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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:
- 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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Signing UpStep 1Recycling an old bike
i got myself an old crappy bike and cut it in two halves along the black line.
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I need to do this even if it is just for the exercise.
My kids will appreciate all your hard work.
if you can choose the size i definitely would go with two 20'' wheels in the front and whatever you have in the back (e.g. 26''; my trike has three 26'' wheels). smaller wheels can withstand bigger lateral forces (AFAIK that's why bmx bikes have small wheels) which can be good if you haul heavy loads.
(I'm not with these guys, and only know enough German to get my mouth washed out with soap. Use Google to translate.) Not many measurements to their plans but there is a 3D model of their bike in the Sketchup Warehouse - search for cargo bike.
They've addressed a couple of the issues that you had. They also use more cut up bike parts - welding fork sections under the cargo frame for brake attachment, and enclosing the wheels, not a bad idea if your cargo includes toddlers. They cant their steer tube forward as well - they don't give an angle but do give measurements. Their main frame is a section of 70mm steel tube.
I'm still curious about cambering the cargo wheels inwards - how much is enough? Is it enough just to get one side of the wheel's spokes vertical? I'm trying to avoid making the box any wider than it has to be while also adding a bit of stability.
in the meantime i've done lots of research regarding all these steering-geometry things. basically i would say that if you use e.g. 20'' wheels at the front no cambering should be necessary. it's probably a bit too much of an effort compared to what you can get out of it since the center of gravity is quite low anyway.
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.
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 :-)
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!
Best regards.
Sergio
Best regards from SPAIN
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.
it looks like the bike from that