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Author Topic: Bearing question  (Read 752 times)

Offline Randy Powell

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Bearing question
« on: April 12, 2008, 11:16:14 PM »
I'm using a OS 46VF that was reworked by Tom Lay. It only has about 10 flights on it. When I run the spinner back and forth, the bearings feel very free, but it makes a just detectable noise like something is rubbing or something. Just sounds funny. But I can't detect any drag or rough spots. And it seems to run fine.

Any thoughts? How tough is it to change the bearings on these engines?

Thanks for any input.
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Offline Greg L Bahrman

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Re: Bearing question
« Reply #1 on: April 13, 2008, 12:12:01 AM »
Randy,
I have done mine in the passed. It was not a problem. Unbolt the front and you get both bearings. Crank came out easy. I heated the front case with a monocoat heater/blower and the bearing came right out, no hassel.
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Offline Ralph Wenzel (d)

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Re: Bearing question
« Reply #2 on: April 13, 2008, 04:10:58 AM »
Before you change them, are the bearings dry or lubed? If dry, you ought to get a whirring sound. If they're lubed, then it's probably time to replace them.

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Ralph Wenzel
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Offline phil c

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Re: Bearing question
« Reply #3 on: April 13, 2008, 08:32:21 AM »
The bearings wear gradually(usually) and will make a screeching noise well above the engine rpm if they are worn out.  disassemble the engine to the point that the shaft is the only thing left in the case and try spinning it.  Ideally it should spin freely and the counterweight should eventually rotate to the bottom when it stops.  You shouldn't be able to feel any grittiness or rubbing when you turn it.
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phil Cartier

Offline Randy Powell

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Re: Bearing question
« Reply #4 on: May 02, 2008, 02:22:31 PM »
The bearing felt fine, just some noise. But it could be that it had just sat around a lot (it was in a baggy in a box for most of 3 years). After gettting about 10 flights on the plane, it doesn't seem to be doing it anymore. Engine runs are dead steady.
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Offline Gordon Tarbell

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Re: Bearing question
« Reply #5 on: May 02, 2008, 07:33:24 PM »
Just curious, are you running it on a pipe or just header muffler?
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Offline Randy Powell

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Re: Bearing question
« Reply #6 on: May 03, 2008, 11:23:38 AM »
Gordon,

An Eather pipe set at about 17.75 inches. It's a weird engine in some ways. Uses a lot (A LOT) of fuel. A touch over 7oz for a 6:45 run. The thing will barely break from a 4 stroke no matter the setting. I've set it for from 10,300 rpm to 11,000 rpm on the ground. At the upper end, it's running in a rich two stroke. As soon as it hits the air, it's running in a hard 4 stroke and pretty much stays that way. With the lower rpm setting, it lugs a bit in high horse power maneuvers, never breaks and is clearly unhappy. At the higher rpm setting same thing except it is clearly starving in the high load maneuvers. When set at about 10,700 rpm on the ground, it will run in a hard 4 stroke with just a bit of break in the high load parts of maneuvers with just a ton of power. Like a really good ST46 ... on steroids. I have no idea what Tom Lay did to it, but I like it.
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 Randy Powell

Offline Bill Gruby

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Re: Bearing question
« Reply #7 on: May 03, 2008, 03:41:35 PM »
 Randy;

  During my 30 plus years with General Motors in their Bearing Division, the noise you are talking about came from a loose seperator. The two piece cage for whatever reason started to come apart allowing it to hit the shield or seal. In an open bearing it will have a slight clattering sound. In any of these cases it is best to change the bearings before they do any damage. Bearings found with this problem were few but they were there. Just one more thing for you to think about.

 "Billy G"
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Offline Randy Powell

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Re: Bearing question
« Reply #8 on: May 04, 2008, 12:30:26 AM »
Great, Bill, now that it sounds fine, I need to change the bearings. I'll see what I get tomorrow. If it's still making noise, I'll change out the bearings. Sigh ...
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Offline Bill Gruby

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Re: Bearing question
« Reply #9 on: May 04, 2008, 05:38:08 AM »
 Randy;

  Sorry to throw that one at you, but it goes like this, they won't fix themselves, they will only get worse over time. The loose seperator will cause premature wear in the bearing because the balls themselves will rotate differently. The seperator holds them in sort of an orbit so to speak. Once they are allowed to leave the givin path, anything can happen.
  On the flip side, my first post was based on the info you gave and what I know to be true about bearings. They can truely be nasty little beasts when you least expect it. I hope they are still sounding OK the next time you fly as it would be a shame to break that engine down at this point.
  I believe your quote says it all.

 "Billy G"
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Offline Randy Powell

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Re: Bearing question
« Reply #10 on: May 04, 2008, 03:54:32 PM »
Hi Bill,

Well, we flew today and after 6 flights, I had everyone feel the thing. Can't discern any grinding, rubbing or rough spots. The engine seems very free. If you listen, you can hear the bearings moving, but not hang up in how it rotates. Sill, I may just go back to the 40VF in this plane and take the 46VF out and pull the bearings. As you note, better safe ...
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