Timken.....  NSK....

Another good thing with PEEK, phenolic and other polymer ball retainers is that they can usually be dismantled for inspection and cleaning.
People often misundetstand the physical properties of ceramic materials for balls. When used correctly, they outperform full steel bearings, there is really no reason to worry about shock resistance. But like with everything, there are good and bad ones available. For our use hey are mostly overkill, though.
WIB is indeed the best, we use them. But at least with special sizes and clearances there is a minimum order of 100 if I remember right. L

Not really, Dennis. Robbie has good contact with them, and I think they are mostly made to special order.
By the way, does anyone have drawings or knowledge about making ball retainers? I should make machined phenolic cages to a cl speed engine. I have some drawings from Russia but it would be nice to understand the reason for certain details.  L

I am rebuilding an ST60 and want to get some better bearing. Looking at the Boca Bearing site (https://www.bocabearings.com/products/bearing-applications) for the ST (OLD) 60. They have listed they have several bearing packages to choose from. The basic package is the SKU: #ENK-044, this is the Economy chrome steel front and rear bear set, the balls and race is from CHROME STEEL 52100 the retainer is listed as CHROME STEEL, they do not give a number. The ball rating is 10 the ABEC/ISO RATING is ABEC#1/ISOP0. Price is $16.47.

The next package is SKU: #ENK-044HS all is the same except the retainer is made from POLYMITE PLASTIC, these bearings are said to be able to handle 15% higher rpm, the fit is listed as C3, price is $27.30. I think the only difference is the retainer material, what does this do for us in stunt?

The next package is SKU: #ENK-044C & SKU: #ENK-044C & SKU: #ENK-044C-HP, these are both Ceramic balls and
POLYMITE PLASTIC retainer, same ABEC rating but the ball rating is 5. Price is $83 -86. This does not seem to be worth it for stunt?

Next is the SKU: #ENK-044RS This is all chrome steel same as the economy spec is the same ball rating is the same just cost $18.45 the RS designation is for rubber seals, does this matter for us?

Last one worth looking at is SKU: #ENK-044RSHS, this is the same as the RS with a POLYMITE PLASTIC retainer, fit is C3, price $30.52. Gee this retainer thing must be pretty special???

Having looked at all this I don't see anything on the site that tells me why any of the steel bearing sets are worth buying over the Economy set. One thing in the description of all the high speed sets the fit is a C3, which I understand is in the middle of the fit rating (C2 -C5 loosest), maybe the fit is worth it?

Best,    DennisT

Dennis,

It all depends on what you need. For a ST60 that will not turn up that fast and probably will be run with lots of oil going thru it (at least the rear bearing), and should not get that hot due to the way people run a ST60 for stunt, the materials choices are simply not that critical.

52100 Chrome steel is a standard for the bearing industry. If you do not have problems with corrosion (and you don't with a stunt motor that is getting dosed with castor oil) it will perform better at lower cost than the stainless bearings.

Practically any ball cage (ball retainer) will work as long as it is properly manufactured and installed. This could be a brass cage, or a steel cage or....  The ST60 rpm is not very fast which is why you are using it. If you had an engine that was turning 20,000+ rpm, you would be more interested in a lighter weight, higher damped one piece non-metallic cage.

Some of the synthetic oil bases used in industry will attack some of the non-metallic retainers. Oils you are going to use in a ST60 should not cause concerns.

Absolutely do not use shields or seals in the main bearing. These will prevent proper lubrication. I'd be surprised if any BOCA sets for model engines would give you a main bearing with these. (But if you are buying your own individual part numbers...now you have to take care of this detail.)  If you worry about fuel leakage out the front of the engine, get a front bearing with one seal and put that on the outside. The crank to case fit near the front of the engine is what is supposed to control the leakage out the front. The tiny extra amount of drag caused by a seal on a stunt motor that is operating well below its power potential is of zero consequence.

A C3 fit is generally a starting point and is commonly stocked. That much clearance should work fine in a ST60 as far as I know--although I have not replaced bearings in an ST60 myself.

Probably more important than buying bearings with more "zoot" is getting them installed so that they are seated, free, and not damaged during the process, or contaminated. For example, never apply installation loads "across the balls."  When done and the assembly is cooled, check for endplay. Ideally, there would be none when checked with a dial indicator. Then, after you run the engine, check it again. If at any time you can feel the balls, you are set up too tight. Either the case/crank dimensions have caused you to duplex the pair too tight, or the radial clearance wasn't sufficient. These are directly related, and not independent. Go look for a diagram showing contact angles to understand how.

Hope these comments help a bit,

Dave

MM,
I think the one we want for the small case engine (ST OLD 60) is - SKU: #ENK-044HP. In this kit the front bearing OD is 19 instead of 22. Since Boca Bearing is not to far south of me I might just take the block with me and make sure the bearings are the correct size.

Best,    DennisT

Guys,
Besides Boca Bearing who else is a retailer of high grade replacement engine ball bearings? I've been looking at the bearings available from Boca and would like a higher grade then their Econ series but want steel balls and retainer. I don't like plastic in bearings and not sure if ceramic balls at least for the main rear bearing is a good application with the vibration and heat it may be exposed to (think ST60). I know many have used the Econ bearing and been happy but I would like a step up just because I want too. Any other quality suppliers out there?

Best,   DennisT

I have  many hundreds  of  bearings in stock,  NOT  all motors,  but  many. Also  phenolic or polymite  retainers  are  NOT bad and  are  not  something  you should  worry about
If I can help please  ask
also  Boca  does have  maNY combinations  of  types of  bearings  steel  chrome  ceramic, hybrid

Randy

Do you remember the numbers for the bearings for the Mk. VII?

Kit# ENK-038C-HP
AL