Thursday, August 21, 2008


Going Round In Circles

I took apart a swivel chair the other day and noticed an interesting ball bearing race in the bottom of it. So I made a RepRap'd version to fit under the Z axis drive rods, which currently sit on a couple of washers and some grease. Suz an I will hopefully fit them to Phoenix today, if we manage to get any time to ourselves.

On my machine it needs some tidy-up with a 5mm drill because I've not got the smooth-moving Arduino board installed on the Darwin yet. But once reamed out, the holes in the bearing race hold eight 4.5mm (.177) BB's normally used in an air pistol to plink at tin cans with in the garden.

It's sort of a compromise between running on bare plastic and using skate bearings - which cost me NZ$6 a piece. BB's cost me less than a cent each and are also available from the same sporting goods stores as the skate bearings.

If they work well enough, I'll add them to the next run of the lasercut design. Ponoko's website tells me that the current one is 60% complete, so hopefully I'll see it early next week.

Vik :v)

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Very nice, just pulled the side guards off a skate bearing they have similar but smaller plastic cage holding the steel bearings in places
Hope that's a typo :p, was that $6 for a set (of 8) or $6 for one bearing!? Trademe usually has sets for under $10 or singles in the $1.5 range
$6 for one bearing in Stirling Sports.
"$6 for one bearing in Stirling Sports."

Bloody hell! That's highway robbery! :-o
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awesome reprap thrust bearings! :)

i use a similar method to keep my lead screws straight except i found a shaft collar + rubber washer after the thrust bearing assembly did a better job than just using nuts.

for those still building there systems, thrust bearings are fairly cheap if you get the nylon type, i believe i got mine for something like 3 bucks..

and if u want something really cheap there is always the brass washer between two steel washer method :)
Revolutionary news! Now reprappers can say..

Have plastic, will travel.
If a BB thrust bearing is possible so should a Taper Bearing.

You do need rollers though but slices of rod will do.

The races are tapered and should be easy enough to RP.

as Should a cage to keep the rollers correctly aligned.

A Taper bearing should work better than a thrust bearing in this application as it has the ability to add a degree of centering to the drive shaft.

Outstanding work though Vik.
Brilliant stuff!

Any reason why you didn't make the inner and outer profiles circles, with a series of circular holes round the middle?
It's nice that you get really round BB's. The copper washed ones you get here tend to have been forged and have seams around the middle. :-)
Adrian, I did it that way so that the whole thing is done with a single-line deposition. At that radius of curvature and without the smoothing on my PIC-based RepRap things get ugly with infill attempts.

Forrest, yes, you have to watch the quality of the BBs out there. The latest batch of Copperheads from Crosman (normally a good supplier) are particularly bad with rust under the plating etc. and Daisy nickel plating is too rough.

Vik :v)
100 skate bearings for $29:

So yes, $6 for one bearing is a bit much!
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