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Ball bearings - shields or no shields, and why?


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#1 Pablo

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Posted 20 May 2013 - 11:16 AM

In both axle and motor ball bearings, why do I need, or not need, shields?

 

I noted on my Lee Gilbert 1971 racer, he said in the magazine article to remove the shields.

 

Thanks for your input ! :)


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#2 MSwiss

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Posted 20 May 2013 - 11:34 AM

Stu Koford, my old boss's opinion was, the open style were easier to flush out, if stuff got in them.

 

Of course, logic would dictate that without shields, more stuff would get in them, and easier.


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#3 Cheater

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Posted 20 May 2013 - 11:57 AM

Mike,

 

Do the shields cause a bit of a drag on the bearing, i.e. does a non-shielded bearing have less friction than a shielded one?


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#4 Rick

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Posted 20 May 2013 - 12:04 PM

I prefer unshielded for the same reasons noted above. Easier to flush out and re-oil...
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#5 John Streisguth

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Posted 20 May 2013 - 12:09 PM

Greg,

The shields should not cause additional drag as they do not touch on both the inside and outside race. Sealed bearings, which are more impervious to outside dirt and liquids, have drag from the seals since the rubber does touch both inside and outside races.
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#6 John Streisguth

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Posted 20 May 2013 - 12:12 PM

I have some VXB bearings on my oldest Retro cars that are unshielded, and they are still in good condition because I can flush them out and re-oil. 

I now typically use Avid sealed bearings, and would love to pop out the shields but I would probably do more harm than good... :sarcastic_hand:
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#7 Cheater

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Posted 20 May 2013 - 12:17 PM

So there are three bearing options: unshielded, shielded, and sealed?

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#8 Jairus

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Posted 20 May 2013 - 01:16 PM

I always assumed that shielded and sealed were the same thing?!?!

And that they don't need oiling?

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#9 Bill from NH

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Posted 20 May 2013 - 01:40 PM

In the day, we would oil the shielded GRW bearings with Tiger Milk. These weren't a sealed bearing, because we used to remove their lubricant with an ultrasonic cleaner before soldering in the motor bearings.

I'm not familiar with the Avid sealed bearings John mentioned. :)

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#10 Pablo

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Posted 20 May 2013 - 02:06 PM

All I remember is that SKF ball bearings were a LOT better than those of today.


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#11 Don Weaver

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Posted 20 May 2013 - 02:20 PM

Shielded bearings have a metal shield between the inner and outer races to keep dust and dirt out. 

 

Sealed bearings have a rubber seal between the inner and outer races and helps with moisture, liquids, etc.

 

Sealed bearings drag on the races whereas the metal shields have very little friction losses. Shielded bearings can be lubricated but not cleaned very well whereas sealed bearings cannot be cleaned or re-lubricated. 

 

A good alternative would be a shielded-one side bearing with the open side facing the wheel/gear. The shield would protect from dirt on the inboard side and he wheel/gear hub would somewhat protect on the open side.

 

Don Weaver


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#12 Jairus

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Posted 20 May 2013 - 02:25 PM

But my point is that "shielded" bearings are NOT lubricated from the factory then?


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#13 John Streisguth

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Posted 20 May 2013 - 02:30 PM

Shielded and sealed bearings are both lubricated at the factory, usually with a light grease suitable for the RPM range the bearings are capable of.  The shielded bearings have enough of a gap that you can get fluids into the bearings, so you can clean them and reoil them, but it's difficult to know how well you're doing either of those.

 

There was some discussion elsewhere on the blog about soaking shielded ball bearings in solvent to get the factory grease out before soldering them into a motor can, because the heat can crystalize the grease, which then acts as an abrasive and contributes to premature wear. Sounds logical to me.


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#14 John Streisguth

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Posted 20 May 2013 - 02:32 PM

I always assumed that shielded and sealed were the same thing?!?!

And that they don't need oiling?

 

These are sold by AVID R/C, and cost around $1.50 each. Most of the guys in Retro East™ use them, and they are pretty good.


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#15 Pablo

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Posted 20 May 2013 - 02:41 PM

So, why do you think Lee suggested "beating" the shields out?


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#16 S.O. Watt

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Posted 20 May 2013 - 02:54 PM

Because back then it was customary to solder, with acid flux, the bearings into the chassis. It wasn't an accepted practice yet to use an adhesive such as Loctite for this task. So to facilitate the cleaning out of the burnt residues inside the bearings created by this process, Lee yarded out the shields.

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#17 Jairus

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Posted 20 May 2013 - 03:15 PM

I keep learning something new each day!

How about that?  :victory:
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#18 macman

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Posted 20 May 2013 - 03:45 PM

Great info!!!

 

Thanks.


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#19 HarV Wallbanger III

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Posted 20 May 2013 - 05:10 PM

Be careful if you have shielded type if you clean them and then use air to blow out the crud you can blow the shields out also. Canned air should not blow the shields.

 

I blow-spin the bearings with a old arm with air and flush if using in a motor and axles. I do the same using a gear on the axle then again flush.

 

You can tell if the bearing has something in it or a bad ball real easy by using canned air to spin them up. Any noise is no good. Do not over-oil them...


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#20 Bill from NH

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Posted 20 May 2013 - 05:27 PM

All I remember is that SKF ball bearings were a LOT better than those of today.

 

Probably because they were made in the US rather than China. :laugh2:  Then, we also had MPB (Minature Precision Bearings) made in Keene, NH.


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#21 Phil Hackett

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Posted 20 May 2013 - 05:39 PM

You don't want SEALED bearings for slot cars: they have drag and cost a lot more.

 

As for shielded vs non-shielded: have you ever tried to lube a BB turning at speed? Now, think of crud trying to get in to a spinning bearing...

 

I preferred non-shielded when I raced.

 

Oh, yes, don't over-lube. Doesn't do anything but throw the lube everywhere, making a mess, and doesn't make the bearing spin any better. In fact, too much oil/lube does attract crud which will find its way into the bearing when it has a chance.


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#22 Don Weaver

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Posted 20 May 2013 - 07:09 PM

... I blow spin the bearings with a old arm with air...

 

Believe it or not, this can be an extremely dangerous thing to do. The centrifugal force of spinning can cause the outer race to expand enough let the balls escape. And when they do it's like a shotgun going off. 

 

Of course, larger bearings are the real danger but even the small ones in the bearings we use could inflict pain and, in the worst case, cause serious eye damage. I urge everyone to think twice before doing this and to always wear eye protection.

 

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#23 HarV Wallbanger III

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Posted 20 May 2013 - 10:17 PM

I do not spin it at 100K RPM (even though theball bearings I use are good for it), Don. I use canned air and just spin it at about 10-15K I would guess.

 

At this speed you can feel a bad bearing.


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#24 Don Weaver

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Posted 21 May 2013 - 10:07 AM

I'm sure that's safe, Barney. It was meant to inform others that this can be a dangerous practice as most wouldn't think that a ball bearing can explode. 

 

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#25 John Streisguth

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Posted 21 May 2013 - 10:24 AM

And you're spinning it with no lubrication, which isn't much good for the bearing...


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