Designing a FAST 3D Printed Spinning Top - 4742+ RPM

Pretty much every kid has played with a spinning top before, right? Spinning it over and over again, trying to get it to stay up for as long as possible. Maybe some of you have tried one of those pretty, precisely-manufactured metal tops.

But what if you stopped worrying about duration, and you started optimizing for maximum speed?

Now, I don't have a fancy metal CNC. That's way out of my budget. However, I do have a 3D printer, and I bet many of you have one too. Plain white PLA plastic will have to do the trick.

It took me six iterations and way too many failed prints to find something that worked. Everything was designed in Fusion 360 with spline profiles and the Revolve tool, printed at 100% infill. I reached a peak RPM of 4742 with my final top. Along the way, I had to reevaluate the physics and features of each top after they were printed, resulting in some drastically different designs.

The most important tool here was my 3D printer (an Ender 3 S1 Pro), but there were other tools that were also crucial to the project such as:

1. A black permanent marker
2. Standard pliers
3. Plastic cutting pliers
4. Metal scraper
5. Ruler
6. Scissors
7. Tweezers
8. Brad nails (18 gauge)
9. Neodynium magnet (for pulling out any stray nails)
10. Double sided tape
11. Digital photo tachometer
12. Reflective tape strip (included with tachometer)
13. Flat mirror
14. Ceramic/glass plate
15. OPTIONAL: Brushless driver or dremel with an adjustable head

This project would not have been possible without a photo tachometer- it makes measuring and optimizing my spins much easier. Thanks to my library teacher for lending me his tachometer.

I spent a while researching and browsing the web for any design guidelines in order to optimize top speed, as well as the physics behind everything. Here's a basic breakdown of the key concepts:

Precession:

"The slow movement of the axis of a spinning body around another axis due to a torque."

This other torque could be gravitational torque, which is essentially gravity pulling your top down along another imaginary axis. Precession is what you see when a top wobbles and starts to fail.

Moment of inertia:

This is a crucial factor in making a fast or enduring top. However, with just simple plastic, you can't have both. You don't have the weight and precision of CNC'd metal, so you have to settle for one or the other.

The basic formula for a point mass is mr², where m is mass and r is the distance from the axis of rotation to the point mass.

Moment of inertia is also used in the formula for kinetic energy, ½Iω². I represents moment of inertia, while ω represents the angular velocity of the object.

Gravity and friction:

Gravity and friction is what kills a top. The more gravity affecting a top, the harder it is to withstand falling. The more friction caused by the rotation of the tip, the more energy it loses. Speed can make your top harder to topple, but once friction slows it down enough, gravity will take its toll. Minimizing these two forces is necessary to create a good top.

Air drag:

The aerodynamics of your top shape is also important. More rounded shapes will glide through air better, creating less air drag. This is why you don't want any sudden, sharp layers in your print. Air drag is more noticeable in thin, "whiskery" tops.

Screenshots from Brian Lemin & Christopher's Factory. Credit to these amazing creators!

Going into my first design, I didn't really know what to expect. I made a streamlined design with smooth edges using spline tools in Fusion (a free, accessible software by Autodesk, great for creating CAD designs) to minimize air drag. I used the Revolve tool; since it's only a top, it's very easy to model.

Here's what my workflow looked like:

1. Create sketch (I used the ZX plane)
2. Decide measurements. Before sketching out the shape of the top, I set down Sketch Dimensions and Construction Lines to mark out how wide I wanted each section of the top to be. If you want to be more precise, I also used constraints to snap to a certain angle or length.
3. Draw out shape. I used lots of Fit Point Splines, Lines and the Blend Curve function to create a cross-section of the top I wanted to make.
4. Add functional details. For many of my tops, I added small, yet crucial details to the design before I make it 3D. I created a small empty space in the bottom of the sketch, measured to fit a metal brad nail for a better tip. For one top, I also added small grooves on the handle to make it easier to spin and increase grip.
5. Use the Revolve tool to create a 3D part. It was as simple as finishing the sketch, selecting the faces, and choosing the axis of rotation. You want to pick the Z axis so the top is created correctly with the correct shape.
6. Save & Export. I exported the file to an STL format for easy printing, but you can also use .stp for CNC machining. Make sure you save your design in the cloud!

This process was repeated and used for all the other tops as well, if you ever want to design one yourself. It's rim weighted to make it spin for a longer time without falling immediately. I made it small and light, only around 3cm in diameter, so it would spin fast. I had the idea to put in a metal brad nail that I cut to size and inserted in a small hole in the bottom, based on the theory that metal would be sharper and more durable than plastic when spun repeatedly. I sliced it in Cura and sent it to the printer at 100% infill, since it was so small. (STL files and print settings are at the end of the Instructable.)

This design spun pretty well, clocking an impressive one minute (by my standards). It spun at an average of 600 RPM.

Based on the previous design, I thought that The Zip spun pretty dang well! For this top, I decided to increase weight on the rim even more and make the diameter larger (almost 7cm) to hopefully make it spin longer. The handle would be a bit thicker to compensate for its weight, and the nail stays.

Frankly, it was a huge fail. It took a whopping eight hours of print time at 100% infill (y'know, for weight) and it failed two times before I got it working. I found out that my printer was missing a little block at bottom and was actually wobbling and vibrating as it was printing, causing the bed's screws to slowly loosen. This raised the bed along with the print, straight into the hot nozzle that melted scars into the plastic surface. Mind you, this was the third day of attempts at printing this- the past two days I had left it running while I went to school and it completely spaghettied everywhere. Nevertheless, I fixed the printer, releveled the bed, and set it to print.

When it came off the bed, I had a sinking realization that it was way too heavy and the handle was not big enough in proportion. It took me a long time to get the supports off with pliers and cleaned it up with a scraper.

Note: metal tools are SHARP and STABBY, and so is 3D printed plastic support material. I accidentally stabbed my fingers multiple times. If your supports are hard to remove, wear gloves before you try to remove them.

The Chonker spins really slow, and with just the force of a finger spin, it goes for two or three rotations before it dies. I got it to spin for a minute by using both palms, and it still just barely surpassed The Zip by a few seconds. It was not fast at all- there was no point in even measuring the RPM.

I think I lost sight of the goal of pure SPEED, and instead went for a design that would spin for longer in the hope that it would accelerate over time. Looking back, that was a really stupid idea resulting in lots of wasted filament.

Following the dramatic failure of the disappointment called The Chonker, I decided to switch lanes and go for a center-weighted design instead. I think I was confused before because a heavy rim sustains acceleration while a heavy centre tends to die out fast. Heavier isn't always better. For pure, explosive speed, center-weighted tops are actually better because we need accelerate fast. We don't care about how long it spins for, as long as we can measure the RPM before it falls.

For The Rip, I wanted to build off The Zip's success but make it spin way faster. I went for a longer handle so it would be easy to spin, and a low center of gravity. The rim would be wide to compensate for the loss of rim weight. It is smooth and tapered at the end to minimize weight. I incorporated the nail into the design.

This top was a delight to print. Everything went smoothly. Upon testing, I realized that the nail was causing it to wobble more since it was already a very skinny top. I remove the nail, allowing it a flatter and more stable base, and it worked much better. It is fast and aerodynamic, and it peaked at an amazing 2194 RPM! Unfortunately, it enters precession almost immediately since there is not much weight to sustain its spin. It only spins for around 6 seconds before falling, but you can't have the best of both worlds.

I was getting excited by the large RPM jump the last top made, but I still felt that it wasn't enough. I wanted to try something different. Or, you could say, something... revolutionary.

So I created Revolution King. I made the handle thinner, but added small bumps to increase grip. I wanted to see what a more geometrical and sharp would do. My mom told me about the tops that she played with as a kid, with a larger, more conical bottom. I incorporated that into Revolution King as well. I also went back to the nail design since it had worked before and kept the same diameter of 4cm.

While testing The Rip, I realized that it kept bumping into the ground. This was a problem for The Chonker as well- the rim was too low (and wide, which made the problem worse). It was stable, yes, but there was also no tolerance for a spin that was even slightly tilted. A lot of its already limited energy budget was lost to friction. I put the rim at a raised angle, like that of The Zip but even more extreme. I decided not to taper the sides of this top because it was already really heavy at the center and I needed to balance it out somewhat.

Design-wise, this is the top that looks the most stylistically different from the other ones. I figured this was my chance to screw around and experiment with different shapes and characteristics. Unfortunately, it was difficult to print- it failed because the supports didn't cover the sharp overhangs at the bottom. This was an easy fix in the slicer.

I took the King for a spin... but it took me a long time to actually get a spin, because the handle was so damn short! I think I put too many random features in and it turned out a mess- like if you put all your favourite foods together in a mixer, but it actually tasted horrible. It didn't spin very fast, averaging around 250 RPM. It only lasted for around 10 seconds before it fell.

Frustrated with my progress, I decided to go back to my research. I rewatched a video (see: Optimizing Spinning Tops picture in Step 1), looked at the Principles of Spinning Top Design again, lined up my previous four tops, and stared them down. I scrutinized those tops from every angle, analyzing every feature, and then

it all clicked.

I didn't need to make everything so wide. The whole time, I was focusing on the wrong things! I looked at the figure skaters again. The pictures and diagrams actually made so much sense now!!

Weight doesn't actually matter that much. It's the diameter of the top that really matters! When skaters perform a scratch spin, they start with their arms outstretched and knees slightly bent. As they turn, they straighten out their legs, rising to their full height, and bring in their arms. They reduce their "diameter" and they speed up dramatically.

The basic formula for moment of inertia is mr². The diameter is raised to the power of two and weighed heavier than the mass.

Wow. It all makes sense now.

Newly inspired and really, really happy (I was actually dancing around the kitchen), I set off to work. I already had a name in mind: Eureka!

I made it a smaller diameter (40mm -> 28mm) and also made it have less weight overall. I added a thin handle, because along the way, I realized that it means your fingers will create more RPM when launching, and therefore, more speed! It skips out on torque, but since the top is so light, it doesn't need much anyway. It's also longer than the other handles so you can spin it with four fingers (two hands, two fingers on each side)!

I also decided to drop the nail, because it was too wobbly for the skinny, tapered design of The Rip. Since Eureka is similar, it would likely negatively affect its speed as well. Instead, I opted for a small yet rounded tip, similar to that of a ball bearing so it would be stable, fairly sharp, and wouldn't wear out too quickly.

It printed quickly and easily, and it took less than 10 grams of filament. Amazing! Not to mention that it spun at a crazy 3056 RPM and stayed upright for a good eight seconds, even though it was so slender!

Eureka was incredible, but I wanted to keep pushing it. Time was running out, so this was my last top, and the most awesome to date.

I made a few adjustments: the handle was extremely long, and I was hoping for a full-on palm spin. I made the tip slightly smaller since the last one was a smidge too wide for my liking. I also shortened the diameter to 24mm making it even smaller and lighter.

Again, it printed well. When I tried to spin it... it toppled.

I was stunned.

The handle was too long, and it wobbled like CRAZY. Good thing is, I trimmed it down with plastic cutters, over and over again marked at 5mm intervals, and kept trimming until it was merely a nub. I spun it multiple times and figured out the optimal length- 35mm to 40mm was the sweet spot (close to Eureka V1). The lower I went, the more stable the spin was. This top was cool because it sort of righted itself when spinning and remained quite still, although not for long (again, eight seconds). It would make for a good desk toy and is very aesthetically pleasing. It was actually pretty interesting and was good food for thought. I wanted to keep going, keep modeling and spinning, but I figured it would be wise to call it for now. I'm sure someone could get Eureka V2 going even faster then I did.

The final number? 4742 RPM.

(Optional Step)

I was feeling curious and tested a few tops with a brushless adjustable driver to see how fast it could get. I saw cool videos of incredibly fast tops. I was disappointed by the results. I think the problem was that they were either too heavy and lost energy fast (gravity & friction) or too small and flew everywhere. I also had a hard time getting the tightness of the driver just right so it would drop out. Overall, none of the tops worked well with the dremel. Perhaps it was because their tops were metal and mine were plastic.

I'd be interested if anyone could figure this out.

Warning: Do not use on the mirror, it would probably shatter and explode. I used a slightly concave ceramic plate instead.

I carefully used a pair of tweezers to apply the reflective tape onto the edge of each top and spun each top many, many times to get accurate measurements with the photo tachometer. Sadly, I did not get all my best spins on camera, but I got a few pretty good ones you can view above! The three best tops I recorded videos of were the Rip, Eureka, and Eureka V2.

I tested it on a mirror because the surface is hard, smooth and clean which minimizes friction and maximizes spin time. The ideal surface would be a concave piece of glass, but I only had a standard flat mirror. I noticed that different surfaces made a big difference in RPM: with Eureka V2 on a ceramic plate, it could only reach speeds of 2000 to 3000 RPM. On my wooden dining table, it was even worse, with a disappointing average of only 1000 RPM.

Although the spinning surfaces plays a large role in how fast your top spins, it is also very important to get a good spin. Your ideal spin should not make large circle when it is makes contact with the surface. It also should not drop onto the surface and bounce- this causes it to lose energy. A perfect spin should be balanced and have it settle into a still and straight rotation almost immediately, with no wobbling of the handle. However, none of this is possible if the top was not designed well in the first place (e.g the Rip and Eureka V1 wobbled significantly when spun.) Do not be discouraged if your first several spins fail: practice is crucial to getting a consistently high RPM.

If you don't have access to a photo tachometer, you can record at 240/120 FPS in slow motion, mark the edge with a bold black permanent marker, and count the frames individually. Then divide FPS by frame count per rotation, then multiply by 60! I have attached a video showing how to use that technique (look VERY closely at the small grey dot rotating around the rim of the top).

Final Table of Results:

The Zip

1. ~30mm, rim-weighted, nail tip
2. ~655 RPM, ~60s spin
3. Solid start, accidentally good at endurance

The Chonker

1. ~70mm, heavy rim, nail tip
2. Too slow to measure, ~63s spin
3. Way too heavy, couldn't spin it properly

The Rip

1. 40mm, center-weighted, nail removed
2. 2,194 RPM, ~6s spin
3. Shifted gears: realized center weight = speed

Revolution King

1. 40mm, mixed features, nail tip
2. ~250 RPM, ~10s spin
3. Too many random features, a mess

Eureka

1. 28mm, center-weighted, rounded tip
2. 3,056 RPM, ~8s spin
3. Small diameter wins, the breakthrough design

Eureka V2

1. 24mm, center-weighted, smaller rounded tip
2. 4,742 RPM, ~8s spin
3. Final champion, handle trimmed to sweet spot

Again, 4742 RPM was achieved by single piece of plastic on a mirror, hand-spun. There were no motors, no launchers, no metal bearings. Now imagine what would be possible if this were CNC'd into a precision-machined metal top with a proper launcher.

The most important top-related concepts I learned from this project:

1. Speed is important, obviously
2. The top must be easy to spin
3. Minimize drag, design tapered and aerodynamic
4. Can't be too heavy or too light
5. More diameter can be restricting
6. Rim weight for duration, center-weight for speed
7. You need a combo of good features that work together
8. Handle length matters
9. Low COG is stable but can cause extra friction
10. A sharp tip isn't always the best
11. Tops are cool

Next steps:

1. Figure out a dremel/driver launch solution
2. Potential ripcord launcher
3. MORE SPEED!

This was a hell of a project. I only found out about this contest with about two weeks to go, and I barely had any time the first week. The large majority of this project was done during the past week and it was really hectic. I was having the time of my life, though. It was really exciting, iterating through designs and solving problems, and I'm glad I did this project. I rarely get to do such a fun, independent project at school, so this was a great break.

I learned a lot of about physics and kinetic rotational energy, moment of inertia, mass, weight, force, precession, etc. You could say that I'm a... top expert now. Haha.

NOW, CHALLENGER, I LEAVE THIS TASK TO YOU.

Print my best top. Beat my record.

Chase >5000 RPM.

LET IT RIP!!!

Here are the STL files of all the tops above. All tops were printed in PLA at 100% infill, layer height of 2mm (you can go down if you want) with the tip facing down. They are all quite light (except The Chonker) but require supports. I recommend using concentric supports with a 0 degree overhang for Revolution King. For tops with a small diameter and base, I used a brim to make sure it doesn't detach from the bed. They are a quick, fun print, each weighing in at 15 grams or less. They are printable on small-sized printers as well!

EurekaV2 is the only one that you must modify before using. Cut the handle 4cm or 3.5cm away from where the rim is (see photos in Step 8), or experiment with different lengths.

If you print a top, please leave some pictures and feedback below!