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Author Topic: Replacement ball bearings, Which grade ?  (Read 1569 times)

Offline YakNine

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Replacement ball bearings, Which grade ?
« on: August 16, 2011, 05:33:42 AM »
I went to Boca bearings website and for a given engine they have several choices of bearing Chrome, Stainless,Super hi speed, Ceramic etc. I am leaning toward Stainless only because of how much my engines will probably sit, I dont think my Perky is going to fly as much as my Akromaster or Peacemaker. You can spend more for replacement bearings than your engine cost new.I was just wondering what other guys have done. T.J.
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Offline Rafael Gonzalez

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Re: Replacement ball bearings, Which grade ?
« Reply #1 on: August 16, 2011, 08:13:18 AM »
Ceramic bearings are in themselves a high speed item. When I was heavy into Q500, I replaced the bearings on my QNelson with Boca's ceramics. They used to make an additive (forgot the name) to add to the gas and it was unbelievable! With only 2-3 drops  and a few runs, it would make the crankshaft rotate to the counterweight with the engine assembled. Did not have many engines do that at the time. (1994-97)

Found this:

 http://www.spsspindle.com/quantum/ceramic_steel.php


Go ceramic! They weigh less, they generate less heat and have less coefficient of friction. Even if we run engines in the 9K-10K range, it is a benefit.

Good luck! Just make sure you do not use any STRIKING FORCE! I replace them by having the crankcase @ 400F in the oven and cooling the bearings with liquid freon on a cup until the liquid covers them. They just drop in!  H^^
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Online Brett Buck

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Re: Replacement ball bearings, Which grade ?
« Reply #2 on: August 16, 2011, 10:29:03 AM »
Quote from: YakNine on August 16, 2011, 05:33:42 AM
I went to Boca bearings website and for a given engine they have several choices of bearing Chrome, Stainless,Super hi speed, Ceramic etc. I am leaning toward Stainless only because of how much my engines will probably sit, I dont think my Perky is going to fly as much as my Akromaster or Peacemaker. You can spend more for replacement bearings than your engine cost new.I was just wondering what other guys have done. T.J.

    I have only used the cheapest types from Boca. So far they have proven to be more durable than the original OS-supplied bearings in the VF.

     Brett
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Offline Peter Nevai

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Re: Replacement ball bearings, Which grade ?
« Reply #3 on: August 16, 2011, 11:08:52 AM »
I'm with Brett, Ceramics are great if you have the need for high RPM's and they are lighter with less rotational mass. They are fragile however and a single crash can cause a fracture. Also when they fail you have no warning they basically just let go. If you don't mind the additional cost and are not crash prone they are a good investment.

Stainless bearings are not as hard as traditional bearings and do wear faster. Remember no steel is really rust proof, just that some are more resistant to corrosion than others. Stick with the standard High speed bearings and just treat the engine well with an after run oil, you should be fine.

Tip: Use the old bearings to seat the new bearings into the crankcase and the crankshaft. This provides a perfect contact area with which to seat the beariings and eliminates the possibility of damaging the new bearing by accidentally applying force to the inner races.
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Offline YakNine

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Re: Replacement ball bearings, Which grade ?
« Reply #4 on: August 16, 2011, 12:48:36 PM »
These are going to be in my Fox 15BB's I was thinking the standard bearings being chrome Thanks T.J. are at least equal to or maybe slightly better than the original bearings that have lasted 20 plus years although I might leave the outer seal on in the front bearing to keep the crud out when my kids and I lawn dart them. Thanks T.J.
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Offline Chris Wilson

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Re: Replacement ball bearings, Which grade ?
« Reply #5 on: August 16, 2011, 04:32:48 PM »
No mention of the 'C' rating or internal clearance?

It can make a difference with what use you put the engine to - C3 typically being used in racing or hot environments.
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Offline Rafael Gonzalez

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Re: Replacement ball bearings, Which grade ?
« Reply #6 on: August 16, 2011, 06:58:26 PM »
Quote from: Rafael Gonzalez on August 16, 2011, 08:13:18 AM
Ceramic bearings are in themselves a high speed item. When I was heavy into Q500, I replaced the bearings on my QNelson with Boca's ceramics. They used to make an additive (forgot the name) to add to the gas and it was unbelievable! With only 2-3 drops  and a few runs, it would make the crankshaft rotate to the counterweight with the engine assembled. Did not have many engines do that at the time. (1994-97)

Found this:

 http://www.spsspindle.com/quantum/ceramic_steel.php


Go ceramic! They weigh less, they generate less heat and have less coefficient of friction. Even if we run engines in the 9K-10K range, it is a benefit.

Good luck! Just make sure you do not use any STRIKING FORCE! I replace them by having the crankcase @ 400F in the oven and cooling the bearings with liquid freon on a cup until the liquid covers them. They just drop in!  H^^

It just kills me when i can remember something... I've been burning my brain since the post I put in here YEEEY!!! It was called "THE MIDAS TOUCH" I feel better now.... #^ y1 <=

 H^^
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Offline YakNine

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Re: Replacement ball bearings, Which grade ?
« Reply #7 on: August 17, 2011, 06:03:49 AM »
Hey Rafael, I am a heavy equipment mechanic for the railroad, I specialize in cranes and we have used dry ice and  liquid nitrogen to get some of the shrink fit bearings on the winch main shafts the one thing you forgot to say is you only get one try to get it right ! T.J.
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Offline Rafael Gonzalez

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Re: Replacement ball bearings, Which grade ?
« Reply #8 on: August 17, 2011, 05:49:34 PM »
Quote from: YakNine on August 17, 2011, 06:03:49 AM
Hey Rafael, I am a heavy equipment mechanic for the railroad, I specialize in cranes and we have used dry ice and  liquid nitrogen to get some of the shrink fit bearings on the winch main shafts the one thing you forgot to say is you only get one try to get it right ! T.J.

YOU ARE RIGHT!!!! LL~ LL~ LL~ LL~ LL~ LL~ IT happened to me in my early days... It went in crooked... LL~ LL~ LL~ LL~ Thank you for the reminder!!!! H^^
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Offline Rafael Gonzalez

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Re: Replacement ball bearings, Which grade ?
« Reply #9 on: August 17, 2011, 06:00:35 PM »
Quote from: YakNine on August 17, 2011, 06:03:49 AM
Hey Rafael, I am a heavy equipment mechanic for the railroad, I specialize in cranes and we have used dry ice and liquid nitrogen to get some of the shrink fit bearings on the winch main shafts the one thing you forgot to say is you only get one try to get it right ! T.J.

So you must be familiar with loads, huh? D>K  One thing we need not worry in our hobby is loads on bearings as the only load is the friction and centripetal force from the  balls... Railroad loads must be unbelievable!... H^^
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Offline YakNine

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Re: Replacement ball bearings, Which grade ?
« Reply #10 on: August 17, 2011, 06:53:44 PM »
With the short boom on it will pick and carry 65 ton off either end but the hoist winch is good for 200 ton by itself, the bearings are a little bit bigger than the ones in my 15 bb. T.J.
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Offline phil c

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Re: Replacement ball bearings, Which grade ?
« Reply #11 on: August 17, 2011, 09:10:21 PM »
most engines are setup with a bit of interference fit between the case and the bearing.  That means heating the case to about 250 deg F and the bearing should come out just by rapping the back of the case on a block of wood.  A few motors(some of the K&B's) had the inner race press fitted on the shaft.  They need a puller to remove.

With the interference fit to the case the cheapest class 5(loosest) bearings are about right.  The case shrinks and takes up some of the clearance.  If you are worried about rust, run a few percent castor in the fuel and make sure the motor is run dry before putting it away.  A small amount of castor will protect the bearing from rust as long as you don't leave it in a humid basement for 10 years.
 
Heat the case again when remounting the shaft.  It should pretty much slide right in with the bearing on it.  Then press the front bearing in before things cool off.  Make sure the inside of the bearing mount area is spotlessly clean.  Even a tiny speck of dirt can get in the wrong spot and make the bearing race twist and bind.
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Offline Brian Hampton

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Re: Replacement ball bearings, Which grade ?
« Reply #12 on: August 18, 2011, 11:07:19 PM »
Quote from: phil c on August 17, 2011, 09:10:21 PM
With the interference fit to the case the cheapest class 5(loosest) bearings are about right. 
My understanding is that bearings come in 4 classes with a standard off the shelf being unmarked then there are the C3, C4 and C5 with the C5 having the greatest clearance. Loose clearance doesn't indicate cheapness but the application it's intended for. If a bearing has to be pressed onto a shaft then the inner race expands and some clearance is lost. If the bearing is heat shrunk into the case then the outer race is compressed so more clearance is lost. The fit of the inner and outer races is simply to ensure that neither can spin under operating conditions. I believe that Nelson engines are fitted so tightly that they recommend sending the engine back to them if the races need to be changed because they have the equipment needed to do it without damage.

Most engines have a slip fit onto the crankshaft (not a good idea though) so inner race expansion doesn't exist which leaves the heat shrink fit of the outer race, which is fairly mild usually, because the crankcase in that area doesn't get hot. A normal fit, or at most a C3, is more than adequate.
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Offline YakNine

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Re: Replacement ball bearings, Which grade ?
« Reply #13 on: August 21, 2011, 03:09:22 PM »
I think I am going to get them from Fox after all, their price is about the same and I need to get a venturi assy any way as my engine still has an R/C carb is the Fox 15 needle valve any better than the one that comes on the .35 or should I go aftermarket? T.J.
.J.
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