Basic stuff

I will call the construction that drives the 6 horses and 2 shuttles the drive.  We have 8 crankshafts on the drive, so we need to make a support frame that holds the 8 bevel gears.  The frame needs to hold 8 vertical axes.

Fortunately it is easy to construct an octagon for that job:

Unfortunately that octagon is a wee bit too big… (see rolling diameters of gears).  The distance between axles on a diagonal should be 168-24=144mm if the 24-teeth gears are to roll smoothly.  A trigonometric calculation shows that it is 146.335052mm

Even when admitting of the small play the vertical axles will have in the connectors, and even admitting that the axles may be slightly tilted, there is still too little play and the octacon with the eight gears does not turn smoothly inside the large wheel.  I plead guilty:  the only solution left was to make the sides of the octagon slightly smaller…  You need to file off less than half a millimetre from each of the eight rods that make the octagon.  The resulting smoothness of the drive is well worth it.

Better

Once we have the basic octagon, we construct another one, including supports, in these stages:

Note:  although the lower octagon must be slightly smaller than it would be with regular Lego pieces, the upper octagon can be a normal one:  there is enough play and flexibility.

The rollers will run on the rim of the big wheel, preventing the assembly to fall through.  They are somewhat like this:

but they are not all the same:  two of them will also support the inner drive wheels, and one of them has to leave room for the cam that switches the music on.

Then there need to be 8 places to attach the crankshaft supports.  They are outward-facing connectors:

The crankshafts with their bevel wheels and supports can then be put in place:

The lot will then run on the rim of the big wheel, and all cranks will be synchronised, they cannot get out of phase: