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HelicopterEngines Plugs Mufflers Fuel › heehee hee YOU better do something OS !!!
05-14-2008 04:21 PM  9 years agoPost 101
mmc205

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PA - USA

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Yes, "hard 3D" as it refers to engine speed and leanness will punish ANY bearing, cheap or expensive, good or bad. If the bearing is fantastic to begin with, it may last a long time even under "hard 3D" conditions.
Here's an experiment for those people who don't think that running condition has anything to do with bearing life. Drain all but a quart out of your car (to simulate a lean or low oil situation) and if the redline of your engine is 6000 rpm, drive around at 5800 rpm for a few weeks. You may find a whole lot of things go wrong, most likely being the oil journal bearings on your crank.

Also, do remember that these engines arn't designed to run long hours, little wear like a automobile engine. A closer comparison would be a nascar engine. high output, can last a while but nowhere near a consumer car engine. They need maintenence, and the harder you run them, the sooner that maintenence will need to occur. As for the bearing problem, i would suggest running a bit richer, and finding the best bearing (abec 3-7) that will fit in the engine.

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05-14-2008 06:08 PM  9 years agoPost 102
DS 8717

rrProfessor

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mmc205,
I stated the same exact thing you just posted but was told i am full of sh!t. You are wasting you breath on deaf ears that only want to believe what they want.

YOU ONLY LIVE ONCE..IF YOU LIVE IT RIGHT THATS ALL YOU NEED

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05-14-2008 06:32 PM  9 years agoPost 103
mmc205

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DS 8717, i agree, sometimes logic means nothing to some people. Don't listen to me, i just do this kind of thing for a living.....

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05-14-2008 06:47 PM  9 years agoPost 104
nivlek

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Norfolk England

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As for the bearing problem, i would suggest running a bit richer,
I'm not saying that you are wrong , but even if the engine is lean you have loads of oil at the bottom end of the engine .

At the end of the day , it gets dark .

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05-14-2008 09:28 PM  9 years agoPost 105
Gearhead

rrMaster

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""I'm not saying that you are wrong""

I'm not saying he is wrong ether,, but then again I did add extra oil to my fuel and ran it rich and my bearing went still bad, and when I removed my back plate there was about a teaspoon of oil/castor in it..

Jim
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05-14-2008 09:46 PM  9 years agoPost 106
Dilbeck

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Springdale Arkansas

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I wonder,,,, Can there be too much oil???? Surely not...

Clint

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05-14-2008 09:57 PM  9 years agoPost 107
GMPheli

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W. Bridgewater, MA USA

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I would say we have a combination of problems here. The cheap no name bearings don't seem to last very long at all. Better quality bearings seem to last longer, but there are still way too many failures. And I would say tolerance stacking probably plays a big part here too. The close to perfect crankcases would be the ones that don't have a problem. Preload is only a band aid. But you guys are way overanayzing this. The bearing is just not up to the task. It is obvious. Giving the specs of the bearing without knowing the actual loads that the bearings are being subject too is meaningless! You even had an engineer reply and say the exact same thing and you still don't believe it. I just don't understand. 50 size motors are putting out close to 60 size power with smaller bearings. Buy the best bearings you can find, keep spares on hand, and get used to changing them!

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05-14-2008 10:00 PM  9 years agoPost 108
mmc205

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PA - USA

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It may have very little to do with lack of oil, and a lot to do with shock loadings and dare i say it...preloading among other conditions bearings don't lke. All of these things will kill bearings early. Oil will do very little to help you if you are pounding the bearing hard enough to leave divots in the race. My sugguestion to run a little richer was only aimed at those who are really running lean. Experience at root cause analysis of a problem has shown that when there is a failure, there is almost never one cause, its usually several factors all contributing. However, if time isn't taken to fully examine the situation, a layperson will see what seems to be a factor and say "thats it". In this case, and i'm learning more from everyone's input (even counterpoints are appreciated as long as there is some kind of substantial data that goes along with them) it seems that

-Some bearings last a long time, some do not. It seems somewhat indepenent of flying style and mixture, though i think we can all agree if someone is running extremlely lean it would be detrimental.
-Stock replacment bearings, as well as aftermarket bearings also go bad in the same engine. (has anyone replaced a stock bearing after a having it go bad quickly and had no problem for appreciably longer than the original, this would be a good data point)
-Some bearings have shown a failure mode at the bottom (opposite from head) of the outside race, as if it were being continously shocked at either TDC or BDC. The inner race shows failure all around as would be expected.
-corrosion doesn't seem to cause this as many that failed had no signs of oxidation, and others that seemed to last forever were very oxidated.

from this i have a few thoughts. We may be dealing with two different causes of failure.
1) One is probably bad bearings, plain and simple. Poorly selected balls, bad races, lots of slop leading to skidding and pitting.

2) Two is probably engines loaded to heavily. Imagine getting the piston at top dead center, and then detonating the fuel while holding the crank. All that energy is transferred through the pistion, through the connecting rod, and into the bearing. Although this isn't the exact case with our helis, if someone were to have pitch/throttle curves set up poorly, the engine could have a heavy load at lower rpm, resulting in heavy loads on the bearing. Imagine going 5 miles an hour in you manual tranmission car and shifting into 5th and slamming the gas, can you imagine that terrible sound it makes? thats the sound of the explosive energy of the combustion having nowhere to go and thus pushing the piston straight into the journal bearing. I have to admit i'd never thought of this second cause but it could be the reason some people who fly very casually and rich might still have a problem, and why some who fly hard 3D with proper rpm and pitch don't have any problem.

These two cases are not mutually exclusive however and if one had both going on at the same time it could really do damage quickly.

Any thoughts (after my long winded post)

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05-14-2008 10:00 PM  9 years agoPost 109
Dilbeck

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Springdale Arkansas

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Getty up.

Clint

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05-14-2008 11:49 PM  9 years agoPost 110
Gearhead

rrMaster

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the guy from Boca told me that their direct replacement bearing kit for the OS 50 is $10, you get both bearings for $10,,

now, High Speed bearing MR6902 THB/C3 is $18, yet it still has an ABEC/ISO rating of #1,,

a 5 rated bearing would be much better for the speed these engines turn !!

Jim
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05-15-2008 12:38 AM  9 years agoPost 111
Dilbeck

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Springdale Arkansas

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Something is way wrong here, Something just doesn't seem right, We have missed something and its on the tip of our noses. We are getting close and I can smell it. Preload, 3D, high rpm, % nitro, Quality of bearings, Oil content, Variance in manufacturing, Hmmm I just wonder if its just an engine size that wasn't meant to be. I sure wish OS would chime in here and clear things up so we could move on to the next level.

Clint

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05-15-2008 02:05 AM  9 years agoPost 112
Gearhead

rrMaster

Vt

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""I sure wish OS would chime in here and clear things up so we could move on to the next level""

I hear that !!!

Jim
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05-15-2008 02:11 AM  9 years agoPost 113
mmc205

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PA - USA

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Your right, some kind of response would be nice, does anyone know a OS rep here on runryder, maybe they are not aware of this thread (and the many others like it)
A free set of bearings would be nice...

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05-15-2008 02:29 AM  9 years agoPost 114
Gearhead

rrMaster

Vt

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hey, checkout this bearing and see what it says on it,,

it's an OS 61 rear bearing, and it says on it "Made in Japan"

http://www.ronlund.com/Merchant2/me...t_Code=OSMG3117

Jim
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05-15-2008 02:32 AM  9 years agoPost 115
Gearhead

rrMaster

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and why does this OS 50 rear bearing have a number on it and a name on it but mine does not,,

http://www.zoomsheli.com/ProductDet...?productID=7926

Jim
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05-15-2008 02:58 AM  9 years agoPost 116
Gearhead

rrMaster

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aaa see what I found,,

see the OS 50 bearing in the top link,, it uses the OSM numbers (OSMG1950) and the .46FX-H
(OSMG1949)

http://www.advantagehobby.com/produ...95&cat=0&page=1

while in this 2nd link OS has changed the OSM number to OSMG3043
http://www.gpdealera.com/cgi-bin/wg....pgm?I=OSMG1951

I wonder what's going on here ????

I tell you if I'm going to buy a bearing I would rather have it say "Made in Japan" than say "China" !!!!!

Jim
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05-15-2008 03:50 AM  9 years agoPost 117
Blade_Master1

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Canada

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Has anyone thought of opening the back plate and adding duralube to the bearings ??

I have done it to my OS37 still works like new

From what I have read and understand
If you run 30% nitro you should be adding a shim to the head to lower the compression.
15% for new engines, 30% for older low compression engines, as 30% will increase the compression since you have to richen the mixture to run 30%.

Personaly I like the 15% nitro.

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05-15-2008 04:59 AM  9 years agoPost 118
impalacustom

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Lincoln Nebraska USA

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I would disagree with the 30% vs 15% theory, the only reason you run more nitro is for more power, and this is because nitro is it's own oxidizer. That is also why you have to richen the mixture, you are getting more oxygen in the mix so you will need more fuel or you will run lean.
Personally I don't own a 50, but I can say my 32 is running great on 30% and has ever since day 1. I do wish I had one of these failed bearings to take to my teachers who is a materials engineer. I graduated as a mechanical engineer and there are many reasons for failures and I could only guess as to why they fail just like everyone else.

If we knew what we were doing, we wouldn't call it research

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05-15-2008 12:22 PM  9 years agoPost 119
mmc205

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PA - USA

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I think the shim comment may be right on, because if i'm not mistaken, running higher nitro % without adding a shim or two (which effectively changes timing by letting the piston come to just past TDC before firing) you will get pre-ignition, or knocking. Preignition could have exactly the kind of effect were seeing. Good thought BladeMaster!!

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05-15-2008 12:31 PM  9 years agoPost 120
DS 8717

rrProfessor

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It also has a lot to do with the brand of fuel and exhaust system you are using as to whether you need a shim or not. Tuned pipes or mufflers usually need a compression adjustment.Tuned mufflers usually need a richer mixture than a std or poorly tuned muffler or you will be too lean when the engine is in it's power band.

YOU ONLY LIVE ONCE..IF YOU LIVE IT RIGHT THATS ALL YOU NEED

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