There’s quite a lot that gets discussed in [Zach’s video series] and there’s also a Facebook group (search “Yoyo Designers”) if you have specific questions. I feel like both of those are superior options to just reading about it. However, if you prefer another, text-based take on the mentality you should take, or a really quick primer, here ya go.
1. LEARN YOUR PROGRAM.
I’m not going to tell you what software to use. They’re pretty much all good, just like all yoyos are good. Inventor, Solidworks, Creo, Fusion 360, all good places to start. What I do recommend, though, is to learn to use software that’s actually 100% free like Fusion 360. It’ll avoid any sort of future issue with licensing, and yoyos are some of the simplest things to design in terms of part complexity and interactions. Any half-decent CAD software will be able to handle it.
2. Learn physics.
Crash course: More rim weight = more spin time and stability. Take a look at pre-existing designs (OD has some side profiles, G2 Jake has his Let’s Cut A YoYo series) and figure out the kind of profile your yoyo should have. Almost all designs have a “heavy” amount of rim weight.
Speaking of profiles… yoyos are designed by sketching one half of a profile. That’s all you need. Your program should have something like a “revolve” command, which will spin that profile around an axis to turn it into a solid shape. That’s basically what the machinist will do in reverse as well – they use the profile to determine where to cut to shape your (insert material here) into a yoyo.
4. Tolerances, dimensions, and notes.
While the most common yoyo companies you’ll talk to will probably be fine with dealing with your design regardless (because they’ll change it up slightly for machinability), get into the habit of adding dimensions to Every. Single. Thing. And if you’re taking it to a shop that doesn’t do yoyos… figure out how precise you need them to be, because 9/10 if you let them decide it’ll result in a vibey yoyo.
Most engineers and machinists love efficiency and practicality, because that’s what they’re paid to do. Make stuff as cheaply as possible within specified limits, because otherwise the price skyrockets. Yoyos are much, much more precise than most mechanical parts people use. Just like “aircraft aluminum” isn’t really a marketing term, “aerospace machining quality” can still leave large errors in tolerance, specifically because they’re designing for crazy amounts of stress/heat and don’t care about it having a 100% smooth transition between parts like yoyoers do.
My dimensioning here is both slightly overkill and kind of improper engineering standard (numbers in the wrong places), but it gets the point across.
5. Logic check your design.
You can easily get stuck interpreting something a certain way, or miss an important step. The way I avoid it is by “assembling” all the parts together. I make a bearing and an axle, and combine it with two yoyo halves to make a full yoyo. Your program may not have that ability. If not, assume your bearing+axle weigh about 3.8g, and do some math to check out your gap width.
Things you may miss:
• Bearing seat post is not half the height of the bearing. It’s shorter. You’ll need to account for the gap when you calculate width of your sketch.
• Axle hole length is similarly affected. You need it to be longer than the axle so it doesn’t bottom out, but you can also account for the gap where the bearing seat doesn’t exist.
• Corners. If you don’t specify how round they should be, your machinist will either complain at you or assume they should be made SHARP. Even sharp-looking edges have a radius of about 0.2mm, and you should do 0.5mm on anything that you want to be a body corner.
7. Practice, practice, practice.
In order to get good at CAD you will need to practice. Just like learning to draw, you can start off by trying to copy stuff you see. The table lamp on your desk, a mug, whatever.
The most important part, in my opinion, is actually making things. Non-yoyo, non-metal things are usually cheaper, so I recommend those. Whether it’s building a workbench, 3D printing out other designs, or making marshmallow guns (I have a great hopper-fed pump action design), you’ll learn more about design and production along the way.