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HelicopterEngines Plugs Mufflers Fuel › heehee hee YOU better do something OS !!!
05-13-2008 05:42 AM  9 years agoPost 81
Gearhead

rrMaster

Vt

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the bearings are strong enough,, see Boca's specs,,

Dynamic Load,,(Kgf) 441 (pounds 972)
Basic Load,,,,,,,(Kgf) 231 (pounds 509)

better or more preload should stop the ball from pounding on the bottm of the outer race..

Jim
Buzz Buzz Buzz

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05-13-2008 07:15 AM  9 years agoPost 82
StillTryin

rrApprentice

Perth, Western Australia

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Here you go Divot - a quote from the inventor of the Coke Can Mod. Seems he is indeed discussing preload.
My last attempt to provide a pre load suffered from oversight on my part but now I took a closer look at the bearing "stack up". It turns out that with the front bearing located in it's proper place the rear bearing has .008" of axial clearance. so to provide a pre load it is necessary to either shim the crank aft or shim the rear bearing aft. it turns out that shimming the bearing is the easiest to do and the method I chose is both locally available and easy to do .

Yep, you guessed it, its is made from an aluminum coke can (using scissors). which is .005" thick so by using two I shim the crank aft by .010". (still plenty of clearance from the crank pin to the aft case.)

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05-13-2008 09:15 AM  9 years agoPost 83
firefox

rrApprentice

Thailand

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For the people that believe that the rear bearing issue comes from over-running the engine (high nitro or high RPMs):
Firstly, I've had them fail on me regularly at 15% nitro, low RPMs, and very, very gentle flight (as in the RUN IN period). I've also seen them fail regularly for sports fliers who use only 0% nitro. I've also seen those who use 30% and fly the hell out of their birds with zero failure.

Secondly, they're rated to be compatible with high nitro, so if they shouldn't be used as such, then they shouldn't be sold as such.

Without bothering to read the whole long, long tedious thread, it's already been written long before that OS has some wide manufacturing tolerances for their bearing spacings (it's been measured), leading to some engines with poorly loaded bearings, and high failure rates and to others with zero bearing failure. That is pretty much the one single reason that fits the symptoms (ie: some having regular bearing failure, others having few failures, and yet others having none, with widely varying flying/fuel/etc).

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05-13-2008 09:32 AM  9 years agoPost 84
Hirobofly

rrApprentice

Horten, Norway

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Hehe, one thing for sure; It is extremely easy to blame the bearing itself.....

And it is also just bad luck, that some purchase engine after engine/bearings after bearings, and all of them are "crap" /fails shortly.
While others just go flying without a single problem for years after years. -How lucky we are.

//RJ

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05-13-2008 12:46 PM  9 years agoPost 85
mmc205

rrElite Veteran

PA - USA

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You state below that the bearings are "strong enough" as the specs below illustrate.
In the world of engineering, which you must not belong too, there are certain parameters that have to be looked at that de-rate these numbers such as mounting specs (extra clearence, radial movement in th bearing mount), shock loadings, L10 life, lubrication, etc... Essentially, a bearing that is truly rated for the below loads for 10x10^6 cycles (which is 58 flights at 17,000 rpm) will last a lot less long if any of the items mentioned above are working against it. Bearings in car wheels for example last a lot longer even though the L10 life is longer mostly because their usually perfectly lubricated, loaded relatively lightly and thier only doing about 600 rpm at highway speed. This probably why even some of the high quality aftermarket bearings fail relatively quickly. This is not to say that running a heli richer and easy would absolutely not kill a bearing. If the manufacturing tolerances of both the bearing and the holder stack against eachother, it probably won't last long, nor will it if the internal races of the bearing arn't close to the nominal spec. When you buy really good bearings, even small ones, you can pay hundreds or even thousands of dollars each for ground races and balls selected from inventory to meet the particular bearing race perfectly.

Dynamic Load,,(Kgf) 441 (pounds 972)
Basic Load,,,,,,,(Kgf) 231 (pounds 509)

***Logo 600 vbar***Henseleit TDR vbar***

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05-13-2008 04:42 PM  9 years agoPost 86
Topher

rrVeteran

Rochester, Michigan

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Like mmc205 stated, I think its pretty obvious that OS is using cheap bearings with very poor quality control which is pretty typical of Asian manufacturers. Bearings and basically all structural engineering is not my field but its pretty obvious that these bearings arent living up to their intended life and premature fatique related failures are the cause. My money is on a cheap chinese manufacturer thats letting anything out the door.

mmc205, thats an awsome sig.

will wash your heli for a quarter

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05-13-2008 07:24 PM  9 years agoPost 87
mmc205

rrElite Veteran

PA - USA

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thanks for the compliment on the sig, i, as many others, have found that out the hard way

***Logo 600 vbar***Henseleit TDR vbar***

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05-13-2008 07:44 PM  9 years agoPost 88
Gearhead

rrMaster

Vt

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mmc205,, if you are talking to me go back and read what I said the bearing specialist told me,

besides it's obvious the bearing IS large enough, after all NOT all the bearings are going bad !!!!!!!

it's a preload problem, if the bearings were preloaded correctly they would not skid so they wouldn't fail as they do

another thing, the bearings that are used in these engines have a ABEC rating of #1,,, a 3 would be a much much better bearing !!!

Jim
Buzz Buzz Buzz

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05-13-2008 07:54 PM  9 years agoPost 89
Gearhead

rrMaster

Vt

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Topher,, you are correct, look at the prices of these 2 bearings

Boca,, $18
http://www.bocabearings.com/main1.a...n=MR6902_THB/C3

MSC/SKF,,$38
http://www1.mscdirect.com/CGI/NNSRI...405252&PMT4NO=0

another thing,, Boca doesn't tell us who makes their bearing !!!!

Jim
Buzz Buzz Buzz

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05-13-2008 08:21 PM  9 years agoPost 90
Gearhead

rrMaster

Vt

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so I called Boca,,

this reply is NOT "NOT" to bash Boca,, they offer and sell a product, they don't make it and they don't make claims saying it's the best, it is up to the individual to buy it or not,,

so I just called Boca,, and I gave the guy the bearing number for the OS 50 and I asked him who makes the bearing and he told me it was made in china,

so I asked him "you can't tell me the brand name", he told me it was no name I would recognize,,

made in china/no name I would recognize= this tells me NOT to buy their bearing for my engine !!!!!!!!!!!!!!!

a cheaper bearing would be less tolerant of an incorrect preload !!

Jim
Buzz Buzz Buzz

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05-13-2008 10:06 PM  9 years agoPost 91
lightningrc

rrElite Veteran

UK

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Like I said in another post my no name bearing failed very early whilst being run rich , rest of the engine is perfect like new condition.

My bearing had no rust , no heat signs but the inner race was badly worn and pitted.

Im in the motor trade , so not new to engines .

And I know my failure was caused by a cheap bearing , has the second hand NTS branded bearing which is in there now is working perfect.

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05-14-2008 02:31 AM  9 years agoPost 92
StillTryin

rrApprentice

Perth, Western Australia

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At this point, I think the Wasp has the answer.

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05-14-2008 02:36 AM  9 years agoPost 93
tchavei

rrProfessor

Portugal

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Has anyone just walked into a bearing warehouse and bought an original INA or NSK bearing and tested it?

Tony


--------------------
"Perfection and patience usually walk side by side..."

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05-14-2008 02:40 AM  9 years agoPost 94
Dilbeck

rrElite Veteran

Springdale Arkansas

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So that would make the price of the OS50 Hyper $240.00 US dollars with the good bearing?

Clint

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05-14-2008 03:22 AM  9 years agoPost 95
cmmicroheli

rrNovice

Manchester VT

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Upgrades

Are there any upgrades for the rear bearing on the .50?

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05-14-2008 03:42 AM  9 years agoPost 96
Divot

rrVeteran

Mesa, AZ

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At this point, I think the Wasp has the answer.
And what is that answer????

Preload..... This is not a new concept. This is also
been explored many times before.

Sorry but the WASP is not paving a new path here.

Once again for the slow folks...preload, preload, preload.
Not the bearing, not the fuel, not the retard term "hard 3d"

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05-14-2008 04:17 AM  9 years agoPost 97
StillTryin

rrApprentice

Perth, Western Australia

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The answer is that some bearings are cheap Chinese rubbish. This brings back a conversation I had with a bearing supplier locally. When I explained what I wanted the bearings for, he replied "Well, I will get you some good quality Japanese bearings, you don't want any Chinese crap in that environment" or words to that effect.

As for preload, like religion, if it makes you feel comfortable, go for it. Just don't be too hard on us heathens.

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05-14-2008 04:24 AM  9 years agoPost 98
Divot

rrVeteran

Mesa, AZ

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As for preload, like religion, if it makes you feel comfortable, go for it. Just don't be too hard on us heathens.
Fair enough

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05-14-2008 05:46 AM  9 years agoPost 99
Gearhead

rrMaster

Vt

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""Has anyone just walked into a bearing warehouse"

not me but I am going to order that SFK bearing, I have my first Hyper 50 with a ceramic bearing in it, that is the engine whereby it's bearing went bad in 2.6 gallons, it has only 2 flights on it with the ceramic bearing so I have heard bad things about the ceramic bearing too so I will remove it and put the SFK bearing in it, I have to rebuild the heli anyway

Jim
Buzz Buzz Buzz

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05-14-2008 11:38 AM  9 years agoPost 100
S Bell

rrApprentice

Nova Scotia Canada

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Various brand bearings come with different ball retainers. Some of the French SKF versions (if memory serves) have a folded retainer. It is not the ideal type for model engines. I've had them fracture and unwind. Next thing to consider is the ball count, bearings with the same dimensions can have a different ball count. I have found the higher ball count lasts longer. I also prefer composite non-metalic retainers. You could put yourself in a worse situation than the OEM bearing by thinking an alternate unit is fine as a replacement.

Some engines are not line bored correctly causing the bearings to be misaligned slightly. The only way to check for sure is to install the crankshaft into the crankcase without the connecting rod and tighten down the fan to seat the system firmly against the front bearing inner race. The slowly rotate the crankshaft looking for a deviation in smoothness or a small hump. If you have any deviation then you know where the problem is, it is most likely not in the bearing.

All I'm saying is to investigate and evaluate the situation correctly before putting the sucker back together.

Stephen

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