Noisy Engine - OS50 Hyper

[Aviation addict]

Guys, I'd been running a Hyper in my Raptor for 5 months with no problems until last week when it started to sound rough - and then occasionally cut out at idle. I stripped it down and found that the back bearing was gritty, the front bearing was fine and the Con rod had been hitting the back of the crankcase and resembled a golf ball!

After discovering this I quickly ordered a new set of OS bearings and a new Con rod [the old Con rod's brass bush had worn significantly] and fitted them.

The difference in sound was very noticeable - she sounded as sweet as a nut again.

Now - only 10 to 15 tanks later the sound is back. I dial gauged the Quick UK fan when the engine was new [5 months ago] and got it to 1/2 0.001" but last week the best I could do was 0.002". Any ideas what's going on? Do I have a bent Crankshaft somehow?

I've never run the engine past luke warm, it's never been crashed, I use the OS locking tool for tightening up the fan and I always run the tank dry to ensure the fuel does not kill the bearings. I'm using Magnum 12% heli in-case that's a consideration.

I'd appreciate your help! :arggg:

[BarracudaHockey]

Take a look at the rear bearing. If its bad get a set of ceramics from
http://www.rc-bearings.com

[flyinfool]

OS bearings are very short lived, don't waste your money on them.
I normally replace front and rear together with bearings from RC-Bearings.

Make very sure that you get all of the shrapnel from the old bearing out of all the nooks and crannies of the engine, any chunks left in will make short work of the new bearing.

Getting the run-out just right on a stock Raptor type fan is mostly just pot luck.
When you thread the fan on there is nothing to adjust, you get what you get.
All you can do is to take it off and put it back on till you find the magic spot.
The exact amount of torque that you tighten the fan and the nut to can have some effect on run-out.

[Aviation addict]

Thanks Guys - I didn't know that OS bearing can have a short life and certainly hadn't heard of Ceramic bearing before but I'm going to buy some now!

Is there any way I can check to see if my Crankshaft is bent while I'm in there stripping things out?

[Aviation addict]

Is it the ball bearing holder that's Ceramic and is it best to go for the ($5) Stainless Steel ball bearing(s) option? Ta.

[flyinfool]

In most of the ceramic bearings that we could use/afford the balls are ceramic and the races are either chrome steel or stainless steel.

There is such a thing as all ceramic bearings but they are very expensive and I don't know if they are well suited to cyclic loading (IE a piston hammering away at them).

Lately I have been using the Stainless bearings from RC-Bearings and have not noticed a significant life difference between the stainless and the ceramic.

[Espeefan]

How many O.S. Hyper 50s have been effected by worn bearings? How much flight time before they start to cause problems? I'm interested to know because I bought a Hyper 50 for my heli and I'd like to avoid any problems. Is there a part number and website for the bearings you guys mention? Will upgrading solve the failure problems?

[flyinfool]

There is nothing that will make the problem go away.
The MBTF can get a lot better by using a non OS bearing.
You must be certain that the bearing you use does NOT have a metal ball retainer.
When (not if) the metal ball retainer fails it will take at least the piston, cylinder, ring and head with it.

I have been pleased with the bearings from www.RC-Bearings.com.

There are a few people that have not had issues with the stock OS bearings, but with the numbers that have had issues, there is a problem, just look at the number one best selling bearing set from RC-Bearings, OS 50 Hyper.

I keep a spare set of bearings in my tool box and can change a rear bearing at the field in about an hour.

[Mylee]

I keep a spare set of bearings in my tool box and can change a rear bearing at the field in about an hour.



How do you change them at the field? I've alway 'cooked' an engine to release and insert bearings?

[Ivan]

You are lucky to get 10 gallons on them. Mine were bad out of the box.

[flyinfool]

In the winter the top of our wood burning heater is enough to release the bearing, otherwise I very carefully use a propane torch to heat the case. A propane torch is part of the standard gear stored in the back of my truck.

[Aviation addict]

Can't believe it! I've changed the bearings out and she has a piercing engine noise (which makes sense as the bearings that came out looked fine).

I dial gauged the Crankshaft and that was perfectly straight plus dial gauged the fan to less than 0.001". My next plan of attack is a new Piston ring/Gudgeon pin and Con Rod. [The exhaust (a MP2) is firmly attached to the engine with no leakage]. Can't think whats creating the noise. :arggg:

I know that I'm not imagining things as my GY611 is drifting a little too and that's something that has never occured before... the saga continues.....

I'm still convinced that I'm not running her excessively Rich or Lean. Anyone got any ideas / similar experiences?

[Aviation addict]

The outcome: I changed the Piston Ring, Gudgeon pin, Con rod to go with the new bearings installed a couple of days ago. But in addition to the above I found two things: First of all I found a loose frame screw (hidden underneath wiring) located just behind the fan. Second while the engine was out I put an old starter shaft into the clutch and compared it with a new clutch. What I found was that I could waggle the shaft around in the old clutch in a cone shape (if you can imagine it) but in the new clutch the needle bearings held the shaft solidly.

I'm not absolutely sure, but I think my old bearings (taken out 2 weeks ago) which were definately gone, gave up or caused, my needle bearings to give up in the clutch. Everything is beautiful in the world now though! Thank goodness for that.

[flyinfool]

Glad to here that you fond it.

[Aviation addict]

Bearings have gone again! When I strip the engine this time I'm putting Ceramic bearings in from RC Bearings. I probably should have done that last time but I was in a rush to get flying again.

I don't understand why she's using (OS) bearings so quickly. I always finish the day by running her dry and I'm not using excessive headspeeds (1850) or running her lean. She's usually luke warm at the most.

Can you get alignment issues with a Raptor 50? I usually just bolt the engine in and go. Will replace the clutch material this time I'm in and balance the fan (for the first time) as well as dial gauge it when I re-mount it on the engine (which I do every time). I never settle for less than 0.001" by the way. :(

[Helos4me]

I have only ran the fuel out of the engine a couple times and then I thought about it. Even at idle, the little balls are screaming around that race much faster than the rpm of the motor. So, as the fuel runs out, the engine goes lean, leaner, leanest! No cooling and no oil. Bad JUJU. I just pump the fuel from the tank with the clamp on, release the clamp and make sure the carb is open and draw any residual fuel there, Close the carb completely and put the butt plug in. That keeps any more moisture from getting in and if it is going to sit for an extended time, which it doesn't then I would put in some after run oil. One other trick an old timer told me is to put about an ounce (I put .5 to .75oz of turbine oil in a full gallon of fuel. Seems to dribble a little more but I think the extra lube is good insurance. Finally I have replaced the bearings in two OS50 cases and things never seemed to run right (New engine in there from the kit now) but I think I'll revive them with some of the stainless steel bearings. The stock ones are pretty weak. And there's my nickels worth.

[kcasser]

I would've started a new thread for this question, but I wanted to tap into this group who seem to know about bearings.

Here's my conundrum. Bearings need to be greased, right? When we install them, we take the back cover plate off the front bearing and grease it. Then we make sure both sides of the rear bearing are coverless, and grease that too. We remove these covers so that the oil in the fuel will flow freely through the bearing, right? So what happens to the grease that's in the bearing? And why do we grease them if they get lubricated with the oil in the fuel? Or, if we want to keep them greased, why do we remove the seals?:confused:

[mondo100]

Bearings can have grease or oil lubrication, depending on the set up.In the case of our model engines the oil in the fuel is used as lubrication.As to why the bearings fail? well mostly caused by lack of lubrication or damaged when fitted.They get a hard life in an engine doing 15000+ rpm,plus the fuel is corrosive.

[bpd964]

The fuel mixture contains moisture and that moisture causes corrosion. Run the engine dry and use after-run-oil after a day of flying will help. But, no matter what you do, you will still collect some type of moisture that will cause corrosion and in turn, cause the bearing casing to breakdown. Using ceramic bearings is probably your best best to solve this issue..

[BarracudaHockey]

Don't bother, they don't last any longer than the cheap bearings.

[RC-Bearings]

I would've started a new thread for this question, but I wanted to tap into this group who seem to know about bearings.

Here's my conundrum. Bearings need to be greased, right? When we install them, we take the back cover plate off the front bearing and grease it. Then we make sure both sides of the rear bearing are coverless, and grease that too. We remove these covers so that the oil in the fuel will flow freely through the bearing, right? So what happens to the grease that's in the bearing? And why do we grease them if they get lubricated with the oil in the fuel? Or, if we want to keep them greased, why do we remove the seals?:confused:

Actually, a few drops of oil on the bearings is sufficient when you reassemble the engine. Grease is overkill and can actually cause problems if the grease isn't compatible with the alcohol or oil in the fuel.

Also, most engines use shielded front bearings, not seals. If you get double shielded front bearings, there is no need to remove the rear shield. The gap between the shield and inner race is many times larger than the gap between the crank and case (where the oil comes from)..

A quick correction to an earlier post. Running the engine out of fuel at the end of the day will not cause the bearings to lose all their lube. A certain amount of oil always sticks around and you would be surprised how little oil is actually needed by these bearings. I experimented with running a Saito .80 on 60% nitro and 8% turbine oil. No lube problems at all. Also, big Supertigres use 8-10% oil in their fuel. The higher oil content in heli fuel is mostly for cooling and conrod bign end lube.

[kcasser]

Thank you for your response, Paul. You've cleared up a lot of my confusion. What you say makes sense.

Ken