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Home✈️Aircraft🚁HelicopterCentury Radikal G20-30 N640 Hawk Predator › Mainshaft gettign polished at lower bearing area, concern?
01-10-2006 06:04 PM  13 years ago
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Disciple4123

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USA

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Mainshaft gettign polished at lower bearing area, concern?
I had the mainshaft apart yesterday and observed that the shafti s getting polished at the lower bearing area. IT is not getting pitted, scorched, or losing diameter though. I have had this happen on other helis and have in times past used loctite to fix the bearing ID to the shaft. Seems that the shaft spins in the bearing causing this condition. Is this a concern? I would thing that would lead to heat, bearing damage, and RFI. By the way this bearing is very smooth at this time, undamaged. If the mainshaft had a horizontal bore at the bearing locations, and some sort of expanding plastic plug at those locations it could possibly help seize the bearing ID to the shaft.
The rest of the heli is without issued or concerns, so that is encouraging.

For reference to the incident leading to dissasembly refer to:
http://www.runryder.com/t224093p1/?...ht=Disciple4123
It was an RFI related crash

Thanks,
Eric
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01-10-2006 07:53 PM  13 years ago
flybarless

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Torrington, CT

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I use green locktite where my shafts pass through the bearing.
the inside race should spin with the shaft or the shaft or bearing will wear causing slop.
Just remember -- if the world didn't suck, we would fall off.
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01-11-2006 03:26 AM  13 years ago
Disciple4123

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USA

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OK, this is a fairly universal problem to heli's. When you manage to dry lubricants off the shaft, and the bearing, then some loctite can hold. But whay happens when you dab locktite and the bearing you're fixing is beside an open thrust bearing with grease present to contaminate it, and to get fixed in place if the loctite reaches it?

When I used to use blue or red loctite on the bergen mainshaft and TR components it held very well. I'll most likely try green loctite like you're saying. I also better make sure the thrust bearings get fully seated the first time, or they may never get preloaded and the main bearing may end up with the axial loads.

Thanks,
Eric
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01-11-2006 07:00 PM  13 years ago
BC Don

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Calgary, AB Canada

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And for those of us that crash from time to time, I don't want the bearings locktited to the main shaft. Did that once and cursed for awhile until I managed to get stuff free.Got Money? Send it to me, I'm a Heli Addict.
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01-12-2006 06:12 AM  13 years ago
Disciple4123

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USA

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Well I took the mainshaft out and q-tipped the bearing bores dry with ether, cleaned the shaft and used a small amount of red loctite on the upper and lower radial bearings. I could not find Loctite 603 locally, so used red threadlock instead. I also did the TR spindle bearing areas the same way.

According to industrial supplier sites that I freqent, #603 is suitable to bearing to shaft locking with the possibility of oil contamination when curing, 609 and others do not mention handling the presence of oil. It would be ideal to use 603, but red is better than nothing.

As far as crashes go, I try to invest more in crash prevention than dissasembly convienience. A soldering gun or torch usually softens the red loctite when needed
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01-12-2006 06:27 AM  13 years ago
chuckhager

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Clovis, CA

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I'm with BC Don. I'm not sure if I want to loctite the bearings to the shaft. Maybe this wear is different for different helis, and I'm sure the service time on the bearings has a lot to do with the wear, but I haven't experienced what I would consider excessive wear on the main shafts of my Raptor 50's.
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01-13-2006 02:06 PM  13 years ago
John Benario

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Las Vegas

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The "proper" way to assemble our models is to use loctite to secure the bearings to shafts, but that can cause a huge issue when it comes time for disaasembly. I use Loctite to glue the tail rotor pieces together since the tail shaft spinning in the bearings is a concern, and the parts can be accessed to press apart.

I once tried securing the main shaft to its bearings to be "right" and ended up having completely disassemble the frame assembly to put the shaft and the bearing blocks in a press to get them apart. Not doing that again. If you are concerned about wear on a main shaft, just spend the $10 every few months to put a new shaft in and be done with it.

If you are careful about the bearing block assemblies and the main shaft can smoothly slide through the bearings with no friction there should not be an issue. If the bearings are misaligned to the extent that the main shaft will not drop through on its own then there will be wear issues.

The 603 and 609 are suitable, but not best. Reread my loctite description from the hover column some years back for more information. The 290 is best when there is no gap, like most main shaft/bearing fits, since it wicks in rather than being pushed aside like the more viscous 603/609.

The 603 and 609 are ok when there is a slight gap like the tail shaft/bearing fits, but the 638 and 641 are better.

John Benario
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01-13-2006 09:01 PM  13 years ago
Disciple4123

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USA

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I read what you posted, I can agree with your perspective. But has shafts slipping in a bore caused RFI to your knowledge? I have damaged bearings on the Bergen in times past separating them out of the mainshaft, but I was able to get them out and replaced without too much of a headache. I just used a very small amount of red. I'll look into wicking 290 when I place my next Mcmaster carr order. I think it can probably be applied well with a toothpick into the crack.

Thanks,
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01-16-2006 03:40 PM  13 years ago
AceBird

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Utica, NY USA

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QUOTE>>>>>>>>>>

I had the mainshaft apart yesterday and observed that the shafti s getting polished at the lower bearing area. IT is not getting pitted, scorched, or losing diameter though.

END QUOTE>>>>>>>>>>


Something has to give.

The ball of a ball bearing is in contact with both the inner and outer race at the same time. The groove in each race is obviously at two different diameters so something has to give as it rotates. Either the outer race must creep or the inner race must creep or the balls slide on one or the other races. Because the shaft is a loose fit the inner race does the creeping unless you lock it, usually with Loc-Tite. I personally don't like to do that because of disassembly. You can however paint the shaft where the race will ride which will snug it up and give a harder surface for the race to ware on. Try your wife's thinned out nail polish. Once a year, give it a new coat.

Ace
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