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bearing help
http://www.sdp-si.com/eStore/CoverPg/Bearings.htm
I'd thought a bearing was a bearing, but it looks like i'm sorely mistaken, and I hate to think i'm missing out. Ball bearings, linear ball bearings, needle roller bearings, thrust bearings, pressure bearings, press bearings, sleave bearings. I think I grasp most of the distinctions, but in terms of FIRST what are the part/application relationships? Specifically, which of these are useful for a press-fit in a gearbox? Which of these make sense to use inside the free-gears of a dog-shifting system? Are some of these not viable with a keyed shaft (needle rollers?). Which can handle our driving loads? Which can handle side loads as per swerve module needs? Thanks all. |
Re: bearing help
most gearboxes will use plain ball bearings, as will a bearing inside a rotating gear in certain shifting mechanisms. I would assume that if you were to construct a swerve drive properly, you wouldn't have any need for a special bearing. As I've never constructed one myself, I can't give you a definitive answer.
Cory |
Re: bearing help
For bearings in a gearbox I suggest flanged bearings. In anything else regular ball bearings will work.
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Re: bearing help
I understand that ball-bearings should work fine for just about anything-- thats what I designed last year's gearbox with. However I notice that other stripes of bearings, particularly roller pin and sleave bearings, have a much lower OD-bore ratio, which I could see being highly advantageous if you're pressing them into tiny gears. And for applications like a swerve drive module, I have to think there are compenents designed with linear forces in mind and I don't see why I wouldn't want to use them. I could go on forever just using the same components and designs every year, but I'd really like to at least learn about what else it out there.
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Re: bearing help
I would recomend you take a look at Small Parts P/n brf-06 and brf-08 That is what we use for everything. They aren't in the catalog but they do sell them for about $5 each or 10 for $40. For specs go to www.firstcadlibrary.com
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Re: bearing help
There's a ton of different bearing types to pick from, and they should be tailored to your specific application. I've found two websites that should help:
Bearing Selection Bearing Application |
Re: bearing help
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<grumbles> Wish I'd found it on my own.... Thanks! |
Re: bearing help
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There are a few types of bearings, I'll list off the ones that come quickly: - Radial: these take the rotational forces of a shaft running in them, as well as take the weight that comes at 90 degrees to that shaft axis. -Linear: these take sliding forces of a shaft sliding through the bearing, as well as the weight that comes at 90 degrees to the shaft axis. - Thrust: these take weight. Most are in the rotational style, they are designed to take the rotation of a shaft, and the weight that comes parallel to the shaft. The shaft needs a flange on it, to ride on the bearing itself. - Angular Contact: these are just like radial bearings, but the contact the balls roll on is at an angle, so they double up as thrust bearings. - Bushings: these are just inserts made of oil impregnated cast bronze. They are self lubricated, and can take lower rpms and pretty good weight loads. Every bushing has its own rating, so they aren't always usable. They come in linear, radial, and thrust styles. However, there are MANY styles of the above bearings (except bushings). Roller bearings use rollers instead of balls, angular contacts come in different angles, radial and angular contact bearings come in one, two, or 4 contacts. There are mostly different types of radial bearings. Thin section, miniature, superprecision, heavy load, etc.. the list goes on forever. And if you're crazy enough, you can make your own bearings. That's what I'm doing this summer, since I can't find the right size for cheap ($150 each and I need 12!!!). I'm just using rollers and cutting steel inserts, hardening and grinding them. When they press into the gearbox and the gears go into them, the rollers can't go anywhere so no flanges or seals needed. Works just as good as ones you can buy. Hope that helps! |
Re: bearing help
For all future needs like this, I heartily recommend Engineer's Edge as a starting point. I will say that I've seen some erroneous or misleading details there, but for the most part, it's very helpful. I also recommend EFunda as a basic reference. And finally, buy Machinery's Handbook if you can at all afford it. It is so massively useful that I can't even begin to describe it. I'll be purchasing my own copy in a few weeks. If you can't afford a copy, I have one more link that got me through a design project this last week, Machinery's Handbook
EDIT: I'm somewhat doubting the need for thrust or angular bearings in a FIRST robot with swerve. Especially with a 3/4" shaft. Deep-groove radial bearings should be more than enough, as they can handle some axial load in addition to radial load. a 3/4" bearing is rated at 1700 lbs radially, so it could easily handle 200lbs axially. |
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