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Author Topic: Choice of bearings for rebuild  (Read 942 times)

Offline Jim Oliver

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Choice of bearings for rebuild
« on: October 21, 2007, 01:26:19 PM »
Guys,

I am about to replace the bearings in a stunt engine.  There are lots of choices available: econo, high speed, high performance, stainless, ceramic---probably others, too.

In the past I have used the econo kit from Boca Bearings. 

Any suggestions for a better choice?

Thanks,
Jim
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Alan Hahn

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Re: Choice of bearings for rebuild
« Reply #1 on: October 21, 2007, 01:59:23 PM »
I am guessing econo is just fine for a stunt engine which gets a goodly supply of oil. Also since we run our tanks dry, there isn't any alcohol left in the crankcase to cause rusting like in RC engines where often the throttle is closed down to stop the engine.
Sometimes better isn't always better. What I mean by this is that you may need a little play in the bearings to allow for machining tolerances.
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Offline rustler

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Re: Choice of bearings for rebuild
« Reply #2 on: October 21, 2007, 03:11:33 PM »
I really shouldn't be answering this because I am still learning about bearings myself. Let's hope someone who knows what they are talking about joins in. What I have learned is that bearings come in several tolerance ranges. Some come with tight clearances and some come with real rattly clearances. The strange thing is that these rattly ones are just as precise as the tight ones. What you use depends on how tight or loose your bearing is in its housing and on the shaft. For high quality engines you use a rattly bearing and tight fits to stop the bearing spinning in its housing and on the shaft. So tight that the outer ring is compressed, the inner ring is expanded, and the rattly clearances disappear! If you put a tight clearance bearing in a tight fit housing the outer ring will compress and the bearing will bind.
Your best bet is to say what engine you are using and hope someone who knows the engine chimes in.
Also be aware that cheap bearings are available and you gets what you pays for. And if you get samples first make sure you get what you choose. I did get some samples from a well known co., and chose and paid for 120 nice Swiss bearings. They sent Chinese ones!
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Offline Rob Killick

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Re: Choice of bearings for rebuild
« Reply #3 on: October 21, 2007, 08:56:14 PM »
Hi Jim ,

I'd go with SKF bearings . FAG Corporation , also make a good anti friction bearing
A good choice would be a high speed 2Z C3 (just remove the shields , both sides) .
They're kind of expensive , but worth it .
Check with your local industrial shop and check to see how the bearing(s) handle thrust . C3's should be fine.
The Asian imports just don't cut the mustard (maybe NTN bearings are ok).
I won't give sizes , as it depends on your engine .
Just remember , that the lube (Castor) doesn't act like petroleum lubricants (ie. molecular attraction and shear strengths) .
Make sure , when you install , to heat them in a can of peanut oil , to about 300 deg. F .
Don't let the bearing touch the bottom of the can (use a wire hook off the side of the can .
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Offline Jim Oliver

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Re: Choice of bearings for rebuild
« Reply #4 on: October 21, 2007, 10:30:23 PM »
Thanks guys,

Rob, never heard the preheat in peanut oil procedure before--please 'splain this for me..... ???

Thanks,
Jim
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Offline wayne scruggs

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Re: Choice of bearings for rebuild
« Reply #5 on: October 22, 2007, 10:17:11 AM »
 Howdy:
 Interesting thread, does anyone have any thoughts about ceramic bearings other than the fact that they are expensive?

Thanks;

Wayne Scruggs
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Offline Bill Little

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Re: Choice of bearings for rebuild
« Reply #6 on: October 22, 2007, 10:35:00 AM »
I have seen the ceramic bearings in use in stunt, but i didn't notice a difference in the engine run.  I have used the "econo" line of Boca bearings many times and I haven't experienced a problem.  All I have seen of the econo line are at least equal to the original bearings.
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Offline RandySmith

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Re: Choice of bearings for rebuild
« Reply #7 on: October 22, 2007, 01:35:08 PM »
Quote from: Jim Oliver on October 21, 2007, 01:26:19 PM
Guys,

I am about to replace the bearings in a stunt engine.  There are lots of choices available: econo, high speed, high performance, stainless, ceramic---probably others, too.

In the past I have used the econo kit from Boca Bearings. 

Any suggestions for a better choice?

Thanks,
Jim


HI Jim

There isn't  really an answer  to the question the way you asked it.  It depends on what motor it is, how it is made, what you want to accomplish, how tight or loose the engine is, what RPMs you are looking at  etc...
Example ,If you have a motor that has a crankshaft that has a loose fit ball bearing or a crankshaft  where the bearing is  pressed onto the shaft, the  clearances  will be  differant... and differant bearing should be used. Also depends on how tight or loose the press into the case ( if any) is.
I have most bearings for stunt engines here, and have tried most everything out there. Creamic bearing will give you a little advantage in speed engines, but in stunt engines NO.

Regards
Randy
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Offline Bob Zambelli

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Re: Choice of bearings for rebuild
« Reply #8 on: October 22, 2007, 02:13:10 PM »
Try and find a copy of the Torrington Service Catalog, Form No. 100-45M-201.

It not only lists a large variety of metric and inch size bearings but all the different load and speed ratings.
The 571  page catalog also covers needle, control, torque tube, roller bearings and rod ends.

The 120 page engineering section in the back explains all there is to know about cages, internal clearances, shaft and housing fits, operating temperatures, lubrication and life calculations.

In the aerospace business, it is truly our "bible" when specifying bearings.

Bob Z.
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Offline phil c

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Re: Choice of bearings for rebuild
« Reply #9 on: October 22, 2007, 05:09:39 PM »
Jim, if you can afford it, get the ceramic bearings.  Then you'll have virtually no worries about corrosion, which is the biggest killer of ball bearings.
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phil Cartier

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