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Roller bearing

by Robo, published

Roller bearing by Robo Feb 28, 2013

Description

I came up with this simple roller bearing when I saw the gear bearing:
thingiverse.com/thing:53451

There is a major design flaw: the rolls tend to turn. However it seems to run much smoother than the gear bearing.

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+1 to this. I came to the same conclusion.
This could work nicely if the rollers were hourglass shaped and the center and outer rings were formed to accommodate.
I once experimented with cages a bit (in conical roller bearings), The main problem was that their minimal printable size made the whole bearing too large. Also printing the tiny rollers separately turned out to be to be tricky.

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Roller bearing by Robo is licensed under the Creative Commons - Attribution license.

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This could work nicely if the rollers were hourglass shaped and the center and outer rings were formed to accommodate.
+1 to this. I came to the same conclusion.
What this needs is a cage. Real roller bearings have a cage or spacers to maintain the rollers' spacing. Probably very tricky to implement something workable for a printed bearing...probably needs to be a separate part that you snap in.
I once experimented with cages a bit (in conical roller bearings), The main problem was that their minimal printable size made the whole bearing too large. Also printing the tiny rollers separately turned out to be to be tricky.
The reason that the printed bearings like this don't work too well is that the rollers can move freely. If they can move together, surfaces moving in opposing directions rub against each other. And if they move apart, they can leave gaps large enough to cause the bearing to be uneven.

With the gearing-based bearing, the rollers are kept evenly spaced by the gearing, so the rollers never touch or get too far apart.
Correct.
Note that with the solution I proposed below there are no gaps and no rubbing only rolling between rollers. This comes at the expense of a high number of rollers so it couldn't be made all that small.
The gear bearing has no inter-roller-sliding but gears have a (very) little friction component in their rolling motion. This one similarily has a little friction at the slanted top & bottom so the slant should be kept minimal. But it also has a lot of (potential) friction between the rollers - and thats a problem.

How serious is this roller axis tilt problem? Could you post a picture? To alleviate this a bit you could remove the inner diameter parameter and auto-calculate it instead such that the gap (new parameter) between the rollers can be specified as very small.

Heureka!
what abut this:
To remove inter-roller-friction completely you could start by allowing only even numbers of rollers. Every even one is a bit further outward then every odd one. Then you add a third set of innermost rollers of which every one is assoziated to one of the otermost ones. (yes I know - quite a bit of rollers are necessary - 12x3 might work) But now there are no more contacting surfaces that move in opposing directions and thus we have waaay less friction. The gaps can be reduced to zero (or at least a nonfusing gap). The central rollers (the odd ones in the description above) that roll only on rollers (on four to be specific) can be kept in place by a outward trapezoid slant similar to your inward slant. The three rows of rollers may have different diameter - lots of trivial trigonometry waiting.

I'am really wondering why no one has made steel roller berings this way ... ? I'd Guess brass cages work well enough and ar less difficult to analyze.

In the parameters:
You should call the rolls "rolls" or "rollers" not "planats" since this term is reserved for planetary gears.
You might add a very short (1mm?) vertical section at the bottom and top to avoid the sharp edges.
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