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:

Step 1 Recycling an old bike

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

Comments

[sillywilly]

I'm not carkat but I have a good suggestion for you. See attached file I have redone to show bigger angle brace between seat post and downtube. I suggest a headtube angle of zero! This will keep the distance between downtube and box the same throughout steering range. You will see in attached drawing that there are two red dots. The one to the left should be location of a fixed castor wheel to aid steering and support box loads at 2nd point. The right red spot is my suggested axle mounting point, centered in box. You will notice that head tube is about 8 inches ahead of center for castor affect. This should ease steering inputs, track true, and might even allow "hands off" riding?

[carkat]

hey, thank you for your thoughtful comment. it seems you know what you're talking about. are you some kind of engineer?

[sillywilly]

Naw, just a lifetime of loving to tinker, build, experiment, etc. I like tadpole trikes (among other things) and would be peddling one now except for a bad knee. My light trike preference is a recumbent-seat with full suspension, motor assist, and a super light full body cover for year-round usage. I belong to a Yahoo group called "CabinScooters" where we confer, toss about ideas, and help each other in the building of covered 2 or 3-wheelers of all sizes from powered velomobiles to super screamer sport performance trikes. they are rated from type 1-to- 5 with 1 being the lightest/slowest and 5 the heaviest/fastest but none over 1500lbs. The reason is because this category can be registered in most states as a motorcycle with a whole lot less restrictions as to builds than 4-wheel cars. http://autos.groups.yahoo.com/group/CabinScooters/

[Quoniam]

This pivot go to support a lot of stress. Look to the reinforcements http://photos.ugal.com/3834/14972/2413/142572/vectocustomphoto.600.jpg Its possible the pivot have some angle to make the bike return itself from the turn.

[carkat]

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]

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]

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.

[mostly water]

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]

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...

[sillywilly]

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]

hey,
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 :-)

[scomstock1]

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]

hi,
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!

[TechDante]

hi great work and dont worry about the oh S**t moment i had teh same problem but only found out while test riding the thing on a hill. built my in a compleatly different way though building the front onto the handle bars. it worked but would not likley last.

[thewmas]

(removed by author or community request)

[carkat]

?

[thewmas]

to be nice > the only thig I see in this pic, is some reflection of som'm and the two diamond tiles on the floor

[carkat]

yeah, it's a bit dark. but i don't have a better one. maybe turning up the brightness on your monitor might help?

[thewmas]

just got a, new used monitor, I can see it nowv !

[carkat]

:-)

[spi]

Thanks a lot for the new details. Just one clarification: which is the meaning of "a camber of wheels?.
Best regards.
Sergio

[carkat]

the angle of the wheels at the bottom of the drawing where it says "better!". my dictionary says this should be the phrase for it...

[spi]

Hello, I got triplets (1,5 year old) and I would like to made my own cargo bike, just to have fun with the kids, and to move around my village with the kids (Cardedeu, SPAIN). I have read all the instructions 3 times, any new comment or improvement? Do you have the final dimensions of the cargo bike available?
Best regards from SPAIN

[carkat]

hola ;-)
i added a last step to the instructable with some final considerations and measurements. hope this will help. if something is missing please let me know!
best regards from austria.

[The nerdling]

have you seen nacho libre?
it looks like the bike from that

[_nicos]

Here's mine: http://www.rat-patrol.org/RPOz/FArt/willRobinson.html Actually, it's more like a generic cargo/stereo/kidCarrier/fire bike...

[_nicos]

Here are some detail shots of the front-end geometry, showing the tilt/rake angle of the headset bearings, and it's position slightly in front of the wheel axles...

[cnmaine]

oh no its on fire lol

[_nicos]

BTW, the 2 verticle tubes (one holding the headset bearings) are super important for heavier loads. Note they are both braced too... and you can un-bolt the bracing to access the bearings for when they need a service.

[carkat]

wow! great trike :-) especially the front-end geometry looks very professional. i guess i will re-work mine in a similar way this winter. but from the photos i would bet this isn't your first bike build, or ist it?

[_nicos]

Cheers carkat! A slightly shorter wheelbase than mine could be a bit more stable when riding without a load on the front.

It's about the 10th bike, but they were all quite different and this one took a while to think through — the guesses were good and it works well (+ holds about half a ton of weight). The cool thing about this trike is it's generic cargo nature: the firebin just drops on, the kid cabin folds up/down as you need it, and the beer shelf is always ready. Turns out this bike gets a lot of use for all kinds of things, yay.

But they are freakbikes, and while my builds tend to hang together pretty well, freakbikes are generally FAR from professional ;)  Checkout my tall amphibious couchbike with world-beating Double V-brake and Steer-by-beer technology: www.instructables.com/id/Tall-Amphibious-Couchbike/

Speaking of crazy dreams, this is my latest hopefully motivational video about what it is to hang glide (but please don't try to make a hang glider!)... enjoy.

[pyrotechnical]

Does anyone have any insight on how a cargo bike like the one featured in the instructable handles when loaded, compared to the two wheeled type pictured below?

[bigbunyip]

wicked bike dude, i've sen them being used on tv, in asian countrys, now i've seen how u made ur's i'm gonna have a go at makin 1, thanks 4 all the exelent details and pics. some good info in the forum 2, gonna try that caster angle bit, thanks

[cararta]

you do not show a good picture of connecting front and back together....I assume done with the pivot only....... Would it have been easier to fabricate an axle between front wheels and install pivot there? guess not as would be in the way of cargo unless at the complete back of the box. Never seen one of these cargo bikes before so just commenting......

[carkat]

connection is done via the pivot only -> see step 12, last picture. afaik the "nihola" bikes have an axle not connected to the box that makes using the trike safer - you don't push the load from side to side.

[sillywilly]

I've given this type of connection a lot of thought and had an idea. Since the pivot point is ahead of the front axles, that adds the possibility of more leverage pushing down in back (if the box is loaded heavier in back) What about installing a small hard rubber wheel (with bearings) upside down on the frame going underneath. Maybe aluminum-plate the bottom so the wheel does not wear a groove? I don't knw, just a thought. I am sure it would stabilize the tendency for the box to do any rocking up/down in back, pivoting on it's axle. Should allow a person to carry a lot more weight if they wanted.
SW

[sweavo]

great job! very inspiring. How is the steering now? I imagine if you power the pedals too hard when it's empty it tries to jacknife? If you build another vehicle, check out "castor angle" when it comes to bikes. I'm not sure how that translates to a beast like this though. I assume the box, when laden, is so heavy that it becomes the main consideration when riding and keeps it all stable. Wish I'd taken more detailed photos of the ice-cream bikes I have seen on my vacations now!

[carkat]

powering the pedals too hard isn't really a problem, it's the speed that makes the jackknife behaviour. yeah, the castor angle... i had a look at this before building but didn't know how to apply it to this trike, too... so i just kept it straight (means 90 degree) after my unsuccessful angle experiments.

[sillywilly]

carkat,
What about adding a couple trunk cartridges. You know, the ones that have a little gas shock in them? It might make it a little harder to turn but should stabilize the thing at higher speeds like little shock absorbers.
Silly Willy

[sweavo]

Yes. I see the problem. Forgive me if I repeat stuff you already know, but I want to be clear so that my point is not lost due to different terminology, etc. In bikes, you draw a line through the center of the headstock to the ground. The angle between this line and the vertical is the caster angle. The key point about this is that this line through the headstock hits the ground IN FRONT of the point where the tire touches the ground. That's what causes the wheel to pull itself straight when the body of the bike is travelling forwards. So "angle" is really a bad name for it. On your cargo bike, as you've discovered, the caster angle must be zero or it tries to lift one wheel off the ground to turn. So given a caster angle of zero, it follows that you must put the pivot ahead of the wheels in order to get the "pulling straight" effect. I think it would only need to be about an inch or two in front. Why do bikes not do this? I guess it's economics and ergonomics --- you'd need quite a lot of extra metal to bring the headstock up and in front of the front wheel. So that's my theory! If the details of your construction make it easy to do so, you could try shuffling the wheels backwards a little or moving the pivot forward a little on your cargo frame. Or both. No guarantees, but would be interesting :-)