Picture of how to build a cargo bike
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:
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Step 1: Recycling an old bike

Picture of 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

Picture of 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.
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urbanyeti1 month ago
Hi, was just wondering about the mesurements from the bottom brack to the pivot of the cargo box.
carkat (author)  urbanyeti1 month ago

hi, that depends. have a look at step 17 in this instructable:

there you have some measurements from where you can calculate the distance. hope that helps!

kehrlich14 months ago

my first foto

kehrlich15 months ago

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

carkat (author)  kehrlich15 months ago

hi, with my first bike i used CO2 (it's called MIG/MAG here, don't know the english term). in the meantime i'm using TIG (WIG in german) which gives much nicer results. if you know how to weld i would recommend the latter one.
all the best for your build!

kehrlich1 carkat5 months ago
Hi, sorry, sorry, sorry, yesterday I tried frame with magnet and it is steel. Everything will be sorted out is simple. Next week we start building :-)
carkat (author)  kehrlich15 months ago

no worries! all the best for your build!

kehrlich1 carkat5 months ago
My problem is: how to combine old and new pipe frame, which is made of iron(steel). The frame of the bike is dural (aluminium)
carkat (author)  kehrlich15 months ago

i'm afraid this will not work. at least you can't weld those materials together. a long time ago i was working on something similar and a friend of mine suggested to glue the pieces together (steel and aluminium) with special industrial-style glue. but i don't have any experience with his (i dropped the project back then). i guess it's better to find an old steel frame and start over. sorry i don't have better news...

kehrlich1 carkat5 months ago
Hi.So it is better to TIG weld. A weld together a frame alloy wheels and steel pipes, or using the dural tube?
carkat (author)  kehrlich15 months ago

hmm, i am afraid i don't really understand what you mean. maybe you start with the front part: welding the tubes for the cargo-box. the next step then would be to make the rear part and connect everything. hope that answers your question?

Ds_man made it!9 months ago

Hello Mr.Carkat

I have no words to express my gratitude to you !

Not only that you gave me self confidence and make

me believe that i can do it,

But you also showed me the way . . .

I Used the Welding machine only once before this project,

Hope i welded them strong enough so thay

wont fall apart when i'll ride :-)

When I ride this Cargo-bicycle

I am sweeping so many compliments from passers-by thanks to you !

carkat (author)  Ds_man9 months ago

wow, what a beauty! thanks a lot for sharing your work here, it's always great to see other builds and improvements :-)
just one question: how long approximately did it take you to build this from start to finish?


Ds_man carkat9 months ago

The first 3-4 days i worked intensive, but after that i went once a week and it tool me about 6-7 weeks to the final result.

As you may know It never really ends, there is always room to improve

But in the meantime I'm satisfied with this,

The only thing that bugged me a little is when traveling at high speed the handlebar get out of control which is a bit scary, maybe the "Steering damper" you came with can solve the problem?!

i was thinking of taking a hydraulic arm from an old car back door, And try to connect it to the central pivot, it might give some stability to the handlebar... (I saw something similar done at the original Christiania bikes)

if i'll do it i'll let you know.
Thanks, Dvir.

paco perez1 year ago
thanks Mr. Carkat
pozole131 year ago
Thank you for the suggestions and the link to the video, which was really inspiring as well! I might add the extra tube to raise the bike as in the video. Another suggestion from a friend who builds motorcycles and rotorcraft was instead of machining a pipe, I could also cut a tube with a slightly smaller diameter and use it as an inner sleeve to hold the bearing cups in place.
pozole131 year ago
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.

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

As always, thanks!!
carkat (author)  pozole131 year ago
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
mick bull1 year ago
Think you have made a dam good job, ive just made 1 for my dog who has arthritis and have used tips from many builders including yourself, glad you were there to help me. Have a look at mine if you have time and tell me what you think, many thanks Mick.
carkat (author)  mick bull1 year ago
thanks a lot for sharing your build, it looks amazing! hope you have a lot of good times with your dogs at the beach :-)
drozio1 year ago
here are some pic, work in progres. hope you like them
carkat (author)  drozio1 year ago
wow, looks awesome! thanks a lot for the pics :-)
drozio1 year ago
hey there, I am trying to build the same cargobike, but I have some problem with the cables to the rear end. to the brakes and to the gear (speeds), I didn't like the way you put them, it look like a big mess. do you have another solution?
carkat (author)  drozio1 year ago
yeah, for running the cables along the frame i'm using short pieces of steel tubes welded to the frame. the inner diameter of these tube pieces is chosen according to the outer diameter of the cables:

but be sure to run the cables from the handlebar downwards in the middle of the back of the box, so that if you turn the box the cables don't get in your way.
pozole131 year ago
I thank you again for this wonderful tutorial and the drawings of the fork pieces. I am in the U.S. and using some U.S. measurements, but this is really a great contribution to those of us who are trying to be "sustainable" all over the world. I am looking forward to getting a successful build and then tinkering with the bike for some time to come.

Sorry for all the questions, but I am curious about the second (lower) long steel tube in Step 8. It looks like it has a nice bend in it, and I am curious as to how you did that. Did you measure the radius of the bend and use a tube bender, or did you bend it in some other ingenious fashion? I can't thank you enough for your work!
carkat (author)  pozole131 year ago
hey :-)
the bending was really low-tech. i filled the tube with sand, closed the ends with tape and bent it over a small piece of tube with a bigger diameter i had lying around.
in the meantime i built myself something similar to this: which is a good investment if you are going to bend tubes more often than once in a lifetime.
carkat (author) 1 year ago
oh, thanks a lot for clarification! never heard of gauge before.
i didn't make any mods since the last one mentioned in the i'ble. but be careful: if you take building this bike seriously it could happen you won't be able to stop building cargo bikes. they are always open to mods and improvements - an endless source of inspirational tinkering :-)
pozole131 year ago
Sorry it took a while to reply, the reCAPTCHA on this site has been a problem. Anyways,thank you so much for the explanation and drawing of the "forks". FYI, Gauge is a U.S. measurement for steel thickness, and 11 gauge is the equivalent of 3mm. Thanks again, really excellent work. Any mods or updates on your cargo bike?
pozole131 year ago
Great work and really inspiring! I have purchased some square tubing and am ready to go. Just a couple of questions:

1. What did you use to create the forks for the wheels on either side of the box? Was it something like 11 GA steel, and if so, what was the diameter of the holes and rectangles?

2. Did you use GMAW welding process, GTAW or something else?

Awesome work, this bike looks great!!
carkat (author)  pozole131 year ago
1. hm.. don't know what "11GA" means. they are made of ordinary mild steel, thickness is 3mm, other measurements see images below.
2. GMAW. but if you're able to do GTAW welding i'd recommend it. looks much better and the stability is the same.
carkat (author)  carkat1 year ago
what i forgot to tell you about the measurements: there are different diameters of wheel axles possible, so you might want to measure the diameters first and then change the diameter of the hole accordingly (i got 10mm axles). and make sure that there is enough space left between the whole and the upper end of the fork so that you can turn the nut easily when mounting the wheel.
carkat (author)  carkat1 year ago
"hole" not "whole" in the last sentence, sorry.
tobiasfjeld2 years ago
Very good post, starting to make my own right now.
how do you turn i wish i had a welder id try somthin like that nice instructable
strangebike2 years ago
I love the point you have left in the cock up's as well and not been too scarred to tell anyone. A great ible I'm possibly coming down with something!!
carkat (author)  strangebike2 years ago
thanks a lot! if you build something based on this writeup please consider sharing some pics.
Quoniam4 years ago
This pivot go to support a lot of stress. Look to the reinforcements Its possible the pivot have some angle to make the bike return itself from the turn.
carkat (author)  Quoniam4 years ago
yep, good idea... maybe i should add some reinforcements, too. after riding the bike for some time now i must say that it's not too easy to ride at higher speeds - the front part becomes quite hard to keep on track. maybe the angle of the pivot helps in such situations.
Quoniam carkat4 years ago
Its possible is better to put the pivot displaced to the front, with the wheel axis behind. This make the front part function like a free-wheel (like the one in the front of a wheelchair).
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