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Author Topic: Bearings  (Read 1287 times)
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marklazarz
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« on: December 12, 2016, 09:48:52 AM »

There seems to be a lot of interest in bearings and their importanc e in kinetic sculpture s, clocks, etc. so I thought a new discussio n thread with the topic might be useful.  Although it is probably obvious to anyone using bearings, one hint is to make sure nothing touches the sides of the outer race of your bearings.  I am fortunate to have a lathe so I can machine washers to an appropria te OD by holding them in a jig designed for the purpose.  The washer is held on a mandrel with a lip slightly less than the thickness of the washer, the lip is machined to the ID of the washer and the washer is held in place by a screw when turning.  Tube spacers are also useful for keeping things properly positione d and allow all component s on a shaft to be tightened securely without compromis ing the reduced friction afforded by the bearing.

Mark



* Washer Jig.JPG (293.86 KB, 1600x1200 - viewed 90 times.)

* Jig Mounted in Chuck.JPG (152.31 KB, 1600x1200 - viewed 94 times.)

* Machined Washers and Spacers.JPG (319.21 KB, 1600x1200 - viewed 99 times.)

* Washers Touching Inner Race.JPG (183.09 KB, 1600x1200 - viewed 85 times.)
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BobL
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« Reply #1 on: December 12, 2016, 01:30:23 PM »

Thanks for the info Mark..


Cheers
Bob
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Bob
Kineticrazy
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« Reply #2 on: December 13, 2016, 05:22:58 AM »

Mark,
   Great idea for a dedicated thread. I'm curious, does anyone else feel that modern skateboar d bearings have far more friction than those from the past? I remember spinning my skateboar d wheels as a kid, they used to spin quite freely. These modern bearings give one or two revolutio ns. I don't remember the bearings being shielded or caged either.

Anyone agree?


Eric
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BillM
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« Reply #3 on: December 13, 2016, 08:22:40 PM »

Another unusual source of  bearings are those used in modern high performan ce yo-yos. They are small but might be good for small scale clocks ot toys made with plexiglas s gears.

Yomega yo-yos are the ones I'm fmailiar with.  They would spin for a long time.

Bill
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Kineticrazy
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« Reply #4 on: December 17, 2016, 06:47:21 PM »

I happened upon a video of bearing manufactu re, a serious kinetic marvel in itself...

https://www.youtube.com/watch?v=7E7n3OtrauU


Eric

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marklazarz
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« Reply #5 on: December 24, 2016, 01:08:21 PM »

Since I use a CNC to cut holes for my bearings, I can make them any size so I decided to investiga te press fits.  I found that with a bearing OD of 0.875", a press fit in plywood was -0.005" and in Oak -0.009".  Kind of surprisin g but I figured it had something to do with cutter flex using a 0.125 end mill.  I'm sure that machine calibrati on is critical when dealing with these small differenc es.  I would be intereste d in hearing what others have found if they did any experimen tation.
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Dan Mauch
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« Reply #6 on: December 25, 2016, 11:58:21 AM »

 If you think the end mill is flexing then instead of running a single pass run it a second time. If it is bore is bigger after the second pass  then you have flex.
Dan Mauch

Since I use a CNC to cut holes for my bearings, I can make them any size so I decided to investiga te press fits.  I found that with a bearing OD of 0.875", a press fit in plywood was -0.005" and in Oak -0.009".  Kind of surprisin g but I figured it had something to do with cutter flex using a 0.125 end mill.  I'm sure that machine calibrati on is critical when dealing with these small differenc es.  I would be intereste d in hearing what others have found if they did any experimen tation.
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