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OS 46 SF bearing removal

Old 03-03-2003, 05:58 AM
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jlovitt
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Default OS 46 SF bearing removal

I'm changing the bearings in one of my OS 46 SF engines. I am at the point where I need to remove the rear bearing which is the last step. I am stumped as to how to get this thing out. There is no exposed portion of the bearing that I can push against from the front(through the shaft opening), and there is nothing for me to pull against from the rear. I know that there must be a trick for this so let me know...

Jeff
Old 03-03-2003, 06:27 AM
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hydroguy
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Default OS 46 SF bearing removal

I got a HB .12 with the same problem. I tried to heat the case up and pull it out but there is nothing to grab or push. Please let us know! Thanks!
Old 03-03-2003, 05:04 PM
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Bax
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Default OS 46 SF bearing removal

Jeff,

If you heat the crankcase, the bearing will usually fall out when you rap the crankcase on a piece of wood block. Of course the engine is fully disassembled except for the bearings.
Old 03-03-2003, 09:18 PM
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ShempHoward
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Default OS 46 SF bearing removal

Heat the crankcase with bearings
to approx 250 degrees F for about 20 mins. Then with good oven mitts on tap the engine back plate side down onto a piece of wood. A few sharp raps and the bearing will fall out. You might need to repeat this proceedure a fews times. Sfter the rear bearing comes out the front should only need a tap from a wood dowel to come out as well.

Getting the bearings back into place wil be the hard part as you will need to again heat the crankcase and freeze the bearings. The front bearing should be easy enough to get into place but the rear is always a chore to get in straight.
Old 12-07-2014, 04:02 PM
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Thanks for this thread. Just did this job effortlessly after looking it up and being directed here. I blasted the crankcase with the heat gun then whacked it on a board. Fell right out. Regarding putting the new bearing in, just put it on the crankshaft and guide the crankshaft in. New bearings are easy because you can heat up your crankcase and drop in a cold bearing. The huge difference in temp allows for easy installation. That has been my experience anyhow.
Old 12-11-2014, 05:05 PM
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I put the bearings in the freezer at -18C for a while, and the case in the oven at 130C. Crank with installed rear bearing usually drops right into place. But I go around the outer race with a small punch and hammer after it's cooled to make sure the race is fully seated in the case. I've had a few instances where the bearings got draggy when I started tightening the prop, it was the rear bearing that wasn't fully seated despite dropping in freely.
Old 12-11-2014, 05:22 PM
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I've done bearing replacements a couple times in the past few months, and I always find it helpful to watch the two part YouTube video that RC Model Reviews published before getting to work.

https://www.youtube.com/watch?v=TuzEco3EDUM
Old 12-11-2014, 06:51 PM
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Originally Posted by Rudeboy View Post
I put the bearings in the freezer at -18C for a while, and the case in the oven at 130C. Crank with installed rear bearing usually drops right into place. But I go around the outer race with a small punch and hammer after it's cooled to make sure the race is fully seated in the case. I've had a few instances where the bearings got draggy when I started tightening the prop, it was the rear bearing that wasn't fully seated despite dropping in freely.
Ive noticed the same thing when installing new bearings. I always install the new bearings, crank, thrust washer and get a prop on it. There is usually a slight bind, warming up the case with a heat gun and then a couple firm wraps on the case with a screwdriver handle makes it smooth as silk.
Old 12-11-2014, 10:17 PM
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combatpigg
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Originally Posted by speedracerntrixie View Post
Ive noticed the same thing when installing new bearings. I always install the new bearings, crank, thrust washer and get a prop on it. There is usually a slight bind, warming up the case with a heat gun and then a couple firm wraps on the case with a screwdriver handle makes it smooth as silk.
Are you doing the last bit of "fine tuning" while the prop is installed tight..?
Old 12-12-2014, 08:03 AM
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Yes but not what I call " flight tight " just enough tension on the bearings to get them to settle in when the shock hits.
Old 12-12-2014, 09:59 PM
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That sounds like a great tip.
It reminds me of how I saw an ace mechanic change a u-joint.
Most of us would be happy to just get the bearing cups pressed back in and clipped in place, but this guy checked to see how well the yoke flopped in any direction. He kept tapping on the bearing cups until there was equal tension on the yoke in all directions.
Old 12-13-2014, 12:47 AM
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Originally Posted by combatpigg View Post
That sounds like a great tip.
It reminds me of how I saw an ace mechanic change a u-joint.
Most of us would be happy to just get the bearing cups pressed back in and clipped in place, but this guy checked to see how well the yoke flopped in any direction. He kept tapping on the bearing cups until there was equal tension on the yoke in all directions.
Believe it or not, that's what I've done when doing a U-Joint. And I'm just a stupid uneducated redneck from Minnesota. Haha.
Old 12-13-2014, 04:39 PM
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Now that I think of it, I saw a Mercedes mechanic tapping the over head cam pedestals as he was torquing them down and checking the drag on the camshaft.
There's a fine line with some of this stuff to get it as perfect as possible.
With our little engines a lot of power can get wasted in a bottom end that is set either too tight or with any slight binds.
Old 12-13-2014, 06:13 PM
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Very true CP. I often tell guys that a well assembled and cared for engine will perform better and last longer. Before I switched over to YS 4 strokes I raced 4 seasons with the same Rossi .45. I know you get it but I take this philosophy with the entire airplane and reap the rewards. You would be surprised how many glossy eyed looks I get when explaining to guys that then need to spend the time to get things dialed in correctly.

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