Advice requested for e-bike kit for Yuba Mundo

[kiltedcelt]

Hello,

First time poster here with a lot of completely clueless questions. I've been searching the forum, reading all the noob questions and honestly trying to figure out what I want to do without having to post the type of question that doubtless dozens or hundreds of other posters have asked already. Sadly, I'm completely overwhelmed with the information and don't have a clue where to begin. I do at least know enough (from reading some stickies), to post some of the relevant background information:

Rider weight: 175 lbs.
Bike: Yuba Mundo v. 4.3
Current location: Chicago, Illinois USA (completely flat)
Note: plans to move to Fort Collins, Colorado within the next 10 months or so - so hills/mountains will likely be in the mix by then - good-bye (and good riddance) to flat, boring commutes/rides
Type of riding: Mostly commuting (currently 22+ per day round trip occasionally more with errands in the mix), cargo hauling heavy and/or bulky items, ability to occasionally haul a passenger desired, touring (potentially some off-road or at least on rough trails/roads)

I ride my bike because it's my exercise and also because I no longer own a car and I really hate the cost and inconvenience of mass transit. I *don't* want an ebike so that I can just turn a throttle and cruise without pedaling, in fact I think most of the time I wouldn't be using the motor unless I was heavily overloaded, or on the days where I'm commuting into work and facing 20-30+ mph headwinds. I'm most interested in what I'm guessing is a pedal-assist kind of motor setup and not really needing to go any faster than 20 mph is fine with me. I'm a competent bicycle mechanic and I built my Yuba Mundo from the bare frame up, with a mix of completely custom components steps well above the quality of a stock Yuba. I do know that I'm mainly interested in a mid-drive motor as I have built my own custom wheels around a Deore LX dynamo front hub and a strong 36 spoke Deore rear hub. The bike currently uses Avid BB7 disc brakes.

I did get a chance to ride a Felt fatbike that uses the Bosch mid drive motor and love the feel of how the motor comes on and just gives you a slight boost to your pedaling without being overly obtrusive. I also liked the different levels of settings for the amount of assist. If possible, I'd like to duplicate that feel in whatever aftermarket kit I eventually choose. Also, a few other criteria I've noticed in reading about the different motors.

1. The entire set up needs to be as durable and waterproof as possible. I will ride in torrential downpours on occasion because I have no other choice. I don't want a motor/controller/battery set up that is going to get ruined because water somehow got into it. Likewise, I will ride in snow and extreme cold too, so the whole apparatus needs to withstand those temperature extremes as well.
2. Because of a hip issue, I utilize slightly shorter than normal crank arms (they're 153mm), to limit range of motion in my hips, so I'd prefer to be able to continue to utilize my own crank arms with any kit.
3. I prefer the Avid "Speed Dial" brake levers in order to tailor the amount of brake modulation that I have, so if possible I'd like to stick with the Avid levers. Is there a kind of motor cut-off sensor that can be installed on existing levers without having to switch to some kind of proprietary lever?
4. For durability's sake I use stainless steel chainrings on my crankset, and I want to maintain the ability to use my full range of gearing whether the motor is in use or not, which I guess eliminates some kits that have their own propriety cranksets.

Finally, budget I guess. I just don't know what I should be looking at. I *do* know that a full-on Stokemonkey or Bionix kit are completely out - WAY too expensive. I can build my own battery if it comes to that for helping to curb the cost. I could stomach a few hundred for the motor/controller/charger so I guess maybe as long as things don't get too far above $1000 or so. Is it even possible to build and install a mid drive motor that is durable and not complete junk for less than $1000 including battery? Again, I simply don't even know if this is possible and the sheer amount of information is overwhelming as to where to begin. If you've read this far, thanks, I appreciate your patience and look forward to reading your suggestions.

 

[wesnewell]

The most reliable system is a direct drive hub motor, simply because it has the fewest moving parts, sheds heat better because of size, and should last many years without any maintenance of the motor itself. The advantages are regen braking for better stopping power. While it doesn't freewheel, it easy to simulate that by pedalling along with the motor using almost no battery power as long as you can provide enough power to reach no load speeds.
Geared hubs can be pedalled with almost no resistance from the motor. That's about their only advantage imo. The disadvantages are no regen braking, clutches and internal gears to wear and break, and limited power. Since they are smaller, they don't shed heat as well as a DD motor.
Mid drives allow gearing through the bikes gear system. That's both the good and the bad. It wears the bikes drive train a lot more. Most mid drive kits afaik use smaller motors that have the same limitations as a geared motor. If it has a DD motor then that would make it more reliable. It's the most efficient of the three, but also requires the most maintenance. Certainly the most versatile of the three.
For a reliable commuter, I'd go with a DD rear hub motor. 48V 1000W kits start ~$250 or less and are suitable for all but extreme conditions. Top speed on 48V and 26" bike will be ~30 mph for motors rated at 470rpm at 48V (~9.75Kv).
1. It will be up to you to handle most of this. You'll need more battery capacity in colder weather to go as far.
2. This shouldn't be a problem.
3. Yes, and they also have separate bake senors that can be use instead.
4. I don't know the answer to this. I would assume it would depend on the kit you bought.

 

[spinningmagnets]

I would consider a direct drive hubmotor system on the rear, combined with a geared hub on the front (they freewheel easily). That way you could have 2WD on uphills and during acceleration, and regen as magnetic brake on long downhills. Just a thought. What's the lowest top speed that would be acceptable?

 

[Chalo]

Given the constraints you have stipulated, I would suggest a geared hub motor (one that freewheels when not transmitting power). There's no real disadvantage to a front hub motor in your longtail application, because a longtail always has plenty of weight on the front wheel, and because your demand for power is modest.

If you feel you must have a rear hub motor, get one that uses cassette gearing, rather than a thread-on freewheel.

 

[snowranger]

A front hub motor would be the cheapest.

The extra wide rear yuba drop-outs require an axle adapter (about $20). Also, you do not need to buy a new freewheel for front drive application.

 

[kiltedcelt]

So, no love for mid-drive systems? I'm guessing maybe they're not as durable as the hub motors, mainly because of size and them not being able to dissipate heat well enough? I kind of wanted to avoid having to completely build a new wheel around a hub motor. What about some of these kits I've seen that mount a hub motor a-midships style like a Stokemonkey. Also, I'd prefer to not put a motor on the front wheel since I already have a high quality dyno hub there for front and rear lights as well as the ability to recharge USB devices (charger is built into the head light). Also, I don't care about going super fast either. I'd be perfectly happy with a top speed of 20 mph.

 

[amberwolf]

I *don't* want an ebike so that I can just turn a throttle and cruise without pedaling, in fact I think most of the time I wouldn't be using the motor unless I was heavily overloaded, or on the days where I'm commuting into work and facing 20-30+ mph headwinds. I'm most interested in what I'm guessing is a pedal-assist kind of motor setup and not really needing to go any faster than 20 mph is fine with me.

Note that with the headwinds plus the speed you wish to go, you will need a setup capable of producing enough power to go 40-50mph with the loads/weight you want to carry, but only "geared" or otherwise setup for 20MPH max speed.

That is a lot of power, especially if you need to sustain it for any length of time.

Power increases a lot past about 20-25mph, so you could be looking at a few kW of capability, from your battery, motor, and controller.

If you use a front hub, just make sure you're using a good dual torque-arm setup.

I use dual DD hubmotors, one front one rear, on my CrazyBike2 long cargo bike, and while I only ride it up to 20MPH, I can hold that speed against 15-20MPH headwinds on the occasions we have them, with no input from me (knee/joint issues), and up what hills we have around here, and accelerate from 0-20MPH in about 4 seconds. Total it's up to around 4KW or so peak, IIRC, capability, between the two motors, and would probably sustain that for a little while. Thankfully the winds that high are shortlived as are most of my rides (commutes, etc), so that's untested.


Build thread for CrazyBike2 is in my signature; stuff about the present version starts around two years ago or so.

It's not PAS at the moment, but the Cycle Analyst is capable of it, and I actually have a THUN BB on there just not hooked up or setup (cuz the V3 CA got damaged thru my ineptness and I haven't got it fixed yet, so the old V2 CA is on there and it doesn't do the PAS).


You can make your own middrive setup easily enough, if you are willing to scrounge bits and do some welding and even just primitive machining. I did one out of powerchair motors with rightangle gearboxes, and that worked ok, but my frame twisted too much from the torque cuz I hadn't built the frame right yet. That's earlier in the CrazyBike2 thread.

You can also use hubmotors for this, as has been done by a number of members here on ES, and that's also how the stokemonkey works.

 

[kiltedcelt]

I guess I should clarify about desire for max speed. My commute is 11.5 miles one way. If I can manage (just with regular pedaling - no e-assist at this time), to keep my average speed around 13-14 mph I can get to work in around 45-50 minutes. On a day with bad headwinds, or in the winter time when everything just seems to be slower and harder, I'd be happy if an e-assist helped me maintain 14 mph average while I was pedaling, mainly so I wouldn't take me over an hour to get to work, especially when it's about 14F or colder. I like to minimize the amount of time I'm outside when it's below 0F. I saw a thread about Yuba Mundos over on MTBR and one Aussie guy made his own mid-drive system using something like a scooter motor with a gear reduction. I think he kept a triple chainring and thus had full gearing. His setup was intended for torque and moving loads and not necessarily for adding a lot of extra speed. I've been badgering him for more detailed information on his setup, but he's not being very specific about what motor he used, controller, etc.

 

[green79]

I come from a similar perspective. I have a surly big dummy, built up my bike, like to pedal and was after an assist for heavy loads and hills and perfectly satisfied with 20mph max. here are my two cents:
- i am a big fan of having a torque sensor (this is what is on the bosch system you test rode). it is definitely the most natural feeling assist and with the right settings (using a cycle analyst v3) it is very unobstrusive - it just feels like you are riding a regular bike. you can replicate that with a torque sensor bottom bracket from ebikes.ca (i have a thun). hopefully your existing cranks use a square taper or ISIS BB.
- with a cycle analyst and switch or potentiometer you can adjust the level of assist on the fly. I have mine set up with a potentiometer that allows me to scale assist levels from 0 to 8x the number of watts I am generating with my legs.
- i also was interested in a mid-drive system but the options for torque sensing are pretty limited. I don't like the pedal assist of the Bafang mid drives where it gives a mostly constant level of assist when pedaling - I find myself switching the assist level frequently. AFAIK for a yuba mundo the only torque sensor option is the cycle stoker (stokemonkey) but that sounds like it is out of your price range.
- i also had a dynamo front hub and ended up going with a rear geared hub motor (ezee, cheaper than the cycle stoker by around $400). this allows you me to keep a triple chainring and my existing front wheel. I have no problems with large heavy loads in a hilly city (Seattle). As mentioned already, a geared hub also freewheels so you don't get drag from a direct drive motor. I like to pedal with the assist off sometimes, e.g. when biking with kids, so for me this was important
- you can modify your existing brake levers using a HWBS (e.g. from em3ev). there are various threads here on how to do this. i ended up replacing my BB7s with hydraulic brakes with a built in cutoff switch. I think having brakes with a cutoff switch is important for a pedal assist only bike as it helps to avoid unwanted motor activation (e.g. when downgearing while slowing down using a derailleur system)

I second Chalo's suggestion for one that uses a cassette. I haven't been entirely happy with the shifting performance of the ezee rear hub as it it uses a lower quality freewheel. Other than that it is great. if I were you I would look at a rear hub motor (Bafang CST is a geared hub motor with a cassette; nine continent is a direct drive hub also with a cassette), controller, a torque sensor bottom bracket (Thun or TCDM), cycle analyst v3. There are plenty of options on the battery front (I use a framepack from em3ev).

 

[ScooterMan101]

Kilted Celt,

I too a few years ago wanted to get a Yuba Mundo, and my own mid - drive,

My idea was, to get a powerful rear hub motor , turn it around in the frame to drive the usual non-drive side, then either , connect it to a crank/chainring on the usually non-drive side , ( picture a crank/chainring on both sides of the bottom bracket, you would have to buy the same crankset you have now, just not use the non drive crank arm. )
or
Do the same thing with the motor, turn it around , and then run a chain to a large sprocket that is bolted with 6 bolts to where you would bolt a disc brake rotor. ( the gas bike conversion people did this in the old days )

I do not like Torque sensors, the reason is , if it is not sensing much torque from your legs , it puts very little power to the motor.
I once test rode a mid drive e-bike with torque sensor on a day I was tired, and my legs were sore from other rides that week, on a side street a little Girl 6 years old or so year was going faster than me on her kick scooter for a distance of about 4-5 houses !
You see, some days you are going to be tired, and/or your legs tired, when that happens the torque sensor is a P.O.S. .
With a throttle you can put in as much assist as you want, and with the right throttle and controller like the infineon, and the Cycle Analyst you can then have cruise control , you peddle as much as you legs want to do that day, or time of day, when you get to the right speed you press the cruise control button , then let off of the throttle. You are still working your legs , you have just put in the amount of assist of the combination of your leg output combined with the throttle position .
ebikes.ca sells some of what I am talking about.

 

[Chalo]

So, no love for mid-drive systems?

Between your budget, your funny crank that you don't want to swap, and your modest power requirement, a mid-drive system is at a disadvantage to a commodity hub motor.

Lacing a new wheel around your hub motor is no trouble at all compared to sorting out the mountings, alignment, and gearing issues in a mid-drive project.

 

[dogman dan]

I totally applaud your desire to have the absolute best possible e bike, tailored to your needs. That's what building your own is all about. But...

Wish I could get every thing you want for $1000 too.

The rude fact is, what you plan on doing would require a stokemonkey, but I'm not sure if even a stoker could use your short cranks. I could be wrong, but I thought you still need a special crank for the current stoker. Same for the BBS02 from bafang. In any case, $1000 budget can get you a very functional e bike, but not all the features you want. It will be suitable for commuting, lightly loaded. But the expedition bike will be very pricy, if it needs to go up 10-12% grades. Battery for expeditions won't be 10 ah, more like 40 ah.

If you didn't care about gears, you could do a very simple mid drive that just drives a low gear on the left side of your rear wheel. The mid drive being in one gear doesn't matter a lot, but you'd want to gear it to go not much faster than your target speed of 20 mph ish.

But you'd also get almost exactly the same effect much simpler, just put a direct drive motor on your rear wheel. One with a winding that will go about 20 mph.

It's not in your budget, but the company I work for does sell exactly this type of kit. It has 1000w, runs on 48v, and top speed for me on my cargo bike lightly loaded is about 21-22 mph. I weigh 190. The kit has a pretty darn water resistant wiring harness, and a well sealed controller. However, no throttle on any kit is fully water proof. So in a downpour, I just lay my palm over the throttle to cover it during the ride. Parked in the rain, just bag your right handlebar some way. Possible to carry a spare, dry throttle too. The controller is very waterproof, but in the wettest climates, you might want to go an extra mile to keep it dryer, some extra sealant, or best of all, enclose it in a well vented housing to keep rain off when parked. and obviously, don't mount it where spray will hammer it when you ride.

Anyway, I have this kit on one of my cargo bikes. It does fine for total loads up to 400 pounds, and grades with that load up to 8%. I weigh 190, and my bike is about 100 with a battery, so that leaves enough capacity to go up many, but not all rocky mountain roads with a pretty good load on the bike. But NOT, a steep grade with a second person weighing 150 pounds on it. No problem to put even more weight on it, if the grade is well under 5% though.

The rule of thumb is you can't load up to the point where 1000w is simply not enough power to make it go 13-15mph anymore. By 10 mph max speed under load, the motor is running inefficiently enough to be a big problem on a long rocky mountain ascent. But you can overload for a short hill, one not repeated again too soon. For example, many an ebike motor has been cooked towing skateboarders up a hill over and over.

Anyway, you'd very likely get 90% of what you want with the same heavy duty kit I have on this bike. I can't afford expensive longtails, so I built one with 14 gears and disc brakes out of a cheap Schwinn.

But for ALL you want, it will simply take more power than 1000w to tow a loaded trailer up the rocky mountains. You could replace the rear motor with a very powerful one. That's what I did with this bike, this is the one I have taken on tours, carrying a full load of camping gear, including two gallons of water. This bike has a larger, very powerful rear motor that I run on 2000w. It will go 15 mph up 8% grades fully loaded with only a bit of help from my pedaling. BTW, the battery alone for a long run on this bike is going to cost close to $1000, and with best quality, more like $2000.

The other approach that's known to work really well on heavily loaded cargo bike in the mountains is dual motors. It could be a rear direct drive motor plus a mid drive, front motor plus mid drive, two dd hubmotors, two geared motors, or my favorite, but as yet untried idea, one rear dd and one geared front motor.

Re the geared motors. DONT try to use one geared motor on a heavy cargo bike in the rocky mountians. It should work fine in Austin, but not up a long rocky mountain pass. I proved this won't work, in a test ride where I killed the motor in about 45 min. This is how E-bike kit came up with our suggested maximum load for our geared motor, of 300 pounds. Rider, bike including battery, and cargo needs to stay under 300 pounds.

Sorry this is so long winded, but good advice can only be so simple. Your 4 requirements.

1. Durable and waterproof. This is pretty easy, except for the throttle all can easily be waterproofed. People ride these bikes in Seattle and Vancouver. And it's possible to mcguyver a cable actuated throttle too.

2 your hip needs the short crank. Unfortunately, this is where you lose nearly every mid drive kit. But with unlimited budget you could manufacture your own crank. In any case, budget alone is pushing you towards hub motors, and really, you need to increase that budget to at least $1500.

3. brake levers. It's no problem to keep your brake levers. I usually do. The ebrakes are just not really needed. If some stupid law requires them, then you can add a reed switch to existing levers, to do the job.

4 Full range of gears. This is easy with mid drives, but harder to do with hub motors. 9 speed screw on freewheels do exist, but it's hard to get the very highest gears with such 9 speed freewheels. 7 speed with 11t highest gears is possible. Some hub motors do have cassette allowing the full range and 9 speeds. I don't know of one you can buy that is really the correct motor choice for a slow, heavy, cargo bike. But on the bright side, riding in the rockies you simply won't really need that 11 tooth rear cog. If you have a 48t front ring, you will have the range you need for the rockies with 48 front, 14 rear gear as your highest gear. Pedal about 20 mph fine. Only if you built a much more powerful bike like my full suspension longtail would you need that higher gear. That bike of mine goes 30-35 mph, and I put a 56t front crank on it. It also still has the very very low gears too.

As you read all this, which is like drinking from the fire hose, bear in mind one thing.

Amberwolf and I have vast experience actually riding very heavy cargo bikes with electric assist. We have become a bit biased, by what worked for us. We both live in the desert, and need a bike that can survive it. In my case, my cargo bike needed to not only survive a 70 mile ride across the desert, but also climb to the tall pines.

Look to those who have really toured for some good advice. Grindz, Kingfish, Justin, and a few others. What I rode to do a fairly easy commute to work for years just doesn't quite cut it, for riding around in the rocky mountains loaded with camping gear.

My last word, you'd be in pretty good shape for 90% of your needs with the kit we sell at E-Bikekit. If you do, get your battery someplace cheaper than EBK. But you'd need double money, to go big and build a really nice cargo bike. You're best choice still remains the stokemonkey, and whatever it costs to use a custom crank.

 

[MadRhino]

You say that you will be carrying heavy loads and occasionally a passenger, in the hills of Colorado. This could require some serious power. A geared motor may do the job, maybe not, but it is your best option actually, since you want to be able to pedal that bike unpowered and save on the cost.

The very best would be a Stokemonkey, that is a mid drive built with a hub motor. Then you could tune the speed and torque with gearing ratio, even use a more powerful DD hub if needed.

 

[wesnewell]

http://kinaye-motorsports.myshopify.com/products/mxus-xf40-45h-45mm-3000w-motor-6t-6kv
http://www.aliexpress.com/store/product/Free-Shipping-48V-1000W-45Amax-BLDC-motor-controller-E-bike-brushless-speed-controller-compatible-for-sensor/313864_497637202.html
20ah of 12s rc lipo, charging system.
Throttle and ebrakes.
Done. Or what I'd do is start with a 48V 1000W kit for ~$250 and then upgrade to this motor if needed later.

 

[snowranger]

I can pretty much go up anything with my bafang mid drive; however, you need to secure that rear axle since the Yuba has large horizontal dropouts. See pic.

 

[cwah]

mxus is nice

 

[Mundo]

Cargo bikes with mid drives rule.
It's like having a tractor.

 

[dogman dan]

Yes, his best choice would be a stokemonkey. But it can be done with a big enough hub motor.

3000w motor like Wes recommended will do er. The downside is to go that fast , heavily loaded, up the big mountains for long requires a battery that costs more than a stokemonkey setup.

Honestly, he'd be better off to start with the stoker and 10 ah battery. But how the hell does he do that and keep that short crank?

Any way you slice it, to fill 100% of his wants, he's going to spend $3000. Time to add money or subtract wants. I suspect that will plenty of assist, his hips might tolerate a longer crank. But it might be best for him to start with a medium cost, but still pretty large hub motor in the rear. Something like the crystalyte H model, or muxus 3000w. To get speed and distance in mountains, then you need to buy a big ass, expensive, battery.

 

[dnmun]

fort collins is very flat. not sure who told you it was hills but they are wrong. you have to go west of fort collins to get up into the front range but the city itself is as flat as kansas.

 

[MadRhino]

Sorry. We hear Colorado and think mountains, at least for us mountain riders. :wink:

 

[dnmun]

ft collins and loveland and longmont and denver are on the east side of the front range. boulder has the flatirons going up to chatauqua park and up into the mountains but the main population is on the flat.

i live west of loveland and i have the same granite uplift in back of my house on my lot like the flatirons. my lot climbs about 200' in 645' depth back from the county road.

but the county road that goes north up to masonville behind, or west, of ft collins is fairly flat. there is a climb west of ft collins behind the horsetooth reservoir but it is short and when you get to masonville it is flat all the way back down to my place south of there.

 

[teklektik]

Your low budget gets in the way of many solutions - particularly since PAS is in the mix. The low speed requirements of heavy hauling or rough trails make hub solutions disproportionately powerful compared to power requirements for running on the flat. Hub motors really work poorly (hot, inefficient - chew through power) under load at really low speeds, so your cost requirements get in the way of appropriately large batteries and hub motor sizing. If you have thoughts of snow riding (since you have no car), things get worse rapidly for hub motor solutions.

As you surmised, a mid-drive looks pretty attractive. Here's some thoughts (from a guy with no mid-drive experience ):

• A dynamo on an electric bike is an odd design strategy. I appreciate that you would like to keep it, but selling it off to put more money into batteries is worth considering.
  
  
• Off-theShelf: A quick build in your price range is to get a Bafang 750 and battery from EM3EV. This gives you pretty much the whole list of wish items - mid-drive, PAS, hidden wire brake sensor, LCD, etc. You can have the kit arms shortened without much difficulty by a local auto machine shop, but it will add to the cost (there may be other options there). This is a fairly well proven out-of-box solution and reliability for a daily driver may be your only concern. Upgrade the battery to the biggest you can afford.
  
  
• Cheap DIY Midmotor: A alternative DIY solution would be to mount up a big geared hubmotor as a mid-motor by fabbing your own mount. Instead of running this as a mid-drive through the right-side rider drive, run it with fixed gearing on the left. Just bolt up a pair of off the shelf sprockets to the motor and hub disc brake mounts with something like a 1.5:1 or 1.75:1 ratio. The gear motor has an internal freewheel so no extra outboard freewheel is required. There will be some bit of increased drag spinning the hub casing from the rear wheel when pedaling unassisted, but the inner motor will not be turning (no cogging effect). Here you can use a heavier chain and sprockets that will give trouble-free operation under severe loads. With a single chain, no external freewheel, and no jackshaft, this is about the simplest mid-motor build possible. You will need to forego your rear disc - probably in favor of a v-brake. Since most of your braking is with the front wheel, this rear brake revision isn't that punishing...
  
  This single speed solution does not offer the torque advantage of the gearing with a right side drive so a small motor is off the table. However, the single fixed ratio will substantially improve torque and a large geared hub will have much improved low speed hauling performance. You want a high speed wind so you can jack up the chain ratio to keep the motor rpms as high as possible with a moderately priced 48V off-the-shelf battery solution. MAC performance goes downhill over 500-550rpm so there is an upper limit to the ratio to be able to achieve your 20mph top speed goal. You could swap gearing for more torque and less speed to get some added help for seasonal inclement weather and road surfaces (winter).
  
  • BTW - If you have over-estimated your need for hill-climbing power, you can easily revert to a 1:1 ratio and get about the same performance as a standard MAC rear hub motor build (minus the disc brake) - or if you use a front MAC as the middie, just re-mount the motor as a conventional front wheel build - or start with a front wheel MAC build and convert to mid-motor if you need more hill assist.
  A MAC 8T is about the most powerful solution for this with very rugged and inexpensive gears and clutch (EM3EV - email Paul to spec this kit with a bare motor instead of wheel build). A larger Bafang should work nicely as well and are often available with PAS controllers and LCD as a kit. There is not a lot of room in the Mundo frame, but a MAC or the slightly smaller Bafangs look like they will fit without issue. Most DD motors are not candidates unless you turn down the spoke flanges, etc. Standard stokeMonkey mounting parts appear to fit a MAC, but the fab does not look that challenging if you want to go the 'sweat equity' route. (I do like the special Mundo Cycle stoker mounting plate concept, but I'm not sure the stock plate is far enough forward for a MAC - you might contact Justin at ebikes.ca and see if they have some left over beta attempts available that you could leverage in your build.)
  
  In this solution you will need to either spec out a controller with integrated PAS support or go with a simpler controller + CA V3 with a simple PAS wheel (more expensive). Obviously, your present drive system and cranks are unaffected. Remember that the controller determines your getaway and hill-climbing torque (Amp rating), so don't low-ball the controller too far.
  
  Here's a quick simulator run showing this with a BMC V2S (equiv to a MAC 8T) and an EM3EV 50V battery.
  
  
  Top speed is 20mph unassisted on the flat and 16mph all day on a 7% grade with no overheating (simulator shows 10+% grade continuous w/o overheating). This assumes a 1.75:1 chain ratio which is fudged into the simulator by dividing the wheel size by the chain ratio (tiny 15in wheel). Estimated no-assist range on the flat is 13 miles with 8Ah of available battery -- at these speeds with pedaling you can double that (since you do it without power already).
  
  In these examples, the intersection of the black Load Line and red Motor Power lines are to the right of the discontinuous peak in the red curve, so we know performance is not controller-limited -- the 35A controller capacity is not impeding operation. Loaded on the 7% incline, the motor is performing at about peak efficiency - so these are pretty happy results...

So - just some thoughts for approaches that may be near(er) your $1000 price tag...

 

[kiltedcelt]

Wow! Thanks for the additional replies that have come in over the last few weeks. It's all given me a lot more to think about. I just built my own HDPE running boards for my Mundo yesterday and realized when I weighed the bike that it currently sits at 64 lbs. That's a lot of weight to get moving and keep moving, but even without the running boards I was still pushing around 60 lbs. of bike with only my own leg power. With only a moderate amount of effort I can ride with an average speed of about 14-15 mph, although that is typically low because there are a couple of areas of my commute where I really need to slow down around pedestrian traffic. Over that 11.5 mile ride, I usually am riding more around 15-16 mph, or the other day with a nice tailwind I was having no trouble managing 20 mph or more for extended periods of time! So, anyway with all the replies I have more questions:

1. If I understand correctly, PAS (pedal assist?), generally only works well with mid-drive motors, or is this more to do with the controller and having a torque sensor? Bionix motors supposedly have PAS (haven't ridden one), but they're all hub motors, correct?

2. Sounds like what I really want is a Stokemonkey, so maybe I just need to come to terms with that and start saving money. I'd then have plug-and-play without having to figure anything out or fabricate anything. It also seems like that would allow me to use my current drive-train without modifications, unless I'm wrong about that. I can't remember whether Stokemonkey uses a proprietary bottom bracket or not.

3. If I did go for a hub motor, it sounds like I want a geared motor that will freewheel, and one with a cassette mount versus freehub. Which manufacturers fit those criteria? Also, a rear hub motor with freewheeling capability and cassette will still allow PAS, correct? Also I could keep my current gearing and the rest of my drivetrain including the funky short cranks?

As a side note, I could always go back to trying 170mm or 175mm cranks - I just haven't since it seemed like the freaky shortie cranks were working just fine for me and I don't know if I'd even have problems if I went back to the longer crank arms.

Although a certain amount of fabrication and piecing together of components doesn't faze me, I think for this project I'd really prefer something that was more of a plug-and-play design. Lacing a rear wheel up around a new hub motor isn't the end of the world and wouldn't bother me any, especially if a rear hub motor would involve less fabrication hassle than any of the mid-drives that I might have to piece together. However, for everything else I'd prefer a design/system where I only needed to follow instructions for basic installation. I think this is what is directing me back towards something like Stokemonkey or Bionx. It would appear that Clever Cycles sells the Stokemonkey for about $1250, but that is apparently without battery. I have no idea what sort of cost I'm looking at with batteries. It seems like most of you guys go with some sort of lithium battery solution, I'm guessing because output is higher based on the weight of the battery than with something like AGM scooter/motorcycle batteries? Is it cheaper to build your own battery by buying single cells and soldering everything together or just buy a ready-made battery and adapt the mounting of it to fit the frame? How much extra cost does battery add to the kit, assuming I don't in fact need some super dense battery, as it sounds like 80% of the time I won't be dealing with extreme grades or heavy loads?

 

[allezdude]

I don't know if this will help you, but I live in the Chicago burbs and just bought an xtracycle edgerunner and plan to fit it with. A 500 W bbs02 from my commuter bike powered by a 36v Allcell summit battery. You're welcome to come check it out. If I didn't already have the bbs02 kit, I'd probably get the stoke monkey kit- seems like a good deal considering it includes in addition to motor & controller, the torque sensing BB, cycle analyst, etc...

Also greenbikes has a 500W, 48v mid drive kit with battery for under your budget. I have no experience with that vendor though.

 

[kiltedcelt]

So, a friend who owns a shop can sell me a Bionx with battery for a pretty good price. I test rode his Bullitt equipped with I think a 48v Bionx. I liked how the ride was similar to the Felt Outfitter with Bosch motor that I rode a couple months back. Is there a way to buy all aftermarket parts and make your own Bionx clone for less money?