Galileo's Bicycle is a kinetic sculpture designed by Clayton Boyer. I built this one as a wedding gift for my best friend, over a period of a few months. It can surely be finished in less time than that, but when you've only got an hour or two of free time per week to devote to it, it can take a while!
Here is the "official" video of Galileo's Bicycle in operation, from Clayton Boyer's website:
OK, so now you're thinking, "if the plans are being sold on the internet, why do I need an Instructable as well? Aren't the instructions that come with the plans good enough?" Well, yes and no. If you're an experienced woodworker, you probably won't learn much more from this Instructable than you already know. But what if you're at the beginner or intermediate level, and need a bit of guidance? This Instructable is for you! My goal is to throw a few tips, descriptions and in-process pics in your direction, to help you along. A bit of hand-holding, but only in a metaphorical way - never hold someone's hand while they're using a power tool.
I am writing this Instructable with the blessing of the designer - I asked for permission first! You won't find the plans here to download - you'll need to pay for them just like I did.
Galileo's Bicycle is probably one of Clayton Boyer's most popular designs. You'll find dozens of videos of it in operation on YouTube. It swoops and spins in a delightful manner, yet the design is actually quite simple when you break it down. This instructable will guide you through building it, though the lessons learned here can be applied to most of his other designs as well. I've also built "Simplicity," so I know of what I speak.
The entire mechanism is made of Baltic Birch plywood, maple, and brass. Oh, and some copper pipe as a counter weight, though you could use anything of sufficient mass.
Step 1: Materials and Tools
"Galileo's Bicycle" plans by Clayton Boyer (37 USD, in case you're wondering)
Can of Spray Adhesive - like Craft Bond (I used 3M Super 77)
1 - 2' x 4' 1/2" Baltic Birch for Triskele, Bobbing Arm and Wheels
1 - 12 x 12" 1/4" Baltic Birch Ply
1 - 12 x 12" 1/8" Baltic Birch Ply
(Apple Ply may be substituted for Baltic Birch Ply)
46" - 1x6" Hardwood stock for frame (I used maple)
4 - 1/4" (inside diameter stainless steel) Flat Washers as Arbor Spacers
3 - 2" Wood screws (countersunk) for mounting Frame to Wall
2 - #4 x 5/8" Sheet Metal screws
72" #18 Nylon Mason's Cord
8" - 1 1/4" Copper pipe & Cap
4 pounds of lead for operation in Mode #1 (Lead shot works well)
2 pounds of lead for operation in Mode #2
6 ounces of lead for floaters
4 - 12" pieces of 1/16" stainless steel rod
1 - 12" piece of 1/8" stainless steel or brass rod (I used brass)
1 - 12" piece of 5/32" OD brass tube
2 - 12" pieces of 1/4" Stainless Steel Rod (I used brass instead)
2 - 12" pieces of 9/32" OD brass tube
1 - 3/8" wood dowel (these usually come in 3 or 4 foot lengths, you'll need a few inches)
48" 50 lb. monofilament fishing line for pallet arms (I used braided trolling line)
20" 15 lb. monofilament fishing line for bobbing arm
Quality wood glue - I used Titebond III
Sandpaper - 220 and 320 grit
The wood can be found at a well-stocked home improvement store. I ended up buying my wood at a smaller dealer, however. I bought the brass rods and tubing from a hobby store - just look for a "K&S Engineering" display, and you'll find what you need. The lead shot and fishing line can be found at a hunting store or gun shop.
A decent scroll saw - I use a Dewalt DW788
A drill press (absolutely required for most holes)
A hand drill (for some awkward side-drills)
A vertical belt sander - makes sanding so much easier
A Dremel tool with metal cutting blade (as suggested in the plans) - also great for polishing the rods!
A band saw (I use a Sears 12" bandsaw) - alternative for cutting brass rods. Also nice for doing the rough cuts.
Quality scroll saw blades - I used Olson PGT 5RG blades for most of this project. Have lots on hand, because you'll burn through a few before you're done...
Quality drill bits - I used brad-point drill bits from Lee Valley, but ordinary split point bits should be OK.
A countersinking bit (use a regular large split-point bit in a pinch)
A few different wood clamps
An X-Acto knife
Step 2: Prep Work
It's very important that you calibrate your scroll saw to be exactly perpendicular. I have a tiny machinist's square that I use for this. I simply hold it between the blade and the table, and adjust so they are at a 90 degree angle.
You'll also need a large work surface for this project. Once assembled, many of the pieces are quite large. I'd suggest a 4x8 table, but you can get away with 3x6.
Step 3: Gluing the Patterns
The patterns arrive on several dozen pages of 8.5x11 paper. Most of the pieces fit on a page, but others are so large that you'll need to tape a few together before gluing them to the wood.
Most notable and critical of these are the 80 tooth gear and the frame. These must be aligned perfectly, or the Sculpture will not run properly. You'll notice registration marks on the multi-page patterns. Use these to help align the patterns. Take your time, take lots of measurements, and tape the patterns together when you're sure they're right.
The patterns are intended for several different thicknesses of wood, from 1/8" plywood all the way up to 3/4" hardwood. Cut out all the patterns, and organize them into piles based on wood thickness. Most pieces will have the thickness printed on them, but for those that don't write it on with a pen so they don't get mixed up.
"Dry" arrange the patterns on the appropriately sized piece of wood. Try to fit pieces together to use a minimum amount of wood. Mustn't be wasteful, right?
I use spray adhesive to affix the patterns to the wood. In this case, 3M Super77. Almost any spray glue should work, but avoid anything that is advertised as very strong or very tacky - we don't want the patterns attached permanently! One or two pieces at a time, spray the backs with glue and let it sit for 30 seconds or so. Then, stick them down in the same location they were removed from. Press lightly to make sure there are no lifted edges.
The frame pattern is somewhat unique, in that you must do a few cuts before attaching the pattern. A dimensional diagram is provided in the patterns, instructing you on how to cut up a 1x6 board to give it an "arm" on the right side. Cut the bottom of the board, then glue it to the side with high-strength wood glue. Be sure to clamp it for the best joint possible.
I usually wait an hour or so before cutting any patterns that have been glued.
Step 4: Rough Cutting
At this point, if any of the patterns become unglued, stick them down again with more spray adhesive. Better now, that when you're doing a fine cut.
Step 5: Drill Holes
It's easier to drill the holes now, while the pieces are in larger chunks. Some of the spacers and caps are pretty small, so having more to hold onto really helps.
There are a number of common drill sizes used; 1/16", 1/8", 5/32", 1/4", 9/32", and others. It's more efficient to chuck one bit and drill all the holes in that size. Each of the holes to be drilled will have the size marked nearby. Again, some of the holes are not straight through so be sure you know which is which.
For through-holes, place a bit of sacrificial wood on the drill press table. For best results, the sacrificial wood should be hardwood, though softwood will work almost as well. Press the workpiece onto the table, and drill through. A sharp drill bit will yield a hole that is sharp and clean, with minimal burrs or tearout on the bottom side. A brad-point bit will yield even better results. The center point makes alignment simple and precise, and the cutting edges give a cleaner hole.
For holes that don't go all the way through, or for countersunk holes, it's important to adjust the depth of the plunge. Some of the holes will have the depth specified; others not. For example, the arbor caps have no depth specified. These should be drilled 1/2 to 2/3 though. Using a piece of scrap wood that is the same thickness as the workpiece, drill a test hole to help determine where the stop should be set on the drill press. Once the correct depth has been set, go ahead and drill the workpiece. And remember - you can always drill deeper if you need to, but you can't drill shallower!
Several pieces have interior cuts (the 80 tooth wheel, for example). Drill a pilot hole for each interior cut using a 1/4" bit.
Step 6: Cut Out the Pieces
And so it begins! By now you're probably eying that 80 tooth wheel with a bit of apprehension - yeah, it's big, and it'll take you a while. So, I suggest starting with some easier pieces first.
The easiest, of course, are the various round spacers and arbor caps. It's easy enough to cut to the line and leave it at that. But if you're new to scrolling, you may want to cut just outside the line, then sand down to the line later. And that's perfectly fine!
Oh! Be sure not to remove the pattern just yet - not until the sanding is done.When the spacers are done, move on to the various medium sized pieces, like the "floaters," "spinner" and click wheel parts.
Next up are the larger Triskele parts. Here it's important to take your time and cut precisely. Some sides are inaccessible for even a 1" wide belt sander, so it's up to you and your skilled handle to get that line cut perfectly the first time. Take your time, and use a fresh blade.
By now you could be feeling a bit more confident, so move on to the harder parts, like the finial, escape wheel, and weight pulley.
One tip regarding the weight pulley. I actually built mine from three layers of wood glued together. To do this, you'll need three copies of the pattern. Two glued to 1/4" wood, one to 1/2" wood. On the two 1/4" thick pieces, cut the outside solid line and drill the 9/32" center hole. From the 1/2" thick piece, cut the dashed line and the center hole. Then, using the center hole (along with some 9/32" brass tube) for alignment, glue the three pieces together to form a pulley. Once dry, use that 9/32" hole again to align the wheel to the center of the 80 tooth gear and mark its location. Only then can the inside of the pulley wheel be cut out.
The frame is a fairly simple cut, but beware of two things: First, if you're using hardwood like maple, it will eat up scroll saw blades faster than the Baltic Birch. Don't be surprised if you burn though a blade or two (or three) just on the frame. Just be sure to change the blade before it gets dull enough to burn the wood, ok? And second, the frame is larger than your scroll saw. What to do? You'll need to cut from two directions. But more than that, I'd suggest making a few "relief cuts" from the sides every few inches, so that the scraps fall off in smaller pieces rather than trapping your blade in a 12" long cut.
And so we have arrived at the most tedious part of the build: cutting out all those teeth in the massive 80 tooth gear (and the equally tiny, though less numerous, 10 tooth gear). Start by cutting around the outside perimeter of the teeth - basically, a circle around the gear, that barely grazes the highest point of each tooth.
Working counter-clockwise, cut down one side of each tooth, from the tip to the center of the valley only - don't try to come back up the other side. Just back out again and move on to the next tooth. This process is tedious, but it helps ensure that each cut is similar, a desirable thing for a gear, right? It is possible to cut that tiny radius and come back out the other side, but there's a chance you'll either twist and break the blade, or burn the wood. Maybe a smaller blade would would work, but you'd use a lot of 'em cutting through that 1/2" wood.
Once all of one side is complete, change your blade for a fresh one. Then, cut the other side of each tooth, rotating the gear clockwise this time. The cutting will probably take an hour or so...
Once the teeth are cut, cut out the five centers of the 80 tooth gear.
Now, you can kill yourself trying to get each tooth cut perfectly, and that's commendable I guess. Or you could get close, and sand to the line. Yes, that's much easier. Onwards, to the sanding stage!
Step 7: Sanding
OK, I'll admit it. I'm from the "cut close to the line, then sand to the line" camp. When I say "close" I mean about 1/64"-1/32". So that's pretty good, I guess. Baltic birch is pretty easy to get close to the line, since it has virtually no grain.
Now, you certainly could sand all the edges by hand, if you're a masochist. I prefer a 1" vertical belt sander with a fine grit belt (220 grit.) Sand each piece to the line, so that about half the thickness of the line is removed. Some pieces will be easy, do them first.
Harder pieces are the curvy triskele arms, the finial, and frame. And, of course, those gear teeth! Some sections simply aren't accessible by the sander belt. Do as much as you can, then move on to the Secret Weapon: the scroll saw sanding blade!
Yes, these magical bits are covered in grit for sanding. Not only do they allow you to get into tiny areas, you can sand inside cuts, like inside the 80 tooth gear and the swirls of the spinner. Great! So, with great tedium, sand each and every one of those gear teeth to the line with the sanding bit. Reward yourself with a soda or a beer when you're done.
Tip: The sanding blades don't last forever. Be sure to use both sides, and remember that you can flip the blade "upside-down" and use the other end of the blade, too!On most of the parts, you may now remove the paper pattern. However, some have side-drills marked out. The ends of the pallet arms, for example, or the bobbing arm arbor support, have side-drills. Before removing the patterns for these pieces, drill the side holes. These can be tricky. If you have a jig for this, use it! Otherwise, do what I did: clamp the piece to a workbench, and drill free-hand with a hand drill. A steady hand is definitely an asset here, as well as a nice brad-point bit that won't skate across the wood!
Tip: If you waited *just* the right amount of time for the glue to dry before sticking down the pattern, then the patterns will peel off like stickers. If the don't come off easily, use a heat gun to soften the glue.
The faces of the pieces may now be sanded. Just a light sanding is sufficient, as you don't want to reduce the thickness of the wood too much. With the sides and faces sanded, lightly hand-sand the corners too, to remove sharp corners and burrs. Some of the arbor caps should have a noticeable radius.
Actually, I lied. There are some pieces that should be heavily sanded - the five "clicks." Sand these so that the thickness is reduced by about 1/32 to 1/16." This is done so that they may move freely inside the mechanism.
Step 8: Cut the Rods and Tubes
Various diameters and lengths of rods and tubes are used throughout the sculpture. Most of them are detailed on a single page, but not all of them. Be sure to look through the entire package of patterns, as there are a few more rods and tubes described elsewhere!
There are a few ways to cut the metal rods. I used a band saw with a metal cutting blade, but a Dremel with a metal cutting disc will work as well. You may also use a scroll saw equipped with a metal cutting blade, though I've found the 1/4" rods are really hard on the blades - you'd go through a few of them! No matter which method you choose, be care ful - the metal gets hot! Try not to burn your fingers.
I suggest cutting the rods and tubes a little bit long, perhaps an extra 1/16", then sanding them down. The band saw will definitely leave burrs, the Dremel less so. I used the vertical sander to precisely grind the length of the pieces, and slightly bevel the edges. I used an x-acto knife to remove burrs from the insides of the tubes.
To make everything run more smoothly, you may want to polish the rods. The easiest way is by chucking them into a drill press, and holding a piece of leather or even a piece of wood against the metal as it spins.
Step 9: Subassembly: Floaters
There are three floaters, attached to the ends of the triskele arms. But we're jumping ahead of ourselves.
Each floater is made of three parts, one Z-shape and two waves. There is also a short tube.
Start by gluing the waves onto the Z-shape. You may find that the edges don't line up perfectly - that's ok! You can sand to the line once the glue is dry.
The floaters need to be weighted, so that they always stay level. This is done by drilling holes into the back of the floater. Alignment, as usual, is important. So how to get the holes exactly centered? Here's where an extra copy of the pattern comes in handy. Print it out, and use a pin to poke a hole into the center of each of the three holes. Lay the pattern onto the floater, and transfer the holes onto the wood using a pin.
Drill the holes on a drill press, being sure not to drill all the way through.
The holes my now be filled with lead shot. Fill at least two, favoring the left or right, to help the floater stay level. If the floater keeps leaning to the left or right despite filling the holes, then you may need to trim a few 16ths off the end of the "heavier" end.
Once the floater is balanced, fill each hole with glue to seal in the lead shot.
Finally, glue the tube in place. It should extend about 1/4" below the hole, and 1/2" above it.
Step 10: Subassembly: Escape Wheel
The Escape wheel is fun to make. It consists of a relatively large wheel, with alternating metal pegs around its circumference.
Start by inserting the pegs. This won't be easy - in fact, it's nearly impossible to do with your bare hands. But, there's a trick! Chuck a large hex-head bolt or even a 4" long piece of 1/4" rod into a drill press. Voila, you've got a press. Place a piece of flat metal on the table of the drill press, to act as a stop so that the peg won't be pushed too far.
The rods alternate which side of the escape wheel they're pressed into. Hold each rod in place over the hole, and press it into the hole by pulling the lever on the drill press. There's no need to use any glue, since they will be held quite firmly by friction alone. Press a peg into ever second hole.
Now, do the other side. You'll need to construct a raised platform of some sort to act as a stop, that is narrow enough to sit between the pegs that are already pressed in.
In addition to the 30 pegs around the circumference, there are 5 shorter pegs close to the middle, upon which the "click" teeth rotate. Glue these pegs in place, making sure they are glued onto the correct side of the wheel.
Finally, slide in the 9/32" tube and the spacer, gluing them in place as well.
Step 11: Subassembly: Triskele
This is probably the largest component of the design, dimension-wise. The Triskele is made up of six parts; three arms and three support arcs. Lay out all the pieces on a flat surface to see how they fit together. If anything doesn't fit quite right, sand or cut until it does.
Apply glue to all of the mating sides, and stick them together all at once. Everything should meet up with no gaps between pieces. Be sure to wipe off any glue that squeezes out right away.
Once the glue is dry, a hole must be drilled in the exact center. Do so now, according to the pattern.
Finally, three rods may be glued into the ends of the three arms.
Step 12: Subassembly: Bobber Arm and Finial
Next, slide in the 9/32" tube and the two support discs. These should also be glued in place. Again, use a clamp to hold the discs pressed tightly against the bobbing arm and finial.
The last step is to insert the short peg into the bobbing arm. In my case, it pressed in permanently with no glue necessary. Make sure that the hole drilled through the peg is facing in the right direction (upward.)
Step 13: Subassembly: Pallet Arms
Two pallet arms move up and down, like a swimmer's legs (or, I suppose, like a cyclist's legs...) Each arm has a small pallet attached to it, thus the name.
On each of the arms, glue in place the short 9/32" tubing at the pivot point.
Note that the two arms are not identical - there is an inner (closer to the frame) and outer arm. On the inner arm, glue on the additional spacer, using a short piece of 1/16" rod for alignment.
Now, press the short 5/32" tubes into the two pallets. These tubes should not protrude past the surface of the wood, so trim accordingly.
The pallets are attached to the arms using small #4 x 5/8" screws. Taking note of which pallet belongs with which arm, carefully drive a screw through the tube and into the small pre-drilled 1/16" hole in each arm (and in the case of the inner arm, the hole in the spacer) The pallet should be able to spin freely, but without much in and out movement.
Step 14: Subassembly: Spinner and Triskele Pulley
The spinner was fun to cut out wasn't it? Now it's time to put it together. The spinner's main purpose is to look pretty and add some tension to the string.
Note that, as far as I can tell, there is no pattern for the spacer that goes between the two halves of the spinner. No matter! Simply cut a third spinner "cap" and drill the hole all the way through.
Assemble the spinner in this order: cap-spiral disc-spacer-spiral disc-cap. A 1/16" rod holds everything together. If necessary, press the rod into place with the drill press. Glue the wood pieces together, ensuring the two halves of the spinner align with each other.
The triskele pulley is a big stack of round spacers. I suggest sliding all the spacers onto the 9/32" rod to check the order against the plans, before gluing anything. In particular, there are a few holes that must be at a certain angle to each other. Once you're satisfied that you're building what's in the picture, glue each layer upon the last, sliding the pieces onto the brass tube. Make sure that you're leaving 1/2" of space at the right end of the pulley, so the triskele will eventually have somewhere to attach.
Step 15: Subassembly: 10T and 80T Gears
Earlier on in the build process, you marked the future position of the pulley wheel on the back of the 80 tooth gear. Now it's time to glue it on. Apply glue to the arms of the gear, using the marks as reference. Then glue on the wheel, again following the marks.
Slide in the brass tube, and the support pieces on either side of the 80T gear. Make sure the smaller support is on the same side as the pulley wheel. Glue the tube and supports in place.
Now, build up the 10T assembly around its 9/32" tube. The 10T gear is on one end, and the click gear on the other. A spacer is between them. It is very important that the click gear is assembled facing the correct direction, or the sculpture won't run!
Step 16: Subassembly: Frame
The frame is simple enough. Hopefully, you managed to glue, cut, drill and sand it to perfection. Note that there are three countersunk holes on the frame. Use a countersinking bit if you have one, otherwise you can get by with using a regular 1/2" split point drill bit. The countersink won't be at the perfect angle, but it'll work OK.
Four 1/4" rods get glued into the frame. The four rods (or arbors) are described on the same page in the pattern set, but make sure you know which is which since they are all similar in length. Glue each into its appropriate hole, using the diagram for reference. The bobbing arm rod requires an additional support piece, glue it in place over the rod, making sure the tiny hole is pointed downwards. Use lots of glue, but make sure to wipe off any excess that squeezes out or it could interfere with the operation of the sculpture.
Each of the arbors also gets a 1/4" flat washer, to prevent the moving parts from rubbing on the frame. I only used three; I didn't bother installing a washer on the bobbing arm arbor since nothing was rubbing.
Step 17: Final Assembly
At last, we've reached the final assembly stage! By now you should have the frame as well as six main components:
The 80 tooth wheel assembly
The Escape Wheel assembly
Two pallet arms
The triskele plus pulley
The bobbing arm
Onto the escape wheel arbor, slide on the inner pallet arm.
OK, now for a bit of a tricky part. Still lying about on your workbench will be the five "clicks." These should be installed onto the five matching pegs on the escape wheel. They must be installed facing the right direction; refer to the diagram or the picture for reference. Basically, the points must engage the click wheel teeth when turned in a certain direction, but pass over the teeth in the other direction. Arrange the clicks in a vague circle, then lower the 10T gear assembly so the click wheel sits surrounded by the clicks. Then, slide the whole thing onto the escape wheel arbor.
Slide on the outer pallet arm.
Next is the bobbing arm. There is a long spare tube that goes on first, then the arm itself.
Last is the triskele and pulley assembly. Slide these onto their arbor.
At this point, it's a good idea to rotate and twist the various moving parts to make sure they pass cleanly over and under the other moving parts. I had an issue with the triskele coming in contact with the bobbing arm cap, so I raised the triskele about 1/4" off the frame.
Once everything seems to be moving smoothly, glue on the appropriate caps, being sure to allow no glue to squeeze out. For obvious reasons, the glue should not be allowed to touch any of the moving parts!
Step 18: Counterweight
The counterweight can really be made from almost anything, as long as it's heavy enough. The instructions recommend copper pipe and fittings, which is what I used.
They actually call for 1 1/4" copper pipe, but I had some 1.5" pipe so that's what I used. If you know any plumbers, they'll probably be able to give you a chunk for free.
The pipe needs to be sealed on both ends, and needs a way of attaching the monofilament. I used ordinary copper pipe caps and an eyelet screw. Here's what I did:
First, mark the exact center of one of the pipe caps. Drill a hole in the center with a 1/4" drill bit (a split point or step bit should work). Clean any burrs form the hole.
Thread a nut and washer nearly all the way onto the eyelet screw. I used a nylock nut and stainless steel washer. Thread the screw though the hole in the cap, and tighten the screw using a second washer and nut.
The cap may now be attached to the pipe somehow. I soldered it on using a propane torch, exactly how you'd solder a copper plumbing pipe. If you don't have a torch or would like to avoid using one, then the cap should hold on just fine with a good slathering of epoxy.
The pipe may now be filled with lead. The weight actually depends one two things; the mode in which the Sculpture is being run, and the friction of operating the sculpture itself. If you're running Mode #1, which runs less energetically but for longer, you'll need to fill the pipe with 4 pounds of lead. Mode #2, which is more energetic but lasts only 1/3 as long, requires just two pounds of lead. I decided to do mode #2, so I filled the pipe with lead and checked the weight with a kitchen scale. The pipe I used is about 5 or 6 inches long, and weights 2.5 pounds when fully filled.
Once filled with lead, don't weld or glue on the second cap just yet. Instead, tape it on for now, in case you need to add or remove weight to make the sculpture run better.
Once you've determined just the right amount of weight, the bottom cap may be attached.
The counterweight is probably dirty now (especially if it was soldered). Wash, then sand or polish the copper until it shines. You may now decide to leave it as it is, or give it a coating of varnish so that the shine never fades. That, is completely up to you.
Step 19: Mounting & Running Monofilament
Step 20: Tuning
The key here is to get the two pallets to "climb" the escape wheel, like one might climb a ladder. Each time a pallet comes into contact with a peg, the tension on the escape wheel (provided by the counterweight) pushes the pallet upward, causing the opposite end of the pallet arm to move downward. This, in turn, pulls the triskele pulley so that the whole triskele spins. In addition to this, both the spinner and bobbing arm gently move up or down.
The movement continues until the other pallet contacts a peg on the escape wheel, causing the first pallet to lose contact with its peg. The escape wheel then proceeds to push the other pallet arm, reversing the direction of the triskele and other parts. The videos here show the sculpture operating in "mode 1."
Got all that? Right. The task now is to fine-tune the lengths of the strings, so that the pallets contact the pegs at precisely the right time, and none of the moving parts crash into each other. It might be a good idea to have a friend positioned under the sculpture, ready to catch the weight in case it comes crashing down - it can happen, if both of the pallets lose contact with a peg!
So, it's sort of a hit-and miss sort of thing. Start by winding the counter weight by turning the 80T wheel counter-clockwise, lifting the weight slightly with the other hand to take pressure off the mechanism. Now, set the sculpture in motion by spinning the triskele or putting pressure on one of the pallets. The sculpture may even start all by itself.
Did it do something? I certainly hope so. The pallet arms should move opposite to each other, like a swimmer's legs (or a cyclist's... thus the name of the sculpture?) Neither of the pallets should move so much that they crash into other parts of the sculpture. Adjust the lengths of the strings to compensate.
The bobbing arm works together with the pallet arms. It is hoisted up when the triskele spins, but also helps reverse the spin at the apex.
Now, the sculpture should sustain itself until the weight hits the floor. But what if it doesn't? Well, then you have a bit more fine tuning to do. Perhaps one of the pallet strings needs to be lengthened or shortened a bit. Or, perhaps the string between the triskele pallet and the bobbing arm needs to be adjusted.
Basically, visit these three parameters in sequence until the sculpture is able to run continuously on its own.
Once you're satisfied with the operation of the mechanism, tie off the strings or epoxy them into their holes.
Now, you may be wondering what's to be done with these four arbor caps. Well, so far we haven't installed them in case the sculpture needed to be taken apart. Now that it's working, you may glue on the arbor caps, being sure not to glue any moving parts.