dkshema
rrProfessor
Location: Cedar Rapids, IA
| What Barracuda is trying to explain is that even when you START the OS50 running in the correct direction (it turns COUNTERCLOCKWISE when you are looking down from above at the end of the crankshaft with the fan and nut on it), if your idle is a bit on the RICH side, the OS50 will easily hiccup -- and without any audible warning -- simply reverse the direction that it is running.
This is a common occurrence with the OS 50. Lean the idle out just a bit, and at the same time, increase your idle speed by moving the throttle trim up a bit.
BUT -- IF your rotor head is actually TURNING and YOU'RE getting airborne, the motor is NOT running backwards. Almost all heli kits these days include an overrunning clutch ("one-way clutch" ) in the main rotor drive train to disengage the main rotor shaft from the rest of the drive train if the engine quits. This one-way clutch is what allows you to maintain/increase head speed during descent in an autorotation.
If your motor hiccups and reverses itself at idle, as you increase throttle, the main centrifugal clutch will engage as it should, but with the motor turning backwards, the one-way clutch will be slipping and you will not get near the head speed needed to lift off. In most cases the motor will rev up while the head just sits there, grinning at you.
-----
If your needles (high and/or low speed) are on the rich side, there will be excess fuel spitting out of the carb at low RPMs. Also, there may be a small amount of fuel coming from around the front bearing. That is normal, as the bearings are NOT liquid-tight, and that small amount of fuel is what carries lube up to the front bearing and the front end of the crankshaft.
-----
You are getting enough RPM on the head to get airborne, but apparently not an overwhelming amount of RPM. That indicates that you are still rich on the high speed needle, AND that the motor is turning the right direction.
-----
| Quote |
| the mixture screw is set to factory and needle valve is two turns out.
|
Those are the default settings from the factory. In general those are settings that will get the motor started, but are usually on the very rich side. You need to adjust BOTH of those settings gradually at first, until you have several tanks of fuel through the motor. You WANT the engine to be on the rich side for the first few tanks of fuel to make sure the motor breaks in well without overheating and damaging the piston, ring, or cylinder.
Also note that the IDLE SPEED is set by the throttle opening (throttle trim lever on the TX), NOT the mixture screw (aka the "low speed needle" ). Read through your OS50 manual again, the section on needle adjustment is key to understanding how to adjust the needles.
-----
The settings that you finally end up with depend to a large degree upon the fuel you are using, the muffler that you have installed, and your pitch and throttle curve values. Temperature, humidity, and altitude also play a role in where those needles finally end up being set.
-----
DO seek local help. It is priceless.
-----
* Making the World a Better Place -- One Helicopter at a time! *
Dave |
