building a cargo e-bike for my kiddo

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Runner23   100 µW

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building a cargo e-bike for my kiddo

Post by Runner23 » Mar 08 2016 4:48am

hi all,

i want to get a bike like the one attached to transport my kid around. But theyre pretty heavy so i wanted to build it into an e-bike and wanted to get some input and recommendations for that purpose.

Do you have any recommendations for type of motor to use for this? I read good things about the MXUS motor. And whether it should be a single motor in the rear wheel or 2 motors in the front wheels? And what about placement of the battery pack?

Thanks in advance
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bowlofsalad   1 MW

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Re: building a cargo e-bike for my kiddo

Post by bowlofsalad » Mar 08 2016 5:13am

Runner23 wrote:hi all,

i want to get a bike like the one attached to transport my kid around. But theyre pretty heavy so i wanted to build it into an e-bike and wanted to get some input and recommendations for that purpose.

Do you have any recommendations for type of motor to use for this? I read good things about the MXUS motor. And whether it should be a single motor in the rear wheel or 2 motors in the front wheels? And what about placement of the battery pack?

Thanks in advance
I'd just get/make an electric bicycle to your liking and add a trailer, probably far cheaper and quicker this way. There are tons of used kid trailers available, but this idea is already readily available for much less than what you'd probably end up spending otherwise. When you aren't hauling a child around you could always detach the trailer and either attach a different trailer(assuming you have cargo needs) or simply ride without a trailer, kind of a nice idea in my opinion. Not a lot of people are probably going to be interested in buying your used trike like what you've shared a picture of, but the separate components, an electric bicycle and kid trailer are probably going to retain a wildly higher degree of versatility and value.

http://www.amazon.com/b/ref=as_li_ss_tl ... 6S24W57QAW Tons of stuff that'll work out of the box but I'd definitely look around locally for used stuff.

I don't have any serious way to answer the other aspect of your question as the variables on that sort of idea are many. Aspects like terrain, ideal top speed and weight all play pretty critical elements. Your gross weight being 400 pounds hoping to go up basically mountains would require a different setup than 200 pounds and a few short hills. My blind guess might be to suggest a mid drive. http://lunacycle.com/mid-drive-kits/

If you go with the bicycle and trailer route, figuring out where to put the battery and such might be a bit easier as well. Although I think if I was going to mount the battery on that trike you shared a picture of I might drape a hanging system on the backside of the box and drill a few holes to pull something through the wall of the box to tie to the battery to give it a bit more stability, or maybe use nuts and bolts for that.

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dogman dan   100 GW

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Re: building a cargo e-bike for my kiddo

Post by dogman dan » Mar 08 2016 5:54am

Single motor in the rear.

I'd be inclined to have the battery on a rear rack. Why? So less wiring has to go all the way to the tub. Short wire from battery to controller, to rear wheel. The battery wire is where you really don't want a lot of movement chafing it, leading to a short.

Easy to watch what kids are up to, in front. But for many, the kid trailer is a good solution.

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Re: building a cargo e-bike for my kiddo

Post by Drunkskunk » Mar 08 2016 10:23am

That trike looks good. there are problems with a rear motor on that trike. the space for that rear hub will be 120mm. a hub motor is 135mm. If the frame is steel, it can likely be stretched wide enough to fit, but that's a job for people with confidence in their abilities to make things.

There is no easy way to mount 2 front motors to that trike. you would need skill and access to a machine shop to make some custom motor axles.

The alternative is a mid drive motor, like a BBS02, or BBSHD. It's easy enough to mount and if you combined it with an IGH hub for the rear, you could haul the kids up any hill.
I agree with a battery on a rear rack. Along with the stated reasons, also to keep it away from the kids for the same reason you would keep a gas tank away from the kids. It's just safer back there.
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Re: building a cargo e-bike for my kiddo

Post by The fingers » Mar 08 2016 2:02pm

http://www.christianiabikes.com/en/product/light/ Shows an electric motor option.http://www.christianiabikes.com/en/addition/e-bike/ Maybe they offer a frame that will accommodate your choice of motor.
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Re: building a cargo e-bike for my kiddo

Post by Runner23 » Jun 20 2016 4:59am

Drunkskunk wrote:That trike looks good. there are problems with a rear motor on that trike. the space for that rear hub will be 120mm. a hub motor is 135mm. If the frame is steel, it can likely be stretched wide enough to fit, but that's a job for people with confidence in their abilities to make things.

There is no easy way to mount 2 front motors to that trike. you would need skill and access to a machine shop to make some custom motor axles.

The alternative is a mid drive motor, like a BBS02, or BBSHD. It's easy enough to mount and if you combined it with an IGH hub for the rear, you could haul the kids up any hill.
I agree with a battery on a rear rack. Along with the stated reasons, also to keep it away from the kids for the same reason you would keep a gas tank away from the kids. It's just safer back there.

just reviving this thread a bit since i still want to go ahead and build one of these. Apparently, the wife didnt like the idea of not being able to sit the kid in front.

I just measured the width between the dropouts on the rear wheel. Its 13mm, but i suppose they can be bent a bit since its all steel. Whats the width of the MXUS motor?
can you recommend some decent other parts- controller, battery etc? Bear in mind its only going to be used for reliability and nice to have decent range from the battery pack

thanks a bundle
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Re: building a cargo e-bike for my kiddo

Post by dogman dan » Jun 20 2016 5:52am

Where are you at? What continent you are on can change our advice as to where you should buy stuff.

The big muxus motors are wider than the normal 135 mm. You will likely also want to do something to add gears, like shown on the motorized Christiania.

How big a motor you really need, will depend on the hills you need to climb. A mid drive might be a better choice than the 3000w muxus motor, if that's the one you were looking at.

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Re: building a cargo e-bike for my kiddo

Post by Dumsterdave » Jun 20 2016 6:10am

Im quite interested in this thread as well. I have the exact cargo bike and want to electrify it. Right now it has an internal gear hub in the rear. This means i would have to convert it to a derailer or maybe use a mid drive. The front hub would be difficult to install since there is nothing to attach the other axle to. I havent bothered to measure the bottom bracket width, but i am a bit worried that it may be a bit wider than a standard BB. Ill check it out and post an update. Also, do you have an idea on where you'd like to purchase from? I am in denmark and my options are pretty limited unless i want to pay some hefty import/VAT/Customs taxes.

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Re: building a cargo e-bike for my kiddo

Post by Runner23 » Jun 21 2016 4:02am

dogman dan wrote:Where are you at? What continent you are on can change our advice as to where you should buy stuff.

The big muxus motors are wider than the normal 135 mm. You will likely also want to do something to add gears, like shown on the motorized Christiania.

How big a motor you really need, will depend on the hills you need to climb. A mid drive might be a better choice than the 3000w muxus motor, if that's the one you were looking at.

i am located in Denmark, where you cannot get many e-bike parts. But online from China/US is ok, ive done that before.

How wide are the MXUS 3000 motors, because it seems that dropouts can be stretched by a professional, as long as its not too much.

Since using the motor will be the main "propulsion" i was thinking that a single gear will be enough
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Re: building a cargo e-bike for my kiddo

Post by Wheazel » Jun 21 2016 5:21am

You might want to consider the leafmotor 1500W aswell if you are thinking about a mxus 3000, and space is a consideration.
You can find my experiences with the leafmotor in my cargobike thread (page4). I also have a mxus 3000 on order, but will probably not put it on the cargobike.

The reason I am raising the leaf up for discussion, is that you can fit a threaded casette on it.
It gives slightly more space than the mxus does afaik.

Being Denmark, I cant imagine you are facing many hills.
The leafmotor has served me well for my cargoloads. I am guessing I have had 80-100kg extra weight at most when pulling the trailer + having some stuff in the cargobox.
When it becomes hilly you can still haul these weights, but the motor will heat up.

I would go for a dd hub any day even if a middrive is more suited for hillclimbing thanks to the variable gearing.
A dd hub is silent, that is worth loads to me at least.

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Re: building a cargo e-bike for my kiddo

Post by Dumsterdave » Jun 21 2016 5:36am

Wheazel wrote:You might want to consider the leafmotor 1500W aswell if you are thinking about a mxus 3000, and space is a consideration.
You can find my experiences with the leafmotor in my cargobike thread (page4). I also have a mxus 3000 on order, but will probably not put it on the cargobike.

The reason I am raising the leaf up for discussion, is that you can fit a threaded casette on it.
It gives slightly more space than the mxus does afaik.

Being Denmark, I cant imagine you are facing many hills.
The leafmotor has served me well for my cargoloads. I am guessing I have had 80-100kg extra weight at most when pulling the trailer + having some stuff in the cargobox.
When it becomes hilly you can still haul these weights, but the motor will heat up.

I would go for a dd hub any day even if a middrive is more suited for hillclimbing thanks to the variable gearing.
A dd hub is silent, that is worth loads to me at least.
The leafmotor would not be of benefit unless he were to convert his christiania bike to use a rear derailer.. As of right now, (if the picture is correct) then he has an rear Internal gear hub. So if he were to install a hub motor it would be a single speed... This is why i think that a mid drive would be a better option. True, Denmark doesnt have many hills, but i would think that you would need the added torque when you are trying to push around a 35kg bike as well as an additional 100kg if you factor in an adult and child. A single gear cargo bike with a dd hub will accelerate painfully slow.

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Re: building a cargo e-bike for my kiddo

Post by dogman dan » Jun 21 2016 8:07am

Best approach might well be mid drive, because of the IGH, or coaster brake, whichever it is.

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Re: building a cargo e-bike for my kiddo

Post by gogo » Jun 21 2016 11:13am

I'd run a DD hubmotor as a friction drive on the rear tire. That would retain the IGH for human power only and allow powered reverse.
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Re: building a cargo e-bike for my kiddo

Post by amberwolf » Jun 21 2016 12:36pm

Dumsterdave wrote: A single gear cargo bike with a dd hub will accelerate painfully slow.
Unless using power levels in the 3KW+ range, I'd agree, based on my experiences with CrazyBike2 and SB Cruiser. Even with those, to get that power with common "cheap" stuff, I use two motors (one in each wheel on CB2, one in each rear wheel on SBC). If I'm not in traffic it's not a big deal but if I'm the last one to a stop light and don't make it thru while it's green, I"ll be the first one in line waiting, with cars stuck behind me; if I can't accelerate fast enough to keep up with them thru the intersection, there's...hard feelings, shall we say. :/


A middrive that can be geared down for torque to get good starts from a stop, then geared up for whatever speed is needed for cruising, would be more efficient and smaller, taking less battery, etc.

As long as you don't hammer an IGH with sudden power, it might still handle the motor driving thru it. You could add a "cush drive" output from the middrive, so it doesn't place sudden loads on the IGH, and also a ramp-up throttle if it doesn't have one, so it never applies hits of high power but ramps up from zero to take up the chain slack and gear lash inside the IGH before applying power to it.

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Re: building a cargo e-bike for my kiddo

Post by SlowCo » Jun 21 2016 4:38pm

http://www.christianiabikes.com/en/product/taxi/

The Taxi model already has an electric motor, will be legal (if that's important) and is made to transport people.

If you still want to build it yourself I would look at a low rpm geared hub motor like the 800W Q128H from BMSbattery:
https://bmsbattery.com/ebike-kit/776-q1 ... e-kit.html

Or remodel the triangle (straighter/higher tube) and fit a BBS02/HD like this guy:
https://endless-sphere.com/forums/viewt ... 26#p899826

BBSHD: http://em3ev.com/store/index.php?route= ... uct_id=243

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Re: building a cargo e-bike for my kiddo

Post by Dumsterdave » Jun 22 2016 7:19am

SlowCo wrote:http://www.christianiabikes.com/en/product/taxi/

The Taxi model already has an electric motor, will be legal (if that's important) and is made to transport people.
All models of the christiania bike have the option to be electric and they are all designed to transport people. A lot of families use the exact model that the OP has to take their children to school and carry cargo. Problem is that Denmark loves IGH's and unless you specifically request your christiania bike to be electric when you buy it then they will install a IGH. Not a huge deal because the bike has the ability to mount a rear derailer, its just annoying. If i were to buy one again i would request to have the derailer installed instead of the IGH

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