What

The set 10196 — Grand Carousel is a beautifully designed model of a merry-go-round.  It has six horses that move up and down and two shuttles that also move.

Rights and Wrongs

It is a set claimed to be for ages 16 and older (that includes me I think).  Its design does contain quite a lot of difficulties, and I can also see very well how the designers tried to reconcile the complexities of the mechanisms with the need to make it fairly easy to build.

So all in all, hats off to the person or team who made this into a sellable product!

But I am an engineer.  When I was a kid and rode the wooden horses of the carousels in the fairs that passed through the city where I lived, I also looked up to see what made my horse go up and down.  I saw at least some parts of the mechanisms.  Later I tried to build one with a Meccano set, but did not have enough pieces.  I did notice a number of aspects that are not reproduced in the Lego version:

1. In a real carousel the cranks that move the horses up and down are synchronised.  That is necessary to ensure that at any time there are as many horses going down as there are going up.  In a real carousel there are usually two or three horses on one shaft, so offsetting the cranks by 180º or 120º is sufficient:  each individual shaft is then always in equilibrium.  But if there is only one horse on each crank and the cranks are not synchronised, then they could turn at unequal rates, and it is then possible that at some point in time all horses are at their lowest point.  If that happens, the engine needs to produce a lot of force to lift all horses at the same time.  The Lego version moves the cranks with rubber wheels running over a smooth track, so they can slip and are not synchronised.
2. A real carousel has the engine in the centre.  The Lego version has it outside. Worse than that:  the engine drives the rim of the bottom platform!
3. The bottom platform of a real carousel is pulled along by the top.  In the Lego version the bottom drives the top.
4. In a real carousel the bottom platform hangs from the top and does not touch the ground.  This is essential for a device that is moved from city fair to city fair:  it is much easier to accommodate uneven ground when the platform floats above it.
5. The shuttles of a real carousel are not moved in the same way as the horses.

They just rock gently (in fact they are usually driven by a rod linked to the horse behind the shuttle, though I have seen some that are driven like in my rebuilt version)

So mechanically speaking this is not a very good model of a carousel:  if it is aimed at 16+ then it should be kinematically better.

I repeat again however that it is a beautiful model, that looks very good and is the most decorative of all models we have in our house.

Rebuilding

After successfully constructing the “official” 10196 set and finding it ran very well, I let it sit there for a while and our granddaughter was the main user, under strict supervision of course as she was only two at the time.  But even at that age she wants to know how things work:

Then I tried to figure out how to remedy the main defect:  synchronising the cranks.

The crankshafts of real carousels have a bevel gear at one end that runs over a toothed track. The toothed track is round, and that is impossible to make with Lego racks.  I needed an enourmous gear wheel.  The largest I could find was from the hailfire droid Star Wars set:

The basic idea then is to link the crankshafts with an intermediate bevel gear to wheels rolling inside the droid ring:

If by now you think that I use a 3D modelling program to illustrate Lego constructions, you are right.  I will make all those modelled parts available in a separate section. [link to come here]

Now, this intermediate gear is an added complexity, and it is not really nice, but unavoidable if we want the synchronisation.

The construction of the synchronised crank drive continues on another page.