Lazy Susan VS Bearing Stack for Turret

What is the benefit of using a bearing stack over just buying a lazy susan for a turret?


Both methods have been used successfully - one isn’t objectively better. One of the main benefits of using a bearing stack, though, is that it’s completely customizable; you can make it the perfect size for your mechanism rather than designing around a COTS component.


The problem with lazy suzan bearings is that they aren’t designed to handle lateral forces - that is, the reaction force of launching a game piece. 3946 wrecked at least two 12" lazy suzan bearings in 2012; do not recommend especially if you’re planning shots from beyond the TARMACs.


Here’s our lazy susan at the end of a match our rookie year.

The benefit of buying the WCP one is that you don’t have to plan out the sprocket and motor assembly.

If you go the build your own route, we used McMaster #18635A52 for our turret last from a recommendation from a team 78 member in the 2020 319 build thread. It worked great, no issues at all. They come with some heavy grease but we degreased them and put in some lighter stuff.

Actually, 3946 had a really simple solution for that rookie year using chain! We made a loop of chain big enough to go around the turret and off to where we would mount the drive motor/sprocket. Putting the turret in the mid position, we anchored the chain to the point on the turret opposite the drive sprocket; I think we used a screw of some sort. It gave us over 270 degrees of rotation. We don’t really want to go all the way around, because that would require slip rings.

Just to throw another pre-designed option into the mix, we had great success with Armabot’s turret240 two years ago. Easy to use and it worked great! Turret240 – ARMABOT


X-contact bearings are more appropriate than Lazy Susan. If you are OK with NOT loading the CARGO through the axis of the turret, you can use one of the ones teams usually use for swerve drives, e.g.

I too favor the bearing stack over the lazy susan for a main turret bearing for several reasons including resistance to lateral forces. We built our own version this last off-season using the WCP turret as a base to work from (though we did modify a few things, like 3D printing the chain ring instead of machining it from aluminum.) If you have a CNC, it’s just a series of plates and stand-offs, plus standard bearings and hardware. It really does let you design the turret to match your shooter exactly and adapt to the ball being shot. We’re doing something different for this season, but it’s a solid design and works well.

We had pretty good luck with this style of lazy susan from 2020:

There’s a number of turntable bearings available that aren’t very expensive, but you would need to make your own sprocket/gear that goes around the turntable

One of many Amazon options (12in)

McMaster 18635A52 has a 10.43" ID

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Use the 10DP pinion and cut your own… that’s what we are doing!

If you either don’t need an encoder, or can attach the encoder to the turret itself, a wheel will drive these just fine.

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Here is a visual of what this looks like. This was done with a lazy susan and belt. It was quite effective for us:


We didn’t have the idlers, and the drive sprocket was a bit closer to the turret, and the chain was attached to the turret, but that’s definitely the same concept!

That’s a sweet idea for limited rotation angle!
Are you happy with that bearing?

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I’ve never used one like that, but I can say that that looks nothing like the one we were having trouble with - that one does look like it is designed for radial loading. We were using something more like this:

That’s what I figured! The pressed steel classic lazy susan is totally unsuitable for this application; no radial capacity to speak of, and no resistance to lifting/bending.

FYI, 5892 is using an Amazon Aluminum turntable bearing: think giant deep groove bearing. We’ll let y’all know how well it works.
The turret crew decided to keep the set of rollers that support the drive gear against vertical loads; they felt needed for the bearing stack design… Probably not needed on the turntable, but they are still going in…

We’ve used the aluminum ring bearings since 2009 and have a lot of experience with them. There is a vast difference in smoothness, tolerances, and strength between the poorly made ones and the good ones. We have had no problems (our 2012 turret bot is still running even after numerous crashes on the turret) with the ones we purchase.

We exclusively stick with Troops BBQ turntables, with a load rating of 300 lbs. We went with a bearing stack this year because the delivery for the turntables was in mid February because of Covid, but if they had been available we would have used them again. We’ve used them in 2009, 2012, 2020 on 6 robots, 3 of which are still running.