The principal is very simple, Once you have
chosen your container, you fix an axle 1/3 of the way up from the
bottom, NO MORE. When the container is full that means that 2/3 is
full and as it is now out of balance it tips over and empties,
returns to the upright position and starts again.
I actually used a very small copper pipe for the axle and
soldered it onto the main copper feed pipe
If you have a bigger or heavier container you may want to use
brass nuts and bolts on either side instead of having it run through,
these you will then have to support by a bracket.
*Your container must have
vertical sides, if it is slightly conical if you use bolts
they will be pointing at an angle (they must be horizontal) and also
1/3 the way up may not work.
Why don't you try making one and send
in a picture for publication?
Water feature ideas
see here