How to Build a Cargo Bike

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three years ago i bought a trailer to get my son to our swimming-place or to the nice playground that's a bit more far away than the small one around the corner. everything is fine with that trailer, though i always have some kind of insecure feelings:
- the trailer is quite low and altough it has a small flag attached to a stick that should make it more visible i think it can easily be overseen by cars on the street .
- sitting in that trailer the kid is around 1 meter behind me so i don't see what he's doing or how he's doing unless i turn around. not a good idea while riding.
visiting copenhagen in december 2008 i saw lots of cargo bikes there used for transporting kids so i decided to get me one. a quick look around convinced me that buying one is no option for me (much too expensive) so i wanted to build one. since this is the first bike i built i had to go through some trial-and-error situations, but in the end all came out well. after some research on the internet i decided to build a bike similar to the christiania bike. this is how i did it:

Step 1: Recycling an Old Bike

i got myself an old crappy bike and cut it in two halves along the black line.

EDIT: If you want to build this make sure you use an old bike made from steel (check it with a magnet). Aluminium won't work!

Step 2: Frame Construction

the next thing was to construct the front frame. i thought that bigger would be better so it became 100 by 100 cm. this was not a good idea, but more about this later. what you see in the pic is the frame made of steel tubes (welded) and the rear part of the old bike.

Step 3: Wheels

the idea now was to mount the front wheels directly to the frame (see detail). looking at pics of original christiania bikes i saw that they put the wheel axis not in the middle but a bit more to the front of the frame. also i wanted to have a handlebar that can be adjusted in height, thus only two short steel tubes were welded to the back of the frame where i wanted to put the handlebar in.

EDIT: the wheel axis at christiania bikes is moved a bit to the front but still behind the pivot. mine was in front of the pivot... i changed it after riding the bike for a few months and now steering is much easier :-)

Step 4: Front Frame Test Assembly

first test assembly: looked good :-)

Step 5: Rear Part

now to the rear part of the cargobike. i took the handlebar's pivot from the old bike, welded it to a steel tube and then welded the steel tube to the rear part of the bike. the angle you see in the pic between the steel tube and the pivot was again something i saw on a pic. this was the second bad idea to do - more about it later.

EDIT: after using my trike for some time with NO angle and some discussions later (see comments below) i must say it would be better to have an angle between the steel tube and the pivot. measured at a christiania bike it should be 9.5 degrees in the direction you see in the pic - which is the opposite direction of the standard castor angle on a bike.

Step 6: Connecting Parts

the inner tube of the handlebar's pivot gets welded to the front frame and then i did a ...

Step 7: Test Assembly II

... second test assembly. it looked great and i was quite happy.

Step 8: Making It Stronger

the rear part undoubtedly had to be stronger. so i added a second steel tube and a bracing.

Step 9: Handlebar

the handlebar consists of three tubes connected with 90 degree tube-angles.

Step 10: Brakes

for the brakes (old ones from another bike) i screwed two steel plates with holes to the frame.

Step 11: Test Assembly 3

test assembly 3: looked good. but as i tried to ride it i recognized i was nearly unable to turn the bike in any whatsoever direction. after some research i discovered that the angle of the pivot might be the problem. also i read that any pedal-driven vehicle above 80 cm in width has to be checked by the authorities here. since i wanted to avoid this i had to make it smaller.

Step 12: S**t...

cutting the front frame, making it smaller and building a new pivot (taken from another old bike) were the next things to do.

Step 13: Frame

finally the frame was done. what followed was to mount the brake cables and all the usual stuff to the bike. one issue that had to be solved was how to operate the two front brakes with one handle. talking to a friend he came up with a nice solution: (see next step)

EDIT: two more improvements were necessary after some time

1) mount some cross beams between the handlebar and the front frame (see pic 2 in this step) and
2) mount some more cross beams on the lower end of the pivot to stabilize it further (see pic 3+4 in this step)

Step 14: Adaptor for the Brakes

this adaptor delivers the power of one handle to two brakes simultaneously. and last but not least one needs a ...

Step 15: Final Assembly

box to transport kids and things with the bike. that's it :-)
further improvements will be some cat eyes and other security stuff.

Step 16: Edit: Adjustable Steering Damper


after improving a few things (see the edits in some of the steps above) the last thing to do to complete this battleship was to add an adjustable steering damper. since these things can be quite expensive i built my own with a spring and a turnbuckle. works fine :-)

Step 17: Edit: Final Considerations

the measurements in this pic are the actual ones of my bike. if i would build one like this again i would change some things:

1) don't make the handle bar straight. it should be bent like in the drawing. this will save some space and allows to sit more straight.
2) use 20'' wheels for the front. this lowers the center of gravity and improves the handling on sloping grounds. the problem that arises is that you can't use the simple pivot i used - there's not enough room left between the ground and the box. a solution would be to
3) use conical roller bearings (these are parts used in cars) instead of the pivot .
4) don't build that double-break-thing for the front wheels yourself. you can purchase a better thing known as "double barrel brake lever" quite cheap which allows for independent adjustment of the two brakes.
5) adopt the size of the box to your needs. for me it's fine - i need to transport two kids and stuff at the same time (some times there are 4 kids and their things in the box...). if you don't need that much space make it smaller! because even the slightest wind is a burden if you have to pedal against it... one way to go would be to build a box from cardboard and to refine it until you think it's good. then build it from wood.
6) a camber of wheels improves the handling even more.
7) before building the frame watch some of these videos, this will help a lot: http://www.youtube.com/results?search_query=Bicycle+Frame+Building&aq=f

if you ever build a bike like this or get infected by the cargo-bike-virus and build some other construction please let us all know. post a pic or a link in the comments-section!

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175 Discussions

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emmettg2

1 year ago

I built a cargo bike similar to yours but when I turn the cargo ares in the front the bike frame leans. If you turn too far it pulls the bike over. Do you have any idea of what causes this and how it can be fixed. My theory is that it is similar to the "wheel flop" that you see on chopper motorcycles and the overall wheel base might be too long.

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carkatemmettg2

Reply 1 year ago

hi, hard to say from a distance. do you have a pic of your bike? there could be a few reasons for this... e.g. if the 90 degree-angle of the pivot is not really accurate the bike leans in turns (this is used with christiania bikes so that it feels more natural to ride the bike in turns). also if you turn too far the weight gets probably shifted to one side while the effective wheelbase gets smaller (think of the points where the wheels touch the ground: with a 90 degree turn they are all in line while the weight is on one side - this can't work :-) ). if you're riding too fast the weight wants to keep on track in turns while you try to move it somewhere else, this can pull your bike over, too, as i experienced in person a few times ;-)

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DanielJ185

2 years ago

Hi guys,

im trying to find some drawings to build this bike in the image. if somebody can help me, i will very appreciate.

any new pls write me : dalarcon798@gmail.com

Thanks in advance!!

Regards from Perú

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pozole13

5 years ago on Introduction

Slowly but surely working on my first one. I am using 20 inch wheels that I found at some garage sales.

I am realizing that I am going to have to use tapered (conical) bearings rather than the steering fork due to the lower ground clearance. I understand that Christiania uses tapered bearings as well.

There are not a lot of instructions online how to set up a shaft and tapered bearings for a cargo bike, but there is one here at 2:20-3:44 that might be useful for some.

http://www.youtube.com/watch?v=XSOTP1xj36Y

carkat, is this the way you envisioned the conical bearings working?

As always, thanks!!

2 replies
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mdubois6pozole13

Reply 3 years ago

hello, i also have 20'' wheels, but i seem to have enough clearance under the pivot (even if it came from a tall bike, my wife's bike pivot is 3,5cm shorter), 4cm, without tyres

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carkatpozole13

Reply 5 years ago on Introduction

hi,
yeah, this would be the pro-approach. i was thinking of using bearings including pre-made housings and somehow attaching them to the frame so there's no lathe needed. examples are here , here and here (e.g. hub II).
another approach would be to adjust the clearance so you can use the bicycle head tube like this guy did here

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dottorbiker

3 years ago on Introduction

Dear friend,
thanks a lot for your instructabls: it's great and now I must make my cargo bike!
I read many times your guide but I have some questions:
-for the cargo are good square steel tubes 30 mm*30 mm (2mm oh thickness)? and for the frame/pivot tube?
-the angle of pivot is right in my photo?
-the dimension are good?I'd like to have a big cargo bike!
thanks for your support and sorry for my english!! =)
Michele

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carkatdottorbiker

Reply 3 years ago on Introduction

hi,
the overall measurements look good to me. for the cargo area i used 20 x 20 mm tubes with 1,5 mm wall thickness and for the frame it was (i think) 25 x 2 mm. the pivot tube is taken from the donor bike (see step 5). and the angle looks perfect :-)
good luck for your build!

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SimonM4

3 years ago on Step 6

Hi, I'm inspired by your project and very impressed. I was looking at another cargo trike project on instructables... the person has put the pivot at the back of the cargo section (see pic of red cargo trike below). The result is that it is a little bit higher than putting the pivot beneath the cargo section so it should reduce the possibility of the pedals hitting the ground. Do you think there are any disadvantages to doing it like this? I was wondering if there would be more stress on the pivot doing it this way?

back pivot.jpg
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carkatSimonM4

Reply 3 years ago on Step 6

hi,
the problem with this position of the pivot is that steering becomes problematic. it works well with (very) high loads and when you're (very) slow, but other than that the steering tries to break free.
imagine you have a two-wheeled cart you DRAW behind you with one hand. the cart moves in the direction where you go / where you draw it to. now, if you PUSH it with one hand it would go in the direction it thinks is best :-) the same happens here pushing (pivot in the back) vs. drawing (pivot underneath slightly in front of the wheel-axis).
if you have problems with pedals hitting the ground you could either change the cranks to shorter ones (which also helps with higher load since pedalling becomes easier) OR maybe find a bigger bike for the project. usually a 26'' should do.

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SimonM4carkat

Reply 3 years ago on Introduction

Thanks for the gems!

I'd like to use a handlebar pivot as you have done under the cargo section but it seems that it makes the bike to low? I'm a bit confused as to why that doesn't work...Does the pivot hit the ground? If I use a bigger bike will that solve the problem?

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carkatSimonM4

Reply 3 years ago on Introduction

mmmh, sounds strange. if you were able to pedal on the bike (which i supppose) before you cut it to make the cargo bike you should be able to pedal now, too... and no, the pivot should never hit the ground...

the only thing i can imagine is that you have a really long handlebar pivot (e.g. as some dutch bikes do) which is too long to place it under the load. in this case you would have to shorten the tube.

do you have a photo or drawing of your bike? maybe that would help to figure out the issue.

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SimonM4carkat

Reply 3 years ago on Introduction

Excuse my confusing way of explaining this! I haven't made anything yet- although I'm planning to start next week. I saw through reading the posts on here that there was an issue with using a handlebar pivot as the pivot for the cargo section (I saw that you recommended the possibility of using a wheel hub bearing instead). Please can you explain why using a handlebar pivot is not a good idea? I'm quite keen to use a handlebar pivot to save money and make use of the part so it'd be great if there is a way to...

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carkatSimonM4

Reply 3 years ago on Introduction

there's no problem with using the handlebar pivot. using the wheel hub bearings just allows for more clearance to the ground. and it looks more professional ;-)

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urbanyeti

4 years ago

Hi, was just wondering about the mesurements from the bottom brack to the pivot of the cargo box.

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kehrlich1

4 years ago on Introduction

Hello Mr. CARCAT how and what you welded steel pipe and dural frame bicycles? TID? MID? CO2? I'm starting to build a coffee bike

Thanks for the answer I'm from Czech Republic

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