Sure, you've seen a Lego carousel before. But have you ever *heard* one? (Photo by David "Fuzzy" Gregory.)
About this creation
This MOC features:
animals that go up and down
animals that rock back and forth
the music "Animal Fair"
lighting special effects
Spybot to power rotation, control lights and play music
a hinged ramp
an exceptionally high deck (it's not a bug, it's a feature)
a fence to keep little minifigs from getting hurt by the massive deck
a roof that isn't domed, and doesn't cover the center (much to Mark P.'s disappointment)
a part-time mechanic (OK, so I can't find any photos of the mechanic--I guess he was off the day of the photo shoot.)
The movement of the animals is driven by friction with the baseplate. I chose this rather than the conventional merry-go-round style of centrally-driven linkages running overhead because I thought it would be simpler. I ended up doing two rebuilds of the lift mechanism. For reasons I'll describe below, there's still periodic slippage between the tyres and the baseplate. If there's a next time, I'll try the conventional way.
The action starts by rotating the roof supports. These are connected to eight vertical axles which are fixed to the deck. Thus the deck rotates. A grippy tyre supporting each lift mechanism is forced to roll. This turns a cam, which lifts a liftarm or rocks a rocker arm. Well, I think technically they're both liftarms, but the former are constrained to move only vertically, and the latter flip forward and back as well as up and down.
The deck is formed from 4 x 8 wing plates and rectangles hinged together on the inside edge. Unfortunately, the slope of 16 of these wings totals more than 360 degrees. In one of the photos you'll see where I had to cheat using some 2 x 4 wing plates and a 2-wide instead of a 4-wide rectangle. Even with this adjustment, however, the slopes total just a hair over 360 degrees, so the deck is always warped somewhere. This means that at some point at least one tyre is probably not making good contact with the baseplate, and therefore isn't doing its job of rotating the cam. In practice probably a third of the tyres were slipping somewhat at any given time.
The music was taken from a MIDI score. I extracted the melody and saved it as an NQC file) using wonderful software called MIDI2RCX by Guido Truffelli.
I added some simple motor control, LED effects and timing, resulting in this NQC program.
Have seven priests carry trumpets of rams' horns in front of the ark. On the seventh day, march around the city seven times, with the priests blowing the trumpets.
Close up of the underside of the lift mechanism.
Notice just below the center of the image where a black axle protrudes into the tyre. This is a 2-stud-length axle cut down to 1.5 studs to make room for the wide Tyre. Normally this axle would be flush with the technic brick, but it has worked loose in this image.
Also visible is the method of snapping the wing plates to the rectangular plates using 2 x 2 corner plates (or bricks) at the only point where the studs line up. Hinge plates are used around the inside edge of the circle.
Another view of the previous mechanism. The liftarm in this case is a 3-stud-length axle with stud on the end. That stud is snapped into a yellow plate above the deck, which is the base of one of the carousel animals.
This liftarm rocks back and forth as well as up and down. Its motion is constrained by the plates around the slot in the deck. The old 2 x 8 white plate is from my mother's Lego collection. I wonder how it got in my collection?
Reinforced axle which attached the drive train to the "rotator", shown expanded. Wedge wheels (pulleys) and friction pins were used to reinforce the central axle. One side benefit of this arrangement is that the pulleys can be stretched apart or compressed together without taking anything apart. This made is easy to adapt the spybot height to the height of the carousel.
The Spybot and drive train, with reinforced axle removed. The axle gets inserted in the 24-tooth gear in the worm gear box (not present in this image).
The curved row of LEDs did special effects while the music played, but you had to be a minifig sitting on the ride to see it well.
Excellent work! I love the design for the lifters...simply ingenious! Also, supporting the deck underneath is easier than the cantilevered setup on real MGR's. I'd give your model 6 out of five too! :)
If the features you claim it has are true (and I have no reason to believe they aren't) then this deserves more smileys than MOC pages can support right now! btw, is that an amputee minifig next to the carousel? Look forward to more pictures!!!