I’ve been watching the MK1 series and Zach the Sloth’s videos—super helpful stuff, so thanks to those who put that content out.
I’m currently designing a yoyo and could use some input on a few things.
The idea is a hybrid build: polycarbonate body, stainless steel core, and stainless steel rims.
A few questions:
1. How much interference should there be between the stainless steel rims and the polycarbonate body? And between the stainless steel core and the poly body?
2. What are the standard thicknesses for stainless steel rims?
3. Should the stainless steel core only hold the axle inserts, or should it also include the full bearing seat?
I’m leaning toward a full stainless steel core with bearing seats, but I want to make sure the design stays solid and doesn’t risk falling apart.
If you’re working with someone like fpm they will make the necessary adjustments for the interface. As for thicknesses for the rims and I guess also for the hub area it comes down to weight, the weight distribution and how you want it to play. There are quite a few hub options that have been used it comes down to weight and cost.
1: Not too sure on this one might have to ask someone more experienced like @MarkD@hobbygod or others.
2: I don’t think there is a standard thickness but I wouldn’t go any thinner than 0.8mm but I would stick to 1mm minimum thickness. I don’t think there is an agreed upon minimum thickness for SS though. Correct me if I’m wrong someone.
3: I would say you can do what you want but I would probably do the hole for the axle and the bearing seat area out of SS and the response pad area out of PC. Something like this:
You need one additional part on the inside for a design like this - a spacer that touches off on the inner race of the bearing and presses against the plastic. Note that this means the hub just has a long straight tube that matches the bearing ID.
Anything 4mm+ is fine for rim interface. You can get away with a little less here, but the more interface the more stable it’ll be (also, you’ll need to draw a buckle for plastic)
.8mm is fine at the thinnest part. You can go thinner, but it can result in warping. (You’ll also need 1mm or more at the stopgap)
I’d advise against this specific set up for the bearing seat. This is how the Yoyojam solid spin system was set up and pretty much all of those failed at a certain point. The insert would either loosen or pop out if pressure was placed on the yoyo. One of the reasons behind the company closing down.
Okay, this is all very cool advice here. @Yalsharqi as you can see I’m not the expert here and it’s always good to ask the professionals.
@MarkD may I ask, why do you use a spacer there as a pose to having the bearing seat also metal? If I may ask, how is your design above different than what @yoyospirit said? I’m just curious because I would love to learn more.
@hobbygod Okay that all makes sense. Good to know. I think you told me some of this before. Thanks for the additional info!
@yoyospirit That’s very interesting. I guess I don’t know how modern plastics are designed? What do people usually do nowadays for modern plastics? I assume what I do with my 3D printed yo-yos is pretty different than machined or injection molded yo-yos.
Good questions! So your design isn’t entirely wrong, it’s just not meant to be a pressfit into yo-yos. There are plenty of plastics such as the Plastic Peak that utilize your design, but the bearing seat is molded into the yoyo and surrounded by plastic, ensuring a tight durable fit.
On the Yoyojam Solid Spin System, the bearing seat was a press fit through the cup of the yoyo. Meaning when people would put the yoyo in their pocket, sometimes that force alone would be enough to pop out the insert, or the surrounding plastic around the insert would crack from the tight fit and the part would loosen.
@MarkD ‘s design includes a change. The bearing post is just one long tube with a flared base that the bearing is centered on, that goes through the cup of the YoYo. On the bearing seat side, a spacer is placed down, that the bearing sits on. With this type of design, and the YoYo tightens, each half is sandwiched between the spacer and the bearing post, and tightens as you tighten the YoYo. Here is an example. The post is what centers the bearing, and the removable spacer is what the bearing sits on.
The spacer is metal too - but it has to be a separate piece in order for the spacer/hub system to hold the plastic in place at a fixed distance from the other half of the yoyo. Yoyospirit is saying the same thing, essentially.
You can design the hub in one piece if there’s something else preventing it from popping out of the yoyo body (eg. overmolded)
Was going to reply but mark beat me to it. That’s the way I’ve been making plastic yoyo’s for years and has some more benefits when it comes to machining yoyo halves as it allows machining almost the complete halve in one setup, minimising possible error when flipping halves in the chuck
