Typically how many flights (or gallons) per OS55 rear bearing ?

[bentwire]

It's been out for awhile now and I'm curious how many flights (or gallons) others are getting on the OS55 rear bearing.

Also, which bearing (stock, stainless, ceramic stainless, etc.) and which fuel might be interesting to know as well.

If you get lots of flights on a bearing, which fuel and how 'leaned' do you keep your motor; is it tuned for lots of power or 'slightly richer' than max power, or really rich.

I've gone through 3 bearings so far and the most I got from any of them was about 65 flights.

[outhouse]

10 gallons seems to the sweet spot for bearings.

I run SS and im still on my first set at over 2 gallons

[bentwire]

Thanks, I can only hope to reach the ten gallon mark with a 55. The Hyper 50's could do it easily, even 20 gallons; but the 55's I have and others I see flying don't seem to be making the ten gallon mark. I do know of one that has over ten gallons through it and it's still going strong but it has generally been run cooler and richer than most.

[smontesdeoca]

I've somehow manage to get a bit over 250 flights with a 50. I used with great result SS ceramic bearings.
Still 40+ flights on the 55, so far, so good. When needed, definitely rc-bearings.com.
Usually tune them a click richer or two. Never above 95C (well ... try to ).
Always Used PowerMaster fuels. Learned to hover with 15% nitro, when starting to move the heli around, switched to 30% nitro, never looked back.
Cheers!

[fastflyer20]

My 55 coughed the bearings in less than 2 gallons. I have RC-bearings SS in it now with over 4 gallons through them and still going strong, running 20% WC.

[mikmerl]

these engines regarding the bearings. Treat them a consumables and change them out frequently.
Thinking out loud it is not really a matter of wear through use but breakdown from corrosion. So I don’t believe it is a X number of gallons (or flights) but how long they have been sitting in a corrosive environment which is our crankcases after running 20 – 30% nitro fuels.
I have decided that I will do two things to try and help my engines survive.
a) Clamp off fuel line until engine stops of fuel starvation.
b) Remove backplate and introduce after run oil.
c) Replace backplate and engage starter for a few seconds to distribute
d) Change the main bearing around every 3 months proactively (the front one has a much easier life and seldom gets damaged.
I am going to keep far away from the ceramic/stainless hybrids (I tried one and it lasted about 10 flights)
If you change them frequently you can even use good quality steel/steel bearings that are very cheap.

[Ah Clem]

"a) Clamp off fuel line until engine stops of fuel starvation."

I respectfully disagree sir.

This is very, very hard on the engine and bearings. All the people that I know locally who insist on doing this change the bearings on their OS Hypers with great regularity. If you do this, you are ending every flying session with a lean run.

Shut it off with the throttle, fill the tank one last time to clear the caustic exhaust from the tank and muffler, then drain the fuel out again and go home.

I have three OS 50 Hypers in service during the last four years or so (one with about 10 gallons through it) and have not blown a bearing yet.

[mikmerl]

I do not disagree with what you are saying.
However this has been common practice by many modelers for ages to ensure that there is no fuel in the crankcase. A bearing requires little lubrication to operate and I doubt that allowing an idling engine to use up its remaining fuel residue and stop has never proved harmful to dozens of glow engines that I have had the pleasure of successfully operating during the last 30 years. There will always be oil from the fuel present in the engine during and after its operation.

[Ah Clem]

mikmerl,

Again, I respectfully disagree sir.

We had this discussion (the group I flew with) back in the 1970's and 1980's too.

41 years of experience with glow engines, 34 in model helicopters has taught me the proper way to treat them.

Running them dry (i.e. leaning them out until they starve) is not it sir.

If one is changing bearings frequently, and has been running the engines dry, the conclusion is obvious...

[mikmerl]

Total and complete respect for disagreement.
However main issue in these heli engines is rust corrosion. Unfortunately they don’t last long enough to wear out from long use. What is required is protection during non use (after run oils etc)
Good discussion.
I hope it is of use to the gentleman who started the thread.

[Ah Clem]

I agree that we agree to disagree, sir!

It was a good discussion!

[bentwire]

I've flown with several folks who do a final crank and let their engine die; I'm just too lazy to do it. From what I've seen we all seem to go through rear bearings roughly at the same rate. At least with the Hyper 50's we seemed to.

I arrived late to an OS tent seminar at Ircha a few years ago and the OS folks and sponsored pros were taking questions at the front. Someone asked about running the engine dry after the last flight of the day and one of the pros laughed and asked if we'd drain our car engines of oil and take off. I'm sure it's not the same and I'm not even sure he was serious but it allows me to feel good about being lazy and not doing it.

My first 55 rear bearing lasted for six days out of the box and 2 gallons before it went rattling badly. I replaced the bearing and it lasted four days (one gallon) and started rattling. The front bearing and all the internals looked like new so I chalked it up to being a lemon and bought a second 55 to replace it. After 15 good flights on that motor I preemptively swapped out the stock rear bearing for the older type OS50 Hyper bearing with the non-metal retainer. That bearing lasted 65 flights and is most I've gotten so far. I just replaced it with a ceramic stainless bearing and I'll see how it goes. I've used them for years in the Hypers 50's and had good service from them.

[mikmerl]

This is a photo of the OS. Max 50 SX- H ring Hyper Care and maintenance section.
These guys build the engines, I follow their instructions.

[bentwire]

I just checked and the 55 manual says about the same thing, on page 33. It now mentions to to turn the starter over for 5 to 10 seconds but it doesn't specifically say to remove the glow plug before you do it. But, the next sentence does say to remove the glow plug and add after-run oil.

It also says... "accepted practice is to cut off the fuel supply while the engine is still running at full throttle, then expel as much fuel residue as possible by turning the engine over 5 - 10 seconds with the electric starter." Maybe we no longer have to remove the glow plug on the 55 when blowing out the cylinder but we have to turn the engine over with the starter twice as long. Who knows.

I'd probably go electric before I go full throttle and cut off the fuel supply; then, remove the glow plug and blow it out some more and then try to get some oil in that little hole. I'm just very lazy. I don't even like cleaning it up.

[mikmerl]

Bentwire sorry for hijacking your thread but it is an issue that is driving me nuts as well.
I have had a lot better luck than you have for sure. My 50Hyper served me well for a year and then the rear bearing started rattling so I changed it for a ceramic/stainless hybrid (or whatever) and that lasted about two gallons.
Unfortunately in my 91 HZ one of the balls in the main bearing split into two one piece remained in the retainer and the other caused mayhem to the entire engine (after about a year of use)
I have flown planes for years control line, pylon, pattern, sport and now giant scale gasoline. In the case of the control line planes we had to wait for the fuel to be completely depleted and for the engine to die until we could land and the engines and bearings lasted forever.
The corrosive byproducts that are created by the burnt nitro methane in our fuels linger in the crankcase long after we have packed up and gone home. That I believe is largely to blame for the corroded steel bearings we are battling with. Only a protective coating film on these steel components when not in use can increase their longevity.

[bentwire]

Corroded steel bearings might be part of it. After six days and 2 gallons of fuel the original stock 55 bearing had some light rust on it in 3 places on the retainer. I couldn't see the balls because of the steel retainer hiding the balls.

On the last failed rear bearing, the original OS 50 Hyper bearing with the plastic/phonoelic retainer, I was able to remove the balls and inspect them with some magnification. The balls looked good to the naked eye but when checked under magnification they had many tiny speks of something, or more likely spots where the chromium had been removed. They were very tiny spots but all the balls had them. And there was some pitting in the races as well.

I don't think I've ever seen anyone at a field use afterrun oil, ever. I do see it sitting on the shelf at the LHS, I may have to grab a bottle and see if it makes a difference. I'm sure it would generate a lot of conversation at the field.

[mikmerl]

I am going to try to discipline myself to remove the back plate and apply the oil directly into the crankcase before leaving the field to go home.
It may make a difference.

[Ah Clem]

I read the instructions for the OS .50 Hyper about running it dry too.

Four decades of experience told me the instructions were incorrect.

I ignored them, and am grateful that I did.

It is interesting that different people have vastly different experiences with the Hypers/bearings.

I also have a .91 SZ,which still has its original bearings in good shape after two and a half years (probably only about 50-60 flights though).

I do think that after run oil would be a good idea, although I have not done it in years.

[John Cook]

Originally Posted by Ah Clem

"a) Clamp off fuel line until engine stops of fuel starvation."

I respectfully disagree sir.

This is very, very hard on the engine and bearings. All the people that I know locally who insist on doing this change the bearings on their OS Hypers with great regularity. If you do this, you are ending every flying session with a lean run.

Shut it off with the throttle, fill the tank one last time to clear the caustic exhaust from the tank and muffler, then drain the fuel out again and go home.

I have three OS 50 Hypers in service during the last four years or so (one with about 10 gallons through it) and have not blown a bearing yet.

++++++++++++++++++++++100

I don't run the fuel out, I fill tank up, plug the muffler, and clamp off the exhaust line with a fuel clip. I have 2 OS55's(just sold one). One with 5-7 gallons, one with 3-5 gallons. The first one has stock bearing that looks and feels like new.

The 2nd I did put an RC bearing SS bearing in it when it was new. It's like new too. Using Outrage fuel. Fuel I think makes a diff as Wildcat, Byron rotor rage and Outrage I feel have the best oil packages. I'm NOT a fan of Coolpower, and I ate a few bearings running Magnum DS(heard they fixed it now).

[mikmerl]

Ah Clem [Quote]
"It is interesting that different people have vastly different experiences with the Hypers/bearings."


The statement above hits the nail on the head.
A problem that has numerous variables and inconsistencies is very difficult to address. There is no one size fits all solution.
Of course there are many reasons that these bearings fail. For simplicities sake we can focus on two.
a) Bad material/workmanship on behalf of the manufacturer. (not too much we can do there other than to replace)
b) Corrosion here we can take measures to reduce the frequency (everybody will develop their own favorite procedures)