On turrets, why do teams make a bearing sandwich?

For an offseason project, were trying to make a turreted mechanism, why do teams make a bearing “sandwich,” and not put small washers, then plates on the outside of a bearing. If you have any questions feel free to ask.

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Can you draw what your describing? It isn’t clear.

In all of the turrets I’ve seen (3647), they have a plate, than a big bearing, a small bearing, another big bearing, and another plate, all on a screw, and the big bearings hold the part that spins in, while the little one spins.
What I am trying to do, is to put a plate, a small washer, a bearing, another small washer, and the other plate on a screw. What is the reason nobody has done this and opts instead for the “bearing sandwich”

If I’m picturing what you’re saying correctly they’re using an inner bearing as a radial bearing and two outer bearings as thrust bearings.

If those outer bearings were replaced with washers they would not roll smoothly and/or have a lot of slop.

Afaik 1323 popularized this bearing stack in 2012, and others have used it since.

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Actually, if you go back to (I believe) the 2006 behind the design book, you’ll find that team 27 Rush used this method. In fact we copied it from them for our 2009 turret. Though 1323 might have been the first to introduce it to the West Coast. I couldn’t say for sure.

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just curious: for the outer bearings, do you need to use bearings suitable for thrust and radial loading? or are just radial loading bearings “ok” enough? it seems like when this has been done in the past, it’s been with just radial loading bearings, but I could be wrong

If you are willing / able to machine a “V” into the edge of the turret plate, you could replace these bearing stacks with V-groove bearings. These bearings can carry the radial loads as well as the thrust loads needed to react the “tipping” moments of the mechanism mounted to the turret. I have seen some designs recently that use these style bearings but a quick search I was not able to find a few of the pictures of them that I was looking for.

Edit: Found the one I was thinking of from Code Orange.

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Like anything else - you don’t need to. But if you want to do it right, you should. Mcmaster has them and they’re very inexpensive.

I think similar concept was used on the 05, 04 and 03 bots too but my memory is getting hazy…

Is it a sammich?

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You can just use regular bearings. We had R4’s as our outside bearings and .5od .25id bearings as our inside bearings