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HomeRC & Power✈️Aircraft🚁HelicopterEngines Plugs Mufflers Fuel › Another one bites the dust !!!
09-09-2006 07:05 AM  14 years ago
Disciple4123

rrKey Veteran

USA

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I agree with your assessment with regard to RPM and stroke length. Now how does that affect my Venture 50 running 9.8:1 ratio with 600's?? Can't be good.

It is time for someone to make a small 2 HP gasser, Nitro engines are like cows, they regurgitate their food. Acidic exhaust fumes being pumped into the fuel tank to generate pressure, come on now
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10-28-2006 11:21 PM  14 years ago
tchavei

rrProfessor

Portugal

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Over a month old post but I just dismantled my OS 50SXH (non Hyper) converted to Hyper head and a 60B carb.

After 287 flights without any maintainance here are the results:


I changed the piston ring as it seemed a little worn out. You can't see the bearing on those pics but it has no signs of rust and still running smooth.

Tony

--------------------
"Perfection and patience usually walk side by side..."
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10-29-2006 12:33 AM  14 years ago
dkshema

rrMaster

Cedar Rapids, IA

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17K cannot be in the normal operating range for this engine
Displacement 8.17 cc (0.499 cu.in.)
Bore 22.0mm (0.866 in.)
Stroke 21.5mm (0.847 in.)
Practical R.P.M. 2,000-20,000 r.p.m.
Power output 1.9 ps / 17,000 r.p.m.
Weight 406g (14.33 oz.)


Straight from the OS 50 SX-H manual and website. The engine is spec'ed horsepower-wise AT 17,000 RPM, and the practical RPM spans 2,00 to 20,000 RPM.

Dave
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10-31-2006 09:50 PM  14 years ago
rotor- shark

rrVeteran

uk

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The problem is engines are running with too much nitro,instead of less nitro and a higher compression ratio.this is the cause of the rust,the synthetic oil is fine for lubricating,but can't help protect against nitric acid in the nitro. if you want to lay the blame somwhere,then let me suggest that the engine manufacturer should machine to higher tolerances in their piston and liner,to ensure higher compression,and let you use less nitro,(0-5%)instead of machining to low tolerances and encouraging high nitro(15-30%)the low tolerance method ensures easy starting and tuning,which is obviously desirable with most pilots.you won't get this severe rusting problem with low to zero nitro enginesall comments are my opinion only!
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10-31-2006 11:56 PM  14 years ago
tchavei

rrProfessor

Portugal

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I use 20% nitro (99,99% purity), 20% KL-198 Heliglow and 60% (99,99% purity) methanol.

The problem isn't only the nitro. Its all the garbage most brands mix into the fuel so it smells better, looks better, doesn't foam too much, doesn't attract so much moisture, has a specific color etc etc.

I used to have alot more corrosion when I used to use brand fuel. It all stopped once I started to mix my own fuel.

Wierd huh?

Tony

--------------------
"Perfection and patience usually walk side by side..."
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10-31-2006 11:57 PM  14 years ago
supertigre

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Castle Rock, Colorado

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Tolerances have nothing to do with whether an engine runs better on higher or lower nitro. Combustion chamber design and compression ratio determines that. Higher compression is required for more power with lower nitro. This also makes the engine far more sensitive to needle adjustments and atmospheric changes. Going with lower compression broadens the fuel tolerance allowing a larger range of nitro levels to be used in the engine. It also allows the engine to develop high peak power with higher nitro while retaining the easy adjustment qualities of lower compression.

Anyone who has tried to adjust FAI pylon engines will attest to that!

Queries to nitromethane producers and chemical engineers indicate that nitromethane is not a large source of nitric acid and that nitric acid does not cause rust. Moisture (water) causes rust.
Paul Mcintosh
Owner-CRCustom.com - custom vinyl lettering, banners, signs
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11-01-2006 12:34 AM  14 years ago
TMoore

rrMaster

Cookeville, TN

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A friend of mine here in town just lost the rear bearing in his Hyper after about 3 gallons. We both fly the same fuel and run our engines in the same manner. So, what's the difference?

Here is what we know. I store my helis in a heated / air conditioned and de-humidified basement and he stores his in a garage that is un-heated and un-air conditioned. Based on the rusting patterns we saw on the crank, this may be a culprit.

TM
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11-01-2006 12:53 AM  14 years ago
Yug

rrMaster

UK. Herts

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The dreaded 3 gallons strikes again.
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11-01-2006 01:31 AM  14 years ago
supertigre

rrApprentice

Castle Rock, Colorado

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Moisture! Colder temps allow more condensation.Paul Mcintosh
Owner-CRCustom.com - custom vinyl lettering, banners, signs
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11-01-2006 02:23 AM  14 years ago
tchavei

rrProfessor

Portugal

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Moisture!
99,99% pure components have alot less water (0,01%) than regular methanol or nitromethane(95% purity - 5% water). Thats only 50 times higher! The methanol and nitro left in the engine at the end of the day has water in it... the more water, the more rust.

Tony

--------------------
"Perfection and patience usually walk side by side..."
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11-01-2006 04:31 AM  14 years ago
turboomni

rrProfessor

East of the Equator

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Here is what we know. I store my helis in a heated / air conditioned and de-humidified basement and he stores his in a garage that is un-heated and un-air conditioned. Based on the rusting patterns we saw on the crank, this may be a culprit.

TM
Do you both run the same fuel?
Just for kicks what are each of your methods when you stop flying at the end of the day? Run dry,,or just shut off and put away?
Setup is everything, All my heli's can fly far better than I can pilot them
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11-01-2006 05:05 AM  14 years ago
dkshema

rrMaster

Cedar Rapids, IA

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Turbo -- there are too many people using a variety of fuels, a variety of shutdown methods, and a variety of storage methods ALL having similar problems with the OS 50. I don't believe that you could log all the different information, compile it, and find a common factor leading to the early and regular failures of these bearings, other than the bearings are rear bearings from an OS 50. Take some time to actually read through the various threads here on RR dealing with this situation. The only common denominator is the motor itself.

If it were fuel, storage, or shutdown methods (or any of a million other variables all having been reported here over the past couple of years) that were the root cause of the bearing failure, then not only should the rear bearing in my two OS 50's die routinely, but also should the rear bearings in the OS 32 SX-H, two OS 37 SZ-H, OS 70 SZ-H, OS 40-FX, OS 46-FX, Supertiger 45 and Supertiger 90 that I own, experience the same failure frequency. I run ALL of these motors on the same fuel, use the same shutdown techniques, and all share the same garage and ambient conditions when not in use. I've run them, dry, not run them dry, used after-run oil, not used after-run oil, and tried the other anecdotal preventative measures. None prevented rear bearing failure in the OS 50.

The OS 50 is the only engine I've had in this assortment that's eaten its rear bearing. So far, in the past two seasons, I've managed to have one rear bearing a season in the 50 go belly up.

We've heard about the crank web mod. It doesn't cure the problem. We've heard about the coke can mod. It extends the life, but doesn't cure the problem. We've read about all sorts of fixes, ceramic balls, stainless steel races. Those fail early, too. High viscosity oil, low viscosity oil, low nitro, high nitro, no nitro fuels. Castor based, all synthetic, a combination of castor and synthetic. Coolpower, Omega, Magnum, Sig, Wildcat...other fuels. The rear bearing still fails at an alarming rate in the 50.

All other motors just run and run and run and...

Dave
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11-01-2006 05:30 AM  14 years ago
turboomni

rrProfessor

East of the Equator

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Seems strange then that my Hyper 50 has completed a full 2 years of flying with no problems ,
1 year 15% nitro,,2nd year 30% and sitting in a garage with no humidity control or after run oil. I run dry and put away..
I use Marvel Air Tool Oil when in long storage of over a few weeks.
I know there are so many variables,,,sorry I asked!
Take some time to actually read through the various threads here on RR dealing with this situation.
I have been following this for some time as you obviously have and you too are at a loss what the real problem is.
But I have not had a problem yet and am curious as you at what the thread is in the rear bearing's demise.

I guess maybe the next logical thing is to ask people with No problems with the Hyper bearings to speak up and tell there story.
How often do you go through bearings in your 50 dkshema??
Setup is everything, All my heli's can fly far better than I can pilot them
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11-01-2006 05:57 AM  14 years ago
turboomni

rrProfessor

East of the Equator

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We've heard about the crank web mod. It doesn't cure the problem. We've heard about the coke can mod. It extends the life, but doesn't cure the problem. We've read about all sorts of fixes, ceramic balls, stainless steel races. Those fail early, too. High viscosity oil, low viscosity oil, low nitro, high nitro, no nitro fuels. Castor based, all synthetic, a combination of castor and synthetic. Coolpower, Omega, Magnum, Sig, Wildcat...other fuels. The rear bearing still fails at an alarming rate in the 50.

All other motors just run and run and run and...
Maybe research is needed on operating parameters. Headspeed motor rpms + pitch at what speed + nitro used. These motors because of there power output are asked to do alot more than say a TT50.
Not that anyone would have the time to test all these variables but maybe ask all Hyper owners With Out problems what their setup is and expectations at what headspeed and pitch etc might be the next step.
Could it just be too high rpms with too much pitch pounding the rear bearing into submission?
Doug,,with the coke can mod said that rust is not the problem unless really bad.

I'd like to see how many don't have problems and how they run them,,
Setup is everything, All my heli's can fly far better than I can pilot them
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11-01-2006 09:48 AM  14 years ago
tchavei

rrProfessor

Portugal

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Headspeed: 1850
Ratio: 8.7
Fuel: 20% nitro, 20% oil
Style: basic acrobatics
Average Humidity: 20% Summer, 70% Winter
Average Temp: 93F Summer, 53F Winter
Maintainance: Rarely

Bearing life: over 1 and a half years with 6 month storage after a crash... even fuel was left inside the engine. 287 flights. Bearing still ok.

Tony

--------------------
"Perfection and patience usually walk side by side..."
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11-01-2006 11:27 AM  14 years ago
Yug

rrMaster

UK. Herts

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Standard bearings
Magnum30
HS = 2000
1 1/4 to 1 3/4 depending on which hyper, weather etc
Backplate temp - finger with no discomfort. I've stopped measuring head temps.
Low needle = 1 oclock
Run heli dry at end of session and turn over with starter for a couple of seconds to purge any remaining fuel.
Bearings get changed a couple of times a year and they do have some rust, but I do get about 300 flights with stock bearings. Unfortunately this doesn't seem to be the case with other bearings.
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11-01-2006 01:10 PM  14 years ago
dkshema

rrMaster

Cedar Rapids, IA

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I've replaced two bearings in two seasons of flying.
Could it just be too high rpms with too much pitch pounding the rear bearing into submission?
Wouldn't that simply point out that the bearing is not properly sized for the job? After all, its in a motor that is spec'ed at 1.9 HP at 17,000 RPM, with a practical operating range of 2,000 to 20,000 RPM.

The OS 50 is also used in nearly every "50 sized" heli out there, and suffers the same problem in all.

I'd like to find a bearing that would replace to rear bearing in the 50 that isn't a ball bearing, but a roller bearing -- one that uses cylindrical rollers, instead of balls. It would seem that the ten balls in the current bearing are being asked to take the brunt of the load. This is a bearing designed to take axial loads, and in the process, it's also absorbing the shock of the combustion process, as well as supporting the moving mass of the piston, rod, and wrist pin. At any given time, there are only about four balls that are taking the majority of the punishment. That's a very small area having to support a large load. A roller-type bearing would have more surface area of more rollers supporting the load, both radially, and axially.

Dave
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11-01-2006 02:19 PM  14 years ago
tchavei

rrProfessor

Portugal

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I forgot to add two notes


1. My Hyper started out as being a normal OS 50-SXHn Ring (don't know what the "n" stands for) and subsequently had a 60B carb fitted. Later on I also got a blue engine head from a friend of mine.

2. An ancient once told me that the rear bearing of an engine was the mirror of the break-in procedure. The better the break-in, the smoother the engine, less lateral vibes which eventually would translate in less radial load on the bearing expanding its useful life.

Don't know if thats a myth or not... just thought it would be interesting to share.


Tony

--------------------
"Perfection and patience usually walk side by side..."
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11-01-2006 02:20 PM  14 years ago
TMoore

rrMaster

Cookeville, TN

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We both fly the same fuel and run our engines in the same manner. So, what's the difference?
We shut them down and put them away. When I shut the 90's down I usually use some oil squirted in the case with the back off.

TM
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11-01-2006 02:31 PM  14 years ago
turboomni

rrProfessor

East of the Equator

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Wouldn't that simply point out that the bearing is not properly sized for the job? After all, its in a motor that is spec'ed at 1.9 HP at 17,000 RPM, with a practical operating range of 2,000 to 20,000 RPM.
It seems logical that may be the case. I would also think just because it makes the most power @ 17,000 rpms doesn't mean the engine bearings are happy at that speed ,or maybe it's the rpms + the amount of load [pitch/cyclic/ super fast servos for heavy 3D that kills the bearings. O roller bearing would be nice with much more surface area to absorb the load.
The OS 50 is also used in nearly every "50 sized" heli out there, and suffers the same problem in all.
You maybe right again but I'd like to see more info from guys with less to no problems in say 2 years time. Also I wonder if the new optional Titan gear ratio [8.7 to 1?] might help as the motor would have abit more torque over the head so it may not work as hard. You have to admit the Hyper really is the stardard for 50 performance for most guys ,,and they are run regularly within an inch of their lives by many.

For me I run 1850 to 1900 head speed [Plastic head]., Magnum 30% 1:30 on the low and a fat 1 1/3 turns on the high. Run dry and spin to get the alcohol out ,close carb . More than a few weeks storage I inject Marvel Air Tool Oil . I am not a hardcore violent 3D flyer that really stresses the heli either.
I'd like to hear more from guys with fewer problems and look at their setup and flying style. May mean nothing but what the hell,thats what this forum is about.
Setup is everything, All my heli's can fly far better than I can pilot them
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