neither crash I had was related to where the motor was.... IIRC I then modified one of hte FWD hubs and put it in the rear, which since it was smaller wheel had better torque with the same motor as the larger front wheel, and handled about as well...but I broke more spokes and had many more wheel problems because of the much higher load on the rear wheel, vs the much shorter spokes (which were also thicker because I used the OEM stuff, and had not yet started using the correct (thinner) spokes needed to fix that (no spoke problems with the ones on the SB Cruiser trike, though I destroy rims and break motor axles cuz they're crappier than bike axles for various reasons)). Then I went 2WD, with separate throttles, and used each wheel in the situations it worked best in (usually both for initial startups from a stop or climbing any slopes).

The RWD version of CB2 successfully climbed Cave Creek Road, which is pretty steep:
https://www.google.com/maps/@33.5815202,-112.0480949,14z/data=!5m1!1e4
from 7th st and dunlap diagonally up to Cactus and then beyond.
https://endless-sphere.com/forums/viewtopic.php?f=2&t=12500&p=552169&hilit=cave+creek#p552169
using a "500w" 9C type hubmotor in a 26" wheel. (Motor was the one I converted to a RWD from an FWD, after having used the FWD for the races), but it took about 1200w to do it at 20MPH.

Later, I damaged the halls from overheating in a similar RWD 26" motor, but not because of hill climbing, it was from start/stop riding in a small neighborhood, where it never got very fast so the load (and current) on it was high all the time it was in use, and never given a chance to cool off. Going faster with the high load is easier on the motor....

If that sounds confusing, you might want to look at the https://ebikes.ca/tools/simulator.html and read the entire page so you know what everything is and how to use it, then setup a system like you want to use, and experiment with different conditions to see what happens. Takes a while to get the hang of, but it's very useful for getting the basic idea of what's going on, and point you in the direction of a system that will do stuff you want for a particular situation. It also has a Trip Simulator that you can get an idea of how the system behaves over an entire trip.


Anyway....FWD vs RWD; some things to think about:

An already rear-heavy cargo bike will be harder on a poorly-built RWD OEM hubmotor wheel, especially if they are using the common 12g or 13g spokes and cheap OEM rim. If it uses a good rim and 14g (or 13/14g butted) spokes in a well-built wheel, it probably won't be an issue (but that's not typically what the cheap kits have). Whcihever kit you get, check the spoke tension both when you isntall the wheel, and after the first ride, and each ride for the first several, at least. If you find that you can tighten it up and it works loose, it may have cracked nipple holes in the rim from too-large spokes needing too-high tension vs what the rim can deal with, and then you have to rebuild the wheel (new rim, spokes) to fix this. (IIRC, I didnt' start breaking my hubmotor wheels until I used RWD--FWD was lightly enough loaded that it didn't cause problems...but every one of the OEM wheels used as RWD on any of my bikes (even the "normal" bikes :lol: ) had spoke and rim problems at some point).

Hubmotor axles seem to be commonly made of an alloy of cheese, pot metal, recycled beercans, and other inappropriate materials. They don't break all the time, but they don't always handle heavy loads, or banging around on unsuspended cargo bikes, etc., very well. (even when used at "normal" power levels, with good torque arms that are properly installed, etc).

The front wheel especially on your bike is loaded much less heavily, so wont' be as hard on either axle or rim or spokes.

RWD hubs will replace your rear wheel...so anything you like about the rear wheel's gear cluster and/or shifting system may no longer be available to you, depending on the differences between the existing rear wheel and the new one. For instance, if you have a cassette freehub on there now, and you get a freewheel thread-on type motor, you can't swap over your existing cassette. The motor may come with a freewheel cluster on it, but it might not match the number / size of sprockets you already have, so you might either be changing your pedal gear ratios, (losing top speed or losing low-end torque, etc), or have to change the handlebar shifter and the derailer on the back to match the new freewheel, or change the freewheel out to match your shifter/derailer / gear ratios, etc. Chainline may change, so you may get frame rub in gears it didn't happen in before.

Also, if you use disc brakes, the motor has to have a rotor mount that matches your rotor, and have clearance between the rotor and hub casing to fit the caliper's inboard section, or else you have to space things out to get it all to work together.

FWD hubs won't be replacing any of the gear stuff; you only have to worry about disc rotor moutning/ spacing if you have disc brakes.

If you use rim brakes, with either FWD or RWD you have to make sure the rim provided is designed for those (they aren't all).

FWD will be more lightly loaded on uphills than RWD, especially with a load on the back, so it wont' have as much traction as RWD in the same situation. If the road surface is loose material, it may not be able to do anything to help you up the hill, if conditions/etc are bad enough.

On flat paved surfaces or similar downhills, it probably wont' make much difference either way.

RWD is "easier" to deal with torque arms or plates, as Yuba already makes stuff just for this purpose you can buy from them. But Grin Tech makes "universal" torque arms that cna be made to fit most mounting situations, whcih would work fine for your power levels for FWD (or probably RWD).

FWD is easier to get to the wheel to change tires/tubes if you have flat problems a lot.


There was other stuff I was thinking of but I forgot it while typing hte above stuff.

 

[dogman dan]

Its all pretty well covered, as usual. I'll just chime in to say yes to rear wheel drive. A cheaper, direct drive hub. 36v can be ok, especially since that may save you a few $$ on the battery. This wheelie problem is only on the steepest bits, and you can just hold down that front end some with body weight. I never rode a yuba, but my longtails have always kept the front wheel down fine, partly because of a lot of battery weight carried up in the front triangle.

But in the long haul, rear wheel will serve you best. However, I rode front wheel bikes for many many thousands of miles, and front can work fine, till you get to that very steep hill. If you had ONLY mild hills, I would say go ahead with front motor.

Overloading the shit outa that DD motor for a few min to get up that hill will be ok. But DONT undersize that motor too much to save money. You will overheat a very small geared type motor. Better to go with the heavier direct drive. Even if its not enough on that hill, its still huge help getting up the driveway. If you have to walk it, with your weight off the bike you can let the bike carry its weight up the hill.

 

[rajbot]

Thanks, good stuff y'all. I'm gonna deeply rethink the geared vs. direct drive based on the feedback. I'm still a bit iffy on the FWD vs RWD. I was going to forward mount the battery so maybe the weight thing isn't such a big deal, that seems to be the main advantage to FWD (not too worried about spacing the disc stuff or having to fiddle with the cassette etc since the drivetrain of this bike needs attention anyways ... although I suppose the devil is in the details).

 

[Grautuefel]

I had some more thoughts, but then I totaled up what I have spent on the bike and its waaay more than a decent car. Cheap has not worked for me.

If you want battery safety without having to move into esoteric battery chemistry, LiFePO aka LFP is a decent compromise of bulk, weight and durability. My LiFePO packs can stand to be neglected and don't seem to mind being left at any charge state or even on the charger, whereas cheaper LiPoly will die if you leave them uncharged. LiPoly are the ones famous for catching fire. That said I have an em3ev NCM pack and its perfectly reliable too.

As for motors I've only had the BBSHD and cyclone mid-drives, once I got the alignment on the Yuba sorted and moved to the rohloff gearhub without a derailleur its utterly reliable.

Almost your budget and easy install (if you found a cheaper charger it would be within)
52V (14S4P) EM3ev Super Shark Options
14S4P EM3ev Super Shark Battery Type 11.4AH $339

58.8V Charger (for 14S, 50/52V Battery) $30

Lunacycle BBS02 kit $450