Bearings for turrets

I want to design my own turret but I am not sure what kind of bearings are used in turrets usually. I don’t know bearings by heart and have no idea which are good to use and which aren’t. Thanks.

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18635A52 and 18635A54 are semi-popular choices from McMaster (and can be found on amazon, ebay, etc…)

Armabot has a turret solution with integrated bearings.

WCProducts sells they GreyT Turret which makes a slew/turret bearing from smaller bearing stacks.

A few teams have used 1/4" X-contact bearings from silverthin or chinese vendors (same style bearing, but larger, as the SDS swerve) in the 7-12" ID range.

All work, but have various pros and cons depending on your resources.

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Thanks this answers it.

Having never used the lazy-susan-esque turntables, what are the cons of them? Only thing I can see off a quick browse of McMaster is the limited sizes.

They’re more work to integrate than the GreyT or Armabot turrets, have some slop, have a lower load rating than all options listed, likely are heavier and will take up more space.

That being said if you’re going custom and don’t have anything more precise than a poor quality router they are pretty easy to integrate.

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Yeah we’ve used them in the past and they’re just not super customizable in comparison to the other options. Plus they seem to have less capability when it comes to turning smoothly.

Some common considerations include needing to feed a game piece up through the center of the turret or not, the option of supporting the turret with both a lower bearing and a higher one, or having to have all the support come from below, and how much mass / moment of inertia must be handled. The bearings are a major part of any turret but depend on the overall mechanism.

We (1923) built our first turret since acquiring our new machining resources on our 2020 robot, and we drew heavy inspiration from the “bearing stack” concept from the Greyt Turret and several other turrets from previous years. It was really easy to build and worked extremely well for us.

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Seconding this. Side loads on a turret (especially ones that aren’t don’t have a COG directly over the middle) can induce some forces you don’t want. The bearing stack design served as well this year and was easy to do maintenance on as well.

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Which bearings should be used( prefered load ratings )? My team is outside the US. We have access to metric bearings.

In general, small radial bearings are used both for the axial and radial loads in a bearing stack. For example, this year 1720 used .625" OD, .25" ID bearings for the axial loads and .375" OD, .25" ID bearings for the radial loads. We did not check load ratings before using the bearings, but had no issues with the setup.

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We also used a bearing stack design for our turret this year, but flipped the idea on its head so the fixed part sits on the inside and the turret and bearings rotate around it on the outside. This design integrated into our robot easier, gave a more stable platform (bearings spaced farther out ⇒ less force on each from twisting loads), and made maintenance easier (to remove the turret just undo two easily accessible bearing stacks and slide the turret out the hole).

We used 605 bearings (5mm ID, 14mm OD) for the sandwich “meat” and 635 bearings (5mm ID, 19mm OD) for the “bread”

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We used 18635A52 and it was perfect for what we needed.

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not to get off topic, but i have to ask…

that launcher backplate is clean! How did your team manufacture that!?

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The hood is made of two 5mm aluminum plates sandwiching three 20mm HDPE plates. At the bottom, a 10mm thick aluminum block is riveted to the turret plate, and screws attach the hood aluminum plates to tapped holes in the block edges. All of the parts were made in-house on our CNC router

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How did the 775s treat you? we went for a dual NEO setup this year, but I was always toying with the idea of 775s because it means no gearing up (in theory).

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I was happy with the amount of power we got from 3x Redlines. I think in the end we went with a 1.5:1 reduction on a 4" wheel. It’s probably comparable to about 2x NEO or Falcon worth of usable power. We didn’t have any problems with slow recovery times, our shooting rate was limited by our feeder speed. We did burn a few 775s in prototyping shooters when we were running them off “dumb” motor controllers without current limiting, but once we added a current limit (around 30A IIRC) we didn’t have that problem anymore.

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In your experience what is the load rating for a Greyt style turret? Would you say it is suitable for a turreted column +shooter setup? (ie 973 2012, 177 2020)? I have minimal personal experience with turrets.

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how does the bearing stack part work? What rotates on it?

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On that setup specifically, the bearing stack is attached to the rotating part of the turret. The bearings, and the plate they’re attached to, spin around the large circular plate.

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