How to build a cargo bike

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:
Remove these adsRemove these ads by Signing Up

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.

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.
Ds_man made it!1 month 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_man1 month 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 carkat1 month 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 perez5 months ago
thanks Mr. Carkat
pozole1311 months 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.
pozole1311 months 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)  pozole1311 months 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 bull11 months 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 bull11 months 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.
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
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)  strangebike1 year ago
thanks a lot! if you build something based on this writeup please consider sharing some pics.
Quoniam3 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)  Quoniam3 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 carkat3 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).
carkat (author)  Quoniam3 years ago
right, sounds reasonable. though in this case it would need a reconstruction of the frame... moving the wheels backwards here wouldn't make much sense, so the only thing possible would be moving the pivot more to the front. this would need a longer bar below the box. i guess in case of a reconstruction both should be done.
I am not sure what the angle is of the pivot post (that would be good to add). Judging from the pics though, could you not just flip the cart around and move the handle bars & brakes to change the the relation of the wheel axis & pivots?
carkat (author)  mostly water3 years ago
would make sense, yes. though since the pivot then is in the middle and the wheel axis behind i think there would be a lot of stress on the pivot if there is some weight in the front part of the box. so there i am again thinking about a reconstruction of the frame as mentioned above...
SW again,
What about eliminating the head stock pivot all-together and replacing it with a lazy susan ball bearing plate? You could then drop the bottom of the box down another 5 to 6 inches thereby lowering center of gravity for loads that much more? You could use one larger tube going underneath the box or two tubes parallel to each other, welded to the outward edges of lazy susan plate. They would have to come together before mating to the crank area so pedals & feet don't hit.
carkat (author)  sillywilly3 years ago
thanks a lot for all your thoughts! hope i can build one or the other idea when i have time again to do some improvements or a new bike :-)
Hi carkat. I am going to build a long john and then a cargo such as the one you show. It seems straight forward but, do you have any idea where the head stock angle finally worked best? You did a great job on this.
carkat (author)  scomstock12 years ago
thank you! since i didn't test any other head stock angle the only thing i can say is that a straight angle works well. you just have to get used to lean into curves when riding but that's all. the angles mentined in the instructable are there because i thought that christiania is building this kind of bike for quite some time now and they probably know what they're doing. . .
also have a look at the last comment from sillywilly with the reworked pic of the trike, he's making a good point there.
good luck!
I just posted looking for DIY plans for a front load tadpole tricycle. Your trike looks like what I am looking for however I need plans for a, "Complete Idiot", I am new to this and not very technically proficient.

Do you know of any companies that sell plans? I can find plans for trikes, bike cars, etc but not front load tricycles. The prices from companies that make the trikes is just o high. Besides I think I would like to learn how to do this.

Any help or directions would help.

Your plans seem clear by the way but as I said I am not very technical and some of the discussions go over my head. Sad but true.
carkat (author)  62learner1 year ago
hi, unfortunately i don't know any decent plans for building such a trike, but the link from FoolishSage in the forum looks really good. in fact the best plan i've seen by now.
on the other side, as i started to build this trike i didn't have any mechanical knowledge at all and my experience in metalworking was very limited. building such a trike is a great opportunity to learn, though it takes time. and it can become much more: based on my experience with building cargo bikes i got a side-job as mechanic with a cargo bike dealer last week :-)
if you are going to build one and need help just let me know! good luck!
Carkat, question on your bike the first photo you talk about cuttin the old bike along the black line -- I don't see a black line -- but I may be blind-- Told you I a clueless hope you don't regre offreing help. :)
carkat (author)  62learner1 year ago
haha, well the line is quite thin. here's the same pic with a nice white line. guess this should work.

Get More Out of Instructables

Already have an Account?


PDF Downloads
As a Pro member, you will gain access to download any Instructable in the PDF format. You also have the ability to customize your PDF download.

Upgrade to Pro today!