Open Vs. Closed

[greg123 0]

Bearings...open vs. closed....

Is there an advantage to having open bearings inside parts that are not exposed to dirt? I don;t think I can find an argument for bushings over bearings. But I wonder why some people use open bearings in things? R/C or not. Is it because they are easier to grease? Maybe easier to clean?...Although it seems that sealed ones won;t get dirty....hmmm...

It seems to make sense to me that sealed bearings are a plus for things that are close to the ground, r/c's, skateboards, rollerblades, rollerskates, 1:1 vehicles. But there has to be some sort of mechanical advantage to open bearings. I searched online, and there is not much debate about it, so thought I would ask some of you guys what you thought.

[MadInventor 3884]

Bearings...open vs. closed....

Is there an advantage to having open bearings inside parts that are not exposed to dirt? I don;t think I can find an argument for bushings over bearings. But I wonder why some people use open bearings in things? R/C or not. Is it because they are easier to grease? Maybe easier to clean?...Although it seems that sealed ones won;t get dirty....hmmm...

It seems to make sense to me that sealed bearings are a plus for things that are close to the ground, r/c's, skateboards, rollerblades, rollerskates, 1:1 vehicles. But there has to be some sort of mechanical advantage to open bearings. I searched online, and there is not much debate about it, so thought I would ask some of you guys what you thought.

Less weight through not having the shields fitted

Where I've acquired second hand cars with seized bearings, I remove the shields, clean and unseize the bearings, then refit them inside gearboxes where the shields are not required. It just means I don't have to chuck the bearings and buy more.

Sealed bearings aren't really sealed. Goop and water can still get in, or bearings would never seize up.

[greg123 0]

Interesting. Do you think the shieldless have less resistance? After researching it a little more, I am wondering if shieldless (on one side anyway) are used more for grease, where as closed have oil used more. Hmmm...

[Jesse James 13]

people often remove the rubber seals to reduce friction, thats obviously on rubber shielded bearings, i generally feel that metal shielded bearings have less friction than rubber shielded ones. once a seal is removed, they are more free, but get dirty very quickly, they require a lot more maintenance

[greg123 0]

That's interesting JJ. So they are more free, but it comes at a higher maintenance cost. So what you are saying is that the performance is better, but requires more labor to maintain the higher efficiency. Interesting.

I found this website:

http://www.tecmetal.com/bearing/mr.htm

It shows a diagram of open verse the closed at the top as well.

As a side note, I wonder why there are no micro bearings like say, 4mmx7mmx2mm, that are full on ceramic? Maybe the tiny bearings are just so small that full ceramic doesn;t make much difference? Hmmm...

[94eg! 834]

In racing you will either find metal shielded bearing or low friction Teflon sealed bearings. They definitely roll more free than rubber sealed bearings. A metal shielded bearing offers some protection, but no extra friction compared to an open-bearing as the shield does not actually touch the inner race causing drag. The trade off is they cost a little more than an open bearing, but not as much as a sealed bearing. Teflon is a true sealed bearing, but the low friction seal causes very little drag. They do cost a bit more than rubber seal, but do offer better performance closer to a shielded bearing.

After the shield/seal selection comes the ball rating. The higher the ABEC number, the more precise the bearing and the faster it will roll. There is also material selection like ceramic vs steel. Ceramic is harder and lighter, so it's also quicker. Problem is the cost goes up considerably.

The real trick lies in the grease though. Most racers will wash all the grease out of the bearings and replace it with a few drops of light machine oil. This really frees up the bearings potential. The trade off is that this requires frequent wash-downs and re-oiling because the oil won't last as long as the grease. This is also really easy to do on metal shielded bearings because solvents like motor spray gets right through. I usually soak my bearings in a shot glass of motor spray. If you wanted to do the same with sealed bearings, you would need to remove the seal and go from there. Some Teflon bearings like TRF bearings have only light oil inside them already. This means your good to go right out of the box. Of course you pay extra for this convenience. Even still, metal shielded bearings are the easiest, cheapest and fastest if your racing on a budget.

Teflon Sealed:

Shielded:

[greg123 0]

94eg, that post is awesome! Thank you!

[greg123 0]

What do you guys think about these:

http://www.ebay.com/itm/RC-Full-Ceramic-Be...=item20a590c181

They are super expensive obviously, but all cost aside....is this like the ultimate bearing an r/c can have?

[94eg! 834]

$60 for one 1510 bearing?!?!?!? That's just insane (especially with no mention of precision). I don't know that anybody would waste that much money on an RC car.

[Skottoman 306]

That's funny, for years I've been buying the duratrax bearings from Tower. They are the cheapest ones on there it seems...

Yet, they appear to be Teflon sealed bearings, which are cheapest on Tower, but more expensive compared to ebay bearings...

http://www3.towerhobbies.com/cgi-bin/wti00...LXD121&P=ML

I use these everywhere...

Cheers,

Skottoman

[speedy_w_beans 4272]

That's funny, for years I've been buying the duratrax bearings from Tower. They are the cheapest ones on there it seems...

Yet, they appear to be Teflon sealed bearings, which are cheapest on Tower, but more expensive compared to ebay bearings...

http://www3.towerhobbies.com/cgi-bin/wti00...LXD121&P=ML

I use these everywhere...

Cheers,

Skottoman

Ditto, except I get the tube of 10 for $13 -- part number DTXC1549.

-Paul

[greg123 0]

94eg!, Yeah I know, right, crazy expensive. but, do you think the performance is there in them? I guess they don;t mention what they are rated at, but i wonder if the design speaks for itself. Hmm.

I just realized what you wrote before about the bearings coming in a light oil. Interesting the the sealed bearings use light oil, and it seems that the open ones use grease. Seams to reason that the grease would cause more friction. Sorry, I am just trying to understand how this stuff works. It's fascinating.

Thanks for the link guys on tower, I think I am going to do an overhaul on my cars to the teflon bearings from Tower.

[Skottoman 306]

Ditto, except I get the tube of 10 for $13 -- part number DTXC1549.

-Paul

Yeah, I do too, but I was just posting that for reference... The 10 tube is the best deal for sure....

Cheers,

Skottoman

[Daves956 157]

I did some comparisons between shielded and non on one of the 956s. unshielded gave a very slight advantage in top end but not enough to make it worth while. This was on exposed bearings, so in a gearcase it would be worth using exposed ones. I work with high speed bearings all the time and I use Kluber isoflex nbu 15 or 16 grease, no comparison to anything else if your serious about bearing life and resistance.

I've never found a stock bearing that didn't have junk grease in it from the factory and that includes large ceramics that sell for thousands. The grease they use is just for rust prevention. I wash bearings with odorless water white kerosene then air dry, never compressed air. Second wash is in denatured alcohol, some of the stuff on them isn't oil based.

I don't do all this with the average speed cars but if a bearing fails on the high speed cars it's different.

Part of my job is rebuilding high speed machine tool spindles, I've been doing it for 25+ years so I have a slight clue about bearings and spun mass.

[greg123 0]

Daves956 that is awesome man, thanks for the professional advice! Bearings are very interesting bearings are very interesting considering how important their function is. I'll see if I can find the grease and cleaning white kerosene you mentioned. Thanks a million for the pro advice on open and closed as well! cheers man!

[WillyChang 1814]

Teflon Sealed:

i call those "fibre" seals

teflon sealed has a solid molded disc of waxy plastic

both teflon & rubber seals are made bigger than the space, they're friction-fit + meant to wear in.

Once the bearing is worn in (only takes a few runs) they're as friction-free as shieldless.