During this summer holiday I decided to give my 20 month old son his own set of wheels, he had already been eyeing the bigger kids on their cycles for some time and I a summer project to hone my woodworking skills as well. Some internet research got my mind set on a balance bike. As it so happens I had some lumber lying around the house for over a year hoping to put to good use.
This is one of those projects which I almost entirely eyeballed with no pre-determined design or plan. If you have any questions about dimensions I can measure it and let you know. The main raw materials for this project are the 12" wheels, 1/2" X 3" soft wood planks from a pallet (wood unknown), screws and some nuts and bolts (6mm dia). I did not use any nails or glue (except for some shims and spacers) and the entire bike can be taken apart and reassembled whenever required.
And last but not the least enjoy making it with your son / daughter if possible (safely ofcourse). Living in an apartment it was kind of hard to actually hide from him while making it, atleast he learnt a few tool names and how to use a spanner, screwdriver and pliers :-)
To start with, first estimate the proportions of the balance bike with respect to your childs height, hand position and comfort. In my case I decided to have the center of the two wheels at about 2 feet distance. This would give me enough space for the seat as well as space for turning the front wheel. Since my son's inseam was less than the diameter of the wheels, the seat would need to be pretty low and between the two wheels. Remember the knees have to be slightly bent when they sit so they can firmly push the bike forward with their feet. The steering handle bar distance should be such that if they say turn left their are still able to hold on with their outstretched right hand to the right side of the handle bar.
First I tackled the easiest part, the rear fork. Two pieces of wood were measured, cut and drilled to hold the rear wheel axle between them. The other end has some pieces of wood cut and inserted to act as spacers and thin plywood was also inserted to act as shims.
The front end of the fork pieces was cut at an angle (to match the angle of the down arm), edges rounded and sanded for safety. This will be more apparent in later steps.