Bearing fits?

[Bob Finn]

It's all in the feel  you use  on the gauge.       I used to machine mine  to line to line fit on the big bearing,   and a .0005 press on the little bearing.    The bearings don't generally vary more than about .0001

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Hey Bob: When you say "line to line" do you mean make the case the same size as the bearing?

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Yes. The tension on the gauge actually gave me just enough to have a "thumb push fit" on the big bearing. (probably .0001-.0002) It can be fit up tighter, IF you run a PM or PMM(loose internal fits) grade bearing. The small bearing has to be about .0005 tighter to keep the bearing from moving in the housing. I've been fitting them that way for 30 years

 

[Terry Keeley]

Thanks! Know what you mean about the front bearing, loose at all and it tends to beat out the case pretty easy...

Any idea how tight CMB fits them from the factory?

 

[Bob Finn]

Thanks!  Know what you mean about the front bearing, loose at all and it tends to beat out the case pretty easy...
Any idea how tight CMB fits them from the factory?

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A full thousandth. They grind the crank a hair undersize and let it slip in the inner race. Some bearings with more internal clearance(Jesa) work better, but they don't last as long. The WIB bearings are much better, but they are fitted tighter than I like.

 

[Jim Allen]

Hi Terry,

The bearings are probably standard clearance (.0001 to .0003 radial play) found in most bearing houses. Even if they were C-3 clearance (.0003 to .0005), interference fits of more than .0005 in any housing would cause rapid failure. As you know, I run T clearance (.0012 to .0014) radial play ceramic bearings with polymide cages in a hardened steel, precision ground housing, with a interference fit of .0008 on a 6002 bearing & .0005 on a 6001. The crankshaft is fastened to the inner races of both bearings with a hardened steel sleeve, that is demensioned for .004 axial play cold. After running motor on test stand for 2 minutes at wide open throttle (30,000 rpm +); end play was reduced .0005 to .0007. This setup runs faster & much longer than comparable setups that are not fastened to the crankshaft.

Jim Allen

 

[izitbrokeyet?]

Hi Terry,
The bearings are probably standard clearance (.0001 to .0003 radial play) found in most bearing houses. Even if they were C-3 clearance (.0003 to .0005), interference fits of more than .0005 in any housing would cause rapid failure. As you know, I run T clearance (.0012 to .0014) radial play ceramic bearings with polymide cages in a hardened steel, precision ground housing, with a interference fit of .0008 on a 6002 bearing & .0005 on a 6001. The crankshaft is fastened to the inner races of both bearings with a hardened steel sleeve, that is demensioned for .004 axial play cold. After running motor on test stand for 2 minutes at wide open throttle (30,000 rpm +); end play was reduced .0005 to .0007.  This setup runs faster & much longer than comparable setups that are not fastened to the crankshaft.  

Jim Allen

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Hi Jim,

Welcome to the board…you picked a great place to post in my opinion.

You seem to be a guy that knows a considerable amount about bearings. Would you agree that there are potentially significant quality differences between different makes/ types of bearings that have the same C-fit?

In other words are all bearings with the same C-fit created equal? I say NOT but some "self professed" bearing experts on this board claim otherwise.

What do you think?

Thanks for any input you may have

 

[Terry Keeley]

Thanks!  Know what you mean about the front bearing, loose at all and it tends to beat out the case pretty easy...
Any idea how tight CMB fits them from the factory?

102303[/snapback]

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A full thousandth. They grind the crank a hair undersize and let it slip in the inner race. Some bearings with more internal clearance(Jesa) work better, but they don't last as long. The WIB bearings are much better, but they are fitted tighter than I like.

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I think I might have stumbled on this by accident, I put a WIB rear bearing in place of the Jesa and it seems to be a little tighter. I kept the Jesa front bearing and when I measured the end play it had a full 0.007"! WIB's in my Picco's usually have 0.002-0.003" and when they get that loose I consider them worn out. I'll know soon when I run them.

 

[Terry Keeley]

Hi Terry,
The bearings are probably standard clearance (.0001 to .0003 radial play) found in most bearing houses. Even if they were C-3 clearance (.0003 to .0005), interference fits of more than .0005 in any housing would cause rapid failure. As you know, I run T clearance (.0012 to .0014) radial play ceramic bearings with polymide cages in a hardened steel, precision ground housing, with a interference fit of .0008 on a 6002 bearing & .0005 on a 6001. The crankshaft is fastened to the inner races of both bearings with a hardened steel sleeve, that is demensioned for .004 axial play cold. After running motor on test stand for 2 minutes at wide open throttle (30,000 rpm +); end play was reduced .0005 to .0007.  This setup runs faster & much longer than comparable setups that are not fastened to the crankshaft.  

Jim Allen

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Hey Jim:

Welcome! Saw you over on Jim's site and thought to myself those guys are tapping into the knowledge tree there. For those that don't know, Jim is a master toolmaker that has made his own bar stock racing engines, dyno's, pipes and anything else you can think of.

I can see where being able to pick your own fits and bearings would be great Jim but what about us mere mortals? Any idea what sort of fits would be optimum in our cast aluminum block motors using ABEC 1 or 3 bearings with C3 internal fits? Should the front fit tighter than the rear in your opinion?

I see that some very high end pylon motors use steel front housings like you mention to keep the fits at operating temps. Do you think our marine bearings loosen at operating temps?

ps: Any chance you have some digital photos of your work to post? There's a great photo gallery here and I know lot's of guys would love to see your work.

 

[Jim Allen]

Terry,

ABEC numbers do not effect radial clearance numbers. ABEC 1 through 9 bearings could have radial clearances from .0001 to .0003 (L) to .0010 to .0014 (T) or special (S): whatever amount is necessary. Henry Nelson had SKF in Canada make high radial clearance (.0012 to .0016) bearings which he uses in aluminum setups with high interference fits (.0005 to .0007). I use these same bearings after replacing 52100 steel balls with ceramic balls of the same size. I purchase these balls from Cerbec. Crankshafts are a heavy push fit in aluminum setups, & mechanically fastened with sleeve in steel setups. I have made a tool to check that radial clearances are correct as ordered. To get these bearings, the entire run (1000 pieces) must be purchased.

Jim

 

[Jim Allen]

Terry,

I have many digital photo's of all motor parts, etc. I need instructions on how to down load ipg disk.

Jim

 

[Terry Keeley]

Terry,
ABEC numbers do not effect radial clearance numbers. ABEC 1 through 9 bearings could have radial clearances from .0001 to .0003 (L) to .0010 to .0014 (T) or special (S): whatever amount is necessary. Henry Nelson had SKF in Canada make high radial clearance (.0012 to .0016) bearings which he uses in aluminum setups with high interference fits (.0005 to .0007). I use these same bearings after replacing 52100 steel balls with ceramic balls of the same size. I purchase these balls from Cerbec. Crankshafts are a heavy push fit in aluminum setups, & mechanically fastened with sleeve in steel setups. I have made a tool to check that radial clearances are correct as ordered. To get these bearings, the entire run (1000 pieces) must be purchased.   

Jim

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Canadian bearings in Nelson motors, no wonder they're so fast. :lol:

I can see where a hot running pylon motor needs a high interference fits but what about our "cold case" marine motors?

 

[Terry Keeley]

Terry,
I have many digital photo's of all motor parts, etc. I need instructions on how to down load ipg disk.  

Jim

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Go to "Intnl Waters.com" http://www.intlwaters.com/ , on the LHS near the top go to "Members Photo Gallery" https://www.intlwaters.com/gallery/, go to "User galleries" https://www.intlwaters.com/gallery/index.php?cat=1. Then go to "Register" at the top. Once you've done this you log on at the top again and you can create albums and upload pictures and add descriptions etc.

Sure hope you can do this for us Jim, your work is amazing and I know the gang here would love to see it!

 

[Jim Allen]

Terry,

I,m registered in the Photo Gallery; will try to create album to up load photo's tomorrow. Thanks much.

Jim

 

[Terry Keeley]

Taking off in the morning to do a little testing before this weekend's race, hope to see some of your stuff Sunday night!

 

[Jim Allen]

Terry,

I think the bearing technology is the same in cold or hot cases. I did not always have steel front ends, but I had very good results with aluminum bar stock front ends.What is really important is to support the outer race with a round (+-.0001) rigid housing & support the inner race with a round (+-.0001) rigid shaft. Since the crankshaft bends under load, to accomplish both require a interference fit or mechanical fastening of inner & outer races for proper functioning. The crankshafts of our motor's are not similar to a high speed (40,000 rpm) ID grinding spindles. These ABEC-9 bearings slip into housings & have shafts that slip through inner races. Even all metal (52100 steel) bearings will last for many hours in a properly set up assembly.

Jim