RLT wood kits
Simple Cycloidal Drive Machine
DaVinci's Ball Bearing Machine
Chinese South Pointing Chariot
Overview (RLT vs. Timberkits)
RLT is another company that produces mechanical wood kits. RLT kits focus on demonstrating the principles of engineering and machinery whereas Timberkits models lean more toward automata. RTL kits are generally larger. This could be a problem where display space is at a premium. But the larger size may be an advantage for those who find Timberkits models to be overly tedious.
RLT kits demonstrate the principles of engineering and machinery.
Timberkits parts are ready to assemble and rarely require any additional sanding. But an RLT model is more like a plastic car kit in that each part needs to be separated from a panel, cleaned up and sanded. I use a cutting disk in a Dremel to separate the parts from the panel. The Dremel is fast and does not damage the parts. Long lengths of dowel need to be cut to length and sanded smooth. Quite a bit of sanding is involved, which leads to a lot of dust. Timberkits is the way to go for those not wanting to make a mess. Timberkits models come with everything needed for assembly. But RLT kits require glue, some basic hand tools, files and sandpaper - lots of sandpaper. I had plenty of glue left over from all the Timberkits models I've built. RLT kits come with better directions. There are several pages of detailed instructions with many color pictures as well as additional background information about the machine.
RLT scraps make great kindling.
Compound Gear Train
Parts and instructions.
The gear train demonstrates the principles of gear reduction. It's a simple kit that went together in just a few hours. Note the two bags of wood caps in the picture above. They do not appear in the instructions and I never figured out what they're for. Perhaps they were inadvertently included in the kit.
Finished model.
Finished model.
Two end caps hold all the gears in place. I like the idea of being able to take things apart. So instead of gluing the caps I drilled through the centers and secured each with a screw.
Cap detail.
Simple Cycloidal Drive Machine
An unusual gear arrangement providing a 2:1 reduction. This is a simple kit that went together in about an hour.
Finished model.
My parts panel had a slight warp to it. The warp was especially noticeable in the large eccentric gear. The warp in the large gear was binding against the face of the plastic bushings on the small trident gear. So I sanded a face of each bushing to reduce its length by about an eighth of an inch.
Finished model.
The two gear mounts fit tightly into base plate so I did not glue these parts. The plastic bushings were bottoming out in the slots of the large eccentric gear. So I adjusted the small gear mount up slightly in the base plate.
An inside view showing the trident gear with its three plastic bushings.
DaVinci's Ball Bearing Machine
Parts and instructions.
The ball bearing machine demonstrates the principles of ball bearings. A heavy object is placed on the platter. Thanks to the ball bearings the handle can be easily cranked to rotate the object.
Finished model.
Finished model with load.
The model has three modes of operation. In the first mode the balls are replaced with a simple friction bearing. The friction bearing offers the most resistance to turning the crank.
Friction bearing.
The second mode is the four ball bearing arrangement. Advantageously, the ball bearings provide far less resistance than the friction bearing.
Four ball bearing arrangement.
The third mode of operation is the three ball bearing arrangement. The three ball bearings are separated by three smaller spacer balls. I believe the three ball arrangement is more efficient than the four ball arrangement. But under heavy load the three ball bearings tend to bunch up and pop the spacer balls out of the race. So the four big balls are the best overall arrangement.
Three ball bearing arrangement.
I drilled three shallow holes in the top frame to store the spacer balls. I added a short peg to the base to store the friction bearing.
Storage for the spacer balls and friction bearing.
Chinese South Pointing Chariot
Align the dragon toward the south and the dragon will continue pointing south regardless of how the chariot is moved. Forward, backward, left or right, the dragon always points south like a mechanical compass. But it only works in theory. To be accurate over any useful distance the chariot would need to be perfectly built with zero tolerances and travel on perfectly smooth roads. Nevertheless, it's a pretty cool mechanical gizmo.
Finished model.
The central heart of the chariot is a geared differential wherein the dragon is fixed to the center of the differential via a vertical shaft. The left vertical shaft connects the left wheel to the top half of the differential. The right vertical shaft connects the right wheel to the bottom half of the differential. When the chariot moves in a straight line the top and bottom halves of the differential equally turn in opposite directions such that the center remains stationary relative to both the ground and the chariot. But when the chariot turns the speeds of the differential halves change such that the center changes relative to the chariot, but remains stationary relative to the ground.
Finished model.
Finished model.
Finished model.