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HelicopterMain Discussion › Trouble in tuning OS 50SX-H ..... frustration !
02-23-2014 08:08 AM  3 years agoPost 1
Vaderluck

rrApprentice

Melbourne - Australia

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Trouble in tuning OS 50SX-H
This is my first nitro engine heli (TREX 600N DFC) and the tuning is much harder than I expected.

At idling and up to 60% power, the engine runs ok and can float the heli for hovering (barely). However, when I up the throttle more, the engine just cannot produce more power, it is not stalling/cut out though, it just cannot lift the heli and it actually reduces the power. Based on engine manual, it appears this problem can be tuned by adjusting the needle valve (manual: mixture control valve for idling/low speed. Needle valve for power at full throttle). But I try both rich and lean setting on needle valve , none of them work.

The pitch curve is -3, 0, 7, 10 degree. So I don’t think it is causing the problem. The fuel I use is 15% nitro, 20% oil. It does not produce a lot of smoke (not as much as what I see on youtube) in either lean or rich setting. Would it be I am using low quality/dodgy fuel?
I am very frustrated because I can’t pin down the problem and no one in our club flying nitro heli to get help.

Any help would be appreciated.

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02-23-2014 11:08 AM  3 years agoPost 2
doorman

rrProfessor

Sherwood, Arkansas

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Adjusting....

Try reseting all needles back to original...
Then in your throttle curve try bringing the 1/2 way point up so the the carb is open a bit over half way(the carb used to be marked for this hover position)
Then in your pitch curve, bring your mid point to 5 degrees..
It sounds as if you were getting too much pitch for the power you had...
Been awhile since I ran "wet" fuel, but I hope this wil lead you in the right direction.

Stan

AMA 2918-Team JR, Spin Blades, East Coast Scale Helicopter,Castle Creations

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02-25-2014 02:36 AM  3 years agoPost 3
Vaderluck

rrApprentice

Melbourne - Australia

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I have rechecked the engine and can't find anything wrong with it.
Now I tend to think I got a dodgy fuel with little or no nitro in it.

Just wondering has anyone tried fuel with 5% nitro 0% ? Can a heli fly with this fuel ?

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02-25-2014 03:04 AM  3 years agoPost 4
rpat

rrElite Veteran

Weirton, W. Va.

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What brand of fuel are you running?

trex 700fbl cal30,minititan,, trx600fbl,trex250,logo 500,Velocity N2

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02-25-2014 04:27 AM  3 years agoPost 5
drdot

rrElite Veteran

So. California, Orange County.

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fwiw..

All my experience with the OS has led me to believe they are much happier on 30 %....Try a gallon of Byron or Coolpower...needle settings are not as critical, engine runs cooler.....I always liked the Enya #4 glow plug as well...If you can still get them.....
try to find someone in your area with glow experience, very easy to burn out engine trying for that last little bit of power...

Good luck!

John.

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02-25-2014 05:21 AM  3 years agoPost 6
dkshema

rrMaster

Cedar Rapids, IA

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First nitro motor. In a heli. No experienced help at hand.

Recipe for fried motor.

It's not your fuel, especially if you bought a new gallon, 15% nitro, 20% oil.

I don't know what you have for pitch curve, or even throttle curve at this point.

But for starters, how about a pitch curve of -2 degrees at low stick, +6 degrees at mid stick, and +10 at full stick.

Then start with a linear 0 to 100% throttle curve.

As for your carb...mechanically you'd want to set the throttle stop screw (this is on the body of the carb) such that when looking down the venturi, as you close the throttle barrel down, it stops just as the throttle barrel closes off the venturi. That would be your low throttle, low trim setting. This will allow you to kill the motor by going to low throttle, low trim. At this setting, you'll also be able to start the motor at low throttle mid trim, it will idle and not engage the rotor system clutch. At low throttle full up trim, you'll begin to spin up the head.

Full throttle -- the carb barrel is completely open, no servo binding or stalling. If everything else is OK, you'll be half way open at half throttle.

-----

Picture above shows an OS 50 carb, particularly the low speed adjustment. The slotted screw at the right, just right of the intersection of the two lines, is the low speed adjustment. IT IS A CAM, not a screw. Its adjustment range is ONLY 1/4 of a turn left or right of factory setting. The slot should NEVER go past (left side of) line number 2.

The two lines intersect at the pivot point of the cam. If you have turned the cam too far, you will find that the pivot point of the cam is now on the right side of the slotted screw, not the left as shown.

Factory setting is pivot point on the left side of the cam as shown, and the slot lined up with line number 1 in the picture.

Clockwise leans out the low speed setting, counter clockwise makes it richer. The setting as shown above is just slightly lean from factory setting, and is probably about where you'll end up with the low speed setting.

-----

Beware going too lean on the high speed needle. You may get away with it for a short time, but if you run too lean, you WILL roast your piston and ring. Cylinder maybe.

-----

If you are hovering, and on the rich side, you will hear the motor speed changing back and forth from a lean four-stroke setting to a rich two-stroke setting. You may find the tail wants to twitch a little each time the motor crosses that boundary. Lean the top end out a few more clicks, the motor should begin to run evenly, but still rich.

-----

Bring the motor to idle, let it sit at idle for about 30 seconds. Open the throttle suddenly, and listen to the motor. If it spits, gurgles, sputters, then picks up, your idle needs to be leaned out slightly.

If, at idle, after a long period, gradually slows down and stops, the idle is too rich.

If at idle the motor gradually speeds up and dies, the idle is too lean.

On the other hand, after sitting at idle, it just dies suddenly, or hesitates, then picks up smoothly, the idle is too lean. Back it off a hair.

The goal is to have a motor that will idle well, evenly, yet pick up instantly the moment you romp on throttle.

When getting the low speed set properly, at the beginning use the throttle trim to maintain idle speed, don't keep leaning out the low speed setting until you have the top end set close to where it will end up.

Second test -- hover the heli for about 30 seconds, land, and let idle for about 30 seconds. This should clear out excess fuel from the crankcase.

Pinch the fuel line just where it enters the carb fuel inlet nipple. The motor should run for about 3 - 5 seconds, then pick up speed. If you continue to pinch the line, it will speed up and die. If it runs much longer than 3 - 5 seconds, your idle is too rich. If it speeds up and begins to die in less than 3 - 5 seconds, the idle is too lean.

-----

To set the top end, take off, hover briefly. Give full throttle/collective and climb vertically as long as you can (and still maintain control). Listen to the motor. If it begins to bog and slow down, your top end is too lean.

When you have the top end set close to where it needs to be, the heli will climb vertically, will climb with authority, and should accelerate as it does, the motor will continue to pull strong and not bog down.

-----

If you are using a governor, disable it until you have the needles properly set.

-----

And don't blame a new jug of fuel for tuning problems. Tuning a nitro motor is a learned skill/art. Be patient and learn. And you're best to run just a bit on the rich side. It makes for a healthy motor.

-----
Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz

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02-25-2014 05:44 AM  3 years agoPost 7
drdot

rrElite Veteran

So. California, Orange County.

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fwiw...

....What he said....+1+

John.

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03-03-2014 02:00 AM  3 years agoPost 8
Vaderluck

rrApprentice

Melbourne - Australia

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Thanks everyone for the advices.
I followed the tuning steps exactly one by one and still no success when flying from mid throttle upward. Idling is good but the engine just not respond when the throttle passes the mid level.
In desperation, I ran around the whole weekend and bought all ingredients and mix my own fuel : 20% nitro, 20% synth oil and 60% meth. Suprise, it works now. The engine is now responsive from mid level upward. Although it is not as responsive as electric but it is good enough for me now. I will fine tune later.

I guess I got a dodgy fuel where it may have a lot less 15% nitro as shown on the label.

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03-03-2014 04:35 AM  3 years agoPost 9
Einzelganger

rrKey Veteran

Campbell, Texas

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Good show Vaderluck!
I've never had any trouble from my OS 50's either SX or Hyper.
I have always run Cool Power 30%.
I lied. Once when I was first starting out, I ran some old 15% four stroke plank fuel. It had apparently gone bad and I thought I had trouble with the engine. I then bought my first gallon of Cool Power 30% heli fuel and I have never looked back or even been tempted.
Congratulations on your good sense and fortune.

Wayne

I love the smell of nitro in the morning.
RIP Roman

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03-04-2014 12:41 PM  3 years agoPost 10
jason46

rrVeteran

MI

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Seems to me there is another problem outside of engine tuning, either mechanical such as something slipping or electrical such as the throttle is not opening all the way or compression is low. If tuning was so poor it were down on power would it keep running or die?

Vaderluck, I'm curious what pipe you're running?

I got a 2nd hand OS50 and it runs like a top at practically any needle setting, and pulls hard IMO.

Dkshema, that is some great info on tuning.

Edit
I missed his last post, was just the fuel..

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03-04-2014 01:10 PM  3 years agoPost 11
meowguy

rrVeteran

Saco, ME

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I ran around the whole weekend and bought all ingredients and mix my own fuel : 20% nitro, 20% synth oil and 60% meth. Suprise, it works now. The engine is now responsive from mid level upward. Although it is not as responsive as electric but it is good enough for me now. I will fine tune later.
Vaderluck,

At first when I saw the effort you went to I said to myself; "why doesn't he just buy a fresh gallon of fuel." Then I saw that you live in Australia. I corresponded with a fellow from down under about 25 years ago who had seen an article I had written for Radio Control Modeller Magazine. His problem was that he could not get the parts he needed to repair his heli and so I sent him what he needed. We corresponded via snail-mail for a couple of years.

Your ingenuity in making your own fuel is really quite admirable. It sounds as though you have solved the problem. One of the joys of using the OS 50 and their 91 is that once they are adjusted you will hardly ever have to make a change in the needles. And they run very nicely on economical 15% nitro which is about 1/3 cheaper than 30%. Our fuel of choice back in the day was K&B 500. Their formula was a closely held secret. So secret, in fact, they took it to the grave with them. We believed it was about 12.5% nitro with castor oil for lubricant. Our club ordered it in 55 gallon drums.

Perhaps some day we will read about "Vaderluck 500" fuel for sale. (:-))

"Sweet dreams and flying machines in pieces on the ground." J. Taylor

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