1/24th scale is used by the majority of fairground modellers who wish to create a fully working and lit ride. In this scale you can pack in a lot of detail whilst keeping the building time manageable. This is also the smallest scale in which it is practical to make the model fully demountable – just like the real thing. It is also the largest scale in which it is practical to keep models set up and still take them to shows. A model Waltzer will be 25” (600mm) diameter which will easily go through a house door.
The larger scales of 1/16th and 1/12th allow even more detail to be added. Inevitably the models take longer to make, cost more because the volume of material used goes up by the cube and need dismantling between shows.
For those new to the hobby I suggest starting with either the organ kit or the striker drawings or kit. These are simple and go together quite quickly, a couple of weekends should be sufficient. Having gained confidence and the skills required you can progress to the generator set or the swingboats and from these to the overboats or one of the MFD organs or trailers. After that you should be ready to tackle one of the major rides or the Helter Skelter. It is very tempting to start with something quite complex, but a wide range of skills will be required and complex things take a long time to complete. Few modellers have all the skills needed to begin with and it is better to start with something simple and build up your skills progressively.