Has anyone in the group has tried building a "Bike-in-a-Kit"- a sort of DIY bicycle, which can be entirely assembled and disassembled by the user and can be conveniently carried in a bag ? I face such problem when I've to take my kid for cycling and have to carry his entire bike in my car. Its tedious and cumbersome and I'm not very fond of those bicycle stands/racks that can be put on cars. Suggestions/Answers are welcome.
You also have folding bicycles
But the don't perform as well a regular bicycle
A break down bicycle is going to have better performance but takes longer for break down and assemble
Break down and folding bicycles are more expensive
On a regular frame you are not going to get much benefit from a full disassemble compared to just removing the wheels. Beyond that lower the seat and maybe spin the bars 90 degrees or remove it. A full disassemble and assemble is hours of work and something I would want to do in a shop with a full set of tools.
Everything has good points and bad points.
Car racks have an moderate expense, initial setup time, and then are very easy to use with virtually whatever bike you purchase (small time investment when needed).
Folding bikes require the purchase of a moderately expensive bike, no initial time investment, but then a time investment EVERYTIME you want to use/transport the bike. They will also generally have less performance and be slightly more fragile than a regular bike. The time investment may be moot if you force your child to do the dissembly/reassembly.
Coupler bikes are similar to folding bikes, but are generally sturdier than a folding bike, have better performance and a higher initial cost.
The drawbacks to couplers and folders also being that you have a limited selection of bikes.
You could look online (YouTube) and watch a tutorial on how to disassemble the bike. I'm not sure disassembling the ENTIRE bike would be necessary, though. I would try taking off both of the wheels and then leaning all three pieces against a seat, or if you fold a seat down, the seat and the wall of the car.
I would try this first. Although still a little cumbersome, it would be the quickest and easiest way.