Conversion of a cargo bike - Advice needed

[Mikelob]

Dear people from ES

I have been reading on this forum for the past week and it's allready tought me a lot, now due to a change of scenario i'm stuck. I need help. First i just needed to convert my MTB to hub drive. This was sorted, i know what to buy and where to get it, no issues. Now, it looks like i'll need to convert our cargo bike instead. I'm running into some issues.

The bike:

First issue: rear hub is a 4 speed nexus gear hub. No derailleur hanger. Stuck with this wheel.

Second issue: Bottom bracket is somewhat weird. Due to it being a cargo bike, the frame is not normal. I'll add a picture. BB width is 68, but a piece of the frame is in the way. BBS02 has 13mm spacing between BB and motor, this frame takes 20mm. I may be able to remove some metal, then the motor would need to go under the rear stays, but the rear wheel might get in the way? (I'll upload a pic that shows this issue).

Third issue: If the mid drive wont fit, i need to find a front hub motor that will accomodate a rollerbrake. Front fork spacing is the standard 100mm. I find kits like this, but they're 36v 250w weak as all hell, or with spacing of 92mm, or something else is wrong. There should be better kit / tech around?

Our needs:
Cruise at 15kmh (9 to 12 mph), max out at 25kmh (15mph).
Range: at least 20km (12miles)
Front wheel is 20", rear is 26".
Weight, well, the bike ain't light. Its a full steel frame with a wooden box. I'm 200lbs squeezed out, and i'd use it for groceries and kids hauling.
Terrain is mostly flat and city stop and go traffic.

Won't need a throttle since its illegal in Belgium, 250w + is illegal aswell but who'd notice if i stick to the speed limit. I'd like a good pedal assist, don't want to break out in sweat every ride.

Budget? Well, i'd love to find a kit on Aliexpress with an okay / good battery and would love to stick to around 800€. I haven't found any kit that would work on Aliexpress with the rollerbrake issue. Cheapest kit i've found to fit is +1000€ for 36V / 250w / 10ah so that kind of stinks.

Thanks in advance for your cooperation. I'll also keep searching offcaurse. Just hoping for some tips or insights. I've never built an e-bike before but i do all my bike maintenance myself + i'm tech savvy enough to do it.

 

[Wheazel]

I don't have experience with the type of mid-drive setup you are looking for, but maybe you can find something useful in my electric cargo bike thread.
See signature if interested. I generally like hub motors for city type riding as it is very maintenance free and quiet.
If I was in your situation I would try to incorporate a hub regardless of the challenges. Even a front wheel hub is quite common for long johns with a stiff fork and 20" wheel.
The small wheel help lower the torque requirements from the hub motor.

You could combine parts yourself to get a good setup with a front hub.
Why not weld attachment points for a disc brake while you are at it? It is a very trivial job for someone with a welder, and you only need to repaint afterwards.

 

[LewTwo]

Just a couple of thoughts.
Normally people dismiss front hub motors because they may not have enough traction however with the weight distribution on the cargo bike this might not be as much a problem particularly if you locate the battery in the front of the cargo bay. The TDCM IGH rear hub might be a valid option for a rear hub motor and give you a minor upgrade to 5 speeds as well.
Reference: https://endless-sphere.com/forums/viewtopic.php?f=30&t=63284

I see think that you major difficulty will be the roller brakes that as you note is not very common option for E-bikes. I looked at the web site for Bakfiets.nl. I notice that they offer both hydraulic disk and hydraulic rim brakes as options. I do want to get a long argument about rim vs disk brakes going but I happen to like rim brakes. They work and they are simplistic to maintain. It might be practical to fit a inexpensive front or rear rim brake to you current setup (in addition to) to see if they would be adequate to your application.

 

[Drunkskunk]

Welcome to the forum. That is an annoying problem. so many options that would almost work...

If this was my own bike, I would use the BBS02 (actualy, I'd use the BBSHD, but I like power). I believe it would be the best (nearly) legal solution to powering a heavy bike at slow speeds for you. Since the frame support needs to be cut, I would add a brace between the steering support and the seat support. If it's a steel frame, it would be a simple welding job, and I'd cut the curved top bar from a used/discarded lady's step through bike. Something that clamped on might also work, but might be harder to fabricate.

But that might not be the best solution for you, depending on your skills and resources available.

Another option is to use a front motor, and a brake change. Some forks can have a center pin style rim brake mounted to the same hole as the fender may be mounted to. it might also be possible to drill a hole in the fork to mount the rim brake. It's not a difficult job , but not possible on every fork, so you would need to make that call.

If the fork can't take a rim brake, then replace it with one capable of either rim brakes, or a disk brake. Because of the very long cable run for the front brake on that bike, a hydraulic disk brake would be the best option.

For the front motor, a 500w geared hub makes sense. I'd get something with a proven record of taking more torque that the more common motors, since it will be hauling more weight than a standard bike. the MAC motor would be my first choice. Something like this: em3ev.com/MAC

 

[amberwolf]

First issue: rear hub is a 4 speed nexus gear hub. No derailleur hanger.

There are plenty of older-style cheap derailers for 3-6 speeds that don't use a hanger, by Shimano, Sugino etc. They slip under the axle nut, and are kept from rotating around by a tab and bolt/nute that go into the dropout slot. If the dropout slot isn't deep enough you can skip the antirotation bolt and use it anyway, you just have to be a bit more handy with holding stuff in place when you tighten the axle nut to keep the right angle on the derailer mounting tab.

If you can't find one new, look around for older cheap bikes. Go this route and you also get the 3-6 speed freewheel to go with it, to thread onto the new hubmotor.

A google image search shows a few, and also shows something I hadn't seen, which is a bolt-on hanger that goes on the same way as the derailer described above,, but then is threaded for a modern derailer.
https://www.google.com/search?q=hangerless+derailers&source=lnms&tbm=isch&sa=X&ved=0ahUKEwikmNeHg-3RAhUEx7wKHVhuBdoQ_AUICigD&biw=1529&bih=925

If you really want to keep the nexus but can't make any derailer options work, you can put the nexus in the frame or under or over it, and run the chain from it to the rear wheel on a singlespeed freewheel. But this will require some DIY to take the dropouts (or a fork) off another bike and mount them on the cargo bike's frame. Not hard if you have a welder and some imagination, but might take a little doing before you get it just right.
first try cuz it was simple:
https://endless-sphere.com/forums/viewtopic.php?f=2&t=67833&start=350#p1227692

Final configuration:
https://endless-sphere.com/forums/viewtopic.php?f=2&t=67833&start=350#p1230328

Note the derailer in there is one like I described above; it's used really because teh chairnings are oval so chain lenght changes. Only reason I used the oval chainrings was cuz I didn't have any other handy crank with a low enough granny gear, as that's all I really needed was the smallest one. If I find a round one then all that stuff will probably go away to simplify it down to just the IGH (which was the original point to doing it).

Third issue: If the mid drive wont fit, i need to find a front hub motor that will accomodate a rollerbrake. Front fork spacing is the standard 100mm.

AFAICR there is a Q-series ("cute") motor that has a rollerbrake mount; can't remember which one though.
Some of the topics that might have info
https://endless-sphere.com/forums/search.php?keywords=cute+roller+brake&terms=all&author=&sc=1&sf=all&sk=t&sd=d&sr=topics&st=0&ch=300&t=0&submit=Search

Weight, well, the bike ain't light. Its a full steel frame with a wooden box. I'm 200lbs squeezed out, and i'd use it for groceries and kids hauling.
Terrain is mostly flat and city stop and go traffic.

If it werent' for the rollerbrake there's a lot of higher power hubmotrs that would work fine for that. Geared will be more efficient in that type of traffic, but there's more to breakdown and the power limits are lower because the heat builds up inside them faster in stop-and-go traffic, vs DD (direct drive) motors.

The smaller front wheel would be a better choice to put it in vs the rear, for teh "gearing down" that gives it. It's why I'm using them in my rear wheels vs in the front--it made a huge difference in the smaller wheel, for torque since I don't need the speed.

Probably any good "500w"+ rated DD hubmotor will do what you want, or any "500-1000w" rated geared hub; neither one will be all that small and light, but given the rest of the bike/cargo it doesnt matter that much.

The only reason for the higher geared hub rating is that stop-and-go-traffic thing. I've used smaller geared hubs for heavy cargo use in traffic here in Phoenix, on the flats, and badly overheated them, even breaking the clutch on one, and though they all still work once repaired....the larger geared hub I used didn't have that problem. (the company that made mine isnt' around anymore, but Bafang / BMC and MAC both make good larger hubs, and I think Ezee does too. )

 

[WoodlandHills]

http://www.treefortbikes.com/product/333222375258/1398/Problem-Solvers-Chain-Tensioner.html?gclid=CPi-zcKS7dECFYOGaQodfQ8ELg

Or you could use one of these......

 

[Mikelob]

Holy shit...

Pardon my language, but i could like... weld a derailleur hanger to the rear stay, and be done with it?

I've got a spare 7 speed rear derailleur, get a 500w DD hub motor with 7spd freewheel and voila...

If this train of thought doesn't reach the station i'd weld V brake lugs to the front fork. I'm trying to work with solutions that are in my reach. I can stick weld, but know people that can mig weld.

Thanks everyone, for all your insights. Amberwolf, thanks for the ideas, it's something i never would have come up with but it's good to know that something like that is even doable. Haven't seen a nexus from the inside.

I'd sure prefer a rear wheel motor, than a front wheel motor. The nexus hub won't go to waste... oh wait, then i'll need to fix rear brakes haha. Oh well, doable! Much thinking to do...

 

[Wheazel]

There is also the Tdcm igh possibility. Have no experience of it myslef but it looks nice for a reasonably powered system.
Might be on the weak-side for steep hills, but should be great functionality overall. I think a front hub would be the cheapest and easiest to set up.

http://www.ebikes.ca/shop/electric-bicycle-kits/tdcm-igh.html

Attaching a threaded ear for a derailleur is very easy to do.
For all my builds I have just cut that small part of a wrecked donor bike.

 

[amberwolf]

Pardon my language, but i could like... weld a derailleur hanger to the rear stay, and be done with it?

Sure, but you don't even have to weld it. The ones shown in that image search are all bolt-on using the axle/axle nut to hold them in place.

Of course, welding makes it simpler to install/remove the wheel without messing with holding the derailer/hanger in place while doing the axle stuff too.

If this train of thought doesn't reach the station i'd weld V brake lugs to the front fork.

You don't have to weld those on either:
https://endless-sphere.com/forums/viewtopic.php?f=2&t=82702&p=1213850&hilit=brake+clamp+fork+CrazyBike2#p1213850
Works fine, even on this very heavy bike (which itself weighs over 200lbs). I did weld the rear ones on, cut off the stays of another bike along iwth some of the tube, so I could more easily align them without a jig, and clamp them on for welding. But the U-brace with them already on it would've been easier if I'd had another one to spare at the time.

I've also welded them on another fork (for a 20" front wheel on Delta Tripper using a BMX fork), and that worked too.

Amberwolf, thanks for the ideas, it's something i never would have come up with but it's good to know that something like that is even doable. Haven't seen a nexus from the inside.

Doesnt' matter what it looks like inside--outside it's jsut a hub, and will fit just like the Shimano 3speed I've got in SBC's frame (as pictured previously).

I'm...different. My brain doesn't work like most people's, and I see alternative solutions to things some people havent' even seen as a problem. :lol: Sometimes my solutions are totally impractical...but work with the materials I have at hand and so I use them even though a better one is available.

(but the better one costs money I don't have...and what I do also recycles thigns that would otherwise go in the trash. Almost everything on SB Cruiser and CrazyBike2 was made from stuff that was tossed out by someone else; almost all the rest of the stuff was used and bought cheaply or donated by someone for the purpose of being used on these "creations").

oh wait, then i'll need to fix rear brakes haha.

Can be added exactly like the front ones, as linked above.

 

[Mikelob]

You sure are diffirent. You're using other people's thrash for your own mobility. Something i greatly admire! I used to build and maintain motorcycles using spare crap aswell. Got out of motorcycles cause of the fuel they need, got into e-bikes cause of the lack of it. Ha!

Quick question, when installing a BBS02, does it matter wich way the motor itself is oriented? Can it be upside down? If i where to use one on this bike, the motor wouldnt face the front of the bike but would need to hang under the rear stays.

 

[dogman dan]

I'm the kind of guy that picks the low hanging fruit. The best solution would be to lose the IGH so you can just put a rear hub motor on it, a low rpm direct drive. It's hard for me to see if you have the right kind of long, semi horizontal dropout needed for a bolt on the dropout type derailleur. The cheaper bike derailleur that has the hanger built in.


Or low rpm direct drive front motor is a good idea, because changing that bike to disc brake is easier than any other modification. Sounds like you weld at least a bit? Welding a home made disc brake mount to a steel fork is real easy.

.

The best solution would still be a lower powered mid drive, I don't think the IGH will love a high powered one. You can cut that bit of frame, provided you don't leave an open hole. Weld some metal into the hole to retain the frame strength. Do this only if the frame is steel.

 

[amberwolf]

Quick question, when installing a BBS02, does it matter wich way the motor itself is oriented? Can it be upside down? If i where to use one on this bike, the motor wouldnt face the front of the bike but would need to hang under the rear stays.

Doesn't matter how it's rotated for operation, though bracing it for anti-twist would be different so you might have to manufacture brackets or bracing to deal with that.

But it has drain holes for any liquids that get into it (cuz it's really hard to truly seal things up), and those won't be in the right place anymore; see some of the various BBS* + *bent threads about mounting htem on booms; same basic problems.