Jim, the SX at our field had a steel cage. Was the one you worked on a Heli engine (SX-H)? Maybe they had a running change in bearing supply.

Harry Baby You sure fool me. For a guy that sticks up for the OS50SX and doesn't own one and just have 2 OS 4 strokes don't make sense. Thats funny I have searched for morgans pink oil for homebrew and all they offer is BLUE and GOLD 2 stroke oil. They said the pink color is added in the factory package. I see your one of the 30% none bearing replacers at your field. The steel cage might have been the second replacement set for a 50.

The .50SX is a good engine. I don't have one either, but I've seen them run hard.

I don't like mine...
So it's been replaced ... trying a new 55ax
I've had very good luck with OS 46 fx and 61 fx in the past...

I really feel my SX is a lemon..... Out of the thousands they make there has to be a bad apple in the bunch.. lol

I'll let you know how the 55ax does.... if it runs bad then it would have to be tank position

Thank
Ron

During a long testing session for RPM and thrust (7 different props in the 10" diameter range) with a ringed OS 50 I observed and made notes:

"All props lose a few hundred RPM as the engine gets warm."

In the 1 to 2 minute range the engine will lose a few hundred RPM which might be a reason engines are sometimes set lean. Normally I always set the high speed needle and back off 3 to 5 hundred and then fly. Usually I will fly a long up line and adjust as necessary. After the long up line adjustment the needle is almost never touched. I thought it unusual that the engine would lose RPM after it ran for a minute or two and have not noticed the same condition on any non ringed engines.

Incidentally I settled on a 10 1/2" X 6" APC prop at 5 pound 8 oz. thrust.

Bill

How do you measure thrust? Do you have a set-up for that? I am thinking of building a testing stand for the little engines 120 and under. . .

I replaced the bearings in two OS 50SX's in summer 2004 that were bought that year. The guy never had a bearing go out in them before I moved from the area in May of 2006. But he did fly into a tree trunk or something with one of them and busted it all up.

Thrust is measured by tying a fish scale to the tail wheel.

The engine was on the airplane and I used a flight table and a fish scale and tie to the fuselage at the tail. There is some inaccuracy at the fish scale.

Bill

Not so, grasshopper...

This is what we use, straight from Morgan Fuels - "Coolpower High Performance Castor / Synthetic Model Engine Oil" in pretty pink.

After getting mine out of the plane...
it has really bad burns down the back of the head... it must have been lean
the head bolts were pretty lose also... i just tighted them up about two runs ago
wonder why they were coming lose? maybe need lock tight
the piston also looks very burned

I was tuning it with a tach... max rpms then back of 500 sometime 300..

strange ... but it's over now.. the 55ax is in... along with a new futaba fast 7ch system... curious to test it
break in the new one tomorrow

Ron

Loosening head bolts is a sign of overheating. Is there plenty of cooling airflow around that engine?

Grant,


I would like to elaborate on this.

When the aluminium head over-heats, it expands severely.
The head bolts, as a result, suffer from plastic stretching deformation.

I.e. the bolts actually become longer than they originally were.
They don't loosen by turning out, but after the engine cools back down, they no longer hold the head down as tightly.
If the bolts don't stretch, it may even be possible for the head bolt threads in the cylinder housing to be pulled out.

Wow...
Thanks for the detailed explanation... that makes sence
It is an extra 300 and has a full cowl... it is open behind the prop and I opeded up the bottom of the cowl to bring air over the engine... but it must have gotten really hot from the looks of it...
Ron

Ron,


Adding holes in the cowl will not persuade the air to actually flow over the cylinder and especially over the head of your engine.

You often, surely in the case of your Extra 300, need to install elaborate baffling within the cowl, to direct the cooling air-flow where it is needed.

Look inside the cowl of any light aircraft.

You would see it appear as if parts of the cylinders are not at all exposed to cooling flow. But no. The cooling flow just comes from another direction (usually from above) and it if forced down, between the cooling fins, by snug fitting baffles.


No one would expect you to do this for your OS.50SX, but air-flow listens to no one, so having even huge intake and exhaust holes, will not make sure the ample flowing air does cool the engine... You have to make and install baffling that will see to that.

I admit when I was flying the smaller glow engines baffling didnt seem important. When you start running gas engines and flying 40% planes you understand its crucial.

I imagine it could only improve the performance even with smaller engines. You have to direct the airflow - otherwise it will be pointless to just make larger holes.

dose any one know the difference between a OS 50sx and a 50sx-H hyper other then the Head ??

Different carb as well, but that's it . . . all other parts are the same and interchangeable.

- Tim

I have one of these engines. Because it is a ringed engine, it took a couple-three gallons of fuel to break in. Not your typical ABC(N) break in. It ran good until about 8 gallons of fuel, then the rear bearing became noisy and went out. I replaced both bearings, front and rear, from Boca Bearings. I have run at least 10 gallons through it since then and it is a very strong engine. I use an APC 12x5 prop on a GP Ultimate Biplane and it just screams. Best engine I have.

The factory bearings should have lasted much longer than they did, but sometimes a manufacturer just gets bad parts. I believe this is the case with the factory bearings. I couldn't be happier with this engine now...

For what it's worth.

Oly

Oly,


Some outlets want you to think they are selling you parts for a fair price... How much did you pay?

...While another actually sells you the same parts from the same sources, for a fair price...

[link=http://www.mcintoshcentral.com/rc-bearings/catalog/product_info.php?cPath=81_87_97&products_id=646&os Csid=49a5a75ae713c888f2cf8e6ef17ad9b4]The RC-Bearings set for your OS[/link] includes the high-speed retainer rear bearing, yet only costs $6.97... How much did you pay, again?

I got a set of ceramic front and rear for $15 + $3 shipping ..... OS gets $18.50 for just the rear

OLY ... sorry but the 50SX / Hyper is a Ring engine not ABC

The Hyper 50 heli engine is known to blow the rear bearing early on. I have a few buddies flying Raptor 50`s that also have experienced this. So buying expensive brand names is no guarantee for success

50sx hyper is still one of the best Heli engine on the market and when you are paying $1000 or more on a heli what is $15 once or twice a year in bearing .... its all in upkeep and mantainace

Russ,


The problem is that often, if the rear bearing has a metal cage and it disintegrates, it will be a bit more...
...Bearing, sleeve, piston, ring...

...Need I say more, about why the bearings should last the lifetime of the engine?


And as to the sum you quoted... it is too high.

See the link below:
[link=http://www.mcintoshcentral.com/rc-bearings/catalog/product_info.php?cPath=81_87_97&products_id=646&os Csid=49a5a75ae713c888f2cf8e6ef17ad9b4]The RC-Bearings set for your OS[/link]

Dar, I think some of us don't want the cheapest bearings on the planet in their expensive engines.

Tim,


Where do you think most bearing manufacturers produce their bearings? I mean NSK, SKF, NTN. IZO...

Do you think they are all made in Japan, or Europe? I have news for you...

I estimate that over 95% of the bearings you are likely to currently encounter, are made in the most populous nation on earth...


Those brought by RC-Bearings, as well as those from Boca are made there too and also some of those sold as 'original replacement parts'.

But some have the nerve to charge you $35-$50, for a set of $0.26 bearings...


RC-Bearings, for the same bearings, charges you under $7 and this is all the difference.


If it makes you feel better to pay $35 and not $7 for these bearings, just go right ahead...

But will those extra $$$ make your engine run better?


WIB bearings are among the only ones made in Switzerland and buying them will actually be a change for the better, without costing you as much as PRC made items... from some of the sources.