- 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
Step 3: Wheels
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 5: Rear part
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
Step 8: Making it stronger
Step 10: Brakes
Step 11: Test assembly 3
Step 12: S**t...
Step 13: Frame
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
Step 15: Final assembly
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
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!