One slightly stuffed bearing

[Alfred]

Fury Expert OS70 SZ-H

This had a low grumble during idle since I got it.
It has seen around 50+ litres of fuel since I got it.
I never did get that GY401 performing like on the other helies, I think I know why now.

[Alfred]

And here is the Front bearing, looking like new as usual.
the brown stain on the inside cage is just oil.

[RC-Bearings]

Alfred,

Was the engine new when you got it? The marks on the outer race look like the bearing was exposed to something corrosive.

[Alfred]

Was the engine new when you got it?
No
But I know the pilot and he doesn't keep any heli for very long. As an extreme 3D flyer and tunes his engines to maximum performance. My guess is that it had a lean run and after that the engine was left with fuel in it.
I always thought that the rattle noise I heard from day 1 was due to the Canopy rattling against something and was chasing the noise.
I flew the heli for 2 years with the noise (I just couldn't trace it).
As I run my engines nice and rich at all times, my guess is that I got away with it for that long.
The inner bearing cage is far worse then the photo. It has whole pieces missing out of it.
Piston/Liner is fine and the engine has good compression + power.
Anyway, I have got ceramic/stainless steel bearing on their way from you :D

I was very impressed with your prize Paul, as the cost including airfreight to Australia was excellent.
I have another YS80 and a brand new YS91 engine which I will order the same kind of bearings from you very soon, so that I have them at hand when the others need replacing.

30 years + with model engines and the only true rust preservative I have seen that really works has been Castor oil, but it's simply not an option for today's heli engines due to it's nusty side effects.
I just can't see myself going back to glazed piston/liners and gummed up mufflers.
Plus the caked on brown stains that you will never get off properly without defacing the surface.
Can you see the front bearing? It's like brand new. All the heli engines that I have serviced all show always the bigend bearing to suffer badly while the fron bearings seem to be not at all or just have been minerly effected compared to aero-engines.
I wonder if the mounting position of the engines being vertically has got something to do with it?

[RC-Bearings]

You can mix up to around 3-5% castor with synthetic oil without getting the brown crap. This also gives a measure of rust prevention. Marvek Air Tool oil (or anything similar) will also neutralize any acids and help prevent rust.

[Alfred]

I received my ceramic/stainless steel bearings from Paul (rcbearings) a couple of days ago.
I didn't know that the ceramic bearings are actually bluish/black?
The price and service was both excellent, you have got a good feedback system there.

The old methods of bearings install don't seem to be adequate anymore.
The bigend bearing wouldn't even slip over the mainshaft. I had to drop the mainshaft into the freezer and the bearing into the oven and pre-heat it to 100 degrees Celsius for the bearing to go over smoothly.
Then let them both settle to the same room temperature, pop them back into the Freezer and the crankcase into the oven at 140 degrees.
The crankshaft would spin very free while still hot but then tightened up a bit too much when cooled down.
Back into the oven at 100 degrees for another 20 minutes and after that the crankshaft was nice and free even after cooling down.
I have changed my methods of assembly by sticking the engine back into the oven after assembly which then gave enabled me to turn all the bolts another small amount tighter using the same moderate torque.
This is now the third time that the old methods proved to be not good enough anymore.
It certainly seems to me that the newer CNC mashined engines have far tighter tolerances and require a more thought out dis-assembly/re-assembly then in the old days.

Paul
If I am happy with those bearings then expect more orders from me in a short time as your prize and service was excellent.

[Janek]

Paul, the staining you see, whilst a very extreme example, is typical of OS bearing run in helicopters, using fully synthetic oil.

When my bearing are replaced, they look very much the same, I always burn off at the end of a days flying, but do not use after run oil as it's too much of a pain to get into the engine, nor any castor.

Alfred, you'll like Paul's bearings :wink:

[Alfred]

They were definit OS bearings Janek.
I don't hold that much hope for the engine anymore, but we shell see.
After carefully cleaning the ring groove, the engine has hardly any compression. I know that it will set itself but there are multiple points that woory me a bit.
There was a rather thick brown gunk in the engine but definit not Castor oil.
Once cleaned up after 3 hours of very careful removel with scotch brite, more showed up.
The crankcase has visible wear inside the crankcase channel.
The piston ring groove had a thick layer of brown gunk inside and once removed now shows less compression.
The bronce bush at the big end bearing end seems to have a rather large amount of play in it, but doesn't seem to be out of round.
the piston itself doesn't show any visible wear and the Liner is fine.
We shell see :?

[RC-Bearings]

I would suggest using a fuel with medium or high viscosity oil with an engine like that. I don't think the LV oil will provide the protection you need with the extra clearances.

[Alfred]

It's all good news :D
The engine has come back with more compression and more power then it ever had.
3 hours of very careful cleaning including the ring-groove left me with an engine with close to no compression (just like a brand new one).
1/3rd of a tank rich/fast idle and it would idle perfect on the next start up without any rpm drop when the glowdriver was removed.
Through the 2nd tank it was taken up into hover at low head rpm 1500-1550rpm and it all looked good.
3rd tank and it managed to make one of my two 8.4Vdc C cells Nicad smoke....it just couldn't turn the engine over :shock:
I had to take out the plug and blow out the engine. It wasn't flooded, but I had to get the engine dry to get it started when the fuel reached the plug. Even my 91 YS never managed that :lol:
Note: The Starter is a Dynatron with two 8.4Vdc packs wired in Series through DEANS plugs.

Switched her into idle1 and did some short burst climb outs here in my backyard.
The engine is running very rich but it climbed out at a speed it has never ever done before :lol:

It has been a complete success :D